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Freshwater Fishes of North-Eastern Australia

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Brad Pusey, Mark Kennard and Angela Arthington

Centre for Riverine Landscapes, Griffith University Nathan, Qld 4111, Australia

Text © 2004 Brad Pusey, Mark Kennard, Angela Arthington and the Rainforest CRC Illustrations © 2004 B.J. Pusey All rights reserved. Except under the conditions described in the Australian Copyright Act 1968 and subsequent amendments, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, duplicating or otherwise, without the prior permission of the copyright owners. Contact CSIRO PUBLISHING for all permission requests. National Library of Australia Cataloguing-in-Publication entry Pusey, Bradley J. Freshwater fishes of north-eastern Australia. Bibliography. Includes index. ISBN 0 643 06966 6 (hardback).

ISBN 0 643 09208 0 (netLibrary eBook).

1. Freshwater fishes – Australia, North-eastern. 2. Freshwater fishes – Australia, North-eastern Identification. 3. Freshwater ecology – Australia, North-eastern. I. Kennard, Mark J. II. Arthington, Angela H. III. Title.

597.1760994 Available from CSIRO PUBLISHING 150 Oxford Street (PO Box 1139) Collingwood VIC 3066 Australia Telephone: Local call: Fax: Email: Web site:

+61 3 9662 7666 1300 788 000 (Australia only) +61 3 9662 7555 [email protected] www.publish.csiro.au

Front cover Hephaestus tulliensis (khaki grunter), photograph by G.R. Allen

Set in 9.5 Minion Cover design by Jo Waide Text design by James Kelly Typeset by J & M Typesetting Printed in Australia by Ligare

To my parents Pat and Jim (dec.) for fostering a love of natural history, and to my family, Moira, Michael and Olivia for their support and tolerance B.J.P.

To my loving partner Lorann and chiens lunatiques Sas´a and Max, for happy diversions and indulgences, and to my family, especially Jill and Colin, for inspiration and encouragement M.J.K.

To my New Zealand family and to Mark, Kirstie, Ayden, Huntley and Liveya, for their enduring love and encouragement A.H.A.


Foreword

This book is the end product of the authors’ extensive research on the ecology and flow requirements of fishes in Queensland rivers. Production of the book has been a major initiative of the Co-operative Research Centre for Tropical Rainforest Ecology and Management (Rainforest CRC) via its fundamental research on biodiversity in the Wet Tropics region, and the CRC’s new Catchment to Reef research program. The Rainforest CRC and the Centre for Riverine Landscapes, Griffith University, have subsidised production of the book and worked together with the publishers, CSIRO Publishing, to achieve its high standard of presentation.

North-eastern Australia contains over 130 native species of freshwater fish which is approximately half of the freshwater fish fauna of the entire continent. This fauna is of great interest for its diversity, scientific importance and value. Many species occurring in this region also extend westward across much of northern Australia and southward through coastal New South Wales, Victoria, South Australia and Tasmania. This makes the book of singular importance as the only text covering the freshwater fishes of this vast region in the richness of detail presented here. The value of this baseline work is potentially enormous. Tropical Australia faces a number of serious problems directly stressing the environment we value so highly. There is increasing demand for water for agriculture and for urban use and we are likely to see our water resources further stressed by increasing climatic variability – one of the likely results of global climate change. There is also international concern about runoff from catchments causing a decline in the health of the Great Barrier Reef and its feeder streams. Fish are important indicators of ecosystem health and this book provides the sort of detailed information needed for a monitoring toolkit that can be used at the stream level by community groups, farmers and scientists concerned with these issues. We continue to lead the tropical world in these fields of science and application.

On behalf of the Rainforest CRC and Griffith University, I congratulate the authors on their dedicated efforts in producing this significant contribution to knowledge, and commend the book as an indispensable compendium, catalogue and baseline reference for anyone with a keen interest in this fascinating component of Australia’s unique biodiversity. Nigel Stork CEO, Rainforest CRC Cairns, Queensland February 2004

vii


Table of contents

Foreword

vii

Acknowledgements

xiii

Introduction

1

Origins, structure and classification of fishes

3

Key to the native and alien fishes of north-eastern Australia

14

Study area, data collection, analysis and presentation

26

Ceratodontidae Neoceratodus forsteri – Queensland lungfish

49

Osteoglossidae Scleropages leichardti – Saratoga

60

Megalopidae Megalops cyprinoides – Tarpon

64

Anguillidae Anguilla australis, Anguilla obscura, Anguilla reinhardtii – Eels

71

Clupeidae Nematalosa erebi – Bony bream

92

Ariidae Arius graeffei, Arius leptaspis, Arius midgleyi – Fork-tailed catfishes

102

Plotosidae Neosilurus hyrtlii – Hyrtl’s tandan Neosilurus ater – Black catfish Neosilurus mollespiculum – Soft-spined catfish Porochilus rendahli – Rendahl’s catfish Tandanus tandanus – Eel-tailed catfish

112 121 129 133 137

Retropinnidae Retropinna semoni – Australian smelt

152

Hemiramphidae Arrhamphus sclerolepis – Snub-nosed garfish

161

Belonidae Strongylura krefftii – Freshwater longtom

166

Atherinidae Craterocephalus marjoriae – Marjorie’s hardyhead Craterocephalus stercusmuscarum – Fly-specked hardyhead

171 180

Melanotaeniidae Rhadinocentrus ornatus – Ornate rainbowfish Cairnsichthys rhombosomoides – Cairns rainbowfish Melanotaenia splendida – Eastern rainbowfish Melanotaenia duboulayi – Duboulay’s rainbowfish Melanotaenia eachamensis – Lake Eacham rainbowfish

197 205 211 221 231

ix

Melanotaenia utcheesis – Utchee Creek rainbowfish Melanotaenia maccullochi – MacCulloch’s rainbowfish

237 242

Pseudomugilidae Pseudomugil mellis – Honey blue-eye Pseudomugil signifer – Pacific blue-eye Pseudomugil gertrudae – Spotted blue-eye

247 254 269

Synbranchidae Ophisternon gutturale, Ophisternon spp.? – One-gilled swamp eels

272

Scorpaenidae Notesthes robusta – Bullrout

278

Chandidae Ambassis agrammus – Sailfin glassfish Ambassis agassizii – Agassiz’s glassfish Ambassis macleayi – Macleay’s glassfish Ambassis miops – Flag-tailed glassfish Denariusa bandata – Pennyfish

284 292 302 306 309

Centropomidae Lates calcarifer – Barramundi

313

Percichthyidae Macquaria ambigua, Macquaria sp. B – Yellowbelly Macquaria novemaculeata – Australian bass Guyu wujalwujalensis – Bloomfield River cod Maccullochella peelii mariensis – Mary River cod Nannoperca oxleyana – Oxleyan pygmy perch

326 337 345 348 353

Terapontidae Amniataba percoides – Barred grunter Leiopotherapon unicolor – Spangled perch Hephaestus fuliginosus – Sooty grunter Hephaestus tulliensis – Khaki bream, Tully grunter Scortum parviceps – Small-headed grunter

361 369 378 390 395

Kuhliidae Kuhlia rupestris – Jungle perch

401

Apogonidae Glossamia aprion – Mouth almighty

409

Toxotidae Toxotes chatareus – Seven-spot archerfish

419

Mugilidae Mugil cephalus – Sea mullet

426

Gobiidae Glossogobius sp. 1 – False Celebes goby Glossogobius aureus, Glossogobius giuris – Golden goby, Flathead goby Glossogobius sp. 4 – Mulgrave River goby Redigobius bikolanus – Speckled goby Awaous acritosus – Roman-nosed goby Mugilogobius notospilus – Pacific mangrove goby Schismatogobius sp. – Scaleless goby

434 440 445 449 456 461 465

x

Eleotridae Eleotris fusca, Eleotris melanosoma – Brown gudgeon, Ebony gudgeon Bunaka gyrinoides – Greenback gauvina Oxyeleotris lineolatus, Oxyeleotris selheimi – Sleepy cod, Striped sleepy cod Oxyeleotris aruensis – Aru gudgeon Giurus margaritacea – Snakehead gudgeon Hypseleotris compressa – Empire gudgeon Hypseleotris galii, Hypseleotris sp. 1 – Firetailed gudgeon, Midgley’s carp gudgeon Hypseleotris klunzingeri – Western carp gudgeon Gobiomorphus australis – Striped gudgeon Gobiomorphus coxii – Cox’s gudgeon Mogurnda adspersa, Mogurnda mogurnda – Purple-spotted gudgeon, Northern trout gudgeon Philypnodon grandiceps – Flathead gudgeon Philypnodon sp. – Dwarf flathead gudgeon

468 473 477 487 491 498 510 521 530 538 544 558 568

Conclusion: prospects, threats and information gaps

575

Glossary of terms used in the text

585

Bibliography

601

Appendix 1: Fish species composition in rivers of north-eastern Australia

655

Appendix 2: Studies undertaken in rivers of north-eastern Australia

674

Index

681

xi


Acknowledgements

Department of Primary Industries, Fisheries), South East Queensland Water Board, South East Queensland Water Corporation, and the Wet Tropics Management Authority.

This book is a product of our research on the ecology and flow requirements of fishes in Queensland rivers, amply funded by the former Land and Water Resources Research and Development Corporation (LWRRDC, now Land and Water Australia), and generously supported by the former Queensland Water Resources Commission, and former Queensland Department of Primary Industries, Land Use and Fisheries Branch (now Queensland Departments of Natural Resources, Mines and Energy, and Queensland Department of Primary Industries, Fisheries, respectively), and Griffith University. Funding from the Co-operative Research Centre for Tropical Rainforest Ecology and Management (Rainforest CRC) supported our research, and the Rainforest CRC and the Centre for Riverine Landscapes, Griffith University, have subsidised this book to make it more affordable. Professor Nigel Stork, Chief Executive Officer of the Rainforest CRC and Jann O’Keefe sought publication outlets for the book and negotiated our contract with CSIRO Publishing. We sincerely thank Nigel and the Rainforest CRC for supporting our research and writing.

We also wish to thank all government agencies and agency staff (e.g. rangers) and the numerous landholders and aboriginal communities who allowed us access to field sites, supported our work and shared their knowledge and insights. The following colleagues, friends and family members have assisted in the field and in the laboratory - we are deeply indebted to one and all: Steven Balcombe, Mark Bensink, Jason Bird, David Blühdorn, Stacey Braun, Stuart Bunn, Peter Buosi, Damien Burrows, Harry Burton, Brian Bycroft, Hiram Caton, Nick Cilento, Paul Close, Dan Clowes, Diane Conrick, Anthony Cutten, Felicity Cutten, Huntly Cutten, Ellie Dore, Ashley Druve, Susan Dunlop, John Endler, John Esdaile, Simon Hamlet, Debbie Harrison, Karen Hedstrom, Alf Hogan, Peter James, Daniel Kennard, Paul Kennard, Alex Langley, Matthew Langworthy, Greg Lee, Bill Macfarlane, Stephen Mackay, Nick Marsh, Chris Marshall, Jonathan Marshall, Peter Mather, Greg Miller, John Mullen, Carl Murray, Peter Negus, Richard Pearson, John Peeters, Tony Pusey, Martin Read, Darren Renouf, Andrew Sheldon, Michael Smith, Errol Stock, Brian Stockwell, Celia Thompson, Chris Thompson, Rob Wager, Richard Ward, Selina Ward, Tony Watson, Gary Werren, Rob Williams and Tim Wrigley.

Preparation of this book has entailed a major review of existing literature and collation of the results of unpublished field research undertaken by the authors in freshwater systems throughout Queensland over the last 20 years. Many people and institutions have assisted with this research or provided funding support, in-kind resources, data and advice. We particularly wish to thank many institutions and individuals for their commitment to the study of freshwater fishes in Australia.

Sincere thanks are due to the following for stimulating discussions on the ecology of freshwater fish and for provision of literature, reports and data, access to specimens of fish species and identification of specimens, including fish parasites: Gerry Allen, John Amprimo, Steven Balcombe, Chris Barlow, Andrew Berghuis, Eldridge Birmingham, Steve Brooks, Culum Brown, Damien Burrows, Niall Connolly, Brendan Ebner, Craig Franklyn, Gary Grossman, Jeff Gunston and Bruce Hansen and many others from the Australia New Guinea Fishes Association, Michael Hammer, Gene Helfman, Brett Herbert, Alf Hogan, Jane Hughes, Paul Humphries, David Hurwood, Michael Hutchison, Inter-Library Loans staff at Griffith University, Peter Jackson, Jeff Johnson, Peter Johnston, Peter Kind, John Koehn, Helen Larson, Keith Lewis, Mark Lintermans, Chris Lupton, Roland Mackay, Chris Marshall, Jonathan Marshall, Mark McGrouther, Craig Moritz, Richard Pearson, Colton Perna, Claire Peterkin, Phil Price, Tyson Roberts, John Ruffini, John Russell,

First, we gratefully acknowledge research grants and inkind support from the following agencies: Australian Nature Conservation Agency, Australian National Parks and Wildlife Service, Australian Water Research Advisory Council, Co-operative Research Centre for Rainforest Ecology and Management, Co-operative Research Centre for Freshwater Ecology, Co-operative Research Centre for Sustainable Tourism, Land and Water Resources Research and Development Corporation, Moreton Bay Waterways and Catchments Partnership, Queensland Department of Environment and Heritage, Queensland Department of Natural Resources, Mines and Energy, Queensland Department of Primary Industries (Fisheries), Queensland Environmental Protection Agency, Queensland National Parks and Wildlife Service, Queensland Water Resources Commission, Walkamin Research Station (Queensland

xiii

Nick Schofield, Clayton Sharpe, Bob Simpson, Jim Tait, Rob Wager, John Ward, Alan Webb, Peter Unmack and Tom Vanderbyll.

acknowledge Mariola Hoffmann for preparing the maps presented in this book. We thank Elly Scheermeyer, Fiona McKenzie-Smith and Darren Renouf for assistance with references. We are also grateful to Maria Barrett, Petney Dickson, Jason Elsmore, Daina Garklavs, Keith Officer, Lacey Shaw, Deslie Smith, Stuart Taylor and many other staff at Griffith University for administrative support and the various tasks that supported the production of this book. We apologise to anyone we have neglected to thank.

We warmly thank the following colleagues for reading and commenting on various chapters: Culum Brown, Damien Burrows, John Endler, Alf Hogan, Helen Larson, Steven Mackay, Chris Marshall, Jonathan Marshall, Dugald McGlashan, Colton Perna, Tarmo Raadik, John Russell, Alisha Steward and Jim Tait. This book would no doubt have benefited from further expert feedback from other colleagues; unfortunately, time constraints precluded this.

Finally, we are indebted to CSIRO Publishing for taking on our book and are particularly grateful to Nick Alexander for his support throughout its production and to Briana Elwood for assistance with formatting and editing considerations.

We appreciate the assistance of Aubrey Chandica and Paul Martin with the provision of maps and gratefully

xiv

Introduction

flowing coastal rivers of Queensland and northern New South Wales, although the range of many extends westward across much of northern Australia and southward through coastal Victoria, South Australia and Tasmania.

North-eastern Australia contains the most diverse freshwater fish fauna in all of Australia, over 130 native species in about 30 families, approximately half of the fauna of the entire continent. This fauna includes some of the most ancient species in Australia – the Queensland lungfish, Neoceratodus forsteri, and the saratoga, Scleropages leichardti – as well as one of the most recently discovered Australian freshwater fish species, the Bloomfield River cod, Guyu wujalwujalensis, found far to the north of its nearest relatives, the cods and basses of south-eastern and south-western Australia. In addition to these freshwater fishes, the freshwater reaches of north-eastern Australian rivers support many species from otherwise marine or estuarine families, such as the Lutjanidae, Carangidae, Gerreidae, Scatophagidae, and even sharks and stingrays (Carcharhinidae and Dasyatidae, respectively). Unfortunately, five families (Belontiidae, Cichlidae, Cobitidae, Cyprinidae and Poeciliidae) and at least 23 species of alien fishes have been introduced into freshwater systems of north-eastern Australia, many of which have established self-sustaining populations, or may soon do so. Attempts to establish other families alien to the continent (e.g. Salmonidae) have so far failed in Queensland freshwaters. This book does not treat these two groups of species in any detail as there is very little information on the ecology of marine or estuarine vagrants in freshwaters, and in the case of alien species, major reviews of their distribution and ecology are currently being written by others. We are here primarily concerned with the native freshwater fishes occurring in easterly flowing drainages of the Australian drainage division known as the North-east Coast Division (Drainage I) as defined by the Queensland Department of Natural Resources, Mines and Energy (see Figure 1 in the section describing the study area). Species found only in rivers draining into the Gulf of Carpentaria and those occurring in Queensland sections of inland systems draining central and southern Australian (Lake Eyre, Bulloo-Bancannia and Murray-Darling drainage divisions) are not fully covered here. Our reasons for restricting the number of species covered are threefold: 1) the fauna of this drainage division is currently most at risk from human activities, 2) it is the fauna we know best and that which we have examined in detail or for which a substantial literature base exists, and 3) species omitted from this treatment are covered to lesser or greater extents in existing texts on Australian freshwater fishes. The 79 species covered in this book generally occur in easterly

The aim of this book is to provide information on the freshwater fish fauna of north-eastern Australia in a format that is rich in detail yet readily accessible to ecologists, ichthyologists, environmental managers and consultants, fishermen, hobbyists and the general public. Our treatment takes the reader on a journey – from a description of each species, and an account of its taxonomy, systematics and evolutionary history, biogeography, distribution patterns and abundance – to its macro-, meso- and microhabitat requirements, environmental tolerances, reproductive biology and development, movement biology and feeding ecology. We provide a pen and ink drawing of each species to illustrate characters for identification, an illustrated key to native and alien species and many figures and tables summarising detailed quantitative ecological information. Each chapter concludes with an account of the conservation status of the species, current threats, knowledge gaps and management issues. The increasing pace of development in north-eastern Australia, particularly agricultural and water resource development, currently places severe pressure on the region’s aquatic environment and biota, including fish. Although initiatives such as the Water Resource Planning process in Queensland, and the move towards regional Natural Resource Management Plans and conservation strategies, are intended to minimise the impacts of increasing development, these efforts are placing increasing demands on scientists and practitioners to provide high quality ecological assessments and technical advice. Managers, scientists and the public urgently need reliable quantitative information upon which to base conservation priorities, management strategies and monitoring protocols. Our coverage of the freshwater fish fauna of northeastern Australia is intended to support and strengthen these planning initiatives, to foster the application of scientific principles and sound ecological data in the management of Queensland aquatic ecosystems, and in consequence, to afford a high degree of protection to the region’s unique fish fauna. Several excellent books published in the last 25 years deal with the freshwater fish fauna of Australia (Merrick and Schmida (1984), Australian Freshwater Fish: Biology and

1


information they contain. All deal most comprehensively with the fauna of southern Australia, an emphasis reflecting the amount of information available at the time of production. Allen et al. (2002) [52] is a welcome and excellent addition particularly with regard to nomenclature, but its field guide format necessarily limits the amount of scientific detail on many topics needed for effective management of the fish of north-eastern Australia. The present treatment aims to complement these texts by providing reference material in a standard format that is both up-to-date and comprehensive, including published material (some dating back over 100 years but still relevant) and unpublished documents (government and consultancy reports, University theses) as well as the authors’ extensive published information and unpublished data sets.

Management [936]; Allen (1989), Freshwater Fishes of Australia [34]; and Allen et al. (2002), Field Guide to the Freshwater Fishes of Australia [52]). Other texts cover in varying detail the fauna of individual regions (Allen (1982), A Field Guide to the Inland Fishes of Western Australia [33]; Larson and Martin (1989), Freshwater Fishes of the Northern Territory [774]; Bishop et al. (2001), Ecological Studies on the Freshwater Fishes of the Alligator Rivers Region, Northern Territory: Autecology [193]; Herbert and Peeters (1995), Freshwater Fishes of Far North Queensland [569]; McDowall (1996), Freshwater Fishes of South-eastern Australia (2nd Ed.) [884]; Cadwallader and Backhouse (1983), A Guide to the Freshwater Fish of Victoria [270]; Koehn and O’Connor (1990), Biological Information for Management of Native Fish in Victoria [732]; Wager and Unmack (2000), Fishes of the Lake Eyre Catchment of Central Australia [1354]; Moffat and Voller (2002), Fish and Fish Habitat of the Queensland MurrayDarling Basin [959]), or selected components (Allen (1995), Rainbowfishes in Nature and in the Aquarium [38]).

