Impact of environmental changes on the fish faunas of Western Australian south-coast estuaries Hoeksema, S.D., Chuwen, B.M, Hesp, S.A., Hall, N.G. and Potter, I.C. Project No. 2002/017 Fisheries Research and Development Corporation Report 1 Impact of environmental changes on the fish faunas of Western Australian south-coast estuaries Hoeksema S.D. Chuwen B.M. Hesp S.A. Hall N.G. Potter I.C. March 2006 Centre for Fish and Fisheries Research Murdoch University Murdoch, Western Australia 6150 Copyright Fisheries Research and Development Corporation and Centre for Fish and Fisheries Research 2005 This work is copyright. Except as permitted under the Copyright Act 1968 (Cth), no part of this publication may be reproduced by any process, electronic or otherwise, without the specific written permission of the copyright owners. Neither may information be stored electronically in any form whatsoever without such permission. The Fisheries Research and Development Corporation plans, invests in and manages fisheries research and development throughout Australia. It is a statutory authority within the portfolio of the federal Minister for Agriculture, Fisheries and Forestry, jointly funded by the Australian Government and the fishing industry. March 2006 ISBN: 86905-879-7 2 TABLE OF CONTENTS NON TECHNICAL SUMMARY................................................................................................................................6 ACKNOWLEDGEMENTS.........................................................................................................................................9 1.0 GENERAL INTRODUCTION ...................................................................................................................10 1.1 BACKGROUND.......................................................................................................................................10 1.1.1 Species composition of fish faunas in estuaries on the central south coast of Western Australia ............. 10 1.1.2 Acanthopagrus butcheri in estuaries on the central south coast of Western Australia.............................. 11 1.2 NEED ........................................................................................................................................................12 2.0 GENERAL MATERIALS AND METHODS............................................................................................14 2.1 SAMPLING LOCATIONS .......................................................................................................................14 2.1.1 Stokes Inlet................................................................................................................................................. 14 2.1.2 Culham Inlet .............................................................................................................................................. 20 2.1.3 Hamersley Inlet.......................................................................................................................................... 23 2.2 SAMPLING REGIME ..............................................................................................................................25 2.2.1 Nearshore, shallow and offshore, deeper waters....................................................................................... 25 2.3 ENVIRONMENTAL VARIABLES .........................................................................................................26 2.3.1 Environmental measurements.................................................................................................................... 26 2.3.2 Additional environmental data................................................................................................................... 29 3.0 FISH FAUNAS OF STOKES, CULHAM AND HAMERSLEY INLETS..............................................30 3.1 INTRODUCTION.....................................................................................................................................30 3.2 MATERIALS AND METHODS...............................................................................................................34 3.2.1 Statistical analyses..................................................................................................................................... 34 3.3 RESULTS..................................................................................................................................................35 3.3.1 Environmental data.................................................................................................................................... 35 Stokes Inlet .......................................................................................................................................................................35 Culham Inlet .....................................................................................................................................................................37 Catchment rainfall ...........................................................................................................................................................42 3.3.2 Abundances and contributions of fish species to nearshore fish communities........................................... 45 Stokes Inlet .......................................................................................................................................................................45 Culham Inlet .....................................................................................................................................................................47 Hamersley Inlet ................................................................................................................................................................47 3.3.3 Abundances and contributions of fish species to offshore fish communities.............................................. 50 Stokes Inlet .......................................................................................................................................................................50 Culham Inlet .....................................................................................................................................................................50 Hamersley Inlet ................................................................................................................................................................53 3.3.4 Numbers of species and densities of fish in nearshore, shallow waters..................................................... 53 Stokes Inlet .......................................................................................................................................................................53 Culham Inlet .....................................................................................................................................................................56 Hamersley Inlet ................................................................................................................................................................58 Comparisons between the basins of Stokes, Culham and Hamersley inlets .....................................................................60 Comparisons between the main tributaries of Stokes and Culham inlets .........................................................................62 3.3.5 Numbers of species and densities of fish in offshore, deeper waters ......................................................... 64 Stokes Inlet .......................................................................................................................................................................64 Hamersley Inlet ................................................................................................................................................................66 Comparisons between the basins of Stokes, Culham and Hamersley inlets .....................................................................68 Comparisons between the main tributaries of Stokes and Culham inlets .........................................................................71 3.3.6 Regional, interannual and seasonal comparisons of ichthyofaunal compositions of nearshore, shallow waters ......................................................................................................................................................... 73 Stokes Inlet .......................................................................................................................................................................73 Culham Inlet .....................................................................................................................................................................79 Hamersley Inlet ................................................................................................................................................................85 Comparisons between estuaries .......................................................................................................................................88 3.3.7 Regional, interannual and seasonal comparisons of ichthyofaunal compositions of offshore, deeper waters ......................................................................................................................................................... 92 Stokes Inlet .......................................................................................................................................................................92