The Life and Times of the Murray Cod

By Paul Humphries

The Murray cod is Australia’s largest and most iconic freshwater fish. Tales of the species have long been part of Australian folklore and this book describes its history, biology, cultural significance and conservation.

The Life and Times of the Murray Cod reveals the many roles the species has played throughout the history of the continent, from its place at the heart of the Aboriginal creation story of the Murray River, its role as a food source for explorers surveying inland Australia in the early 1800s, to it forming the basis of a commercial fishing industry up to the early 2000s.

Living for upwards of half a century and growing to astonishing sizes, today the Murray cod is a hugely popular target for recreational fishing, but its future is anything but assured. In the face of climate change, river management and fishing pressure, much needs to be done to ensure this extraordinary fish swims confidently into the future.

The Life and Times of the Murray Cod draws on historical, anecdotal and scientific sources to reveal what makes this remarkable species so special, and will appeal to fishers, natural resource managers, conservationists and any reader interested in natural history.

• Language: English
• Publisher: CSIRO PUBLISHING
• Release date: May 1, 2023
• ISBN: 9781486312344

Paul Humphries

Paul Humphries is a river ecologist and academic with 40 years’ experience in research in many parts of Australia and overseas. Paul co-edited Ecology of Australian Freshwater Fishes (CSIRO Publishing) with Keith Walker in 2013, which won the 2013 Royal Zoological Society of NSW Whitley Medal for outstanding zoological publication.

Book preview

halftitle

To Keith Walker and Sam Lake – your friendship,

science and humanity inspire me every day.

title

© Paul Humphries 2023

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 owner. Contact CSIRO Publishing for all permission requests.

Paul Humphries asserts their right to be known as the author of this work.

A catalogue record for this book is available from the National Library of Australia.

ISBN: 9781486312320 (pbk)

ISBN: 9781486312337 (epdf)

ISBN: 9781486312344 (epub)

How to cite:

Humphries P (2023) The Life and Times of the Murray Cod. CSIRO Publishing, Melbourne.

Published by:

CSIRO Publishing

Private Bag 10

Clayton South VIC 3169

Australia

Telephone: [phone]

Email: [e-mail]

Website: www.publish.csiro.au

Sign up to our email alerts: publish.csiro.au/earlyalert

Front cover: The Murray Cod Perch, Oligorus Macquariensis [Maccullochella peelii] (illustration by Arthur Bartholemew). From McCoy, F. (1885) Prodromus of the Zoology of Victoria. Melbourne, Robert S. Brain

Back cover: Old central Victorian map of the goldfields (1851). From The Illustrated Atlas, And Modern History Of The World Geographical, Political, Commercial & Statistical, edited by R. Montgomery Martin, Esq. illustration by J. Raspkin, H. Warren, J. Rogers, J. and F. Tallis, London and New York (David Rumsey Historical Map Collection); Aboriginal Australian man spearfishing from canoe (illustration by Tommy McRae). 1881, National Library of Australia.

Edited by Adrienne de Kretser, Righting Writing

Cover design by Cath Pirret

Typeset by Envisage Information Technology

Index by Indexicana

Printed in China by 1010 Printing International Ltd

CSIRO Publishing publishes and distributes scientific, technical and health science books, magazines and journals from Australia to a worldwide audience and conducts these activities autonomously from the research activities of the Commonwealth Scientific and Industrial Research Organisation (CSIRO). The views expressed in this publication are those of the author(s) and do not necessarily represent those of, and should not be attributed to, the publisher or CSIRO. The copyright owner shall not be liable for technical or other errors or omissions contained herein. The reader/user accepts all risks and responsibility for losses, damages, costs and other consequences resulting directly or indirectly from using this information.

CSIRO acknowledges the Traditional Owners of the lands that we live and work on across Australia and pays its respect to Elders past and present. CSIRO recognises that Aboriginal and Torres Strait Islander peoples have made and will continue to make extraordinary contributions to all aspects of Australian life including culture, economy and science. CSIRO is committed to reconciliation and demonstrating respect for Indigenous knowledge and science. The use of Western science in this publication should not be interpreted as diminishing the knowledge of plants, animals and environment from Indigenous ecological knowledge systems.

The paper this book is printed on is in accordance with the standards of the Forest Stewardship Council® and other controlled material. The FSC® promotes environmentally responsible, socially beneficial and economically viable management of the world’s forests.