We hope that this book will encourage greater research effort on the region’s fish fauna and provide a comprehensive information resource allowing other researchers to adopt a more quantitative and strategic framework for their research. We have endeavoured to identify knowledge gaps where they exist and suggest promising new avenues for research. We also hope that this book will have wide general interest and that readers will find this component of Australia’s unique fauna as interesting as we do.

Several books [34, 884, 936] have become the ‘standard’ reference texts for Australian freshwater fishes and essential research tools for many aquatic biologists, yet are now somewhat out of date, and limited in the amount of

2


The origin of fishes The bony fishes (Class Osteichthys) are the most successful and diverse group of vertebrates on Earth. Three major groups or subclasses make up the Osteichthys: the rayfinned fishes (Actinopterygii), the lungfishes (Dipnoi) and the predatory lobe-finned fishes (Crossopterygii). The Actinopterygii are the most speciose group of living fishes, containing more than 23 000 species, whereas the Dipnoi is restricted to four species in three genera: Lepidosiren from South America (1 species), Protopterus from Africa (2 species) and Neoceratodus from Australia (1 species). The subclass Crossopterygii is restricted to a single species Latimeria chalumnae, the coelocanth. (Some classification schemes group the Dipnoi and the Crossopterygii within a single subclass, the Sarcopterygii.)

and diversification during the Devonian period, similar to that observed in the Dipnoi and Crossopterygii. These early fishes, the palaeoniscoids, were characterised by a long slender body, a large mouth gape with many small teeth, small scales and a poorly ossified axial skeleton. By the end of the Devonian however, the mouth gape had shortened, the opercula bones had enlarged and the micromeric scales characteristic of early palaeoniscoids had been replaced by larger, rhombic scales. Over 40 separate families of palaeoniscoid fishes had evolved by the Permian period (250–290 m.y.b.p.). Actinopterygian evolution had given rise to the neopterygian fishes (to which belong the teleost fishes) by the end of the Permian. These fishes are characterised by a vertical suspensorium (where the lower jaws articulate with the upper jaws by a vertically oriented quadrate bone), free cheek bones, the condition where the dorsal and anal fin rays are supported by an equal number of small bones, fusion of the upper jaw bones along the midline and the development of pharyngeal tooth plates. The first teleostean fish evolved in the Triassic period (205–250 m.y.b.p.). These fishes are characterised by the presence of uroneurals (small bones that stiffen the dorsal lobe of the tail and support a series of dorsal fin rays), free movement of the premaxilla independent of the maxilla and development of unpaired toothplates on the basibranchials. These changes in jaw structure resulted in the evolution of a protrusible mouth, which when coupled with the previous change in the suspensorium, allowed huge diversification in feeding mode. Changes in fin structure (possession of rays and of uroneurals) greatly enhanced mobility and manoeuvrability. Thus, the stage was set for the explosive radiation evident in the extant teleost fishes. Many of the modern groups of teleost fishes, at the family level, had appeared by the Eocene period (45–57 m.y.b.p.) [820].

The evolutionary history of the bony fishes is described by John Long [820] and is very briefly summarised here. The origins of the Osteichthys date back to the Late Silurian (approximately 410 million years before present), a time when the seas were dominated by the Chondrichthyes (sharks and rays), Acanthodii (spiny-finned fishes) and especially Placodermi (armour-plated fishes). The Dipnoi originally arose in marine environments during the Devonian (355–410 m.y.b.p.), but have been confined to freshwaters since the early Carboniferous (~340 m.y.b.p.). The Dipnoi experienced a very rapid rate of evolutionary change during the Devonian and early Carboniferous periods, resulting in the evolution of many different species. During this period, there was a transition from gill-respiration to lung-assisted respiration and a transition from a shredding to a crushing feeding mode. In addition, there also occurred a change from the possession of two equallysized dorsal fins, separate anal fin and heterocercal caudal fin to the possession of a shortened first dorsal fin and merged second dorsal, caudal and anal fins (the condition observed today). Fossils of Neoceratodus forsteri, the Queensland lungfish, indicate that it has persisted in its present form for over 100 million years.

The origin of Australia’s freshwater fishes Australia’s freshwater fishes include both primary freshwater species (entire evolutionary history restricted to freshwater) and secondary freshwater species (freshwater forms secondarily derived from marine stocks). However, unlike other parts of the world, Australia has few primary freshwater fishes. These include N. forsteri, Scleropages jardinii, S. leichardti and Lepidogalaxias salamandroides, and possibly members of the Galaxiidae and Retropinnidae [888, 936]. These fish may have ancient Gondwanan origins. For example, fossils of Neoceratodus species have been found

The Crossopterygii also arose during the Devonian. This group of predatory fishes experienced rapid diversification during this period, especially during the Carboniferous, and persisted throughout the Mesozoic era (250–135 m.y.b.p.). Some crossopterygiian species reached an estimated size of 6–7m. The Actinopterygii (ray-finned fishes) first appear in the Late Silurian fossil record followed by significant radiation

3


in Cretaceous deposits in Australia and South America [52]. Similarly, the presence of bony-tongued fishes (Osteoglossidae, the saratogas) in South America, Africa, South-east Asia and Australia–New Guinea suggests that the origins of this family also predate the fragmentation of Gondwanaland [820]. Other families with a possible Gondwanan origin include the Retropinidae, Prototroctidae, Galaxiidae, Aplochitonidae and Percichthyidae [888, 936]. These families are predominantly restricted to the southern half of the Australian continent and are mostly inhabitants of cooler waters. The presence of the percichthyid Guyu wujalwujalensis, a possible Cretaceous relic [1091], in the Wet Tropics region, and of Macquaria species in the Fitzroy River basin and drainages of central Australia [52], suggests that these southern Gondwanan elements may have once been more widespread on the Australian continent.

with increasing latitude is less apparent, and spatial variation in species richness (at the basin level) is best explained by variation in the magnitude of mean annual discharge and seasonality/perenniality of the flow regime. More species occur in rivers with large mean annual discharge (which is not simply a function of catchment size) and less species occur in rivers with a highly seasonal flow regime [1093]. Second, Unmack [1340] observed that the extent of endemism (the unique occurrence of a species in a single region) varies across Australia, being greatest in western (east and west Kimberley, Pilbara and south-western Western Australia), southern (south-western Victoria and southern Tasmania) and central (Lake Eyre Basin and Murray-Darling Basin) regions. The only region east of these regions for which endemism is high is north-eastern Queensland, which includes the Wet Tropics region. Unmack’s analysis revealed a surprisingly high level of endemism in the fauna; 47% of the Australian fauna occurred in one region only. Third, classification analysis of regional variation in faunal composition divided the fauna into two major groups, basically equating to northern and southern Australia. The Fitzroy River south to the Queensland border was included in the southern group. The northern Australian group, excluding the arid central regions (Bulloo, Lake Eyre and Barkley Tablelands), divided into a cluster containing regions (Burdekin, north-eastern Queensland and southern Cape York Peninsula) located to the east of the Great Dividing Range and a larger cluster located to the west.

The majority of Australia’s freshwater fishes are secondary freshwater species derived from marine ancestors with tropical Indo-Pacific affinities [1409]. Some authors suggest that this component of the fauna is evolutionarily young and that colonisation of the Australian continent by marine ancestors probably occurred in the last 10 million years or so (a late Miocene origin at maximum) [52, 936, 1409]. However, others have suggested a more extended occupation of the Australian continent by some families. For example, Vari [1346] postulated that ancestral terapontid grunters may have populated the northern shores of the Gondwanan supercontinent. Crowley [343] suggested that freshwater invasion of Australian freshwaters by craterocephalid hardyheads occurred during the Cretaceous or Palaeocene (>60 million y.b.p.). Families typical of northern Australia and New Guinea such the Ariidae, Plotosidae, Terapontidae and Eleotridae have undergone substantial speciation in freshwater environments, yet elsewhere are almost entirely marine or estuarine. Freshwater habitats on the Australian continent have undergone enormous change during the period over which the teleost fishes arose, including several marine transgressions as well as changes in climate and periodic aridity. Undoubtedly such events have led to extinctions of freshwater fish species and opened the way for colonisation of freshwater habitats by estuarine fishes.

Unmack’s [1340] analysis of the biogeography of Australia’s freshwater fishes was restricted to freshwater fishes that complete their entire life history in freshwater (a definition more restricted than that used in this book). As a consequence, many diadromous species with an estuarine or marine interval in the life history, such as eels and many gudgeons or gobies, were not included. Their inclusion does not alter the broad outcomes of Unmack’s study however, except to perhaps emphasize the distinctiveness of those rivers draining east of the Great Dividing Range [1093]. Rivers of northern Australia tend to have more such species than do rivers of southern Australia. Moreover, a catadromous reproductive strategy (i.e. migration out of freshwaters to breed) is common in northern Australian fishes. Cappo et al. [278] suggested that the higher water temperatures of northern Australian rivers may confer a metabolic advantage to euryhaline species enabling more efficient osmoregulation. Gross et al. [481] examined global trends in diadromy and found catadromy to dominate in tropical regions and anadromy to dominate in temperate regions. They proposed such a pattern to be driven by latitudinal differences in the relative productivity of freshwater and marine habitats. In

Unmack [1340] recently examined the biogeography of Australia’s freshwater fishes and the major features of that analysis are summarised below. First, species richness decreases significantly with latitude, echoing a general global trend for greater freshwater fish diversity in tropical regions [1007, 1057]. In addition to this gradient, arid regions are less speciose. A more recent analysis of biogeographical patterns in north-eastern Australia by Pusey et al. [1093], revealed that the trend of decreasing diversity

4


SUPERORDER Acanthopterygii ORDER Perciformes SUBORDER Percoidei FAMILY Terapontidae GENUS Hephaestus SPECIES Hephaestus fuliginosus (Macleay, 1883)

tropical areas, the productivity of freshwater systems exceeds that of marine systems. The classification of fishes All living organisms are related to one another in some way, either closely as in the case of species within genera, or distantly as in the case of species within different phyla. Classification systems seek to organise a naming system that reflects this degree of relatedness. Ideally, such a system should reflect evolutionary history.

Some of these groups may be further subdivided. For example, the Cairns rainbowfish Cairnsichthys rhombosomoides is placed with the tribe or clade Bedotiini, within the subfamily Melanotaeniinae, within the family Melanotaeniidae. Subgenera may also be designated (e.g. the subgenus Chonophorus in the genus Awaous). Species may often be divided into subspecies (e.g. the various subspecies of Melanotaenia splendida such as Melanotaenia splendida splendida and Melanotaenia splendida inornata).

Classification systems have been in existence for millennia. The famous 19th century anatomist Georges Cuvier provides a fascinating account of the early development of fish classification from the time of the ancient Egyptians, to early Greek natural philosophers such as Aristotle, to the European naturalists of the 16th and 17th century such as Guillaume Rondelet and Hippolyte Salviani [354]. Indeed, natural classification schemes have probably existed since the development of human language and possibly reflected similarities in edibility, gross form and risk of injury to the hunter or gatherer. However, early classification schemes often poorly reflected the relationships between organisms. For example, the cetaceans (whales, dolphins etc.) were included with fishes in most classification systems well into the middle of the 17th century [354].

Note that in the sooty grunter example listed above, the species name is followed by the name of the authority that first described this species, and the date in which this occurred. In the case of H. fuliginosus, the name and date are enclosed within parentheses. This is a nomenclatural convention to denote that this species was first described under another name (Therapon fuliginosus) and that the present name was allocated following a revision of the species. The authority and date are not enclosed in parentheses when the original name stands unaltered.

Peter Artedi, a Swedish natural philospher of the early 18th century, attempted a consistent ichthyological classification scheme, building on the work of the English natural philosophers John Ray and Francis Willughby. Artedi’s scheme, based on the consistency of the skeleton, the opercula and the fin rays, was published in his 1738 treatise Ichthyologia, sive Opera omnia de piscibus (edited and published posthumously by his friend Carolus Linnaeus following Artedi’s death by drowning in an Amsterdam canal after a night of socialising at the age of 30). Linnaeus’s most significant achievement was to formalise a system of natural classification within a system of binomial nomenclature. In this system, closely related species were arranged within genera and closely related genera were arranged within families, and so on. It is a hierarchical system reflecting different degrees of relatedness and is the system we use today (with some modification and addition). Below is an example of a full classification for a common north-eastern Australian fish, the sooty grunter.

The freshwater fishes (including alien species) of northeastern Australia can be arranged in the following classification scheme (to family level only). This classification is based largely on that provided by Paxton and Eschmeyer [1041], and Long [820]. PHYLUM CHORDATA SUPERCLASS AGNATHA (JAWLESS FISHES) CLASS CEPHALASPIDOMORPHA Order Petromyzontiformes Mordaciidae (Shorthead lampreys) SUPERCLASS GNATHOSTOMATA (JAWED FISHES) CLASS OSTEICHTHYES (BONY FISHES) SUBCLASS DIPNOI Order Ceratodontiformes Ceratodontidae (lungfish) SUBCLASS ACTINOPTERYGII (RAY-FINNED FISHES) INFRACLASS NEOPTERYGII DIVISION TELEOSTEI Subdivision Osteoglossomorpha Order Osteoglossiformes Suborder Osteoglossoidei Osteoglossidae (saratoga) Subdivision Elopomorpha Order Elopiformes Megalopidae (tarpon)

PHYLUM Chordata SUBPHYLUM Gnathostomata CLASS Osteichthys SUBCLASS Actinopterygii INFRACLASS Neopterygii DIVISION Euteleostei

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Eleotridae (gudgeons) Suborder Anabantoidei Belontiidae (gouramis – alien) Order Pleuronectiformes Suborder Soleoidei Soleidae (soles)

Order Angulliformes Suborder Saccopharyngidae Anguillidae (eels) Subdivision Clupeomorpha Order Clupeiformes Suborder Clupeoidei Clupeidae (herrings) Engraulididae (anchovies) Subdivision Euteleostei Order Cypriniformes Cyprinidae (carp – alien) Cobitidae (loaches – alien) Order Siluriformes Ariidae (fork-tailed catfishes) Plotosidae (eel-tailed catfishes) Order Salmoniformes Suborder Osmeroidei Retropinnidae (smelts) Galaxiidae (galaxiids) Order Cyprinodontiformes Suborder Cyprinodontoidei Poeciliidae (topminnows – alien) Order Beloniformes Suborder Exoceotoidei Hemiramphidae (halfbeaks) Belonidae (longtoms, needlefish) Order Atheriniformes Suborder Atherinoidei Atherinidae (hardyheads) Melanotaeniidae (rainbowfishes) Pseudomugilidae (blue-eyes) Order Synbranchiformes Synbranchidae (swamp eels) Order Scorpaeniformes Suborder Scorpaenoidei Scorpaenidae (stonefishes) Order Perciformes Suborder Percoidei Chandidae (glassfishes) Centropomidae (barramundi) Percichthyidae (bass, pygmy perch) Terapontidae (grunters) Kuhliidae (flagtails) Apogonidae (cardinal fishes) Toxotidae (archerfish) Kurtidae (nurseryfish) Cichlidae (tilapia – alien) Suborder Mugiloidei Mugilidae (mullet) Suborder Labroidei Cichlidae (tilapia – alien) Suborder Gobioidei Gobiidae (gobies)

Modern classification schemes strive to reflect the evolutionary history of a group rather than the overall gross similarity of taxa within a group. That is, they try to represent the phylogeny of that group. Therefore, species within a genus should be derived from a common ancestor and be more closely related to one another than to species in another genus. When species share a character that is derived (an apomorphic character) from a common ancestor, that character is said to be synapomorphic. Plesiomorphy, in contrast, refers to primitive characters. For example, in the terapontid grunters, the plesiomorphic condition of the gut is one of simple structure with no looping or coiling. The more derived condition is one in which the intestine is composed of more than one loop. Genera such as Hephaestus, Scortum, Pingalla and Syncomistes all share the synapomorphy of a gut possessed of at least six loops. Pingalla and Syncomistes both possess a gut composed of 11 loops. Thus, the derived or synapomorphic condition in these two genera is 11 loops whereas the plesiomorphic condition is six loops. Note that there are different levels of apomorphy. Every level of apomorphy defines the temporal order of modification occurring between the pre-existing (plesiomorphic) and emerging (apomorphic) characters of the transformation [868]. Although modern classification schemes strive to reflect the evolutionary history of a group, this is not always achieved. Occasionally a species, or number of species, is allocated to one genus by one researcher to be later found more closely allied to another genus. For example, many of the gudgeons of north-eastern Australia were first placed in the ‘catch-all’ genus Eleotris but were later found to be more properly placed within a larger number of genera. Such a generic grouping is therefore unnatural and does not accurately reflect the group’s evolutionary history. The genus is therefore termed paraphyletic. Modern classification schemes strive to arrange species or genera (or any level of classification) in monophyletic groups. Classification schemes are constantly being reviewed and changed as new evidence becomes available or when new evidence is inconsistent with current views. The introduction of modern genetic techniques such as DNA sequencing has been of special significance in this regard.

6


soft-rayed dorsal fin spinous dorsal fin (second dorsal) (first dorsal) dorsal spines dorsal scale sheath operculum soft ray dorsal filament posterior nostril adipose fin anterior nostril lateral line scales premaxilla caudal or tail fin

pectoral fin horizontal scale rows barbel

papilla maxilla

Figure 1.

pelvic fin ventral scutes genital papilla anal spines

caudal peduncle anal fin anal scale sheath

Basic external anatomy of a generalised bony fish.

Fish anatomy The classification of fishes is largely based on their anatomy. It is therefore necessary to have some understanding of the general anatomy and osteology of fishes in order to identify and classify them in the field or laboratory and to understand, in many cases, their ecology. Extreme diversity of form is a feature of the bony fishes more than any other vertebrate group and no description of a single species is adequate to convey all the morphological variation present within the group. Figure 1 illustrates the basic external morphology of a generalised bony fish.

gill rakers on upper limb gill rakers on lower limb gill filaments

The head region is clearly distinct from the body and distinguished by a bony gill covering termed the operculum. This structure covers the gill arches and gill filaments that function predominantly in gas exchange between the fish and its environment (Fig. 2). The gill arches are distinguished by a series of protrusions termed rakers on the anterior face of the arch. In some species, these rakers are long and flexible, in others they may be shortened and reduced to transverse plates or ridges, whereas in others they may be reduced to a series of papillae only. The gill rakers may function as sieving apparati in filter feeding species. Gill rakers may be confined to the first and second arches only and the shape and number are useful characters for distinguishing between different species.

Figure 2.

The structure of a gill arch of a bony fish.

located on the snout and are distinguished by reference to their relative anterior or posterior position. Sensory pores connected by canals may be present on the head of many fishes. Similarly, many fishes possess rows of sensory papillae or pit canal organs on the head, and these structures are usually located above and below the eyes, and on the cheek or preoperculum. Some fish possess barbels that aid in the detection of food. The number, length and position of the barbels are important characters used to distinguish between species. Barbel placement and nomenclature are shown in Figure 3.

The upper jaw is divided into two sections, the premaxilla and the maxilla (Figs. 1 and 7). Two pairs of nostrils are

7


V–VII; I, 11–15, indicating that this species possesses five to seven spines in the first dorsal fin and one spine and 11 to 15 soft rays in the second dorsal fin.

nasal barbel maxillary barbel

The anal fin is located on the ventral midline posterior of the anus. This fin may contain both spines and segmented rays. The final medial fin is the caudal or tailfin. Spines are absent from this fin and support is provided by a series of bones associated with the terminal vertebrae and by the fin rays (Fig. 4). The caudal fin may be of a variety of different shapes. The most frequent caudal fin shapes are illustrated in Figure 5.

inner mental barbel outer mental barbel

epurals (3) Figure 3. catfish.

procurrent rays

uroneurals (2)

Barbel placement and nomenclature in a plotosid

fin rays antepenultimate vertebra

The shape, position and orientation of the mouth are all useful characters for distinguishing between species. Position is most frequently described as terminal (end of the snout), supraterminal (upper surface of the end of the snout) or subterminal (lower surface of the end of the snout), often accompanied by descriptions of the angle of the gape (i.e. straight or oblique). In addition, the relative prominence of the upper and lower jaws is frequently used as a distinguishing character.

penultimate vertebra urostyle (ultimate vertebra)

hypurals (6)

Figure 4. Generalised diagram of the teleost caudal skeleton. (Redrawn after Cailliett et al. [276].)

