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7 Review of diadromous fish distribution in the upper 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, 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 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 Department of Sustainability and Environment, Heidelberg, Victoria (unpublished).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, 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 ( maraena ) ...... 5 Lampreys ( mordax and australis ) ...... 5 ( Anguilla australis and A. reinhardtii )...... 6 Broad-finned ( 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

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iv

Acknowledgements

The 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.

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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 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 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 ( 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 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 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 the tunnel is also severely reduced, which can be a behavioural impediment to fish movement (O’Brien 1999, Thorncraft and Harris 2000, Fairfull and Witheridge 2003). Restoring fish passage connectivity around the Horseshoe Bend Tunnel along the old course of the Thomson River would increase the opportunities for the Australian Grayling and other diadromous fish species to access the upper reaches of the system. Restoring fish passage past the tunnel supports the need to restore access to rivers for Australian Grayling in accordance with the National Recovery Plan for Australian Grayling (Backhouse et al. 2008) and represents an important step toward restoring connectivity and biodiversity of native fish communities in the Thomson River system. Restoring fish passage past Horseshoe Bend Tunnel would facilitate access to a further 22 km of the Thomson River upstream to the Thomson Dam, 63 km of the , and numerous tributary streams, including streams in the . Recommendations on the timing and magnitude of flows to facilitate fish passage along the old course of the Thomson River around Horseshoe Bend Tunnel are also provided.

2 Arthur Rylah Institute for Environmental Research Client Report Review of diadromous fish distribution in the upper Thomson River system

1 Background

Approximately 70% of native freshwater fish species in coastal catchments in Victoria exhibit diadromy (Harris 1984, Koehn and O’Connor 1990, Raadik 1995, Drew 2008) - they undertake migrations between freshwater and marine environments (McDowall 1988). Several different kinds of diadromy exist, including anadromy, catadromy and amphidromy (Myers 1949, McDowall 1988). Anadromous fish enter rivers as mature adults and migrate to upstream spawning grounds, with juveniles later migrating downstream to the sea (e.g. Short-headed Mordacia mordax , Geotria australis , Australian Lovettia sealii ) (McDowall 1999). Catadromous fish enter rivers as juveniles, and adults return to the sea to (e.g. Tupong Pseudaphritis urvillii, Short-finned Eel Anguilla australis , Long-finned Eel Anguilla reinhardtii ). Adult amphidromous fish live and spawn in fresh water, and the larvae drift downstream to the sea and later migrate back into fresh water (e.g. Australian Grayling Prototroctes maraena, Broad-finned Galaxias Galaxias brevipinnis ) (McDowall 1999). In all categories of diadromy, migrations are undertaken by different life-history stages, and consequently by different sizes of fish (e.g. adults, juveniles and larvae). Swimming ability varies with each life history stage and between species and consequently the speed of movement and the degree of penetration (or distance inland) upstream into freshwater environments varies. Migratory freshwater fish comprise about 70% of the native freshwater fish fauna of the coastal- draining Thomson River system in West Gippsland. The current distribution of Australian Grayling and most of the other migratory fish species is considered to be confined to the lower and mid reaches (Hall 1989, Raadik 1996, Koster and Crowther 2003). Australian Grayling is a nationally threatened species, and is listed as vulnerable under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 and threatened under the Victorian Flora and Fauna Guarantee Act 1988 . Key threats to Australian Grayling include barriers to migration, altered flow regimes and habitat loss and degradation (Backhouse et al. 2008, DEWHAC 2010). In the national recovery plan for the Australian Grayling, preservation of the Thomson River population is identified as necessary for the long-term survival and recovery of the species (Backhouse et al. 2008). The aim of this project was to determine the distributions of Australian Grayling and other diadromous fish in the upper Thomson and Aberfeldy rivers, and identify, where possible, any factors potentially impeding diadromous fish distribution, based on a review of published and grey literature (including technical reports) and fish survey data (Victorian Aquatic Fauna Database managed by the Arthur Rylah Institute for Environmental Research - ARI). The report also addresses a number of particular concerns (e.g. alien fish species, fish stocking) regarding reinstating or improving diadromous fish passage in the system.