Jan23_01

Foreword

Minda W. Murray, Yorta Yorta and Duduroa

I remember Christmas when I was seven years old. My family were camped up on ‘the narrows’, in the Barmah Forest on the Murray River. Being Christmas and the height of summer, it was stinking hot. Our little camp was nestled under the red gums and wattles, with a gentle breeze blowing through off the river, a slight relief from the harshness of the season. My dad was there, a proud Aboriginal man. I remember his excitement upon arriving at the camp, ‘gonna catch a big cod, good snags here’. I watched him for a whole week. His ritual of getting up in the morning, baiting a line, negotiating with some unknown force whether to put worms, cheese or bardi grub on the hook. ‘What are the cod biting on today?’ he pondered. He would sit for hours on end, meditating, listening for the bells attached to his fishing rod – the ringing was a sure sign that he had a bite, and maybe the all-important cod. He taught me that summer how to set up a rod to catch my own fish. He even taught me how to make sinkers, digging little holes in the earth with a spoon and filling them with melted metal. It used to mystify and puzzle me, his (and a lot of my family’s) obsession with catching this fish. It was a seemingly religious practice for him and my uncles and some aunties.

Now that I am older and writing the foreword for this book, I realise the significance of that summer. My father was passing down a ritual. He was instilling in me thousands of years of cultural practice, what his father and his grandfather and the ancestors before them, had shared together. It was survival, and it was spiritual. What is special about this species of fish is that its significance straddles cultures, across lifespans, through generations. Nowadays, this species mystifies and captures the interest of countless people from all walks of life, mostly for recreational fishing but also for study, cuisine, environmental indicators of river health and even for beloved pets. There are few species in Australia that are so dynamic and central to our modern Australian culture as the cod.

This book is authored by a friend of mine, one of my lecturers from my undergraduate days of university over a decade ago. Even back then, Paul’s passion for this species shone through. I wish to congratulate him and extend my gratitude to him and all who contributed to this publication. This book, with its excellent contributions by some of the most passionate and knowledgeable authors on the subject, takes the reader on an important journey of understanding. It looks at the origins, biology, life characteristics, history and significance of the Murray cod. It also looks to the future. The Murray cod faces many challenges, including climate change and river regulation. This fish – the Murray cod – has been the creator, lifegiver, spiritual being and carer, for my people for thousands of years. It is now all these things for all of us. For everyone who lives in Australia now. I urge the reader to go on this journey with us, into the past and into the future, and to share in our knowledge of this beautiful and all-important species, the great Murray cod.

Contents

Foreword

Minda W. Murray

Cultural sensitivity warning

Preface

Acknowledgements

About the contributors

An introduction to the life and times of the Murray cod

Part I: Origins

1. In the beginning: the origins of the Murray cod

Part II: Biology

2. Next generation: the spawning of Murray cod

3. The young and the restless: the early life of the Murray cod

4. ‘A lazy fish’: diet, habitat and movement of adult Murray cod

5. From little fish big fish grow: age, growth and the biggest Murray cod

Part III: People and Murray cod

6. Murray cod and First Nations people

Minda W. Murray and Paul Humphries

7. European encounters: colonial explorers and early contact with the Murray cod

8. Fish in abundance: the Murray cod is introduced to Western science

Part IV: Fisheries

9. Land, sheep and fish: settlement and the origins of the Murray cod commercial fishery

Colour plates

10. Gold-fish: the gold rush and the commercial Murray cod fishery

11. ‘A trade of extermination’: overfishing and Aboriginal loss

12. Recreational fishing

Katherine E. Doyle, Cameron G. McGregor and Paul Humphries

Part V: Conservation and the future

13. A fish in troubled waters

14. Past and future conservation of the Murray cod

15. Epilogue

References

Index

Cultural sensitivity warning

Readers are warned that there may be words, descriptions and terms used in this book that are culturally sensitive, and which might not normally be used in certain public or community contexts. While this information may not reflect current understanding, it is provided by the author in a historical context.

This publication may also contain quotations, terms and annotations that reflect the historical attitude of the original author or that of the period in which the item was written, and may be considered inappropriate today.

Aboriginal and Torres Strait Islander peoples are advised that this publication may contain the names and images of people who have passed away.

Preface

This book is devoted entirely to an extraordinary Australian fish – the Murray cod. The fish is remarkable because of its enormous size. But as you will learn throughout The Life and Times of the Murray Cod, there is much more to the fish than just its size. It has swum in Australian rivers for eons, persisting despite huge changes to the continent’s climate and its environment. It has swum alongside and been an important source of food for Aboriginal people for many thousands of years. And during the last 200 years, it has endured intensive commercial fishing, struggled upstream against altered flows and water temperatures and butted its head on the concrete walls of dams. It has at the same time competed with alien species like common carp, all the while trying to avoid the hooks and lines of eager anglers.