Two sets of paired fins, the pelvic and pectoral fins, are present in most species. The pectoral fins are located in the anterior third of the body whereas the location of the pelvic fins may vary in position among species (and may often be an important diagnostic character) but invariably they are located in the anterior two-thirds of the body. These paired fins possess bony segmented fin rays. In many taxa, the first ray of the pelvic fin forms a thickened spine. Three to four medial rayed fins are also present. The first and second dorsal fins are located, as the name suggests, on the midline of the dorsal surface. A second dorsal fin is not present in some groups of fishes and, in some groups, the first dorsal fin is deeply notched to give the impression of two dorsal fins. A third fleshy adipose fin may be present in some species. The first dorsal fin is usually supported by a series of spines whereas the second dorsal fin may contain both spines and segmented rays. In the second dorsal, pectoral, pelvic and anal fins of some species (e.g. Craterocephalus spp.), a single unsegmented ray sometimes separates the fin spine and the segmented rays. The unsegmented ray is counted together with the segmented rays in this book. In taxonomic descriptions, counts of the number of spines present are usually distinguished from fin ray counts by the use of Roman numerals to denote spines. For example, the dorsal fin formula for the Cairns rainbowfish Cairnsichthys rhombosomoides is

a

b

c

d

Figure 5. Common shapes of the caudal fin: a) rounded; b) truncated; c) emarginate; d) forked.

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actually exposed. In some species, the scales may extend out as a sheath onto the dorsal and anal fins (Fig. 1). There are two main types of scale: cycloid and ctenoid (Fig. 6). Another common type of scale is termed the lateral line scale. These scales have a small tube or canal on the surface that allows water to flow through to the lateral line sensory system. The number, position and type of lateral line scales are important characters for distinguishing between species. A fourth type of scale, the ganoid scale, which is rhombic in shape, is present in some primitive teleosts such as gars and sturgeons. As fish grow, the scales also grow by increments of bony tissue. Daily increments (circuli) are wide during periods of rapid growth and narrow during periods of slow growth. Successive periods of slow growth result in the narrow circuli being located in close proximity to form a growth ring or annulus. These periods of slow growth usually occur with a return frequency of one year, hence the term annuli, and can thus be used to age fish.

The external surface of many fishes is covered by a layer of scales, each deeply embedded in the epidermis and overlapping one another so that only about 30% of the scale is

a

circuli annulus focus ctenii

b focus

Fish osteology The principal components of the teleost skeleton are the axial vertebral column and caudal fin, the head (consisting of the cranium, upper and lower jaws and the gill coverings, which are comprised of the opercular bone series, preopercular and branchiostegal rays), the paired pectoral and pelvic fins, and the medial dorsal and anal fins (Fig. 7).

Radii Figure 6.

Teleost fish scales: a) cylocid; b) ctenoid.

lepidotrichia pterygiophore vertebra

neural spine hypurals

pectoral fin opercula bones preoperculum cranium premaxila

dentary maxilla

branchiostegal rays pectoral girdle

Figure 7.

haemal spine pleural rib pelvic girdle pelvic fin

Skeleton of a generalised perciform teleost fish. (Redrawn after Norman [996].)

9


small part, to successive changes in the structure of the suspensorium and separation of the previously fused maxilla and premaxilla, coupled with changes in the attachment points of the respective muscles [276].

The head is composed of many individual bones, either fused to one another, or free (although connected by cartilage) and articulating against one another (Fig. 8). The head can be divided into two separate components based roughly on this distinction [276]. The skull is comprised of the neurocranium (10–11 bones), the orbital region (19 bones, including the lachrymal), and the otic region (20 bones). These bones unite to form a solid housing to contain the brain and associated sensory systems (i.e. optic, olfactory and auditory systems), and the roof of the upper jaw, as well as a point of attachment and articulation for many of the bones within the branchiocranial series.

Finally, the last bony component of the branchiocranial region is the opercular series. This series is comprised of the operculum (large flat bones comprising most of the gill cover), the interoperculum, and the suboperculum and preoperculum (a large pair of bones anterior of the opercular bones that partially cover the hyomandubular and carry elements of the lateral line canal). The second major region of the branchiocranium is the hyoid region, comprised of the unpaired glossohyal and urohyal bones, the paired interhyals. epihyals and ceratohyal bones and the branchiostegal rays. These bones collectively comprise the back of the buccal cavity and the points of attachment of the gill arches. Each gill arch is comprised of five bones, the pharyngobranchial, epibranchial, ceratobranchial, hypobranchial and basibranchial, and collectively these arches form the third and final region, the branchial series.

The branchiocranial series is composed of over 60 separate bones organised into three distinct regions: the oromandibular region, the hyoid region and the branchial series. The oromandibular region is comprised of the upper jaw, the lower jaw, the suspensorium and the opercular series. The 36 bones that comprise this region are all paired (i.e. 18 pairs). The lower jaw is composed of two large pairs of fused bones, the dentary and the angular (or articular), a third pair of much smaller bones termed the retroangulars, and a fourth pair of bones termed the sesamoid angulars which are involved in the attachment of the mandibular adductor muscles responsible for mouth closure. The shape, size and orientation of these bones are often useful in the identification of different species or reveal the phylogenetic relationships between taxa. hyomandibular parietal parasphenoid sphenoid endopterygoid frontal nasal

There are several bones in the teleost skull that may bear teeth (Fig. 9). The structure, size, type, position and arrangement of teeth are all important characters used to distinguish between different species.

a supraoccipital exoccipital

premaxillary maxillary vomerine

post temporal

palatine

lachrymal premaxilla

pharyngeal mesopterygoidal operculum

dentary maxilla

first gill arch

suboperculum articular quadrate circumorbital

interoperculum preoperculum metapterygoid

b dentary

Figure 8. Superficial facial bones and suspensorium of a generalised teleost fish. Note that many of the bones mentioned in the text are covered or obscured by the superficial bones depicted here. (Redrawn after Calliette et al. [276] and Hildebrand [575].)

tongue pharyngeal basibranchial (hyoid)

The lower jaw articulates against the suspensorium, a series of pairs of bones comprised of the palatines, endopterygoids, metapterygoids, ectopterygoids, quadrates, symplectics and hyomandibulars. The phenomenal diversity and success of the teleost fishes is due, in no

Figure 9. Bones within the mouth or buccal cavity that may bear teeth in bony fishes: a) upper jaw, b) lower jaw. (Redrawn after Calliette [276].)

10


groups of fishes (e.g. synbranchid eels and percichthyid perches, respectively). Pterygiophores form the base of the two medial fins. They are imbedded in the epaxial (dorsolateral) and hypaxial (ventrolateral) musculature. At the proximal end of each pterygiophore is a small bone termed the basal against which the fin ray articulates. Each fin ray is controlled by three similar sets of muscles, the erector, depressor and inclinators, which control forward, backward and lateral movement, respectively. The caudal fin is composed of modified terminal and preterminal vertebrae, which support and strengthen the caudal fin (Fig. 4). In many teleosts, the urostyle (the terminal segment of the vertebral column) is comprised of the last two vertebrae fused into a single element. Modified neural spines and neural arches form plates termed the epurals and uroneurals, respectively, which when coupled with the modified haemal arches known as the hypurals, form a strong yet flexible base for the caudal fin rays.

The paired medial fins are part of two separate series of bones known as the pectoral and pelvic girdles. These structures form the point of attachment and articulation of the fins and the associated fin rays. The term girdle is most appropriate for the pectoral girdle as it almost encircles the entire body just behind the opercula. This series of bones is connected to the neurocranium by the posttemporal bone at attachment points on the epiotic and oposthotic bones [276] (Figs. 8 and 10). The nature of the posttemporal bone is important in the identification of different genera of terapontid grunter and the structure of the entire girdle is important in the systematics of the percichthyids (cods, bass and pygmy perches). The simpler pelvic girdle is inserted under the pectoral girdle and consists of a pair of plates called basipterygia to which the fin rays and pelvic spines (when present) attach and articulate.

Meristic and morphometric characters In addition to characters associated with skeletal anatomy, many systematic studies use a combination of meristic and morphometric characters to distinguish between species. Meristic characters include such characters as the number of fin spines and rays, number of gill rakers, number of lateral line scales, vertical scale rows, number of cheek scales. Note that these characters are all expressed as counts.

post temporal supracleithrum

cleithrum

Morphometric characters, in contrast, describe the condition or size of certain characters. For example, the size of the head or of the eye, or the distance between the snout and the start of the first dorsal fin (predorsal length) are all morphometric characters. Figure 11 depicts many useful and frequently used morphometric characters. Most morphometric characters vary in size with increasing fish size, therefore they need to be standardised in some manner so that comparisons may be made between specimens of differing size. The most frequent mechanism for standardising morphometric characters is to describe them as a proportion of fish length, usually standard length (the distance from the tip of the snout to the hypural crease). Another frequently used denominator is head length: thus it is not uncommon to see characters such as mouth gape or maxilla length expressed as a proportion of head length. In this way, the size of any particular character may be reasonably compared across fish of different size. Calliette et al. [276] provide a useful discussion of the issues associated with standardisation of morphometric characters.

scapula actinosts

coracoid Figure 10. The pectoral girdle of the percichthyid Guyu wujalwujalensis. (Redrawn after Pusey et al. [1091].)

The axial skeleton (which technically includes the skull) contains two types of vertebra. The precaudal vertebrae of the abdominal region bear ribs, intermuscular bones and neural spines but not haemal spines (Fig. 7). The caudal vertebrae bear few ribs and have prominent neural as well as haemal spines. The absolute number of caudal and precaudal vertebrae and the relative number of these bones are both important characters in the systematics of some

Standardisation by dividing by standard length or head length assumes that the relative size of a character remains constant with varying size of the fish. This is not always the

11


series of steps, to a final identification of an unknown fish. The key is based to a large extent on characters that do not require the use of a microscope or dissection to discern (i.e. number of gill rakers or vertebrae), however such characters are sometimes the most useful for separating species and their use is therefore unavoidable. Furthermore, small-bodied species cannot be examined with great accuracy unless a microscope or magnifying glass is used. We recommend that this key be used as a guide only, and that tentative identifications derived from it, be checked against the comprehensive description provided for the relevant species or sent to a relevant taxonomic expert at a museum.

case. For example, in a study examining the distribution of the rainbowfish Melanotaenia eachamensis in the Wet Tropics region of northern Queensland, Pusey et al. [1105] compared the meristics and morphometrics of many populations of rainbowfishes with those of known populations of M. eachamensis and M. splendida splendida. Very few morphometric characters were found to remain invariate with increasing size: predorsal length, body depth, snout length, and peduncle depth were the only characters to satisfy this criterion. Other characters: head length, head depth, eye diameter, mouth length and peduncle length, all varied with length in an exponential fashion, with an exponent less than one. Thus these characters were all relatively greater in smaller individuals than in larger individuals. In such cases, better standardisation may be achieved by dividing by standard length raised to the power best describing the relationship between that character and standard length.

The species covered in this key include both native and alien species (non-native, introduced from other countries) found in north-eastern Australia. The key contains some species not covered in depth in this book but which may be encountered in rivers of north-eastern Australia. Some species found occasionally in easterly flowing streams of Cape York Peninsula are more properly considered fauna of drainages discharging into the Gulf of Carpentaria, west of the Great Dividing Range; these species are not covered in this book other than inclusion in this key. When in doubt about a species’ identification, consult widely and use the services of museum specialists. The systematics of many groups of fishes is often in flux

Identification of the freshwater fishes of north-eastern Australia The identification of fishes can be a difficult task for the non-specialist and specialist alike. We have included a dichotomous key to aid in the identification of different fishes in the field and laboratory. A dichotomous key is basically a set of either/or questions that should lead, by a

total length caudal fork length standard length

snout length

body depth

caudal peduncle length

predorsal length head length

caudal peduncle depth

head depth

eye diameter maxilla length Figure 11.

Commonly used morphometric characters. (Redrawn after Pusey et al. [1105].)

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have used generic or family level reviews. Figures 21, 22, 23, 24 were redrawn after Allen [34] and Figures 38, 39, 41, 42 were redrawn after Allen and Cross [43]. In those cases where undescribed species have been assigned species numbers, we have retained the numbering system presented in Allen et al. [52].

and the use of varied information sources is prudent. The use of limited or out-of-date systematic resources too often leads to circumstances where identification and distributional information become less than useful. Ideally, fish ecologists, aquatic biologists and consultants should try to keep abreast of changes in the systematics of freshwater fishes. The key included below is based on a number of different sources [34, 37, 43, 47, 773, 1346] but where possible we

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Key to the native and alien fishes of north-eastern Australia (alien species are denoted by *)

1a 1b 2a 2b 3a

3b

4a 4b

5a 5b 6a 6b 7a

Body elongated and eel-like........................................................................2 Body not elongated and eel-like .................................................................4 Barbels present (alien)..................................................................Cobitidae Misgurnus anguillicaudatus* Barbels absent..............................................................................................3 Pectoral fins absent ..............................................................Synbranchidae Aa Gill opening a slit-like fold across ventral surface of head, not attached to isthmus...........................................................................B Ab Gill opening pore-like, triangular shaped, and internally attached to the isthmus .........................................................Monopterus albus Ba Colour blackish-green to reddish-brown; mottled; eye positioned forward of the middle of the distance between end of mouth and snout tip (note that there may be a number of undescribed species of Ophisternon present in freshwaters of Queensland and the species referred to as O. bengalense may not occur in Australia) .......................................................................Ophisternon bengalense Bb Colour brown to green; ventral surface lighter in colour; eye positioned posteriorly of the middle of the distance between end of the mouth and snout tip........................................Ophisternon gutturale Pectoral fins present...................................................................Anguillidae Aa Colouration mottled, dorsal fin originating well in front of vertical line through line anus (Fig. 1) ............................Anguilla reinhardtii Ab Colouration uniform, dorsal fin originating only slightly in front of anus (Fig. 2).......................................................................................B Ba Jaws reaching back to eye or slightly beyond, vomerine tooth patch broad, distribution does not extend north of the Burnett River ............................................................................................A. australis Bb Jaws reaching well beyond eye, vomerine tooth patch long and narrow, distribution does not extend far south of the Pioneer River .............................................................................................A. obscura Eyes not on the same side of head; body not greatly flattened ................5 Eyes on same side of head, body flattened .....................................Soleidae Aa Dorsal rays 66–78; caudal rays 16; anal rays 53–59; caudal fin narrow and pointed; lateral line scales 84–97 ...Brachirus salinarum Ab Dorsal rays 70–75; caudal rays 18–20; anal rays 55–60; caudal fin rounded; lateral line scales 77–81 .....................................B. selheimi Pectoral and pelvic fins thick and flipperlike (Fig. 3) .......Ceratodontidae Neoceratodus forsteri Pectoral fins not thick, fleshy and flipperlike, fin rays easily visible (Fig. 4)..........................................................................................................6 Barbels present on lower jaw, may or may not be present on upper jaw (Figs. 5 and 6) ..............................................................................................7 Barbels absent from lower jaw, but single pair of barbels may be present on upper jaw ............................................................................................... 9 Barbels short and paired (Fig. 5).........................................Osteoglossidae Aa Dorsal rays 20–24; anal rays 28–32......................Scleropages jardinii Ab Dorsal rays 15–19; anal rays 25–27 (Fitzroy River system only unless translocated)..........................................................S. leichardti 14

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Key to native and alien fishes of north-eastern Australia

7b 8a

8b

Barbels long, 3 or 4 pairs (Fig. 6)................................................................8 Barbels in 4 pairs; dorsal, anal and caudal fins fused to form one continuous pointed fin...........................................................................Plotosidae Aa Second dorsal fin originating either just anterior to or posterior to vertical line through anus (Fig. 7)....................................................B Ab Second dorsal fin originating well posterior to vertical line through anus (Fig. 8) ......................................................................................C Ba Jaws without teeth.............................................Anodontoglanis dahli Bb Jaws with teeth.....................................................Tandanus tandanus Ca Dorsal profile of head frequently concave; eyes relatively low set on side of head; tail more or less pointed; few dorsal rays in fused fin ......................................................................................................D Cb Dorsal profile of head straight or slightly convex; eyes set in higher position approaching dorsal profile; tail more rounded and extending relatively further onto dorsal profile ..........................................F Da Lateral line discontinuous .......................................Porochilus obbesi Db Lateral line continuous .....................................................................E Ea Dorsal fin with sharp spine and 4 soft rays; pectoral fin with sharp spine and 7 soft rays .........................................................P. argenteus Eb Dorsal fine with spine and 5–7 soft rays; pectoral fin with sharp spine and 9–11 soft rays.....................................................P. rendahli Fa Dorsal fin tall; dorsal spine reduced to flexible cartilaginous ray (Fig. 9) ........................................................Neosilurus mollespiculum Fb Dorsal fin short or moderately elongated; dorsal spine rigid (Fig. 10).............................................................................................G Ga Dorsal fin short; nasal barbels extending back beyond eye .....................................................................................N. brevidorsalis Gb Dorsal fin moderately elongated; nasal barbels not extending back beyond eye ........................................................................................H Ha Confluent dorsal, anal and caudal fin comprised of 120–160 rays; dorsal fin with 5–7 soft rays; pectoral fin with 11–13 rays; snout elongated...................................................................................N. ater Hb Confluent fins comprised of 115–135 rays; dorsal fin with 5–6 soft rays; pectoral fins with 10–11 rays; snout not elongated ...N. hyrtlii Barbels arranged in 3 pairs...............................................................Ariidae Aa Raker-like processes present on back of all gill arches ....................B Ab No raker-like process on back of first 2 gill arches .........................C Ba Barbels long (30–47% of SL); palatal tooth patches arrayed as in Fig. 11, vomerine and palatine patches in inner row separate in smaller specimens ..........................................................Arius berneyi Bb Barbels short (17–40% of SL); palatal tooth patches arrayed as in Fig. 12...................................................................................A. graeffei Ca Head broad; snout well rounded to squarish; maxillary barbels long (22.7–50% of SL); inner row of palatal tooth patch consisting of united palatine and vomerine patches as in Fig. 14.........A. leptaspis Cb Head rectangular; snout squarish or truncate; maxillary barbels short (16.6–24% of SL); inner row of palatal tooth patches composed of four separate patches as in Fig. 13.............................D Da Gill rakers on first arch 15–17, 16–19 on last arch, eye relatively large, 12.9–21.8% of HL ...................................................A. midgleyi Db Gill rakers on first arch 10–11, 11–14 on last arch, eye relatively small, 8.9–15.3% of HL .......................................................A. paucus

15

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14


9a 9b 10a 10b 11a

11b

12a

12b 13a 13b 14a

14b

15a 15b 16a 16b 17a 17b 18a

18b 19a

Single dorsal fin (Fig. 15), but may be notched to give the appearance of two separate fins (Fig. 16).........................................................................10 Two separate dorsal fins (Fig. 17).............................................................25 Mouth very small, oblique ........................................................................11 Mouth not very small and oblique or if small, head with short beak ....12 Lateral line present and curved, male anal fin not modified, oviparous (alien) .........................................................................................Belontiidae Trichogaster trichopterus* Lateral line absent, male anal fin modified to form intromittent organ (gonopodium), viviparous (live-bearing) (alien) .....................Poeciliidae Aa Body deep, 50% of SL, prominent dark blotch at base of caudal fin, body colour blue..........................................Xiphophorus maculatus* Ab Body not noticeably deep, 50 in midlateral series (except for O. nullipora) ..................................................................................................O Nb Scales larger, usually 55.........................................................................S Second dorsal I, 12–14; anal I, 10–12; predorsal scales 35–40; 3 head pores forward of eye, 4 pores on preopercle margin and 2 on operculum .................................................................................O. aruensis Second dorsal I, 11–12; anal I, 11–12; predorsal scales 37–45; 2 head pores forward of eye, 5 pores on preopercle margin and 5 on operculum ...............................................................................O. fimbriata Head strongly depressed, width about 1.5 times depth; mouth large in adults, reaching to, or beyond, middle of eye; side of head scaleless .....................................................................................................U Head rounded or truncate in side view, width about 0.8–1.2 times depth; mouth smaller, ending below or before anterior part of pupil; side of head scaled .................................................................V Pectoral rays 16–20, usually 18–19; total gill rakers on first arch 14–20; gill openings reaching forward to below eye ................................ .......................................................................Philypnodon grandiceps Pectoral rays usually 15–16; total gill rakers on first arch 11–12; gill openings restricted, reaching to below rear margin of preopercle ....................................................................................Philypnodon sp. Pectoral rays 18–19; midlateral scales 36–40 .....Gobiomorphus coxii Pectoral rays 14–16; midlateral scales 30–34 ...................G. australis

25



with the fishes of the North-east Coast Drainage Division (Fig. 1), a relatively narrow strip bounded by the Great Dividing Range and the Coral Sea. Although this drainage division represents only 5.8% of the continental area, its rivers discharge almost 25% of the total annual discharge of 34.6 x 107 ML [1409].