Arthur Rylah Institute for Environmental Research Client Report 3 Review of diadromous fish distribution in the upper Thomson River system

2 Distribution of Australian Grayling and other diadromous fish in the upper Thomson River system

Data on fish distributions in the Thomson River basin, and from more widely in coastal Victoria, where applicable, has been sourced from the Victorian Aquatic Fauna Database and published and grey literature (including technical reports). Survey data extends back to the mid 1960s. Earlier surveys (i.e. pre mid 1980s) were typically focused on recreational angling species (native and exotic), and may not have targeted or recorded all native non-angling species. The actual distributions of native non-angling species in the Thomson River system in this earlier period may therefore be under-represented. Data on the occurrence of native migratory species in adjacent or nearby similar coastal catchments were included to provide support for possible historic ranges within the Thomson River system. More recent surveys conducted in the Thomson River system have been designed to provide representative information on species distributions or biodiversity (e.g. Saddlier and Doeg 1998, 2002, Koster and Crook 2006, Koster and Dawson 2008, Koster et al. 2009, Lieschke unpublished [Sustainable Rivers Audit - SRA] data). No fish survey data was available for the upper Thomson River system prior to construction of the Horseshoe Bend Tunnel (1911–12), located on the upper Thomson River upstream of Coopers Creek. Ten native freshwater migratory fish species have been recorded from the Thomson River basin to date (Table 1), including the Australian Smelt ( Retropinna semoni ), which was recently found to be partly diadromous (Crook et al. 2008a). As diadromy appears to be facultative (not obligatory) in Australian Smelt because only some individuals or populations undertake migrations, this species was not considered further in the review.

Table 1. Common and scientific names of migratory freshwater native fish recorded from the Thomson River basin, including migratory phases.

Migration direction and life stage

Common Name Scientific Name Downstream Upstream

Short-headed Lamprey Mordacia mordax Juvenile Adult

Pouched Lamprey Geotria australis Juvenile Adult

Short-finned Eel Anguilla australis Adult Juvenile

Long-finned Eel Anguilla reinhardtii Adult Juvenile

Broad-finned Galaxias Galaxias brevipinnis Larvae Juvenile

Common Galaxias Galaxias maculatus Adult + larvae Juvenile

Australian Grayling Prototroctes maraena Adult + larvae Juvenile

Australian Smelt Retropinna semoni Larvae Juvenile

Australian Bass Macquaria novemaculeata Adult + larvae Juvenile

Tupong Pseudaphritis urvillii Adult Juvenile

4 Arthur Rylah Institute for Environmental Research Client Report Review of diadromous fish distribution in the upper Thomson River system

Australian Grayling ( Prototroctes maraena ) Australian Grayling adults undertake downstream migrations to the lower reaches of rivers during autumn to spawn, usually coinciding with rises in flow, then migrate back upstream (Koster and Dawson 2010a,b). The larvae are washed downstream to the sea, where they remain for about five months before returning back upstream as juveniles into the freshwater reaches of rivers in spring– summer (Berra 1982, 1987; Crook et al. 2006). Australian Grayling have been recorded in the Thomson River as far upstream as Walhalla, where a single individual was collected near the bridge on the Walhalla Road in 1985 at 220 metres above sea level (masl) (approx. river distance inland 160 km). This is the only known record of the species in the system upstream of the Horseshoe Bend Tunnel, despite numerous recent surveys (i.e. late 1990s onwards) in the upper Thomson River designed to provide representative information on species distributions or biodiversity (e.g. Saddlier and Doeg 1998, 2002, Koster and Crook 2006, Koster and Dawson 2008, Koster et al. 2009, Lieschke unpublished SRA data). Australian Grayling have been recorded, however, at several nearby sites (e.g. Coopers Creek – 200 masl, C5 Track – 190 masl, Bruntons Bridge – 190 masl), but these are all downstream of the tunnel in surveys since the mid 1980s. The sites at Coopers Creek, C5 Track and Bruntons Bridge are located approximately one, three and nine kilometres downstream of the tunnel, respectively. Throughout its range, the Australian Grayling is known to occur at high altitudes and is able to move large distances inland. For example, Australian Grayling have been recorded in the to 400 masl (approx. river distance inland 230 km), the near Bindi Station at 440 masl (approx. river distance inland 160 km) and in Craigie Bog Creek ( system) to 760 masl (approx. river distance inland 340 km). Australian Grayling could be expected to occur in the upper reaches of the Thomson River system to about 400–450 masl, including the lower reaches of the Aberfeldy River. This is much higher than the current range of 190–220 masl. It should also be noted that this range is based on records following construction of the Horseshoe Bend Tunnel (1911–12).