Ever since Mark Kurlansky’s epic book Cod: A Biography of the Fish that Changed the World came out in 1998, I wanted to write a book about our own, and in my mind equally deserving, cod. With every year I procrastinated, I thought that someone else would come along and save me the trouble. But they didn’t. And so I gritted my teeth and submitted a book proposal. Not long after, I found out that Stuart Rowland, the ‘Codfather’ and guru of all things cod-related, was also writing a book on the subject of cods. A cold shiver ran down my spine. How could I compete? I can’t. And I didn’t try. Stuart’s book is brilliant and his experience, intimate knowledge and love of fish and especially of the cods is unrivalled, except perhaps by those of fish biologist John Koehn. The work of both scientists has been a big influence on me for decades. As you will see in the pages of this book, I draw heavily on Stuart’s and John’s research as both of them have been instrumental in progressing our knowledge and conservation of the Murray cod. Stuart’s book and mine take different paths and complement each other well. The Life and Times of the Murray Cod connects the Murray cod to key events in the history of Australia and fleshes out in detail some remarkable stories. My passion for history has led me down all sorts of rabbit holes, some whose relevance to the Murray cod may seem obscure. But if you come along for the ride, you won’t regret it. I also illustrate fundamental aspects of the biology of the species, as it swims from cradle to grave, giving a foundation in fish biology as we go. I believe that to better understand the nature of something – in this case the Murray cod – it is always enlightening to see when, where and how it fits into the bigger ecological, social and cultural landscapes. Together, The Life and Times of the Murray Cod and Stuart Rowland’s The Codfather will give you a comprehensive understanding of what makes the Murray cod tick, and the ecological role of the fish in our rivers more generally.

The Murray cod has played parts in the historical drama of Australia that will surprise many. To tell these stories, I have drawn mostly on written and historical sources, although my co-authors and I have used a smattering of contemporary interviews for the First Nations and recreational fishing chapters. Don’t get me wrong – a book devoted to interviews with these two groups on fish and fishing in general, and the Murray cod in particular, would be wonderful to write and enlightening to read. But I could not do justice to both historical and contemporary perspectives in one book and keep it a reasonable size. Furthermore, there are many recent excellent books and dozens of magazine articles on fishing for Murray cod that include fishing stories and that will at least satisfy the keen angler. For this book, I have consulted a broad range of historical sources including Aboriginal legends and stories, anthropological studies, newspaper articles and advertisements, government commission and committee reports, petitions to government, peer-reviewed scientific studies, government reports, parliamentary papers, conservation assessments, journals of explorers, diaries and accounts of settlers, books and articles by natural historians, books and reports on fisheries, university theses, oral histories, poems and stories in magazines, illustrations, paintings and photographs in collections at libraries and museums – and more. Note: descriptions of historical observations, practices and events will specifically make reference to the groups of people involved based on the above sources, and quotes will retain the language of the times.

History runs through this book because we need time to properly appreciate the significance of the Murray cod. Also, to understand our current and future relationship with the species and the environment in which it swims, we need to know about the processes and events that got it here and our role in those. The Murray cod has been around, more or less in the same form, for perhaps 10 million years. Its biology has been forged by evolution over that long timespan in response to the challenging conditions of the Australian environment. We are all fortunate that the species is still with us and hasn’t gone the way of other extinct Australian megafaunal monsters. There is much we can learn about survival and resilience from the Murray cod’s continued existence.

A historical perspective also provides the context for the deep and enduring connection of First Nations peoples with the Murray cod. It is a connection that has the fish front and centre in the creation of the Murray River itself and all the species of fish that live in it. Taking a historical perspective also allows us to see the important role of the Murray cod in inland colonial exploration and settlement. I argue that without the Murray cod, the explorers would have had a much tougher job than they did. And there is the undeniable link between the gold rush in Victoria in the 1850s, the rise of the Murray cod commercial fishery and the development of regional towns and trade. The fishery also contributed to the dispossession of Aboriginal peoples from their traditional fishing grounds. Following the two World Wars, the rivers and the Murray cod provided opportunities for soldier settlers to make a living, which further contributed to the growth of inland river towns. The livelihoods of the professional fishers dwindled over time, however, because fishing pressure, changes to the condition and management of the rivers, construction of weirs, dams and barrages, the regulation of flows and the rise of recreational fishing, all meant that commercial fishing for the Murray cod was ultimately unsustainable.