Study area Australia can be divided into 12 major drainage divisions based on climate, landform and the distribution of aquatic habitat types (Fig. 1) [52, 936, 1409]. The biogeography of Australia’s freshwater fishes is highly congruent with these drainage divisions [1340]. This text is primarily concerned

AUSTRALIAN DRAINAGE DIVISIONS

Philippin es

I II III IV V VI VII VIII IX X XI XII

Pacific Ocean

Malaysia New Gu inea

Solomo n Islands

Ind onesia Vanu atu Coral Sea

Australia

Ind ian Ocean

Fiji New Caledon ia New Zealand

Tasman Sea

North-east Coast Division South-east Coast Division Tasmania Division Murray-Darling Division South Australia Gulf Division South-west Coast Division Indian Ocean Division Timor Sea Division Gulf of Carpentaria Division Lake Eyre Division Bulloo-Bancannia Division Western Plateau Division 152°31'00" -42°00'00"

Arnhem Land

Alligator Rivers Region Darwin

Kimberley

VIII IX

Pilbara

XII

I

VII

X Brisbane

XI Perth

V

IV II

VI

Sydney Adelaide

Canberra Melbourne

N

116°00'00" -40°01'00"

0

500

1,000

III Hobart

Kilometres

Figure 1. Map of Australia showing the major drainage divisions and some localities mentioned in the text. Base data reproduced with the permission of the Queensland Department of Natural Resources, Mines and Energy.

26


QUEENSLAND DRAINAGE BASINS Gulf of Carpentaria & Wester n Cape York Peninsula 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928

928

927 137°13'00" -11°20'40"

101 926 102 924

925

Easter n Cape York Peninsula

Settlement Mornington Island Nicholson Leichhardt Morning Flinders Norman Gilbert Staaten Mitchell Coleman Holroyd Archer Watson Embley Wenlock Ducie Jardine Torres Strait Islands

101 102 103 104 105 106 107

Jacky Jacky Olive-Pascoe Lockhart Stewart Normanby Jeannie Endeavour

Wet Tropics 108 109 110 111 112 113 114 115 116

Daintree Mossman Barron Mulgrave-Russell Johnstone Tully Murray Hinchinbrook Island Herbert

South-eastern Queensland

Central Queensland 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135

Black Ros s Haughton Burdekin Don Proserpine Whitsunday Island O'Connell Pioneer Plane Styx Shoalwater Water Park Fitzroy Curtis Island Calliope Boyne Baffle Kolan

136 137 138 139 140 141 142 143 144 145 146

Burnett Burrum Mary Fraser Island Noosa Maroochy Pine Brisbane Stradbroke Islands Logan-Albert South Coast

103

923

Coen 922 104

Gulf of Carpentaria and Western Cape York Peninsula

Eastern Cape York Peninsula 106

921 920 105

107

919

108 109

911

110

Cairns 918

914

Wet Tropics

111

910

112 113 114 115 117

116 912

917

916

Townsville 118 119

913

121

120

122 123 124

IX

915

Mackay 125

I

Mount Isa

Central Queensland 126

129

Rockhampton 127 128

X

131 132 133 134 135

130

137

South-eastern Queensland 139

Maryborough

136 138

140 141

IV

XI

Brisbane

142

144

143

146

N

145

154°00'45"

0

250

500

-29°45'00"

Kilometres Figure 2. Map of the coastal drainage basins of Queensland and some locations mentioned in the text. Drainage basins designations and numbering follow the Queensland Department of Natural Resources, Mines and Energy. Base data reproduced with the permission of the Queensland Department of Natural Resources, Mines and Energy.

27


The North-east Coast Division contains almost one half of all species of freshwater fishes found in Australia. Moreover, many of the fishes of the North-east Coast Division are widespread, occurring across northern Australia to the Kimberley region or southward into the South-east Coast drainage Division, which extends down through New South Wales, Victoria and into South Australia. In addition, some fauna are shared with the Murray-Darling Drainage Division. The material presented in this book concerning the ecology of fishes of the North-east Coast Division has broad relevance for eastern Australia.

specifically for Australian climatic conditions, they do serve to illustrate the diversity of climate present across the continent. North-eastern Australia (as defined here) traverses the tropical zone (from Cape York Peninsula south to about Mackay) and the area further south which is transitional between the tropical type and the warm temperate type [1361]. Figure 3 illustrates some aspects of the climatic diversity present in north-eastern Australia. The climate of eastern Cape York Peninsula is typified by rainfall and temperature data recorded at the township of Coen. Mean monthly maximum temperatures rarely fall below 28°C and mean monthly minima drop below 20°C only during the period June to September. Very little rainfall occurs over the period April to November. The period of greatest rainfall is related to the development of the southern monsoonal trough and most occurs in association with the passage of tropical cyclonic weather systems. The climate of the Wet Tropics region is also monsoonal. Only minor seasonal variation in climate is experienced in Cairns, located at sea level. Mean monthly maxima exceed 33°C in December only and fall below 27°C in June and July only. Minimum monthly temperatures average about 20°C and fall below 17°C in July and August only. Maximum temperatures at Atherton, located at an elevation of 753 m.a.s.l. on the Atherton Tablelands to the immediate west of Cairns, are slightly lower and vary more throughout the year. The range in monthly mean temperatures at Atherton exceeds that for Cairns. Mean monthly temperatures may approach 10°C during the drier months and short periods of frost may occur then also. Both Cairns and Atherton experience the majority of rainfall during the summer monsoonal period but also experience consistent rainfall during the period May to November. Moisture laden south-easterly winds deposit substantial rain during this period as they cross the coast and are forced over the mountainous terrain typifying this area. This region contains Queensland’s two highest mountains (Mts. Bartle Frere and Bellenden Kerr, both exceeding 1500 m in height) and is notable for being the wettest region in Australia [27]. Although rainfall is basically seasonal in occurrence, there is little seasonal signal in the number of rain days per month [27].

The North-east Coast Division (Figs. 1 and 2) extends through more than 18° of latitude. Accordingly, there is an enormous diversity of climate, flow regime, landform and river type across this gradient. On the basis of these physical features, the North-east Coast Division can be further subdivided into four secondary drainage divisions (Fig. 2), which also correspond with variations in fish species composition (Appendix 1) [1340]. These four subdivisions are: Eastern Cape York Peninsula, the Wet Tropics region, Central Queensland, and south-eastern Queensland; each is composed of a number of separate drainage basins. The majority of drainage basins are relatively small, with few exceeding 10 000 km2. Note that some of these drainage basins are composed of more than one, albeit small, separate river systems. Throughout this book, the four secondary drainage divisions of the Northeast Coast Division, and the separate drainage basins within them, are used as the basic spatial template for discussions of fish species distribution and ecology. We follow the drainage basin designations and numbering system used by the Queensland Department of Natural Resources and Mines. Climate Bridgewater [226] provides an overview of the Australian climate in which he notes that of the seven major global climate types identified by Walter and Leith [1361], four occur in Australia. These are: • Tropical type, characterised by some seasonality in temperature and a concentration of rainfall in the warmer months; • Subtropical dry type, characterised by very low rainfall, high summer maximum temperatures and low winter minima; • Transitional zone with winter rainfall, characterised by very little summer rainfall, typically no winter cold season but permanent summer drought; and • Warm temperate type, characterised by no noticeable winter and year-round rainfall.

Climate records for Ayr located near the mouth of the Burdekin River are typical for central Queensland and reveal a climate dominated by maximum temperatures and rainfall during the period December to April (Fig. 3). Diel variation in temperature, particularly during the drier months, is a feature of the region and although frosts are not common at sea level, they may occur in the headwater areas of the Burdekin River. Rainfall is erratic in incidence, strongly influenced by cyclonic weather systems and varies greatly from year to year [1089].

Whilst these are very broad categories intended for characterisation of global climate regimes rather than

28


Discharge regimes A river’s discharge regime is defined by the temporal variation in the amount of water being carried within its channel as a result of temporal variation in climate (rainfall, temperature and evaporation). In addition, evapotranspiration and groundwater inputs also markedly affect discharge regime. Flow regimes vary markedly throughout north-eastern Australia. The Normanby River in Cape York Peninsula has a distinctly seasonal flow regime with most (86%) discharge occurring in January, February or March (Fig. 4). Wet season flows break out of the stream channel and inundate floodplain waterbodies. Very little flow occurs from June to November and the river contracts to a series of large isolated within-channel pools. Notably however, while reduced flows during the dry season are predictable in occurrence, wet seasons flows are less predictable in timing and magnitude. The coefficient of variation (CV) of mean annual discharge (standard deviation of the mean/mean x 100) is high (up to 105% [697]) indicating that many years lack a summer flood (‘failed wet seasons’).

The climate of south-eastern Queensland, typified by that recorded at Gympie in the Mary River drainage, and Beaudesert in the Albert/Logan River drainage, is more seasonal. Mean monthly thermal maxima and mean monthly minima vary by about 10°C and 15°C, respectively, throughout the year. The pattern of rainfall is less strongly dominated by the summer monsoon and frequently influenced by the northward extension of temperate weather systems [1095]. As detailed above, this region is transitional between the tropical and warm temperate climate types identified by Walter and Leith [1361]. In summary, the climate of north-eastern Australia changes with latitude. Although maximum summer temperatures vary little across the latitudinal gradient encompassing north-eastern Australia (cf. Coen and Beaudesert), the extent of diel variation increases significantly from about 10°C in the north to about 15°C in the south. Moreover, the difference between mean summer and winter temperatures increases as one moves south, mainly as a result of a decrease in mean monthly thermal minima. Seasonality is defined more by temporal variation in rainfall at low latitudes in the north whereas temporal variation in temperature defines seasonal shifts in climate in the south. 35

Coen

30

500 400

25

35

The flow regime of rivers of the Wet Tropics region is in stark contrast to those of Cape York Peninsula. Rivers of this region vary little in discharge from year to year (i.e. 500

Cairns

30

400

25

5

35

200 15

100 0

Ayr

30

500 400

25

100

10 5

35

500

Gympie

30

400

100

10

35

0

Beaudesert

30

500 400 300

20

200

2

0

200

0

15

15 100

200 15

300 20

10

300

25

25

15

400

5

0

300 20

500

20

200

10

30

300 20

15

Atherton

25

300 20

35

100

10

™

100

10

™

™

5

0

Month

5

0

Month

5

0

Month

Figure 3. Plots of mean daily minimum temperature (closed squares), mean daily maximum temperature (open squares) and mean monthly rainfall (open circles) for each month at selected locations in eastern Queensland. The period of data record from which means and ranges were calculated was >80 years for each location except Cairns (~50 years). Data source: Queensland Bureau of Meteorology.

29


they exhibit low annual CV values). For example the Mulgrave and Johnstone rivers have CV values of 28% and 34%, respectively [1096, 1100]. Rivers of this region are perennial. The Johnstone River may cease to flow in as few as 1 in every 50 years. Wet season flows dominate the monthly hydrograph as they do in the Normanby River (Fig. 4) but discharge during the dry season remains high, contributing about 25% of mean annual flow. Two features of the region contribute to this pattern. First, rainfall remains high during the dry season (Fig. 3). Second, much of the catchments of some rivers of the Wet Tropics region are composed of porous basalt, which acts as a large aquifer contributing significant amounts of the groundwater throughout the year. Thus even small tributary systems such as the upper North Johnstone River at Malanda are perennial. Dry season flows tend to remain very stable and there is a low likelihood of spates occurring during the period June to October [1093, 1096]. It should be noted that the Mulgrave and Johnstone rivers are located in the centre of the Wet Tropics region. Rivers to the north and south grade into more seasonal flow regimes characterised by a reduced contribution of dry season flows to the annual total. 300 250

200 Normanby Riv er Gauge105101A 2

150

(2,302 km )

The flow regimes of rivers of central Queensland, such as the Burdekin River, are similar to those of eastern Cape York Peninsula (Fig. 4). Most of the discharge occurs during a well-defined summer wet season, with very little discharge occurring outside of the months April to November. The flow regimes of the Burdekin and Fitzroy rivers have been identified as amongst the most variable in the world [1076]. Wet season flow are dominated by one or rarely two large flood events associated with cyclonic weather systems which may occur at any time from December to April [1089]. Wet seasons fail regularly in this region leading to substantial year-to-year variation. The CV of annual flow in the Burdekin River itself exceeds 100% whereas in some tributary systems, particularly in the south-west, annual flows may be even more variable [1089]. In contrast to the perennial flow regimes typical of the Wet Tropics region, the flow regimes of rivers of central Queensland are typified by long periods of very little flow occasionally punctuated by extreme flood events. The flow regimes of rivers in south-eastern Queensland are different to that described for rivers further north. The majority of stream flow occurs in the summer months of

Lower Mulgrav e Riv er Gauge111007A 2

40

30

(520 km )

Upper Nth Johnstone Riv er, Gauge112003A 2

(165 km )

200 150

100

20

50

10

0

0

100 50 0

1500 1250

300 Burdekin Riv er Gauge120002C

Mary Riv er Gauge138001A

250

2

2

(36,260 km )

(4,755 km )

1000

200

750

150

500

100

250

50

0

0

40

30

Albert Riv er Gauge 145196A 2

(722 km )

20

10

Month

0

Month

Month

Figure 4. Variation in mean total monthly discharge for selected eastern Queensland Rivers. The catchment area (km2) upstream of each gauging station is given in parentheses. The period of data record from which means were calculated was >20 years for each gauge. Data source: Queensland Department of Natural Resources, Mines and Energy.

30


Figures 5 and 6 and Table 1 for details of drainage basins and rivers examined within these regions), the details of which are in the process of being published (see also [706, 707, 708, 1100, 1107, 1108, 1109]). This study was undertaken over the period 1994–1997 in the Wet Tropics region and 1994–2003 in south-eastern Queensland. It involved quantitative sampling of fish assemblages at 416 locations, 959 separate samples (location and sampling occasions) and the collection of over 199 000 individual fish from 68 species (almost all of which were returned alive to the water at the site of collection).

January to March, followed by a second minor peak in discharge between April and July as a result of northern penetration of low-pressure temperate weather systems [1095]. The incidence and magnitude of these secondary peaks in flows is quite unpredictable, as are summer wet season flows, and thus rivers of this region tend to show high annual CV values (100% or greater) [1100]. Tributary streams tend to be considerably more variable than lowland river systems and variability in discharge decreases markedly with distance downstream [1095]. Despite the high variability in summer wet season flows and therefore of total mean annual discharge, flows during the dry season period of July to October are relatively stable and vary little [949, 950, 951, 1095].

To simplify discussion of species frequency of occurrence, abundance and biomass, data has been summarised for rivers and streams in the Wet Tropics region grouped according to drainage basin designation (Fig. 5), and for south-eastern Queensland, also according to geographic proximity and geomorphological similarity (Fig. 6 and Appendix 1). Rivers and streams sampled in the Sunshine Coast region (Noosa Basin 140 and Maroochy Basin 141) generally drain sandy acid-wallum landscapes and have been grouped together. Short coastal streams of the Logan-Albert Basin draining into Redland Bay (Basin 145a – Appendix 1) are small catchments quite dissimilar to the Logan-Albert River proper and so have also been grouped with other morphologically similar coastal streams of the greater Moreton Bay region (i.e. those in the Pine Basin – 142) (Figure 6). All other rivers and streams have been grouped according to their drainage basin designation (Mary River – Basin 138; Brisbane River Basin – 143; Logan-Albert River – 145a,b; South Coast rivers and streams – Basin 146) (Fig. 6).

Study basins and site locations The species summaries in this book are based on many different sources of information gathered by many individuals and groups. Our own studies have occurred in a variety of areas including basins in Cape York Peninsula [697, 1099, 1101], the Wet Tropics region [49, 1085, 1087, 1091, 1096, 1097, 1100, 1104, 1107, 1108, 1109], central Queensland [1079, 1081, 1082, 1089, 1098] and southeastern Queensland [84, 99, 104, 205, 699, 700, 701, 702, 704, 709, 1095, 1100, 1107]. The reader is referred to these studies for more detail concerning site location and sampling methods. Much of the information contained in this book, especially that concerning habitat use, variation in abundance and biomass, and aspects of life history, is drawn from a recent comparative study undertaken in the Wet Tropics region and south-eastern Queensland (see

Table 1. Sampling intensity in rivers and streams of the Wet Tropics region and south-eastern Queensland. See Figures 5 and 6 and Appendix 1 for river basin and sub-basin locations and designations. Region/River

Number of locations

Number of samples

Number of fish species collected

51 56 11

83 190 11

32 37 19

7959 27 267 717

118

284

39

35 943

50 29 20 111 68 20

225 42 37 165 174 32

27 24 21 28 28 21

83 198 2557 4310 26 536 43 162 3558

Wet Tropics region Mulgrave Russell River (Basin 111) North and South Johnstone rivers (Basin 112) Tully River (Basin 113) Sub-total South-eastern Queensland Mary River (Basin 138) Sunshine Coast rivers and streams (Basins 140b; 141) Moreton Bay rivers and streams (Basins 142; 145a) Brisbane River (Basin 143) Logan-Albert River (Basin 145b,c) South Coast rivers and streams (Basin 146)

Number of individuals collected

Sub-total

298

675

38

163 321

Total

416

959

68

199 264

31


146°06'00" -16°55'00"

Cairns

111 Mulgrave-Russell Basin

Mulgrave-Russell Rivers Johnstone River Tully River

Innisfail 112 Johnstone Basin

N

145°30'00" -18°01'00"

113 Tully Basin 0

10

20

kilometres

Figure 5. Location of study sites in the Wet Tropics region of northern Queensland. Base data reproduced with the permission of the Queensland Department of Natural Resources, Mines and Energy.

32


152°28'00" -24°52'00"

Fraser Island Mary River Sunshine Coast rivers and streams Moreton Bay rivers and streams Brisbane River Logan-Albert Rivers South Coast rivers and streams

138 Mary Basin 140 Noosa Basin !! !

! ! ! !

!

!

'' '

'

141 Maroochy Basin

'

!!

'

''

!!

'' ' ' ''

'' ' ' ' ' ' ' ' '

' '

' '

' ' '

'

' '

' '

N

=

' ''

!

'

Moreton Island = = = = = = = = = = == = = = '=

' ' '' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' '' ' ' ' ' ' '

Bribie Island

' ' ' ' ' '

'

'''

'

!

'

' ' '

143 Brisbane Basin

!

' ''

''

'

' ''' '

142 Pine Basin Moreton Bay

Brisbane = ' = = =

North Stradbroke Island

South Stradbroke Island

146 South Coast Basin 153°58'00"

0

35

70

-28°14'00"

kilometres 145 Logan-Albert Basin Figure 6. Location of study sites in south-eastern Queensland. Base data reproduced with the permission of the Queensland Department of Natural Resources, Mines and Energy.

33


lowland reaches of rivers in the Wet Tropics region further constrained our ability to sample these habitats by these methods. The ecology of fishes in lowland river reaches of north-eastern Australia remains one of the least studied aspects of this field in Australia and offers exciting potential for further research. The majority of study locations in both the Wet Tropics region and south-eastern Queensland were relatively undisturbed. However, some of the sampling in south-eastern Queensland was undertaken as part of a project to examine the effects of human activities on freshwater fish assemblages [709, 1255], and some sites in this region were therefore impacted to varying degrees by land use activities (e.g. land clearing, grazing, cropping and urbanisation), water resource development and local riparian and in-stream habitat degradation.

Site selection and spatial distribution The location of the individual sampling sites in the Wet Tropics region are shown in Figure 5 and that of sampling locations in south-eastern Queensland in Figure 6. Fish and habitat sampling was conducted with the intention of characterising as much of the environmental and biological variation possible in each selected stream reach within the hierarchical organisation of habitats characteristic of river networks. In south-eastern Queensland streams, at least two contiguous hydraulic habitat units (i.e. riffles, runs and pools) were usually sampled in each reach in order to encompass this variation (Fig. 7), except during dry periods when surface waters occasionally contracted to shorter isolated pools. In rivers of northern Queensland, a single hydraulic habitat unit was usually sampled at each location. Study sites in the Wet Tropics region were, on average, 34.1 ± 0.9 m in length and 347.1 ± 17.6 m2 in wetted area, and those in rivers of south-eastern Queensland were of similar size: 38.6 ± 0.5 m stream length and 313.3 ± 10.6 m2 wetted area. Note that all error terms are listed as Standard Error throughout this book unless otherwise stated.

Study sites were sampled over a range of seasonal and hydrological conditions effectively encompassing the range of flow conditions expected in these rivers and regions (Fig. 8). Although fish assemblages were not sampled during large floods, samples were frequently collected as soon after flooding as practicable. The reader should note that we sometimes present summaries of information in which sampling occasions are grouped (e.g. length-frequency data). We have used traditional seasonal groups (i.e. summer, autumn, winter and spring) for data collected in south-eastern Queensland but not the Wet Tropics regions, as application of such seasonal categories is not appropriate in the latter region due to its tropical climate (see above).