Lampreys ( Mordacia mordax and Geotria australis ) Two species of lamprey have been recorded from the Thomson River system — the Short-headed Lamprey and Pouched Lamprey. Adult lampreys migrate upstream in winter–spring and spawn in the upper reaches of rivers (Koehn and O’Connor 1990, McDowall 2000). Juveniles gradually migrate downstream and go to sea the following winter, remaining there for 3–4 years before returning to fresh water as adults (McDowall 2000). Short-headed Lamprey have been recorded at several sites upstream (e.g. The Narrows, Walhalla Road Bridge) and downstream (e.g. Coopers Creek, C5 Track, Bruntons Bridge) of Horseshoe Bend Tunnel in various surveys from the mid 1980s to the present. Pouched Lamprey have been recorded in the Thomson River upstream to The Narrows in the mid to late 1980s, and occasionally farther downstream in the system (e.g. Bruntons Bridge, Cowwarr, Rainbow Creek). Throughout their range, both species of lamprey are known to penetrate large distances inland and upstream to high altitudes. For example, Short-headed Lamprey have been recorded in the Tambo River near Bindi Station to 440 masl (approx. river distance inland 160 km) and Menaak Creek to 350 masl (approx. river distance inland 155 km). Pouched Lamprey have been recorded in the to 240 masl (approx. river distance inland 85 km) and up to 300 masl in the system (approx. river distance inland 130 km).

Arthur Rylah Institute for Environmental Research Client Report 5 Review of diadromous fish distribution in the upper Thomson River system

Both species of lamprey should occupy the lower to mid reaches of the Thomson River system, with Pouched Lamprey upstream to about 300 masl and Short-headed Lamprey penetrating farther upstream to over 400 masl, including the lower reaches of the Aberfeldy River. Lampreys are known to climb wet rocks and vertical surfaces (Harris 1984, Sloane 1984), so they can be found upstream of instream obstacles.

Eels ( Anguilla australis and A. reinhardtii ) Two species of eels — the Short-finned Eel and Long-finned Eel — are found in the Thomson River system. Adults migrate downstream to the sea to spawn during summer–autumn with migration documented as being associated with high flow events (Koehn and O’Connor 1990, Crook et al. 2008b). Juveniles enter fresh water during spring and summer (Koehn and O’Connor 1990). Short-finned Eels can withstand periods out of water and can climb over substantial barriers, although this behaviour is most common in the juvenile phase (<120 mm) (McDowall 2000). Short-finned Eel have been recorded in the Thomson River as far upstream as the Thomson– Jordan Divide Road, upstream of Thomson Dam in 1988 (500 masl, approx. river distance inland 200 km) and have been recorded at several sites (e.g. Beardmores Track, The Narrows, Walhalla Road Bridge) upstream of Horseshoe Bend Tunnel, as well as in the Aberfeldy River, in various surveys since the late 1970s. Short-finned Eel have also been recorded downstream of Horseshoe Bend Tunnel at several nearby sites (e.g. Coopers Creek, C5 Track, Bruntons Bridge) in various surveys since the late 1970s. Long-finned Eel have been recorded at several sites upstream (e.g. The Narrows, Walhalla Road Bridge) and downstream (e.g. Coopers Creek, C5 Track, Bruntons Bridge) of Horseshoe Bend Tunnel in various surveys between the 1980s and the present. Throughout their range, Short-finned and Long-finned Eels are known to penetrate to high altitudes and large distances inland, and Short-finned Eel may penetrate as far as headwater reaches. For example, Short-finned Eel have been recorded in the Wonnangatta River to 400 masl (approx. river distance inland 230 km), the Tambo River north branch and Bendoc River to 960 masl (approx. river distance inland 185 km and 355 km respectively), with individuals found as high as 1340 masl in the upper Snowy River system (approx. river distance inland 350 km). Long-finned Eel have been recorded in the to 370 masl (approx. river distance inland 200 km), the Tambo River south branch to 560 masl (approx. river distance inland 170 km) and Butchers Creek (620 masl, approx. river distance inland 110 km), with the highest recorded elevation in the Snowy River catchment at 755 masl (approx. river distance inland 360 km). Consequently, Short-finned Eel are expected to be found throughout the Thomson River catchment, including the upper reaches, with Long-finned Eel penetrating upstream to approximately 450–500 masl including the lower and mid reaches of the Aberfeldy River.