While both the Murray cod and the rivers that support its existence have suffered over-exploitation and degradation for almost 200 years, our knowledge of the biology of the fish and the fish’s ecology has come on in leaps and spurts in the last few decades. Scores of champions – First Nations people, recreational angling and community groups, conservationists, ecologists, geneticists, hatchery workers, modellers, statisticians, hydrologists and natural resource managers – have worked to ensure that the Murray cod and many other native freshwater fish have a future. What the 2018–19 fish kills in the Lower Darling–Baaka told us was that the fate of our riverine fish, especially the Murray cod, is important to all people. People care about rivers and people care about fish. May it ever be thus.

This book begins with an introductory chapter and then is divided into five Parts: Origins, Biology, People, Fisheries, Conservation and the Future. Part I: Origins (Chapter 1) outlines what we know of the evolution and relationships of the Murray cod and its relatives. Part II: Biology (Chapters 2–5) describes in what types of rivers and habitats the fish lives; how much it moves; when and where it spawns; what its young do during their first few weeks of life; what it eats as it grows up; and how big it gets when it does grow up. Part III: People (Chapters 6–8) includes the significance of the Murray cod for Aboriginal peoples historically and now. It also details early interactions with European explorers who traversed the land looking for pasture and places to settle. Part IV: Fisheries (Chapters 9–12) chronicles the background to the commercial fisheries for Murray cod that sprang up in rivers throughout the Murray–Darling Basin, especially the one centred around Echuca in Victoria; the subsequent decline in the commercial fisheries; and the history of a popular recreational fishery. Finally, Part V: Conservation and the Future (Chapters 13–15) looks at the conservation status of the Murray cod and the historic and contemporary threats to its populations. It also provides some guiding principles for future conservation and management of this iconic species.

Paul Humphries, Albury–Wodonga, August 2022

Acknowledgements

To the First Nations Peoples of the Murray–Darling Basin, I want to acknowledge your long history and connection with the land, the waters and the animals and plants – and especially the Murray cod. Reading about, and listening to, historical and contemporary stories of what the Murray cod means to you, has enriched my world immensely. Your knowledge and your ancestors’ knowledge has not always been recognised nor appreciated. I am glad to see that that is changing, and I hope this book goes a small way into helping this process along.

To all the scientists, managers and conservationists, past and present, on whose shoulders I wobble, I am truly grateful for all the work you have done. Your work over many years has given us a much greater understanding of the ecology of the Murray cod. To play a small part in that knowledge gathering has been a privilege. I hope that I have done your work justice. I am sure you’ll let me know if I haven’t …