Study sites were arrayed widely throughout each catchment from headwaters to downstream reaches, however study site location was constrained by our choice of sampling methodology (back-pack electrofishing and seine-netting – see below). This limited our ability to sample fish assemblages effectively and quantitatively in large lowland river reaches with a depth of greater than 1.5 m. In addition, the presence of estuarine crocodiles in

River

Reach

Hydraulic unit In-stream habitat sampling point

Distance upstream (m)

40 Pool

Riffle

Sampling location Run

35

Bank habitat sampling segment

30 25

Flow

20 15 10 5

Hydraulic unit

0 E

D

C

B

A

1/6w 2/6w 3/6w 4/6w 5/6w

Right bank

Transect

Left bank

Figure 7. Spatial scale at which individual hydraulic units within each river reach were defined for sampling fish and habitat. Also shown are the sampling points within each hydraulic unit where measurements of in-stream habitat and bank habitat structure were undertaken.

34


25

These data were collected as part of the process for determining distribution and abundance at larger spatial scales. The following data were estimated for each individual collected during electrofishing and recorded on data sheets: • Mean water column velocity (portable flow meter) • Focal point velocity (portable flow meter) • Total water column depth (graduated stick) • Focal point depth (graduated stick) • Proportional substrate composition in one square metre immediately below the fish (i.e. mud, sand, fine gravel, coarse gravel, cobbles, rocks and bedrock) • Distance to nearest potential refuge (i.e. microhabitat structure) • Distance to bank

Wet Tropics (n=284) South-eastern Queensland (n=675)

20 15 10 5 0

Summer

Autumn

Winter

Spring

Summer

Month/Season

For fish less than 0.2 m from the nearest refuge, the type of potential cover with which it was associated was recorded (note that 0.2 m is an arbitrary distance only). The cover elements identified were: the substratum itself, submerged aquatic macrophytes, filamentous algae, leaf litter, emergent vegetation, submerged bank-side vegetation, submerged overhanging vegetation, large woody debris, small woody debris, undercut banks and root masses. Fish >0.2 m from the nearest potential cover were recorded as being in open water.

Figure 8. Distribution of sampling occasions in months and seasons throughout the study period.

Collection and quantification of fish abundance levels Fish assemblages at each site were intensively sampled using the procedures detailed in Pusey et al. [1107]. Each hydraulic unit was blocked upstream and downstream with weighted seine nets (11 mm stretched-mesh) to prevent fish movement into or out of the study area. The site was sampled using a combination of repeated pass electrofishing (Smith-Root model 12B Backpack Electroshocker) and supplementary seine netting until few or no further fish were collected. Usually four electrofishing passes and two seine hauls were required to collect all fish present within a site. The intensive sampling regime described here has been demonstrated to provide accurate estimates of species composition and abundances in wadeable stream sites [1107].

Two problems with this method can be identified immediately. First, it relies on the investigator being able to see the fish in question and to see its position within the habitat milieu prior to it being stunned. Second, it must be assumed that the observed microhabitat use does not differ from a hypothetical condition that might exist without the presence of the observer and his or her electrofishing gear. These are potentially important biases and we sought to minimise their influence in three ways. First, microhabitat data was only collected when water clarity was sufficiently high to allow observation. Second, microhabitat data was not recorded or used if the position of the fish was unknown prior to it being stunned. Third, microhabitat data was only recorded for fish collected during the first electrofishing pass, the assumption being that the behaviour of fish changed significantly after they had experienced the observer and the electrofisher for the first time. In addition, we have, on occasions, conducted snorkelling surveys and recorded habitat use data prior to electrofishing in an attempt to assess the accuracy of habitat use data recorded during electrofishing. Habitat use data generally matched quite closely for the two methods. One possible exception is the estimation of focal point depth and velocity for fish located in the bottom-third of the water column but not in actual contact with the substrate, especially when depth exceeds 1 m.

All fish collected were identified to species, counted, measured (standard length to the nearest mm) and all native fish were returned alive to the point of capture. Alien fish were euthanased (using benzocaine – MS222), and were not returned to the water (in accordance with the Queensland Fisheries Act 1994). The weight of each fish (both native and alien species) was estimated by reference to previously unpublished and existing relationships between body length and mass for each species. Fish abundance and biomass data were transformed to numerical densities (number of individuals.10m–2) and biomass densities (g.10m–2) at each site. Quantification of fish microhabitat use Microhabitat use data for many of the fish species covered in this text were colleted during sampling in the Mulgrave and Russell rivers in the Wet Tropics region and in the Mary and Albert rivers in south-eastern Queensland.

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1:100 000 topographic maps using a digital planimeter and also using Geographical Information System (GIS) data. Riparian cover was estimated from multiple measures (usually three) at each site on each occasion, using a handheld densiometer. Estimates of variables describing habitat structure at the meso- and microhabitat scale within each site and on each occasion were based on multiple samples within a combined bank transect and random points scheme. An imaginary grid (40 rows and five

Quantification of habitat structure at macro-, mesoand microscales A range of catchment and local scale environmental variables describing habitat structure (Table 2) was measured at each site and on most sampling occasions according to a standard protocol briefly described in Pusey et al. [1100] and more fully here. Catchment descriptors for each site (upstream catchment area, elevation, distance from stream source and distance to river mouth) were estimated from

Table 2. Environmental variables estimated at each sampling location. Variable/Measurement Unit Catchment variables Upstream catchment area (km2) Distance from stream source (km) Distance to river mouth (km) Elevation (m.a.s.l.) Site physical characteristics Wetted stream width (m) Riparian cover (%) Water depth (cm) Mean water velocity (ms–1) Site gradient (%) Substrate composition (% surface area) Mud Sand Fine gravel Coarse gravel Cobble Rock Bedrock Microhabitat structure (% surface area) Aquatic macrophytes Filamentous algae Overhanging vegetation Submerged vegetation Emergent vegetation Leaf litter Large woody debris Small woody debris Undercut banks (% bank) Root masses (% bank) Water chemistry Water temperature Dissolved oxygen pH Conductivity Turbidity

Description Estimated using 1:100 000 topographic maps and digital planimeter or GIS Estimated using 1:100 000 topographic maps and digital planimeter or GIS Estimated using 1:100 000 topographic maps and digital planimeter or GIS Estimated using 1:100 000 topographic maps and digital planimeter or GIS Horizontal distance measured perpendicular to stream flow from bank to bank at existing water surface using tape measure. Hand-held densiometer. Vertical distance from existing water surface to channel bottom measured using graduated stick. Speed at which water moves downstream. Measured with a Swoffer current velocity meter at 0.6 of water column depth. Measured for each hydraulic habitat unit using staff, dumpy and tripod. (Visually estimated) 128.0 mm (Visually estimated) Submerged aquatic macrophytes and charaphytes. Overhanging terrestrial vegetation in contact with water surface. Submerged terrestrial vegetation along river margins (e.g. grasses and annual weeds). Semi-aquatic vegetation (e.g. sedges and rushes). Accumulations of leaf litter and fine woody material (15 cm minimum stem diameter. Woody debris of 500 m) on the Atherton Tablelands. Despite these differences at the landscape or macrohabitat scale, study sites were arrayed similarly across the gradients of stream width, gradient and riparian cover. Approximately 20% of sites in south-eastern Queensland had localised patches greater than 1.25 m deep whereas such depths were uncommon in streams sampled in the Wet Tropics region. Mean site depth varied little between regions however. Although sites within both regions covered similar ranges in maximum current velocity recorded in each site, comparatively fewer sites in the Wet Tropics region had average current velocities less than 0.01 m.sec–1 (i.e. still water). This reflects the differences in regional hydrology. Rivers and streams of the Wet Tropics region rarely cease to flow.

Estimates of proportional cover and substrate composition derived from both schemes were then combined to give an overall representation of the habitat structure of each site by weighting the area characterised by each method (i.e. estimates derived from bank transects characterised 20% of the wetted area whereas the random points scheme characterised habit structure in the middle 80% of wetted area).

Substrate composition differed slightly between the two regions (Fig. 10). Coarse gravel was the dominant particle size in streams of south-eastern Queensland, whereas rocks were the dominant particle size in streams of the Wet Tropics. Bedrock was present in streams of this region also, but was almost absent from streams of south-eastern Queensland. The average contributions of mud, sand and fine gravel were very similar in both regions.

Ambient water quality conditions (Table 2) at each site on most sampling occasions were characterised by the mean of three measurements for each parameter taken at each site. A pilot study comparing measures taken at each of the

The two regions differ substantially with respect to the types and abundance of different cover available to fishes. Aquatic macrophytes and filamentous algae both

37


Figure 11 shows the frequency distribution of the random points measures of current velocity, depth, substrate composition and microhabitat cover elements. This figure differs from data presented in Figures 9 and 10 wherein the distribution of overall site means is presented. For example, although aquatic macrophytes comprised, on average, less than 1% of the area of sites in the Wet Tropics region (Fig. 10), 6% of the random point measures were positioned over a 1 m2 quadrat containing aquatic macrophytes. Comparing the same data for sites in south-eastern Queensland indicates that aquatic macrophytes were more commonly encountered and more extensive in areal coverage in this region. Data in Figure 11 is intended to allow

comprised about 10% of the area of sites located in streams of south-eastern Queensland but were essentially absent from study sites in the Wet Tropics region (Fig. 10). Whether this is due to regional differences in hydrology, canopy cover or nutrient status is unclear. Submerged vegetation (para grass in the Wet Tropics region) was, on average, more common in streams of the Wet Tropics region but note that median values differ little between regions. It is worth noting that para grass (Urochloa (=Brachiaria) mutica) is able to establish in well-shaded streams and is a potentially significant threat to the maintenance of habitat structure in rainforest streams [108, 250, 1092] and to freshwater fishes [94].

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Figure 9. Macro and mesoscale habitat characteristics of study sites located in rivers of the Wet Tropics region (solid bars, n = 118 locations and 284 mesohabitat unit samples) and south-eastern Queensland (open bars, n = 278 locations and 790 mesohabitat unit samples).

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microhabitat preference would require that microhabitat availability at only those sites in which a species occurred, rather than across all sites examined (as is presented in Figure 11), was used to base the comparison. To present this information for individual species and study river was beyond the scope of this text (see also section on Macro, meso and microhabitat use below).

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Figure 11. Microhabitat availability in the Mulgrave and Russell rivers, Wet Tropics region (closed bars, n = 5589 habitat sampling points), and the Mary and Albert rivers, south-eastern Queensland (open bars, n = 9456 habitat sampling points). Note that these data represent the frequency distribution of random points measurements of different microhabitat parameters.

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The ranges of water quality parameters encountered during the study period are shown in Figure 12. Streams of the Wet Tropics region tended to be warmer than those in south-eastern Queensland, reflecting the latitudinal gradient shown in Figure 3. Very few sites were examined in which temperature might be thought to be approaching extreme levels. Similarly, most sites examined where welloxygenated. Streams of the Wet Tropics region tended to be slightly more acidic than those of south-eastern Queensland, although most were circum-neutral in acidity. Water clarity was high in both regions except in the tannin-stained aquatic habitats of the coastal wallum (Banksia dominated) ecosystems of south-eastern Queensland. The two regions differ most with respect to

Figure 10. Box plots of variation in the substrate composition and microhabitat structure of mesohabitats in rivers of the Wet Tropics region of northern Queensland (closed circles, n = 284 mesohabitat unit samples) and south-eastern Queensland (open circles, n = 790 mesohabitat unit samples). The lines at the top, middle and bottom of each box represent the 75th percentile, median and 25th percentile, respectively. Upper and lower bars represent 90th and 10th percentiles and means are represented by symbols.

the reader to assess the match between micohabitat use by individual species and the availability of different microhabitats. Note however, that a quantitative assessment of

39


[1420]; an updated version of which is available online at www.marine.csiro.au/caab.

electrical conductivity. Streams of the Wet Tropics region rarely exceeded 100 µS.cm–1 whereas the majority of streams examined in south-eastern Queensland exceeded 250 µS.cm–1. 40

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Description This section is intended to provide the reader with a detailed mechanism for confirming the identification of a specimen determined through use of the dichotomous key provided. We present standardised diagnoses and descriptions (meristics, morphometrics and colour patterns) of species in life and in preservative. Where possible, we provide length/weight relationships based on our own data or sourced from the published literature. Geographical or subspecific variation in appearance is discussed and features allowing differentiation between closely related species are highlighted. Wherever possible, we have used the original description or subsequent taxonomic reviews as our main source of information. However, when such sources contain limited or erroneous data, we have used alternative sources or our own data sets. A drawing is provided for each species that should enable the reader to check meristic and morphometric characters listed in the text. In most cases, these drawing were of preserved specimens and the size, sex, locality and date of collection are given. Occasionally, figures were based on photographs of specimens. The year in which the figure was drawn is also given.

40

Systematics The nomenclatural history and details of synonomy are given. Wherever possible, the results of morphological or genetic studies examining phylogenetic and phylogeographic relationship are presented and discussed. The chapters are arranged in approximate phylogenetic order (after Paxton and Eschmeyer [1041]) and the systematics of a particular family or genus is described in the summary for the first species listed in each family or genus.

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Turbidity (NTUs)

Figure 12. Water quality in streams of the Wet Tropics region (closed bars, n = 233 mesohabitat unit samples) and southeastern Queensland (open bars, n = 778 mesohabitat unit samples).

Distribution and abundance A detailed account of the distribution of each species is presented based on literature accounts and our own survey results. The distribution of all fish species in coastal drainage basins of Queensland is given in Appendix 1 and the combined reference sources for these data are given in Appendix 2. We present information on distribution at a variety of scales from global, national, regional and individual river basins. We have not included maps detailing the distribution for each species. Information regarding the distribution of a particular species is often drawn from a variety of sources, yet some basins may not have been sampled adequately and it may be unknown whether a species does occur there. Maps tend to give an overall impression of distribution and do not highlight those basins in which a species may be naturally absent or those

Data presentation and format of species summaries Nomenclature We have primarily followed the nomenclatural conventions used in Allen et al. [52] except where we have received advice to the contrary from other taxonomists. Common or vernacular names are given where available and follow those given in Allen et al. [52]. Common names often vary markedly across a species’ range, with the attendant risk of confusion between different researchers. If common names are to be used and the potential for confusion removed or minimised, we recommend the adoption of standardised common names. We have also listed a unique code number of each species. This code is derived from CSIRO’s Codes for Australian Aquatic Biota (CAAB)

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25% of sites examined, some fish with limited distribution may be dominant (high rank) in those sites in which they occur, perhaps because they have highly restricted habitat requirements, but contribute little to abundance over all sites examined. Similar summaries are given for biomass data. For each species the average and maximum numerical density and biomass density, respectively, for those sites in each basin in which each species occurred are also presented and discussed (note that biomass data was not collected for a small proportion of samples in south-eastern Queensland).

for which inadequate data exists. We feel it important that these factors be identified and that readers have the necessary information to make their own judgements about patterns of distribution. We have presented data concerning the abundance of species in a variety of ways. First, data collected by us over the period 1994–2003 is presented in a consistent tabular format to facilitate comparison within and across drainage basins and between regions. For example, Table 3 lists data for the Fly-specked hardyhead Craterocephalus stercusmuscarum fulvus in drainages of south-eastern Queensland. Data are listed for each basin and for all basins combined. The proportion of the total number of locations in which this species was collected is given as an indication of how widespread each species is. For example, C. s. fulvus is a relatively widespread species in south-eastern Queensland, occurring in about one quarter of all locations examined. Note that although this species is moderately common in many river basins, especially the Mary River, it is absent from the Logan-Albert River and rare in some other streams and rivers. The proportional contribution of this species to the total number of fish collected is given as % abundance, as an indication of how abundant this species is relative to other species found in the region or within individual basins. Similarly, an indication of its ranked abundance is also given. For example, C. s. fulvus was the 10th most abundant species collected in rivers of southeastern Queensland but contributed only 2.8% of the total number of fish collected, and much less of the total biomass. Also listed in parentheses are the equivalent summaries at only those sites in which this species occurred, to give an indication of the local abundance and biomass of each species. For example, C. s. fulvus is relatively more common and contributes more to the total number of fish collected in this reduced number of sites. Although this is to be expected for a fish occurring in only

Second, we have attempted to summarise the findings of studies in which quantitative electrofishing estimates of abundance and biomass are not available but in which abundance data are presented as catch per unit effort or as relative abundance. We identify potential problems associated with comparison across studies employing different methodologies. Information drawn from the literature concerning distributional limits and abundance must be interpreted with care, taking into account differences in concentration of sampling effort and study site location, as well as differences in survey methodology (i.e. electrofishing, seine-, gill- and hand-netting, bait trapping, visual census, ichthyocides). Different methods are often selective with respect to the particular species or size of fish they collect. However, abundance information derived from our sampling of wadeable streams is directly comparable, as it has been collected using standardised quantitative sampling methods. The distributional information summarised in Appendix 1 has been drawn from many studies undertaken over a relatively long period. Some literature sources used were published in the 1880s, for example. The abundance and distribution of many species, particularly migratory

Table 3. Distribution, abundance and biomass data for Craterocephalus stercusmuscarum fulvus. Data summaries for a total of 4608 individuals collected from rivers in south-eastern Queensland over the period 1994–2003 [1093]. Data in parentheses represent summaries for per cent and rank abundance and per cent and rank biomass, respectively at those sites in which this species occurred. Total

% locations % abundance Rank abundance % biomass Rank biomass

Mary River Sunshine Coast Moreton rivers and Bay rivers streams and streams

Brisbane River

Logan-Albert River

South Coast rivers and streams

25.8

62.0

3.4

15.0

36.0

—

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2.82 (7.96)

3.82 (6.90)

0.04 (2.27)

1.55 (14.47)

5.05 (11.90)

—

0.59 (40.39)

10 (6)

9 (7)

22 (5)

9 (2)

6 (2)

—

14 (1)

0.21 (0.69)

0.27 (0.63)

0.01 (0.03)

0.24 (0.41)

0.63 (1.24)

—

0.11 (0.43)

19 (10)

14 (10)

14 (6)

10 (7)

10 (7)

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13 (3)

Mean numerical density (fish.10m–2)

0.99 ± 0.13

1.06 ± 0.17

0.03 ± 0.03

0.51 ± 0.16

0.88 ± 0.18

—

0.39 ± 0.37

Mean biomass density (g.10m–2)

0.68 ± 0.32

0.71 ± 0.14

0.03 ± 0.03

0.25 ± 0.03

0.58 ± 0.15

—

0.34 ± 0.34

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Table 4. Macro/mesohabitat use by Craterocephalus s. fulvus in rivers of south-eastern Queensland. Data summaries for 4608 individuals collected from samples of 232 mesohabitat units at 76 locations between 1994 and 2003 [1093]. W.M. refers to the mean weighted by abundance to reflect preference for particular conditions.

species, is known or suspected to have contracted in recent years due to deteriorating catchment condition, increasing human pressures and an increase in the number of artificial barriers to fish movement caused by dams, weirs and other infrastructure. The impacts of anthropogenic disturbances on fish species’ distributions and abundances are treated in detail in the section on Conservation status, threats and management requirements.

Min. 2

Catchment area (km ) Distance to source (km) Distance to mouth (km) Elevation (m.a.s.l.) Stream width (m) Riparian cover (%)

Macro, meso and microhabitat use We have presented data concerning macro- and mesoscale habitat use in a consistent tabular form in order to facilitate comparison between species within regions or within species across regions. Ontogenetic variation in habitat use is examined for some large-bodied species and additional information available in the literature is also discussed. For example, Table 4 lists the habitat use of C. s. fulvus in rivers of south-eastern Queensland. The minimum and maximum values for each parameter are given to provide an indication of the range of conditions over which a species may be found. These data can be used in conjunction with information concerning a species’ distribution within a catchment or region (e.g. Table 3) to gain a better understanding of distribution and habitat use at large and local spatial scales. For example, C. s. fulvus occurs in catchments ranging from only 19.3 to 1540 km2 in area (Table 4), yet data presented in Table 3 indicates that it is not necessarily evenly distributed across that range. The average of each habitat parameter calculated across all sites in which each species occurred is also presented. In addition, we have included an estimate of mean habitat conditions weighted by the density of fish at each site. In effect, each fish is the sample unit rather than the site. Weighting the mean by density gives an approximation of particular habitat conditions in which this species is most abundant and which may be especially favoured or selected by a species. For example, the difference between the average and weighted average values for site gradient, mean water velocity and the proportional contribution of sand to the substrate composition (Table 4) indicate that, although C. s. fulvus occurs on average, in streams with a gradient of 0.3%, an average current velocity of 0.14 m.sec–1 and 18.4% sand substrate, this species is more abundant in sites in which the gradient and current velocity are comparatively reduced and sand is more abundant.