Broad-finned Galaxias ( Galaxias brevipinnis ) Broad-finned Galaxias adults spawn in the upper reaches of streams during autumn on high flows (O’Connor and Koehn 1998). Larvae are then washed downstream to the sea and move into rivers and migrate upstream as juveniles about six months later, during spring (Koehn and O’Connor 1990, McDowall 2000). Broad-finned Galaxias are also known to form landlocked populations in many lakes (McDowall 2000). Only a single individual Broad-finned Galaxias has been recorded in the Thomson River, from the mid reaches near Cowwarr in 2002. The species is relatively uncommon in the entire Gippsland

6 Arthur Rylah Institute for Environmental Research Client Report Review of diadromous fish distribution in the upper Thomson River system

Lakes catchments (Tambo, Mitchell, LaTrobe and Thomson River basins) with only a few populations known from the lower Mitchell and Avon River systems, though a landlocked population exists in Lake Tarli Karng in the system (Thomson River basin). Given the difficulty in identification of Broad-finned Galaxias in the juvenile stage (morphologically similar to other Galaxias spp.), the available dataset for this species in the Thomson River system is considered to be poor. Throughout its range in Victoria, Broad-finned Galaxias are known to penetrate large distances inland and upstream to high altitudes. They have been reported to 1625 masl (approx. river distance inland 400 km) in the upper Snowy River system, reaching to 620 masl in the (approx. river distance inland 170 km), to 360 masl (approx. river distance inland 210 km) in the Mitchell River system, and to 850 masl (approx. river distance inland 230 km) in Lake Tarli Karng in the Thomson River basin. Broad-finned Galaxias is commonly found to 400 masl and above, and should occupy the lower and mid reaches of the Thomson River system, with small, isolated populations possibly found higher in the catchment. Broad-finned Galaxias are known to climb moist, vertical barriers by using their downward facing pectoral and pelvic fins to adhere to substrates using surface tension (McDowall 2003). Consequently they can be found in small, steep tributaries, and upstream of waterfalls.

Common Galaxias ( Galaxias maculatus ) Common Galaxias adults migrate downstream on the new or full moon, mostly during autumn, and spawn on spring tides in the upper tidal reaches of estuaries (Benzie 1968, McDowall 1996). The larvae then go to sea, and migrate back into the freshwater reaches of rivers as juveniles about six months later, in spring–summer (McDowall 1996). Common Galaxias have been recorded in the Thomson River as far upstream as Walhalla, where 21 were collected near the bridge on the Walhalla Road in 1988. This is the only known record of the species in the system upstream of the Horseshoe Bend Tunnel. Common Galaxias have been recorded, however, at several nearby sites (e.g. Coopers Creek, Bruntons Bridge), but these are all downstream of the tunnel in surveys since the mid 1980s. Throughout its range, the Common Galaxias is known to penetrate to high altitudes and large distances inland. It has been recorded in the Wonnangatta River to 570 masl (approx. river distance inland 250 km), the Tambo River near Bindi Station to 440 masl (approx. river distance inland 160 km), the Suggan Buggan River to 370 masl (approx. river distance inland 155 km) and to 410 masl (approx. river distance inland 165 km) in the Wentworth River. Common Galaxias are usually found in the lower reaches of river basins, but are common to over 400 masl and could be expected to be found in the upper Thomson River system to above 450 masl, including the Aberfeldy River.