This book would not have been possible without the support and assistance of many, many people. Darren Baldwin, Heather Goodall and Sue Jackson for assistance with research and references. University of Technology Sydney librarian Duncan Loxton for help with oral history. Ian McNiven for advice on dates of fish traps. Brenton Zampatti and Chris Bice for references and information on South Australian historical fisheries. Will Mooney, formerly of Murray and Lower Darling Indigenous Nations, for advice and contacts. Brendan Kennedy for discussions and advice on Indigenous issues, language and terminology. Tarmo Raadik and Peter Unmack for discussions on taxonomic nomenclature. Scott Dealy for information about his ancestor Joseph Rice. Matt Colloff, John Koehn and Luke Pearce for advice on conservation matters. Matt McLellan and Brett Ingram for Murray cod early life history information and advice. Nick Bond and Matt Colloff for help with data and figure construction. Kate Burndred, Margaret Byrne, Alessio Capobianco, Giovanni Caselli, Meaghan Duncan, Tom Espinoza, Tim Kaminskas, Brendan Kennedy, Jamie Knight, John Koehn, Rudie Kuiter, Sharon Marshall, Kate McBride, Katharine McBride and Rob McBride, Graeme McCrabb, Sandra McLaren, Daryl Nielsen, Catherine Nock, Matt O’Connell, Craig Poynter, David Rumsey, Christopher Scotese and John Trethewie for kindly providing photographs or other images for the book. Simon Kaminskas for his incessant wake-up emails on forgotten historical fish matters. The library staff and especially Andrew Sergeant from the National Library of Australia, who were always extremely helpful and patient with all my research demands. And to the National Library of Australia, the people, its content and its facilities I owe a huge thanks for what it does for this country and scholarship generally: it is truly a national treasure. My postgraduate students while I was writing this book – Dale Campbell, Jarrod Chapman, Luke McPhan and Matt O’Connell – who were always willing to listen to my ramblings and give me honest feedback on ideas and to whom I apologise, because I suspect they were at times neglected because of this book. My many colleagues, especially Lee Baumgartner, Rob Cook, Dave Crook, Alison King, Keller Kopf, Nick Nicholls, Bruce Pennay, Amina Price and Dave Watson, who at times acted as sounding boards for ideas relating to this book and gave good advice. To the administrative staff of the former Institute for Land, Water and Society, Margrit Beemster, Simone Endahl, Kris Gibbs, Andrew Hall, Kylie Imlach and Deb Noy, thanks for all the logistic and financial help. The map whiz, Deanna Duffy at Charles Sturt University’s SPAN, who went above and beyond the call of duty, making the wonderful maps scattered throughout the book. Ray Armstrong, Matt Colloff, Brendan Kennedy, Sam Kohne, Daryl Nielsen and Luke Pearce for providing helpful comments and advice on drafts of chapters. Howard Brandenburg, for selfless giving of his time, marvellous compositions, beautiful illustrations, patience with my meanderings and sound advice. My co-authors, Minda Murray, Katie Doyle and Cameron McGregor: your collaboration, ideas and contributions make this book so much richer. CSIRO Publishing, especially Eloise Moir-Ford, Mark Hamilton, Adrienne de Kretser and Tracey Kudis, who provided frequent advice on things editorial and put an enormous amount of work into improving the quality of all aspects of this book. Andrew Boulton and Sam Lake for their background support that gives me the confidence to do something like this book. Ralph Snr, Joan, Ra, Shuwana, Lilly and Sam, for always being interested in how the book was going, and showing enthusiasm for a project that I think baffled them most of the time. My dear friends, Craig Barden, Peter Davies and Hubert Keckeis, although they are probably unaware of it, their encouragement and faith in all that I do (while probably poor judgement on their part) is much appreciated … and reciprocated. Sally Stephens for hosting me in Canberra, feeding me copious quantities of vegies from her amazing garden, lending me her weird bike, taking me to dinner or films when I needed distraction, and just making me feel so welcome all the time. Nicole McCasker for encouragement, wise words, and especially patience with my raves, book-related and otherwise, during our countless rides and cups of coffee. And without the constant love, support and encouragement of my family – Glenys, Odie, Max and Til – this book would never have come to pass.

About the contributors

W. Howard Brandenburg is an artist, science illustrator and fish biologist.

Katherine E. Doyle is a passionate natural historian, with a PhD in freshwater ecology. She is currently a research scientist at Charles Sturt University.

Cameron G. McGregor has a Bachelor of Environmental Management and Ecology, has fished Australian native fish all his life and is a professional fishing guide.

Minda W. Murray is a proud Yorta Yorta Duduroa woman, who is currently completing her PhD in Aboriginal self-determination and agreement-making in Victoria.

An introduction to the life and times of the Murray cod

According to a legend there was a great earth shock or earth tremor at the sources of the Murray. This continued for days, and suddenly the earth was rent right along where the Murray now flows, but there was only a small amount of water, just trickling and winding its way to the Southern Ocean. Presently another earth tremor, more severe than the first one, when suddenly there burst forth from the depth of the earth a huge fish, a Pondi, and as it came out of the earth it was followed by a great flow of water, the cod struggling along this narrow stream, acting like those great steam shovels, digging with its head, making the river deep and swinging its powerful tail, causing all the bends in the river until it reached what is known as Lake Alexandrina. Then Nebalee, the great prophet, caught it and cut it in pieces and threw the small fragments into the river and named them Tcherie, Thookerri, Pummerrie, Pil lul kie, Ploongie, which are the fishes caught in the Murray and its tributaries. (Ngarrindjeri legend) – David Unaipon, 2001 [209, pp. 17–18]

But the cod, the unapproachable cod, who shall sing its praises, and in enumerating its excellences exhaust the list of its perfections? – The Australasian, 5 November 1864

Whichever way you look at it, the Murray cod is an impressive animal. Not just because it is Australia’s largest freshwater fish – although that has a lot to do with its appeal to the general, and especially the fishing, public – but the Murray cod is an evolutionary gamble that paid off. It is also impressive because it is a species of contradictions, or perhaps more correctly, a species that does not fit neatly into a well-defined box. It is, as we shall see, unlike any other fish on Earth. That doesn’t mean that we cannot learn from what we know of other species to better understand this wonderful creature. But we would be wise not to rely on how we think big fish like this live, when we are making decisions about how we manage Murray cod populations or regulate its fisheries. In more ways than one, the Murray cod is a fish that swims alone (Fig. i.1).