Max.

Mean

W.M.

19.3 10211.7 9.0 270.0 4.0 311.0 0 240 0.7 46.8 0 80.0

1540.1 73.5 193.1 83 12.3 28.9

996.0 56.1 220.8 89 11.5 24.1

2.86 1.08 0.85

0.30 0.43 0.14

0.17 0.43 0.09

Gradient (%) 0 Mean depth (m) 0.05 Mean water velocity (m.sec–1) 0 Mud (%) Sand (%) Fine gravel (%) Coarse gravel (%) Cobble (%) Rocks (%) Bedrock (%)

0 0 0 0 0 0 0

99.6 100.0 56.7 70.9 65.8 41.1 76.0

8.4 18.4 21.9 30.1 16.8 3.0 1.4

7.5 31.8 22.6 24.7 12.1 0.9 0.4

Aquatic macrophytes (%) Filamentous algae (%) Overhanging vegetation (%) Submerged vegetation (%) Emergent vegetation (%) Leaf litter (%) Large woody debris (%) Small woody debris (%) Undercut banks (% bank) Root masses (% bank)

0 0 0 0 0 0 0 0 0 0

64.5 65.9 26.7 65.7 43.3 43.3 31.0 15.5 50.0 58.8

19.8 11.8 1.5 8.6 2.3 9.1 3.8 3.0 8.5 12.1

23.2 15.5 0.9 15.0 3.5 6.9 2.9 2.4 3.9 6.9

0.20 m.sec–1). An example of microhabitat use histograms for C. stercusmuscarum collected from the Wet Tropics region and south-eastern Queensland is given in Figure 13. The microhabitat use data presented does not necessarily give an indication of habitat preference thus must be interpreted with caution. Preference for a particular depth class or sediment particle size for example, requires that fish use such microhabitats more frequently than predicted by chance due to the relative availability of that habitat element in the environment. Although it is possible to represent a species preference for certain habitat configurations by standardising habitat use data in relation to data on habitat availability, we have not done this in a systematic quantifiable manner here as such a method of standardisation still does not ensure that habitat preference information is transferable across sites with varying habitat structure. The microhabitat use summaries presented here were usually generated from a large

Mesoscale data describe the type of habitat (e.g. riffle, run or pool) in which an individual species is found whereas the microhabitat data reveal the type of conditions which species occupy within that habitat. Microhabitat use data is presented as a series of frequency histograms showing the proportion of the total number of fish collected within different categories (e.g. current velocity between 0.11 and

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consistent tabular format detailing minimum, maximum and mean values. Mindful of the potential for geographic variation in water quality tolerance, we have presented data for different populations wherever possible. The number of samples upon which the summaries are based is also given in most cases. We have relied extensively on the information provided by Bishop et al. [193] concerning ambient water quality conditions experienced by fishes in the Alligator Rivers region. In such cases, the number of samples from which summaries are based, varies between parameters. We have not listed sample size when these data are presented. Note however, that the research by Bishop et al. [193] occurred over a two year period, study locations were sampled many times over a range of seasonal and hydrological conditions and sample size for some parameters was often very large (>100 replicate measures). These data are therefore very comprehensive and represent the most detailed examination of the habitat requirement of fishes in north-western Australia. We also present summaries derived from the published work of other researchers, particularly that of Hamar Midgley ([944, 946]). In such cases where minimum, maximum and mean values are not explicitly stated we have reanalysed the data presented in the original reports.

number of fish collected from a large number of sites and sampling occasions and hence environmental conditions. They do therefore represent a general guide to the microhabitat conditions commonly used by each species. 60

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Figure 13. Microhabitat use by Craterocephalus s. stercusmuscarum in the Wet Tropics region (solid bars) and C. s. fulvus in south-eastern Queensland (open bars). Summaries derived from capture records for 78 individuals from the Johnstone and Mulgrave rivers in the Wet Tropics region and for 558 individuals from the Mary River, south-eastern Queensland, over the period 1994–1997 [1093].

We must place several caveats on the extent to which data describing ambient water quality conditions represents tolerance per se. First, the data represents the conditions in which fish occur. However, the fact that a species occurs in particular conditions does not indicate that it prefers such conditions nor does it indicate that its biology is unaffected by those conditions. Sublethal stresses may impact on the fitness of an individual, yet it may, for whatever reason, be forced to endure such conditions (e.g. during circumstances when fish may be restricted to isolated pools during extended periods of zero flows). Second, if the lethal tolerance levels of a particular species are exceeded at a site, then it will no longer occur there, and as a consequence this site will not be included in the sample. Third, the majority of study sites were selected on the basis that they were largely undisturbed, thus we intentionally avoided sites with poor water quality. The main exception to this was for a subset of moderately to highly degraded sites in south-eastern Queensland.

Environmental tolerances The tolerance of north-eastern Australian freshwater fishes to extremes in water chemistry or toxicants is unknown for most species. We review experimental data for each species where available. In the absence of such data we have presented summaries of ambient levels of five major water quality parameters (temperature, dissolved oxygen, pH, conductivity and turbidity) drawn from our own field studies and the research of others. Data are presented in a

It is important to note that environmental tolerances are likely to vary between life history stages (i.e. eggs and larvae might be especially vulnerable) and may vary considerably between different geographic populations and between populations occurring in different habitat types. For example, populations occurring in wetlands may be more tolerant of hypoxia than are populations occurring in streams, and populations occurring in high elevation, well-shaded streams may be less tolerant of

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appropriately applied to all species. These different maturity classifications are compared in Table 5. Another method used to quantify reproductive development in individuals and populations is the Gonadosomatic Index (sometimes referred to as Gonosomatic Index) and abbreviated as GSI. It is a measure of the relative contribution of the weight of the developing gonads to the total weight of the individual and is estimated according to the formula: GSI = gonad weight/total body weight x 100. Ideally, body weight should refer to the body weight minus the weight of any material within the gut. It is an effective way of comparing temporal changes in reproductive development. For example, in some species the spawning period is highly concentrated within a short period. Temporal changes in GSI will reflect this, being low for most of the year, then rapidly increasing as the spawning period approaches, and peaking during the spawning period. Other species with a more protracted spawning period show a more gradual increase in GSI values. GSI values are effective for comparing the reproductive investment of individuals or populations. High GSI values are indicative of high investment into reproduction. Short-lived species often have high GSI values as they have a limited time in which to reproduce. Longer-lived species may be able to spawn over several years and therefore do not need to invest so much effort in reproduction in any one year. Female fish typically have higher GSI values than males.

elevated temperatures than are populations occurring in lowland open streams. Notwithstanding these caveats, the information presented here is the first comprehensive and consistent examination of the water quality requirements of the fish of north-eastern Australia. Experimental examination of sublethal and lethal effects of varying water quality is urgently required. Reproduction In this section we review all known published studies for each species. In addition, we present previously unpublished data concerning the life history of a small number of species; the reader is referred to Pusey et al. [1108] for details of methods used. In addition to the review of reproductive biology, summary data are listed in standardised tabular format allowing the reader to quickly access information and identify knowledge gaps. Data listed covers various aspects of reproductive biology such as fecundity, spawning phenology, critical environmental thresholds, and cues and age at maturity. Information concerning embryology and larval development is also presented where available. The methods and terminology used in studies of fish reproductive biology often vary greatly. We have attempted to standardise terminology as much as possible, particularly that relating to fecundity. In many species, especially those characterised by small size at maturity, the intraovarian eggs are not all at equivalent stages of development. Rather, groups of eggs develop in concert, are simultaneously ovulated, and then oviposited in a batch. Another batch then begins to develop. We have used the term batch fecundity to refer to the number of large ovulated or near ovulated eggs within an ovary in such species. Total fecundity refers to the number of ovulated and follicular eggs other than primary oocytes (i.e. all yolked eggs) present within the ovaries of an individual female. It is an instantaneous estimate of fecundity. Total fecundity can sometimes be taken to mean the total number of eggs produced in a spawning season which may be much higher for batch, repeat or protracted spawners. There is no real way to estimate this latter version of fecundity unless individual females are followed throughout their reproductive life.

Movement Fish move over a variety of spatial scales and for a range of biological and ecological incentives. Some fish may only move within their own home range, which may be as small as a single pool or riffle, juveniles of some species may undertake mass upstream dispersal movements, whereas others may have a spawning migration into freshwater habitats other than those occupied in periods outside of the spawning season. Others may migrate out of freshwater to estuarine or marine ecosystems. Migratory movements may occur in the larval, juvenile or adult phase. Movement is a critical aspect of the ecology of many riverine fishes and one that is very easily disrupted (e.g. by artificial barriers), often with deleterious effects. Mallen-Cooper [852] provides a very useful summary of migration in freshwater fishes and McDowall [890] discusses in depth the various types and functions of diadromous migration undertaken by fishes. We provide a review of the movement/migration biology of each species (i.e. migration pattern, time of year, age at which migrations occur, critical habitats, anthropogenic factors impeding movement) where such information is available. A better understanding of the movement biology of the fishes of north-eastern Australia is urgently required and represents one of the greatest impediments to better management of the fauna.

A number of schemes have been developed to characterise the developmental stages of reproductively mature fishes based on the visible appearance and size of the gonads. Variation in the proportional contribution of different reproductive stages to the total adult population can then be used to estimate the timing and length of the spawning period, and whether maturation occurs in one habitat or another for example. However, the various schemes available and used in studies of species occurring in northern Australia are not always consistent with one another or

44

Table 5. Generalised classifications of maturity stages in fishes, with approximate correspondence between them (modified from Bagenal and Braum [120]). Note that allocation of a given individual to a particular maturity stage is partly subjective, species dependent (different fish species have varying reproductive morphology) and dependent on whether specimens are fresh or preserved (it is difficult to extrude eggs and milt in preserved specimens). Pollard [1061], Bishop et al. [193]

Davis [360]

Beumer [173]

Milton and Arthington [949, 951]

Pusey et al. [1093, 1108]

I Virgin. Very small sexual organs close to vertebral column. Testes and ovaries transparent, colourless to grey. Eggs invisible to naked eye.

I Immature. Young individuals which have not yet engaged in reproduction; gonads of very small size.

I Immature virgin. Testes and ovaries thin and threadlike, translucent and colourless; sexes usually indistinguishable.

I Immature virgin. Testes are strap-like with little folding and twisting, translucent and almost colourless. Ovaries are narrow and small, colourless and generally translucent. Some opaque white oocytes are visible to the naked eye in larger ovaries.

I Juveniles. Immature individuals where sexes are indistinguishable. Gonads are very small.

I Juveniles. Gonads small, testes almost indistinguishable, extremely thin and almost colourless. Ovary thin, translucent, without visible oocytes (X40 magnification).

I Immature. Gonads not visible or small, thin and strap-like.

II Maturing virgin. Testes and ovaries translucent, grey-red. Length half, or slightly more than half, the length of ventral cavity. Single eggs can be seen with magnifying glass.

II Resting stage. Sexual products have not yet begun to develop; gonads of very small size; eggs not distinguishable to the naked eye.

II Developing virgin and recovering spent. Testes thin and strap-like, translucent and greyish, sometimes with melanophores. Ovaries more rounded, translucent and colourless, eggs not evident to the naked eye.

II Developing virgin and recovering spent. Testes of developing virgins are thicker, translucent and white, and they begin to twist and fold. Testes of recovering spent fish are thicker, the main body of the testes showing numerous translucent regions and the lobes tending to be opaque off-white and rough in texture. Ovaries are more rounded, the ovary wall is thick and opaque, and oocytes are creamy white and opaque.

II Inactive. Immature (sexes distinct) and recovering individuals. Gonads small. Oocytes distinguishable under X40 (L. unicolor) and X10 (M. splendida) magnification.

II Inactive. Immature virgins and recovering spent fish. Testes thin, strap-like and creamy-white. Ovaries small, regularly shaped and elongated. Oocytes distinguishable (X10 magnification).

II Early developing. Testes elongate, whitish sac; ovary pale orange, with few oocytes, visible at X20 magnification.

III Developing. Testes and ovaries opaque, reddish with blood capillaries. Occupy about half of ventral cavity. Eggs visible to the eye as whitish granular.

III Maturation. Testes change from transparent to a pale rose colour; eggs are distinguishable to the naked eye; a very rapid increase in weight of the gonad is in progress.

III Developing. Testes thickening, opaque and greyish-white, smooth texture. Ovaries thickening, opaque and pale yellowish, eggs small but visible to the naked eye.

III Developing. Testes are increasing in size, the main body becoming opaque and white, and the tips of lobes and lateral margins becoming creamy-white. Ovaries increase in size, the ovary wall becoming thinner and translucent, and oocytes of various sizes are present, larger oocytes being creamy white and opaque.

III Maturing. Gonads increased in size. Testes swollen, pale, twisted and folded and occupying at least half of the body cavity. Ovary swollen to fill width of abdominal cavity, oocytes visible to naked eye.

III Developing virgin and resting adult. Testes grey-white; Ovaries orange, often with red flecks, eggs opaque, just visible to the naked eye, small oil droplets present in larger oocytes.

IV Maturing. Testes enlarged, opaque and whitish, smooth texture. Ovaries enlarged, opaque and yellowish, eggs large.

IV Maturing. Testes are large, occupying half of the body cavity, and the lobes and lateral margins are creamy-white and rough in texture. Ovaries occupy over half of the body cavity, and the current season’s oocytes are distinct in size from reserve oocytes and are opaque and yellow.

III Maturing. Gonads increasing in size. Ovary of M. splendida visible to the naked eye and of L. unicolor distinguishable under X10 magnification. Tips of filaments on oocytes of M. splendida first begin to appear.

IV Developing. Testes reddish-white. No miltdrops appear under pressure. Ovaries orange reddish. Eggs clearly discernible; opaque. Testes and ovaries occupy about two-thirds of ventral cavity.

IV Late developing. Testes opaque, white to grey-white, no milt present; ovaries orange, eggs clearly visible, opaque, larger oil droplets present throughout oocyte.


Nikolsky [993]

45

Kesteven [713]

Nikolsky [993]

Pollard [1061], Bishop et al. [193]

Davis [360]

Beumer [173]

Milton and Arthington Pusey et al. [949, 951] [1093, 1108]

V Gravid. Sexual organs filling ventral cavity. Testes white, drops of milt fall with pressure. Eggs completely round, some already translucent and ripe.

IV Maturity. Sexual products ripe; gonads have achieved their maximum weight, but the sexual products are still not extruded when light pressure is applied.

V Mature. Testes fill most of the body cavity, opaque and creamy-white, smooth texture. Ovaries fill most of body cavity, opaque and yellow, eggs large.

V Mature. Testes are generally opaque and creamy-white, but regions of the main body are still slightly translucent, and the testes occupy up to two-thirds of the body cavity. Ovaries occupy most of the body cavity, the ovary wall is very thin and translucent, and oocytes are large and yellow, tending to become translucent.

VI Spawning. Milt and roe run with slight pressure. Most eggs translucent with few opaque eggs left in ovary.

V Reproduction. Sexual products are extruded in response to very light pressure on the belly; weight of the gonads decreases rapidly from the start of spawning to its completion.

VI Ripe. Testes fill body cavity, opaque and pure white, smooth and crumbly texture, milt extruded by pressure on abdominal wall. Ovaries distend body cavity, translucent pale golden, eggs large and extruded by pressure on abdominal wall

VI Ripe. Testes are opaque and white, and milt can be extruded by applying pressure to the abdominal wall. Ovaries distended the body cavity. Oocytes are large, translucent and lemon coloured, and can be extruded by slight pressure on the abdominal wall.

IV Ripe. Gonads have achieved maximum size and weight with oocytes plainly visible in ovaries. This stage culminates in running ripe fish when milt or oocytes may be readily extruded from L. unicolor in response to light pressure on the abdominal region. L. unicolor oocytes have a single distinct oil-vacuole, while M. splendida oocytes are completely enveloped by the filaments and have between 14 and 30 oilvacuoles.

IV Ripe. Gonads have reached maximum size. Testes opaque and white; milt can be easily extruded with slight abdominal pressure. Ovary distends body cavity. Oocytes large, translucent yellow, easily extruded with slight pressure on abdomen.

VIII Spent. Testes and ovaries empty, red. A few eggs in the state of reabsorption.

VI Spent condition. The sexual products have been discharged; genital aperture inflamed; gonads have the appearance of deflated sacs. The testes usually containing some residual sperm, and the ovaries a few left-over eggs.

VII Spent. Testes thin and flaccid, greyish, sometimes white areas (residual sperm). Ovaries thin and flaccid, translucent and colourless to pale yellowish, sometimes contain large opaque-yellow residual eggs.

VII Spent. Testes are thin and flaccid, irregular in texture, and become translucent while regions remain opaque and white (residual sperm). Ovary wall is opaque, and ovaries are flattened and irregular in shape. Some large residual eggs may be present. These tend to become opaque and creamywhite, and reduce in size as they are reabsorbed.

II Recovering spent. Testes translucent, greyred. Length half, or slightly more than half, the length of ventral cavity. Single eggs can be seen with magnifying glass.

II Resting stage. Sexual products have been discharged; inflammation around the genital aperture has subsided; gonads of very small size. Eggs not distinguishable to the naked eye.

VII Spawning/spent. Not yet fully empty. No opaque eggs left in ovary.

46

V Spent. Gonads virtually empty. Testes normally with some residual sperm and ovaries with some remaining oocytes.

V Spent. Gonads reduced in size, irregularly shaped. Testes thin, flaccid and virtually translucent. Ovary reduced, small and flaccid, some enlarged oocytes remain but are irregularly distributed within ovary.

V Gravid. Testes white, and extrude milt with pressure; ovaries yellow-orange with some translucent, round eggs, oil globules forming single polarized mass. VI Running ripe. Testes extrude milt without pressure. Ovaries with large numbers of ovulated eggs.


Kesteven [713]


Trophic ecology Dietary information for each species was obtained from a variety of sources including published literature, unpublished governmental and consultancy reports and unpublished data sets held by colleagues and collated elsewhere [705]. In instances where the dietary data from each study was presented separately for different sites, seasons and/or size classes for an individual species, we summarised the diet composition for each species within each study as a weighted average (weighting based on abundance). Means were weighted by abundances so as to represent the average condition for a given species and study. A full list of sources for the diet data used in the present study is given in the bibliography.

except when no volumetric, gravimetric or abundance data was available for a particular species. Frequency data was transformed so as to approach proportional representation by first ranking different items on the basis of their frequency (i.e. the most frequent was ranked 1, the second ranked 2, etc.), then inversed and divided by the sum of all inverse ranks. For example, the proportional contribution of the most frequently encountered item equals 0.66 when the diet is composed of only two items and 0.54 when there are three items. Dietary data was summarised to the maximum taxonomic resolution possible but we were constrained by the minimum level to which diet categories were distinguished in the literature and the manner in which diet items were pooled in many studies. Nevertheless, we distinguished between food sources of autochthonous and those of allochthonous origin, and between animal and vegetable material, and we grouped items according to general similarities in prey habitat occupation and size. We were able to distinguish 15 functional diet categories (Table 6).

Dietary information can be summarised in a variety of forms, each method being subject to varying degrees of bias and accuracy in estimating the relative importance of individual dietary items to the total diet. The volumetric contribution of individual items to a total diet, per cent abundance (the numerical proportion of each diet item), per cent dry weight and per cent wet weight were the most commonly used method for data presentation across the range of studies examined. We assumed that these methods estimated diet similarly. In studies where dietary data was expressed using more than one of these methods for a single species, the method approximating the volumetric and then gravimetric contribution was preferred over abundance data, although in the overwhelming majority of such studies both methods indicated similar dietary habits. We avoided using frequency of incidence data

We also discuss major spatial and temporal patterns in the diet of each species where such information was available in the literature. Ontogenetic variation in fish diets was examined for large-bodied species for which sufficient data was available. In these cases, age classes were recognised (termed juveniles and adults) and the body size delimiting each age class was presented. Very little information on the trophic ecology of larval fishes is available in the literature but was discussed where possible.