Australian Bass ( Macquaria novemaculeata ) Australian Bass adults migrate downstream to estuaries during autumn and winter to spawn, before returning upstream (Harris 1986). Juveniles migrate upstream in spring–summer. Males mostly remain in lower tidal waters, while females travel farther upstream (McDowall 1996). Downstream migration of adults has been linked to flooding (Harris 1986). Most Australian Bass recorded in the Thomson River were found in the lower reaches around Myrtlebank and Longford.

Arthur Rylah Institute for Environmental Research Client Report 7 Review of diadromous fish distribution in the upper Thomson River system

There are surprisingly few records from the mid reaches to more upland regions of many streams, considering that females are able to move long distances upstream (e.g. Snowy Falls, approx. 240 km river distance inland). Anecdotal angler reports from other coastal Victorian streams suggest Australian Bass were once found up to about the mid reaches of many larger systems, to around 300 masl. Consequently, Australian Bass should be found in the Thomson River in the lower and mid upper reaches, but not extending upstream as far as the Aberfeldy River.

Tupong ( Pseudaphritis urvillii ) Tupong undertake downstream migrations to the sea during autumn and winter to spawn, coinciding with increases in river flow (Koster and Dawson 2009, Crook et al. 2010). Juveniles migrate upstream into rivers about six months later during spring–summer (Hortle 1979). Males mostly remain in estuaries, whilst females travel further upstream (Hortle 1979). Tupong have been recorded in the Thomson River as far upstream as Beardmores Track below the Thomson Dam wall (290 masl, approx. river distance inland 190 km) and at several other nearby sites upstream of Horseshoe Bend Tunnel (e.g. The Narrows, Walhalla Road bridge) in various surveys since the late 1970s. They are more common downstream of Horseshoe Bend Tunnel, having been recorded at several nearby sites (e.g. Coopers Creek, C5 Track, Bruntons Bridge) in surveys since the late 1970s (Tunbridge 1997, Koster and Crowther 2003, Koster et al. 2009). Throughout its range, the Tupong is known to penetrate to high altitudes and large distances inland, such as the Wonnangatta River to 570 masl (approx. river distance inland 250 km), the Tambo River north branch to 640 masl (approx. river distance inland 180 km), the Suggan Buggan River to 690 masl (approx. river distance inland 170 km) and Thirty Mile Creek in the Mitchell River basin to 890 masl (approx. river distance inland 220 km). Most Tupong are found in the lower reaches of coastal river systems, but it appears that larger females are found upstream (Hortle 1979). Consequently, Tupong should be found throughout the Thomson River catchment, including the upper reaches to about 500 masl, including the Aberfeldy River.

8 Arthur Rylah Institute for Environmental Research Client Report Review of diadromous fish distribution in the upper Thomson River system

3 Factors impeding the distribution of Australian Grayling and other diadromous fish in the upper Thomson River system

Thomson Dam The Thomson Dam has greatly modified the hydrology of the river downstream of the storage (Gippel and Stewardson 1995, Cottingham et al. 2001, Earth Tech 2003, TMEFT 2004). Changes to hydrology in the Thomson River most likely impact on the distribution of diadromous fishes over the length of the river through the loss of important biological cues (e.g. high flows) for fish migrating into the system or throughout the river (TMEFT 2004). There was also a short period in 1984–85 when hypolimnetic water at 9–11 °C was released from the dam. However, a multi-level offtake has since been used to maintain release water temperatures within target levels specified in Schedule F5 of the State Environment Protection Policy (Waters of Victoria) . Based on limited data, excluding the period in 1984–85 when hypolimnetic water was released, Gippel et al. (1992) reported that dam regulation increased mean water temperatures below the dam by around 3 °C in winter and reduced mean water temperatures by 3 °C in summer. The reduction in summer water temperatures persisted downstream to Coopers Creek, but winter temperatures were only increased by 1 °C at The Narrows and not at all at Coopers Creek (Gippel et al. 1992). The presence of the diadromous Short-finned Eel, Long-finned Eel and lampreys, which are capable of climbing over barriers, in the Thomson River below the dam nonetheless suggests that suitable migration and attraction cues (i.e. flows) for fish exist in this reach. 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) 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.