The Murray cod can be found throughout the 1 million square kilometres of the Murray–Darling Basin, which makes up 14% of the total land area of Australia. At times it will cruise around in the deepest and widest lowland parts of the Murray River, while at others, it can be seen negotiating a tiny, newly flowing creek, its dorsal fin cutting the surface as it tries to make its way upstream in search of food or a new place to live. It thrives in the warm summer low flows that are typical of our largest inland river basin, but can breed at 15°C and withstand much lower temperatures. It will zealously guard a sunken river red gum log – a snag to you and me – for months, then travel 100 km looking for the best place to spawn, after which it returns to the exact same snag. How it does this is anyone’s guess.

Fig. i.1. The Murray cod. Source: Courtesy of Tim Kaminskas.

The species is still with us after millions of years, during which it weathered warm, wet, sub-tropical conditions that we’d associate with flamingos and crocodiles. It also survived the freezing aridity of glacial periods. Despite the Murray cod’s hardiness and resilience, because of all that we humans have thrown at it over the last 200 years or so, it has been listed under national and international conventions as a threatened and even a critically endangered species.

Part of the reason that the Murray cod defies simple explanation and description is because it is larger than itself. By that I mean the fish is more than just a fish, it is a symbol of inland Australia: of its long, long Aboriginal history and of its much more recent colonial, settler and Western scientific history. The Murray cod is synonymous with slow-flowing, meandering rivers that cross thousands of kilometres through an arid and seemingly inhospitable land, succeeding where all the odds are stacked against life, let alone such a wonderfully big, beautiful example of it. The Murray cod also swims as tangible evidence of all that our inland rivers can be – flourishing, teeming with life, bountiful. But at times it floats belly up, dead, as testament to what can go wrong with the way we manage our rivers. Pale tides of bloated, metre-long Murray cod force us to take notice of what tough climate and river regulation can do to a river and its inhabitants when poorly managed.

Aims of this book

This book describes the history, cultural significance, biology and conservation of the charismatic Murray cod, from Aboriginal, pre-European times to the present day. Its biology and ecology are intimately linked to the intrinsic diversity and uncertainty of the Australian environment, and its struggle for existence since European settlement of the Murray–Darling Basin in the 1830s is entwined with the massive changes since that time. This book, first and foremost, describes the life and times of an Australian icon in all its fishy, slimy glory. But it will do much more than this. It will connect you to Australia and the Australian environment – especially rivers – through the lens of this particular fish’s eye.

This introduction emphasises why Murray cod deserves to be the focus of an entire book, as we identify the fish’s place in the environment, history, culture and psyche of Australia. I ask why we should care about the Murray cod’s continued survival. What does that mean for Australia, its rivers and other fish? For those interested in how our largest fish does what it does, for those who want to catch one, take a photo and throw it back, and for those whose primary motivation is to conserve one of nature’s wonders, we need to know as much as possible about its life history, its ecology, its preferences and tolerances, its vulnerabilities and its strengths. We also need to open our eyes to the reality that what is happening to our river catchments may threaten populations – and perhaps the very existence – of the Murray cod. Some threats are obvious and uncontroversial, others are insidious and contested. Some are relatively new, others began almost two centuries ago. The threats are relatively easy to identify, solutions much less so.

Introducing the Murray cod

The Murray cod, known scientifically as Maccullochella peelii (Fig. i.2), is endemic to the Murray–Darling Basin (Fig. i.3) and scientists think it evolved west of the Great Dividing Range around 10 million years ago. That means that the species does not naturally occur anywhere else. Of course, given it is Australia’s largest freshwater fish, individuals can be found in zoos and aquaria all over the world. And many years ago, acclimatisation societies – organisations which, in the wisdom of the times, brought all sorts of alien animals and plants into Australia – attempted to export Murray cod overseas. Individuals were successfully translocated to, among other places, Western Australia, the Yarra River near Melbourne, lakes in western Victoria, and Lake George near Canberra, where it formed a commercial fishery for a time.

Unlike its cousin, the golden perch (Macquaria ambigua), the Murray cod is a main-channel specialist: it spends most of its life cruising around the flowing parts of rivers, streams and creeks, nowadays rarely venturing onto floodplains or into billabongs. When it does, these trips are mostly short-lived. It seems that in general the