Table 6. Dietary categories used throughout the text. Diet category

Description

Unidentified

Includes the unidentified fraction, together with unidentified items often referred to as ‘other’ or ‘miscellaneous’ Terrestrial insects (primarily Hymenoptera, especially Formicidae), arachnids and other terrestrial invertebrates (e.g. annelids, isopods, gastropods) Aerial forms of adult aquatic insects (primarily Diptera and occasionally Trichoptera, Ephemeroptera and Odonata) and water surface invertebrates (e.g. Araneae, Gerridae and Collembola) Mammals, birds, reptiles and amphibians Terrestrial wood, bark, leaves, buds, fruits, seeds and pollen Includes organic detritus and occasionally mud or sand Includes aquatic macrophytes and charophytes Includes filamentous and non-filamentous epiphytic algae and phytoplankton Includes larval and adult stages of all aquatic insects occurring in the benthos and water column Bivalves and aquatic gastropods Decapod crustaceans Copepoda, Cladocera, Ostracoda and Chonchostraca Includes amphipods, isopods, oligocheate and polycheate worms, nematodes, Nematomorpha and Hirudinea Hydracarina, Rotifera, Hydra Includes bones, scales and eggs

Terrestrial invertebrates Aerial and surface aquatic invertebrates Terrestrial vertebrates Terrestrial vegetation Detritus Aquatic vegetation Algae Aquatic insects Molluscs Macrocrustaceans Microcrustaceans Other macroinvertebrates Other microinvertebrates Fish

47


existing and potential threats for each species or for different populations based on published data, recovery plans, consultancy reports, and our own information and interpretations. Each chapter concludes with a forecast of the future conservation status of the species and/or our perception of the major management issues needing attention by means of restoration, recovery or conservation actions.

Conservation status, threats and management The current conservation status of each species is given as listed in the Action Plan for Australian Freshwater Fishes by Wager and Jackson [1353], and the Australian Society for Fish Biology Conservation Status of Australian Fishes – 2003 [117]. We also report the conservation status of species listed under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) and State legislation, where applicable. Following this we summarise

48

Neoceratodus forsteri (Krefft, 1870) Queensland lungfish

37 046001

Family: Ceratodontidae

Description Neoceratodus forsteri is a large species growing to 1500 mm, commonly to about 1000 mm [52]. Larger fish weighing 20 kg are not unusual [672, 690]. The largest lungfish caught by Illidge [626] from the Burnett River, south-eastern Queensland, in the 1890s weighed ~12.3 kg. O’Connor [1008] recorded a range of 825–1125 mm for 109 fish from the Mary River, south-eastern Queensland. Brooks and Kind [238] reported that lungfish from the Burnett River spanned 345–1420 mm TL and weighed 485–25 000 g, with a mean length of 906 ± 199.63 mm and mean weight of 7523 ± 4563 grams; most (80%) lungfish exceeding 1200 mm TL were females. The equation best describing the relationship between length (TL in mm) and weight (W in g) for 2361 individuals from the Burnett River (range 450–1305) is W = 9.96 x 10–6 L2.98, r2 = 0.956, p560 mm , growth rates of males may be greater than females [756]

Longevity (years)

? at least 7 years [1386], probably in excess of 8 years

Sex ratio

?

Peak spawning activity

Mid-October [756], September/October [934], October/November [1194]

Critical temperature for spawning

>23°C [756], 22–23°C [934]

Inducement to spawning

? Temperature

Mean GSI of ripe females (%)

?

Mean GSI of ripe males (%)

?

Fecundity (number of ova)

Low: 30–130 [14]; 78–173 [756]

Fecundity/length relationship

78 eggs at 476 mm TL, 110 eggs at 550 mm TL, 173 eggs at 660 mm TL [756]

Egg size

10 mm [756]

Frequency of spawning

Once per season for females, twice or more for males with long recovery period (several weeks) between spawnings

Oviposition and spawning site

Unknown, spawning probably takes place at night [934]

Spawning migration

?

Parental care

Buccal incubation by female, incubation and brooding may last 5–6 weeks [126, 756, 934]

Time to hatching

10–14 days at 23-30°C [756]; 5–6 weeks [14]

Length at hatching (mm)

15 mm [934], newly hatched larvae 36 mm TL [756]

Length at feeding

At maximum 35–0 mm TL [934]

Age at first feeding

At maximum, 30 days post-hatch

Age at loss of yolk sac

?

Duration of larval development

Hatch at advanced state of development, larvae with adult appearance with the exception of presence of large yolk sac [756]

Length at metamorphosis

? 15–25 mm

62

Scleropages leichardti

Movement Other than that described above, little is known of the movement biology of this species. Scleropages leichardti has not been recorded moving through fishways.

expressed. However, given the large number (15 and rising) of impoundments in the Fitzroy River basin, it seems critical to determine whether such habitats are indeed beneficial to this species. Any fish exhibiting the life history traits of delayed maturation and reduced fecundity as shown by S. leichardti will be more vulnerable than early maturing highly fecund species. Scleropages leichardti is exploited by both recreational fishers and the aquarium fish industry (collection of brood stock only), the extent of which is controlled by bag limits and collecting restrictions [1194]. This species is widely translocated in Queensland and the collection of broodstock may also place pressure on this species.

Trophic ecology No quantitative information on the trophic ecology of S. leichardti is available. This species has been described as a surface feeder on insects, crustaceans, frogs and fish [52]. Scleropages jardinii in the Northern Territory has a diet dominated by aquatic insects (54%), terrestrial insects (12%), terrestrial plant material (10%) and fish (9%) [191]. Sambell [1194] believed that S. leichardti were less adept at catching small fish than S. jardinii because of the dorsal orientation of the eyes.

Water regulation has greatly altered the natural flow regimes of the various rivers in the Fitzroy River basin [380]. The extent to which these changes interfere with the reproductive phenology of adults and the development and recruitment success of juveniles remains unknown. Similarly, many aquatic habitats of the river are seriously degraded [380]. Loss of riparian integrity and of bank associated structures (i.e. woody debris, root masses and undercuts) is likely to impact on this species by reducing food supply (i.e. terrestrial insects) and habitat quality. The fact that this species is territorial suggests that localised reductions in abundance are unlikely to be naturally remediated by colonisation in anything but the medium to longer term.

Conservation status, threats and management Scleropages leichardti was listed as Rare in 1993 [1353] and more recently as Lower Risk–Near Threatened [117]. Midgley [942] expressed concern about declining numbers of this species in 1979, but in more recent research in the Fitzroy River, Berghuis and Long [160] believed that the population was secure because the creation of impoundments in the Fitzroy River basin had increased the area suitable for this species. However, Berghuis and Long failed to collect S. leichardti at sites close to those established by Midgley and failed to collect any specimens in the upper Dawson River, although unpublished data apparently suggests that this species still commonly occurs there. Moreover, Midgley’s study included impounded waters and S. leichardti was absent from these habitat types despite being present in earlier years. The two studies are difficult to use to determine the current status of S. leichardti given differences in sampling regime and the manner in which abundances were

Given the endemic status of this species, its phylogenetic significance, and unique biology, we find it very surprising and alarming that so little is known about S. leichardti. This in itself is one of the most serious threats to the continued survival of this species, especially given that it is restricted to one of the most developed river basins in Queensland.

63

Megalops cyprinoides (Broussonet, 1782) Tarpon, Oxeye Herring

37 054001

Family: Megalopidae

anterior margin of the eye. The lower jaw is prominent, its two branches separated by a bony gular plate. Eyes large and covered by an adipose eyelid. Scales large; lateral line well-developed with tubes branching. Pectoral fins set low on profile and with long axillary process. Axillary process also present on pelvic fins. Well-vascularised swim bladder present and lying below and in contact with skull. Tail deeply forked. The extended filament of the dorsal fin is absent in specimens below about 56 mm in length. Colour in life: bluish-green to olive dorsally grading through silver on flanks and white on belly. Fins frequently a pale yellow. Colour in preservative: essentially the same as in life except silver colour of flanks and yellow colour of fins less vibrant.

Description First dorsal fin: 16–21, last ray forming prominent filament; Anal fin: 24–31; Pectoral fin: 15 or 16; Pelvic fin: 10 or 11; Gill rakers on first arch: 15–17 + 30–35; Lateral line scales: 36–40; spines on fins absent [37, 422]. Figure: composite, drawn from photographs of adult and juvenile specimens, Burdekin River; drawn 2002. Megalops cyprinoides is a large fish with a fusiform, compressed body, unlikely to be confused with any other species except in the juvenile stage, when it may be confused with juvenile clupeids. Maximum sizes reported for this species vary from 1000 mm [936, 977] to 1300 mm [37] and as large as 1500 mm [470]. Fish of this size are rarely collected (especially from freshwaters) and maximum sizes of less than 500 mm are more the norm [193, 313]. Coates [313] reports a length/weight relationship for tarpon from the Sepik River of W = 9.96 x 10–6 L3.1; n = 156, r2 = 0.95 where W = weight in g and L = SL in mm. Bishop et al. [193] report a length weight relationship for tarpon in the Alligator River region of W = 2.4 x 10–2 L2.83; n = 155, r2 = 0.833 where W = weight in g and L = CFL in cm.

Megalops cyprinoides produce a leptocephalus-like larva that is flat, band-like, transparent and with a forked tail. Larvae develop teeth early in life at about 11 mm [594, 1347]. Although M. cyprinoides provides excellent sport on light line, opinions vary as to its culinary quality. Early accounts suggest it is good eating but Grant [470] dismisses it as poor quality even after extensive preparation. This species is an important component of the subsistence fisheries of Papua New Guinea [313].

The mouth of M. cyprinoides is terminal, toothless in the adult stage, oblique and large, extending back beyond the

64

Megalops cyprinoides

Megalops cyprinoides has been recorded from most drainages of the eastern side of Cape York Peninsula including the Olive, Claudie, Lockhart, Pascoe, Stewart, Starke, Howick, McIvor, Endeavor, Harmer, Normanby and Annan rivers [571, 697, 1349] as well as some smaller streams (Massey Creek and Three Quarter Mile Creek) [571] and dune lakes of the Cape Flattery region [1101]. Tarpon are found in most rivers of the Wet Tropics region, being been recorded from the Daintree, Saltwater, Mossman, Barron, Russell/Mulgrave, Johnstone, Moresby, Tully/Murray and Herbert River drainages [583, 584, 643, 1177, 1183, 1184, 1185, 1187, 1349]. This species was not collected from the smaller systems of the Hull River, or Maria and Liverpool creeks [1179].

Systematics Megalops cyprinoides has been variously placed within the Elopidae (the giant herrings) or Megalopidae, with the latter being currently accepted [406]. Both families are ancient: Merrick and Schmida [936] suggest that megalopid fossils have been found in Upper Jurassic deposits, Wilson and Williams [1413] list fossil Elopidae in Late Cretaceous deposits, and Long (1733] provides a drawing of a fossilised otolith of the extinct Megalops lissa from the Miocene. The extant Megalopidae contains a single genus comprised of two species: Megalops atlanticus and M. cyprinoides. Phylogenetic relationships among the superorder Elopomorpha, a grouping which includes all teleost fishes that possess a specialised leptocephalus larva (including the Megalopidae and Anguillidae), are discussed in Obermiller and Pfeiler [1437] and Inoue et al. [1434].

Further south, M. cyprinoides has been recorded in the Black Alice River [275], St. Margarets Creek [1053], the Houghton River [255], the Baratta wetlands [1046] and the Burdekin River [587, 591, 847, 940, 1098]. Its distribution in the Burdekin River extends upstream to include the Bowen River although it is no longer common in this system due to the barrier imposed by the Clare Weir. It is still common in wetlands of the Burdekin delta (C. Perna, pers. comm.).

Megalops was first erected by Lacepède in 1803 with the type species for the genus being M. filamentosus (=cyprinoides). Megalops cyprinoides was first described and placed in the genus Clupea by Broussonet in 1782, based on material collected during Captain Cook’s voyages in the Pacific. Not unexpectedly, given the large range of this species, there are numerous other synonyms for M. cyprinoides. These include: M. cundinga Hamilton 1822, M. curtifilis Richardson 1846, M. indicus Valenciennes 1847, M. macropthalmus Bleeker 1851, M. macropterus Bleeker 1866, M. oligolepis Bleeker 1866, M. setipinnis Richardson 1843, and M. stagier Castelnau 1878.

Megalops cyprinoides has been recorded from the Pioneer River [1081] and the Shoalwater Bay region [1328]. Tarpon were formerly widespread in the Fitzroy River but the numerous impoundments on this system have reduced its present distribution [659, 942, 1274]. Impoundments have similarly affected this species in the Burnett River [11, 700, 1173, 1276]. Tarpon have been recorded from the Burrum, Mary, Noosa, Brisbane and Logan-Albert rivers [168, 643, 701, 702, 881, 1349] and from Moreton Bay [881, 969] and North Stradbroke Island [988]. This species has been recorded from artificial habitats (e.g. golf course lakes) in the Gold Coast region of southern Queensland (J. Tait, pers. comm.).

Distribution and abundance Megalops cyprinoides is a very widespread species, its range extending from east Africa to South-east Asia including Japan, Australasia and some islands of the west Pacific. The Australasian distribution is similarly large. This species occurs in rivers of both northern and southern Papua New Guinea and Irian Jaya [37, 42, 46, 51, 316, 495]. The Australian range includes rivers of the Kimberley region [45], being recorded from the Fitzroy [620, 779], Carson and Ord rivers [620]. This species is widespread across the Northern Territory and has been recorded from the Victoria [946] and Daly [945] river systems, drainages of the Alligator Rivers region [193, 772, 1064, 1416], and drainages of Arnhem Land [944]. Tarpon have been recorded from the Leichhardt River in the Gulf region of Queensland [1093] and is probably present in most rivers of this region. Rivers draining the western side of Cape York Peninsula in which M. cyprinoides has been collected include the Embley, Mitchell, Coleman, Ducie, Watson, Archer, Edward, Holroyd, Wenlock and Jardine rivers [41, 571, 643, 1349]. Its distribution in the Mitchell River extends as far upstream as the Walsh River [1186]. Tarpon have also been recorded from swamps and lagoons of the Weipa area [571].

Lake [748] lists M. cyprinoides as a member of the freshwater fish fauna of New South Wales and later suggested that it was restricted to the northern rivers of the state [755]. Krefft reported catching M. cyprinoides on fly in the Hawkesbury River in the early 1860s [741]. It appears to be uncommon or no longer present in New South Wales as it was not collected in the recent comprehensive NSW Fisheries survey [554]. Macro/meso/microhabitat use The life history of Megalops cyprinoides is complex, involving a variety of different habitats at different life stages. The habitat requirements of the larval and juvenile forms are more fully described in the sections on reproductive and movement below. Subadult and early-maturing adult

65


Table 1. Physicochemical data for the tarpon Megalops cyprinoides. Summaries are drawn from two separate studies undertaken in northern Australia [193, 697]. Note the difference in units used to described turbity.

forms are found in a variety of freshwater habitats and may penetrate many hundreds of kilometres upstream. Roberts [1147] reported M. cyprinoides 905 km upstream in the Fly River of Papua New Guinea and Coates [313] reports it present 530 km upstream in the Sepik River (although it may have been present further upstream where little sampling was undertaken). Similarly extensive upstream distributions have also been reported for Australian rivers (see above). In the Sepik River, tarpon have been recorded from the main river channel, major lowland tributaries, oxbow floodplain lakes and on the floodplain itself [313]. However, it was reported that the floodplain was not the preferred habitat, that tarpon were absent from low order streams and deep water habitats were preferred. In contrast, tarpon in the Alligator Rivers region have been recorded from escarpment habitats near the headwaters. The majority of fish collected by Bishop et al. [193] were from lentic habitats such as floodplain, lowland muddy and corridor lagoons as well as the main channel. These authors noted that M. cyprinoides was most abundant in lagoons with plentiful submerged and floating-attached macrophytes, but that at times would move out of such habitats to feed extensively on migrating rainbowfishes. Bishop et al. [193] noted a preference for deeper waters also.

Parameter

Min.

Max.

Mean

Alligator Rivers region (n = 20) Water temperature (°C) 23 34 Dissolved oxygen (mg.L-1) 1.9 9.7 pH 5.3 9.1 Conductivity (µS.cm-1) 2 200 Turbidity (cm) 4 270

86

Normanby River floodplain (n = 12) Water temperature (°C) 22.9 29.4 Dissolved oxygen (mg.L-1) 1.1 7.1 pH 6.1 8.2 Conductivity (µS.cm-1) 9.8 391 Turbidity (NTU) 2.1 8.1

23.9 3.6 7.1 220.6 5.3

29.8 6.2 6.5

with dissolved oxygen levels of 0.2 mg O2.L–1 [583]. This species is obviously very tolerant of low levels of dissolved oxygen primarily because of its ability to extract oxygen directly from the atmosphere. Megalops cyprinoides was not recorded in a large fish kill in Magela Creek for which hypoxia was implicated as the primary cause [187] and Bishop et al. [193] attributed its survival to its ability to breath air.

Coates [313] observed that tarpon fed extensively underneath floating mats of Salvinia. This same behaviour has been observed in floodplain habitats of the Burdekin River delta (C. Perna, unpubl. obs.). Floodplain water bodies experience precipitous declines in water quality, especially dissolved oxygen levels, when floating weeds such as Salvinia and water hyacinth (Eichhornia crassipes) proliferate. In such cases, tarpon (which is a facultative airbreather), and other species capable of accessing the relatively well-oxygenated layer of surface water (e.g. the alien Gambusia holbrooki), are the dominant species.

Air breathing in M. cyprinoides has not been studied but has been for M. atlanticus [444], a summary of which is included below. This species is a bimodal breather with gas exchange occurring across the walls of the swim bladder. Species of Megalops are the only marine nektonic species to use bimodal breathing and the only marine fishes to use respiratory gas bladders. The wall of the gas bladder in M. atlanticus has four rows of highly vascularised tissue. The extent of vascularisation of the bladder in M. cyprinoides is greater in fish collected from hypoxic waters than in welloxygenated waters (C. Perna, pers. comm.). In M. atlanticus, air is expelled from beneath the opercula as the fish rises to the surface. If denied access to air after exhalation, M. atlanticus cannot maintain neutral buoyancy. Air is inhaled by expansion of the buccal and opercular cavities, accompanied by abduction of the gular plate. The inhaled air is forced into the gas bladder, after the mouth closes, by compression of the buccal and opercular cavities. This behaviour of rising to the surface and gulping air has been termed ‘rolling’ and has been observed to occur in leptocephalus-like larvae also [594]. Bishop et al. suggested that rolling was more frequently observed when oxygen levels were low [193]. Air breathing, or at least the ‘rolling’ behaviour associated with air breathing, has been observed in larval M. cyprinoides also [302].

Environmental tolerances Megalops cyprinoides is a tropical species and the water temperatures given in Table 1 reflect this distribution. However, given that its distribution extends down the east coast to at least Brisbane, this species may be able to tolerate lower water temperatures than indicated here. The closely related M. atlanticus has been recorded from temperatures as low as 12°C [444]. Megalops cyprinoides has been recorded across a wide range of dissolved oxygen concentrations and is tolerant of hypoxic conditions (Table 1). Oxygen levels in floodplain habitats of the Burdekin River delta, in which this species is common, frequently descend as low as 0.2–1% saturation (C. Perna, pers. comm.). Hogan and Graham recorded this species in wetlands of the Tully Murray River

66

Megalops cyprinoides

The related species M. atlanticus is not an obligate air breather, surviving for at least two weeks when denied access to air. This species will however, breath air in normoxic waters, presumably to maintain buoyancy [444]. Air breathing frequency in M. atlanticus increases with increasing temperature and decreasing oxygen saturation. At temperatures above 29°C, the frequency of air breathing is independent of oxygen levels [444]. The frequency of air breathing in M. atlanticus increases with increasing sulphide concentrations also. High levels of sulphide inhibit respiration by disrupting the function of both haemoglobin and cytochrome c. Megalops atlanticus is tolerant of very high levels of sulphide (240 µmoles.L–1) when air breathing frequency is higher than that recorded for anoxic conditions.

probably achieves sexual maturity in the second year of life when lengths in excess of 300 mm are attained. Juvenile individuals smaller than that observed by Bishop et al. [193] have been recorded from freshwaters elsewhere. Taylor [1304] reports the presence of a 66 mm juvenile in a freshwater lagoon with connection to an estuarine mangrove habitat in Arnhem Land. Small fish of this size have been collected from lagoons of the Burdekin River delta also (C. Perna, pers. comm.). In an early dry season survey of the fishes of Gunpowder Creek, approximately 200 km from the river mouth of the Leichhardt River, we collected numerous M. cyprionoides between 25–50 mm SL [1093]. Obviously such small fish must be capable of rapid extensive movement. The spawning habitat of M. cyprinoides is unknown other than it occurs in the near-shore marine or estuarine environment. This species produces a leptocephalus-like larva that undergoes most of its development in saline supralittoral tidal swamp environments. Opinions differ as to whether the leptocephali actively migrate into such habitats [29] or are simply passively carried in on rising tides [302], however Wade [1347] demonstrated that postlarvae were capable of independent movement and migration. Davis [370] studied the temporal dynamics of supralittoral swamp fishes near Darwin and found M. cyprinoides to be very common, accounting for 13% of all fish collected during the early wet season. Leptocephali were present in the tidal swamp from October to March, although peak numbers occurred in December and January. Initially, numbers appeared greatest during the full moon phase until numbers increased sufficiently to swamp any apparent temporal variation in recruitment. Juvenile fishes (i.e. those having undergone metamorphosis) were, in contrast, present only from December onwards and abundances levels were correlated with tidal phases. Megalops cyprinoides was the most numerically dominant species during neap tides and was amongst the top three species with respect to length of residency. Russell and Garrett [1174] also found M. cyprinoides larvae during December in supralittoral swamps of the Norman River estuary, northern Queensland; they were uncommon however.

