7 Review of diadromous fish distribution in the upper Thomson River system W. Koster and T.A. Raadik 2010 Arthur Rylah Institute for Environmental Research Client Report Arthur Rylah Institute for Environmental Research Client Report Review of diadromous fish distribution in the upper Thomson River system W. Koster and T.A. Raadik Arthur Rylah Institute for Environmental Research 123 Brown Street, Heidelberg, Victoria 3084 2010 Arthur Rylah Inst itute for Environmental Research Department of Sustainability and Environment Heidelberg, Victoria Report produced by: Arthur Rylah Institute for Environmental Research Department of Sustainability and Environment PO Box 137 Heidelberg, Victoria 3084 Phone (03) 9450 8600 Website: www.dse.vic.gov.au/ari © State of Victoria, Department of Sustainability and Environment 2010 This publication is copyright. Apart from fair dealing for the purposes of private study, research, criticism or review as permitted under the Copyright Act 1968 , no part may be reproduced, copied, transmitted in any form or by any means (electronic, mechanical or graphic) without the prior written permission of the State of Victoria, Department of Sustainability and Environment. All requests and enquiries should be directed to the Customer Service Centre, 136 186 or email [email protected] Citation: Koster, W. and Raadik, T.A. 2010. Review of diadromous fish distribution in the upper Thomson River system. Report to West Gippsland Catchment Management Authority. Department of Sustainability and Environment, Heidelberg, Victoria (unpublished). Disclaimer: This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication. Front cover photo: Australian Grayling (Tarmo A. Raadik) and upper Thomson River (Wayne Koster). Authorised by: Victorian Government, Melbourne Printed by: Snap Printing, Heidelberg Contents Acknowledgements............................................................................................................................v Summary............................................................................................................................................1 1 Background .............................................................................................................................3 2 Distribution of Australian Grayling and other diadromous fish in the upper Thomson River system.......................................................................................................................................4 Australian Grayling ( Prototroctes maraena ) ......................................................................................5 Lampreys ( Mordacia mordax and Geotria australis ) ........................................................................5 Eels ( Anguilla australis and A. reinhardtii )........................................................................................6 Broad-finned Galaxias ( Galaxias brevipinnis )....................................................................................6 Common Galaxias ( Galaxias maculatus ) ...........................................................................................7 Australian Bass ( Macquaria novemaculeata ).....................................................................................7 Tupong ( Pseudaphritis urvillii )...........................................................................................................8 3 Factors impeding the distribution of Australian Grayling and other diadromous fish in the upper Thomson River system ....................................................................................................9 4 Restoring connectivity of fish passage for Australian Grayling and other diadromous fish in the upper Thomson River system.......................................................................................12 5 Conclusions and recommendations.....................................................................................15 iii iv Acknowledgements The West Gippsland Catchment Management Authority (WGCMA) funded this project. Thanks to David Stork from WGCMA for his role in the coordination of the project. David Crook, Jason Lieschke, Jeremy Hindell and Matthew Jones from the Arthur Rylah Institute for Environmental Research (ARI) provided valuable comments on an earlier version of this document. Thanks to David Dawson from ARI for his assistance in collating fish distribution data. v vi Review of diadromous fish distribution in the upper Thomson River system Summary This report documents the findings of a review of the distributions of diadromous fish in the upper Thomson River system in West Gippsland. Diadromous fish undertake migrations between freshwater and marine environments and comprise about 70% of the native freshwater fish species in the Thomson River system. They are currently considered to be confined largely to the lower and mid reaches (Hall 1989, Raadik 1996, Koster and Crowther 2003). Specifically, the aim of this project was to determine the distributions of the nationally threatened Australian Grayling ( Prototroctes maraena ) and other diadromous fish species in the upper Thomson and Aberfeldy rivers, and identify, where possible, any factors potentially impeding diadromous fish distribution, based on a review of fish survey data and published and grey literature (including technical reports). The results of this review indicate that Australian Grayling and most other diadromous fish species in the Thomson River system are confined to the lower and mid reaches. Exceptions include eels and lampreys, which are capable of climbing over barriers. Based on historic, current and potential distributions of diadromous fish species, including comparisons with the fish communities present in nearby catchments (e.g. Mitchell, Tambo, Snowy), Australian Grayling and several other diadromous fish species should be found in the upper reaches of the system. A range of factors are potentially impacting diadromous fish distribution in the mid to upper Thomson River. The Thomson Dam has modified the hydrology and water temperature of the river, which could result in the loss or disruption of important biological cues (e.g. high flows) for fish migrating into the system or throughout the river (TMEFT 2004). Issues with coldwater releases have been alleviated to some degree by the use of a multi-level offtake to maintain release water temperatures within target levels. The presence in the upper Thomson River of the diadromous Short-finned Eel ( Anguilla australis ), Long-finned Eel (Anguilla reinhardtii ) and lampreys ( Mordacia mordax , Geotria australis ) suggests that suitable migration/attraction cues (i.e. flows) exist in the upper reaches. The presence of self-sustaining populations of non- migratory native fish species (e.g. Southern Pygmy Perch Nannoperca australis , River Blackfish Gadopsis marmoratus , Australian smelt Retropinna semoni ) in the Thomson River below the dam also indicates that water temperature and flow are not preventing the establishment of fish populations in the upper Thomson River and that native fish are able to survive in this reach. The degree of impact of recent fires on fish habitat in the upper Thomson River catchment is unknown, but is not likely to be a major cause of the lack of diadromous fish species in that part of the system. Given that diadromous fishes in south-eastern Australia typically undertake annual upstream migrations from marine environments into rivers, and different species migrate at different times, at least some diadromous fish species should be present at any given time. Even if habitat was extremely unsuitable, small numbers of fish would be present, replaced by new recruits (Lyon and O’Connor 2008). Surveys conducted in the Thomson River since the fires have collected the diadromous species Australian Grayling, Tupong (Pseudaphritis urvillii ) and Common Galaxias (Galaxias maculatus ) at various sites in areas that were burnt (e.g. Coopers Creek, C5 Track, Bruntons Bridge), but not from sites upstream of the Horseshoe Bend Tunnel. The Horseshoe Bend Tunnel on the upper Thomson River has been identified in the Victorian State Fishway Program as a barrier to fish movement (McGuckin and Bennett 1999). The tunnel was constructed in 1911–12 with most of the river flow diverted through the tunnel and bypassing the one kilometre reach of the Thomson River known as Horseshoe Bend (LCC 1991). Opportunities for fish to migrate through the old river channel are limited, as the flow in the channel is estimated to occur about 3% of the time (Koster and Crowther 2003). In contrast, diadromous fishes in south-eastern Australia migrate over an extensive time frame encompassing Arthur Rylah Institute for Environmental Research Client Report 1 Review of diadromous fish distribution in the upper Thomson River system much of the year (Koehn and O’Connor 1990). Migration of fish through the tunnel would also be impeded, particularly by steep gradients and sudden drops in height. Water velocities within the tunnel (1.2–6.2 m/sec) are also known to far exceed the swimming capabilities of small diadromous fishes (Saddlier and O’Connor 1997, Boubee et al. 1999). Natural light within