Megalops cyprinoides has been recorded across a reasonably wide range of pH (5.3 to 9.1) (Table 1). We have collected adult M. cyprinoides from dystrophic dune lakes of the Cape Flattery region, where pH levels may frequently be in the range of 4–5 [1101]. The conductivity levels depicted in Table 1 indicate fresh waters but given that both larvae and adult tarpon occur in marine and estuarine environments, salinity tolerance must extend across a wide range. Larval tarpon are able to withstand abrupt transfer from brackish to freshwater but acclimation is generally a gradual process [29]. The range of water clarity across which it has been collected suggests that tarpon are tolerant of elevated turbidity. However, the extent to which high turbidity interferes with the ability of tarpon to locate prey remains unknown. The conditions in which M. cyprinoides has been recorded and the tolerances inferred from these conditions plus insights gained from comparison with M. atlanticus, suggest that tarpon are hardy and well-adapted to inhabit seasonal wetlands that experience substantial fluctuations in dissolved oxygen, turbidity, pH and sulphide levels. Reproductive biology Detailed information on many aspects of the reproductive biology of Megalops cyprinoides is lacking, principally because this species moves out of freshwater environments to spawn. Bishop et al. [193] records some information on reproductive biology of this species, however sample sizes were not large. Most fish collected were immature, with the length frequency distribution being essentially unimodal with a mean of 246 mm CFL. The smallest fish collected by these authors was 137 mm CFL occurred in the mid-wet and mid-dry seasons, suggestive of a recruitment pulse occurring during the mid-wet when estuarine connections occur. Male maturation commenced at the end of the dry season. Based on growth estimates provided by Alikunhi and Nagaraja Rao [29] and Bishop et al. [193], M. cyprinoides

Fecundity estimates are unavailable for M. cyprinoides. Hollister [594] cites data for a 56 kg M. atlanticus producing 12 million small (0.67–0.75 mm), non-buoyant, nonadhesive eggs. Given that M. cyprinoides does not reach such large size, it is unlikely to be a fecund as its congener. Nonetheless, this species probably produces hundreds of thousands of small eggs similar to M. atlanticus. Estimates of reproductive effort in M. cyprinoides indicate a maximum female GSI of about 7% [313]. Bishop et al. [193]

67


Table 2. Life history data for the tarpon Megalops cyprinoides. Age at sexual maturity (months)

12–24 months

Minimum length of ripe females (mm)

Alligator Rivers region – 300 mm CFL (estimate only) [193] Sepik River – 410 mm female recorded with developed gonads [313]

Minimum length of ripe males (mm)

Alligator River region – 300 mm [193]

Longevity (years)

?

Sex ratio (female to male)

?

Occurrence of ripe fish

?


Summer wet season [193] India – suggestions of a year-round breeding phenology with a peak during the monsoonal months [1347]


?


?


7% [313]


45 years [1244]

Sex ratio

A. australis – ? Females often more abundant in freshwaters than males [936, 1360] A. reinhardtii – ? Females often more abundant in freshwaters than males [936, 1360]


A. australis – ? Outward migration to spawning grounds occurs over an extended period during summer and autumn; spawning possibly occurs between June and September [645] A. reinhardtii – ? Outward migration to spawning grounds occurs over an extended period during summer and autumn; timing of spawning is unknown


?


A. australis – ? Cues for migration to spawning grounds probably involve a combination of biological (e.g. body size, lipid concentration, stage of gonadal development) and environmental (temperature, day length, discharge) factors


A. australis – ? Up to 3.5% in migrating eels [891, 1324, 1325]


?

Fecundity (number of ova)

A. australis – ? 1.5–3 million eggs in migrating eels [1324] A. reinhardtii – ? ‘several million’ eggs [936, 1393]

Fecundity/length relationship

?

Egg size

A. australis – Intravovarian eggs of migrating eels 0.22 mm diameter [891, 1324, 1325], 1.55 mm post-fertilisation [819]

Frequency of spawning

Anguilla spp. – Adults probably spawn once and then die [891, 1308]

Oviposition and spawning site

Anguilla spp. – ? Probably in the Coral Sea and at considerable depths [891, 1308]

Spawning migration

Anguilla spp. – Facultative catadromy (see text for details)

Parental care

Anguilla spp. – None known

Time to hatching

A. australis – ~45 hours [819]

Length at hatching (mm)

A. australis – ~2.5 mm TL [819]

Length at feeding

?

Age at first feeding

?

Duration of larval development

A. australis – Variable, mean 153.4 days ± 16.8 SD for specimens from Albert River [912] A. reinhardtii – Variable, mean 124 days ± 15.8 SD for specimens from Albert River [912]

Length at metamorphosis

A. australis – 47–73 mm TL (early-stage glass eels) [401] A. reinhardtii – 46–65 mm TL (early-stage glass eels) [401]

87


substrate [936]. Some anguillids also show marked diel variation in activity; A. australis and A. dieffenbachii in New Zealand were demonstrated to be nocturnally active (associated with foraging) and to seek refuge within the substrate during the day [453, 1191].

Collins [769] recommended that mean and maximum velocities through fishways should not exceed 0.30 and 0.75 m.sec–1, respectively. To further facilitate passage, several researchers [747, 769, 954, 1275, 1277] have advocated the inclusion of roughening substrates within the cells of existing and future vertical slot fishways, and the construction of eel passes that may specifically permit the passage of glass eels and elvers.

Trophic ecology Anguilla australis is a carnivorous species, relying on generally small-sized food items as juveniles and switching to larger diet items and a more diverse array of food types with growth (Fig. 5). The diet of elvers and subadults (≤200 mm TL) is dominated by aquatic insects (86.0%); small amounts of molluscs (11.0%) and macrocrustaceans (3.0%) are also consumed. Adult fish consume a wide range of food types, probably reflecting the wide array of habitats in which this large mobile predator can forage. Aquatic insects (30.0%), fish (22.9%), and material foraged from the water’s surface (terrestrial vegetation (7.4%), terrestrial invertebrates (4.5%) and terrestrial vertebrates (3.1%)) were the most important diet items consumed by adults. Large crustaceans (6.5%), molluscs (5.8%, aquatic algae (5.1%) and microcrustaceans (4.4%)

A number of studies in south-eastern Australia [175, 1208, 1244], have described a trend of decreasing abundance and concomitant increasing size and age of A. australis and A. reinhardtii with increasing distance from the sea, although this is less evident in rivers and streams of south-eastern Queensland [1093]. This pattern may be due to an avoidance of habitats characterised by low permanence, lower winter temperatures and reduced food availability (in the form of catadromous forage fish such as galaxiids) in high elevation upland streams [1, 1208, 1244]. Predation by larger eels may be important also. Migrating eels must pass through a series of environmental ‘filters’ imposed by physical barriers, sub-optimal habitats and biological interactions on their progressive movement upstream. Little information is available concerning the local movement patterns of Australian eels during the long period of residence in freshwaters. Beumer [175] undertook a study of the local movement of A. australis in a lentic freshwater wetland of coastal Victoria. Of 1051 eels tagged and released, 194 were recaptured over the two-year study period. The maximum linear distance travelled was 3715 m for two individuals at liberty for 36 and 79 days, respectively. Three individuals recaptured after just 24 h had moved between 145 and 200 m. There was no relationship between eel size and number of days at liberty or distance moved. Instead, movement activity was closely related to variations in water temperature and feeding. The majority of individuals exhibited limited movement (77% of fish moved 400 m or less within 150 days of liberty) leading Beumer [175] to estimate a home range of around 400 m for this species. Pease et al. [1438] concluded that A. reinhardtii has a very restricted home range of 300 m or less. Beumer [175] and others (see Tesch et al. [1308]) have suggested that eel home range size is strongly related to the size of the waterbody in which they occur. The presence of large eels may influence the movement of smaller eels. In a defaunation experiment in river reaches of the Wet Tropics region, the removal of a large individual was usually accompanied by the subsequent appearance of a number of smaller eels. Interestingly, the combined biomass of these interlopers was often very similar to the biomass of the eel removed [1093]. Movement activity may be much reduced at low temperatures (below 10°C) when eels are thought to become dormant, burying themselves in the

A. australis juveniles (n = 24) Macrocrustaceans (3.0%) Molluscs (11.0%)

Aquatic insects (86.0%)

A. australis adults (n = 513) Unidentified (1.9%)

Terrestrial invertebrates (4.0%) Terrestrial vertebrates (3.1%)

Fish (22.9%) Terrestrial vegetation (7.4%) Detritus (0.1%) Aquatic macrophytes (0.5%) Algae (5.1%)

Other microinvertebrates (0.1%) Microcrustaceans (4.4%)

Macrocrustaceans (6.5%)

Molluscs (5.8%) Other macroinvertebrates (8.3%)


Figure 4. The mean diet of Anguilla australis juveniles (≤~200 mm SL) and adults (>~200 mm SL) (sample sizes for each age class are given in parentheses). Data derived from stomach contents analysis of fish from New South Wales [1133, 1134], Victoria [175, 595] and Tasmania [758, 1244].

88

Anguilla australis, Anguilla obscura, Anguilla reinhardtii

vegetation (7.7%) and terrestrial invertebrates (4.3%) were also consumed. Bunn et al. [248] noted that the isotopic signature of a small number of eels from Bamboo Creek, a degraded lowland tributary of the Johnstone River, indicated a diet dominated by terrestrial insects. Anguilla reinhardtii is likely to be an important top predator in many aquatic environments of north-eastern Australia, given its size, high local density and predatory habit. Beumer [175] observed that A. reinhardtii in a coastal Victorian wetland fed throughout the year and that feeding activity was greatest in spring and summer. Beumer [175] reported that A. reinhardtii was cannibalistic and Sloane [1244] observed the remains of A. australis in the stomachs of A. reinhardtii and further suggested that

also formed minor components of the diet of this species. Anguilla australis has been reported to go without food for up to 10 months and may cease feeding at low water temperatures [936]. Beumer [175] observed that A. australis in a coastal Victorian wetland fed throughout the year but that feeding activity was greatest in spring and summer. Sagar and Glova [1191] reported diel feeding activity in A. australis in New Zealand: individuals of all sizes fed between dusk and dawn irrespective of size, but smaller individuals were more crepuscular. Beumer [175] reported the presence of unidentified eels in the diet of A. australis in coastal Victoria, and suggested that cannibalism may be a feature characteristic of eel species. Very little information is available concerning the diet of A. obscura but it is likely to be very similar to that observed for A. reinhardtii and A. australis. The diet of three individuals from the Wet Tropics region of northern Queensland (330–400 mm SL) comprised terrestrial invertebrates (33.0%), molluscs (21.0%), aquatic insects (13.0%) and unidentifiable material. These data most likely do not adequately represent the true diet of A. obscura.

A. reinhardtii juveniles (n = 76) Fish (0.8%) Macrocrustaceans (3.4%)

Unidentified (3.0%) Terrestrial invertebrates (2.7%) Detritus (0.5%) Aerial aq. Invertebrates (0.5%)

Unidentified (33.0%) Molluscs (21.0%)


A. reinhardtii adults (n = 321)


Unidentified (0.9%)

Terrestrial invertebrates (4.3%) Terrestrial vertebrates (0.7%) Terrestrial vegetation (7.9%)

Fish (28.2%)

Detritus (0.5%) Aquatic macrophytes (0.1%) Algae (4.6%)

Terrestrial invertebrates (33.0%)

Figure 5. The mean diet of Anguilla obscura. Data derived from stomach contents analysis of three individuals from the Wet Tropics region of northern Queensland [1097]. Aquatic insects (30.3%)

The diet of A. reinhardtii is generally similar to that of A. australis with carnivory and ontogentic variation features of the diet (Fig. 6). The diet of elvers and subadults (≤200 mm TL) is dominated by aquatic insects (89.2%). Only small amounts of microcrustaceans (3.4%), terrestrial invertebrates (2.7%) and fish (0.8%) are consumed occasionally. Adults prey upon a wide range of food types, including macroscopic items such as fish (28.2%), macrocrustaceans (21.4%) and terrestrial vertebrates (0.7%). Aquatic insects (30.3%) were an important component of the diet of this species and aquatic algae (4.6%), terrestrial

Macrocrustaceans (21.4%) Molluscs (0.7%)

Other macroinvertebrates (0.4%)

Figure 6. The mean diet of Anguilla reinhardtii juveniles (≤~200 mm SL) and adults (>~200 mm SL) (sample sizes for each age class are given in parentheses). Data derived from stomach contents analysis of fish from eastern Cape York Peninsula [599, 697, 1099], the Wet Tropics region of northern Queensland [1097], central Queensland [1080], south-eastern Queensland [80, 205], New South Wales [1133, 1134], Victoria [175] and Tasmania [1244].

89


species for export and aquaculture operations is becoming increasingly prevalent in eastern Australia. The world aquaculture production of freshwater anguillids is currently thought to exceed 216 000 t per annum, worth over US$915 million and is based largely on the culture of the European eel A. anguilla, and the Japanese eel, A. japonica [462]. Despite a decline in eel stocks in many areas over recent years due to a combination of overfishing and environmental changes impacting on recruitment [289, 290], commercial eel production has increased substantially due in part to improved aquaculture techniques and sourcing of alternative seedstock [462, 464]. Interest in the potential for eel culture in Australia has increased over recent years [462, 464]. Currently, eel production is based on A. australis and A. reinhardtii and total production is estimated as 5000–7000 t per annum, worth AUD$4–6.5 million (as at 2002) [462]. The vast majority of production in Australia comes from the harvest of elvers and subadults from wild riverine fisheries. These life stages are then transferred to semicontrolled lentic waterbodies (e.g. lakes, swamps and wetlands) where they are grown under natural conditions until they reach a marketable size and are exported to Europe and Asia [464, 1240].

interspecific competition for food and space between these species may be intense at times in the Douglas River, Tasmania. The frequent observation of eel bite marks on eels in the Wet Tropics and the observation of replacement by smaller eels following defaunation, also support suggestions that eels compete intensely for food and space. Conservation status, threats and management Anguilla australis, A. obscura and A. reinhardtii are listed as Non-Threatened by Wager and Jackson [1353]. We suggest that these listings remain valid on the basis of existing data. The status of A. megastoma in north-eastern Queensland is uncertain as a single individual has been collected from the Daintree River only [1085, 1087]; the presence of this species in north-eastern Australia requires confirmation. The widespread distribution of north-eastern Australian eels and their complex life cycle: involving marine and freshwater stages, distinct migration phases, remote spawning grounds, extended larval stage and long period to sexual maturity suggests that they may face and be vulnerable to a range of threats throughout the long lifespan. The frequently high local abundance of these largebodied species in freshwaters, together with their usual position at the top of the aquatic food chain, indicates that eels may play an important role in the structuring of fish and aquatic invertebrate communities and the transfer of energy within trophic levels at local scales. Although it is premature to label eels as ‘keystone’ species, it is difficult to conclude that the presence of a 20 kg, highly mobile predator ranging over 400 m of stream, is without effect. Any natural or anthropogenic impacts on the distribution and abundance of eels may have far-reaching consequences for other aquatic and semi-aquatic species.

Recent interest has focused on the potential for harvesting of wild glass eels for subsequent grow-out in aquaculture facilities [462, 464]. Recent major studies by Gooley et al. [464] and Gooley and Ingram [462] have attempted to evaluate the status of glass eel stocks in eastern Australia, but the high spatial and temporal variability in glass eel recruitment to eastern Australian estuaries has precluded a reliable estimate of the total eel stocks in this region [462]. Effective informed management of the glass eel fishery in Australia is also hampered by an absence of fundamental information on basic life-history attributes of Australian anguillids, an absence of long-term data on eel stocks in Australian waters and hence the ability to accurately assess the determinants of variability in glass eel recruitment, and ignorance about the role that eels play in the ecology of rivers.

The movement of millions of glass eels and elvers across marine/estuarine/freshwater ecosystem boundaries represents an enormous transfer of marine-derived carbon, the significance of which is unknown but potentially high. The migration of adult eels out of freshwaters and estuaries represents a similarly large transfer of energy across ecosystem boundaries. Despite the undoubted climbing ability of eels, the imposition of barriers to movement by structures such as dams, weirs and tidal barrages is an important determinant of eel distribution and abundance. Changes to the natural flow regime (e.g. timing, magnitude frequency and duration of flows), independent of the imposition of barriers, may also impact on eels by affecting possible cues for downstream migration of adults, and cues for the recruitment of glass eels into estuaries and the upstream migration of glass eels and elvers to freshwaters.

It has been suggested that commercial harvesting of particular eel species may be undertaken with minimal environmental impact in areas where a disproportionate ratio of migration of A. australis to A. reinhardtii into estuaries occurs, compared with recruitment into the catchment proper. Areas at the extremes of the natural range of each species have been suggested as candidate locations for intensive eel harvesting (e.g. south-eastern Queensland in the case of A. australis). Although, numbers of A. australis recruiting to the adult population in freshwaters of south-eastern Queensland may represent only a very small proportion of the number of glass eels attempting to

Overfishing is one of the most serious threats to eel populations in Australia as commercial harvesting of several

90

Anguilla australis, Anguilla obscura, Anguilla reinhardtii

biodiversity [184, 912]. Large quantities of small-bodied and juvenile fish species (some of commercial importance), cructaceans and other aquatic invertebrates are frequently caught during passive netting of glass eels and mortalities are reported to often be very high [912]. Semiaquatic reptiles and mammals and birds are also occasionally captured during eel harvesting [184]. Options for bycatch reduction are the subject of continuing research and management planning [22, 462].

do so, it would seem that additional impact on glass eel abundance in estuaries by harvesting would further decrease the likelihood that A. australis will enter freshwaters. Clearly further evaluation and long-term monitoring are required before it could be concluded that commercial harvesting of glass eels could be undertaken in an ecologically sustainable manner in these areas or elsewhere. Eels have traditionally been an important source of food for the indigenous rainforest people of the Wet Tropics region. Concern about a decline in eel numbers over the last 50 years has been expressed to the senior author by some elders. That such concern exists in the absence of widespread harvesting of glass eels in this region suggests that other factors may currently place pressure on these species.

The wide distribution of Australian eels in the Asia-Pacific region necessitates the coordinated management of eel stocks across state and national boundaries, an imperative facilitated by the establishment in 1997 of the Australia and New Zealand Eel Reference Group (ANZERG), comprised primarily of Government aquaculture and fisheries representatives [914]. It is hoped that ANZERG will help to ensure conservation and management of South Pacific eel stocks in an environmentally sustainable manner.

Bycatch of aquatic and semi-aquatic biota during intensive glass eel harvesting in estuaries and lowland rivers is another potential source of impact on aquatic ecosystem

91

Nematalosa erebi (Günther, 1868) Bony bream, Bony herring, Australian river gizzard shad

37 085019

Family: Clupeidae

collected by seine-netting but also list a maximum Total Length of 419 mm (in their Table 3). A maximum length of 350 mm SL was recorded by us in a sample of 3123 fish from the Burdekin River [1093]. Note that the type of length measurement used varies between studies. By applying conversion factors (1.14 for CFL, 1.23 for SL) [422], estimates of maximum total length for the Northern Territory and Burdekin River populations of 410 mm and 430 mm may be made. These data suggest little difference in maximum size across this species’ range.

Description Dorsal fin: 14–19; Anal: 17–27; Pectoral: 14–18; Pelvic: 8; Vertical scale rows: 40–46. All fins spineless. Last ray of dorsal fin elongated to form a long filament in larger fish. Distinct line of scutes present on ventral margin, particularly between pelvic and anal fins. Head scaleless. Snout blunt and rounded, mouth small, lower jaw with central notch that fits a central groove in the upper jaw on closure. Body deep and laterally compressed. Scales cycloid, easily dislodged [52, 936]. Nematalosa erebi is easily recognised and unlikely to be confused with any other species except in northern lowland rivers that may be colonised briefly by other clupeid species. The sexes are externally indistinguishable. Figure: composite, drawn from photographs of adult specimens, 221–262 mm SL, Burdekin River, November 1991; drawn 2002.

Bishop et al. [193] list the relationship between length (CFL in cm) and weight (in g) as: W = 0.012 L3.12; n = 845, r2 = 1.0, p

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