Bushfires The immediate impacts of fires such as increased water temperature and decreased dissolved oxygen levels, as well as the associated effects of fires, such as sediment deposition into streams, can impact fish communities by decreasing pool depth by filling with sediment, reducing food supply and reducing the useable resting and spawning habitats. Impacts of fire usually decrease with time as catchments recover and sediment is flushed from the system. The degree of impact of recent fires (e.g. 2006-07) on fish habitat in the upper Thomson River catchment (and hence the ability for the catchment to support diverse fish communities) is unknown, but is not considered a major factor in 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 Australian Grayling, Tupong and Common Galaxias at various sites in areas that were burnt (e.g. Coopers Creek, C5 Track, Bruntons Bridge) (Figure 1), but not from sites upstream of the Horseshoe Bend Tunnel (e.g. Koster and Dawson 2008, Koster et al. 2009).

Arthur Rylah Institute for Environmental Research Client Report 9 Review of diadromous fish distribution in the upper Thomson River system

( a) (b )

Figure 1. Fish survey sites at C5 Track (a) and Bruntons Bridge (b) following the 2006-07 fires.

Horseshoe Bend Tunnel The Horseshoe Bend Tunnel (Figure 2) 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 length of the Thomson River downstream of the tunnel is approximately 128 km. The length of river upstream of the tunnel is approximately 22 km to the Thomson Dam and 63 km to and including the Aberfeldy River. The tunnel (approximately 220 metres in length) 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). The record of an Australian Grayling and the records of other diadromous species upstream of the tunnel indicate that some migratory fish have been able to move upstream, possibly taking advantage of infrequent but appropriate flows through the old river channel. Opportunities for fish to migrate through the river channel are extremely limited, however, because flow in the channel is estimated to occur only about 3% of the time (Koster and Crowther 2003). Overflow into the bend occurs only during high flow events typically only two to three times per year and usually lasting only for a few days on each occasion (Koster and Crowther 2003). In contrast, the timeframe over which upstream and downstream migration of diadromous fishes in south-eastern Australia occurs is far more extensive, encompassing much of the year, with different species also migrating at different times of the year, and under varying flow conditions (Koehn and O’Connor 1990). Migration of fish through the tunnel would also be impeded. Reluctance of fish to move through tunnels has been reported for a range of fish species (Ahmad et al. 1962, Pavlov 1989). The Horseshoe Bend Tunnel presents several major impediments to upstream and downstream fish passage, including steep gradients and sudden drops in height (Figure 1). At the upstream and downstream ends of the tunnel the surface comprises smooth rock and gradients exceed 15 °. Baker and Boubee (2006) found that juvenile and adult Common Galaxias were unable to pass over ramps 1.5 m long, sloped at 15 ° with a bare surface. At the upstream end of the tunnel there is also a turbulent cascade and large drop (>200 mm) in height. Various studies suggest that juveniles and adults of Common Galaxias are prevented from moving upstream by vertical drops of only 100 mm and 200 mm respectively (McDowall 2000, Baker 2003). The white water and turbulence at the upstream end of the tunnel would also disorientate fish and provides no resting areas for several metres. Boubee et al. (1999) predicted that Common Galaxias had a maximum burst swimming distance of only 3.3 m at a velocity of 0.70 m/sec, which declined to 2.1 m at 1.0 m/sec. Water velocities within the tunnel (see below) exceed these values. In addition to steep gradients and drops in height, the tunnel presents several other impediments to fish passage. Water velocities within the tunnel have been measured under low flow conditions

10 Arthur Rylah Institute for Environmental Research Client Report Review of diadromous fish distribution in the upper Thomson River system

(240 ML/day) and range from 1.2 to 2.5 m/sec (Thiess Environmental, unpublished data). For a high flow period (1682 ML/day), data modelling indicates water velocities of approximately 6.2 m/sec in the tunnel (Snowy Mountains Engineering Corporation, unpublished data). This range of velocities (1.2–6.2 m/sec) is known to far exceed the swimming capabilities of small diadromous fishes (Saddlier and O’Connor 1997, Boubee et al. 1999). Saddlier and O’Connor (1997) found that juvenile Tupong were unable to negotiate an artificial channel 2 m long at velocities ranging from 1.1–1.9 m/sec, although some larger fish (190–200 mm in length) could negotiate the channel. The ability of Common Galaxias to negotiate the channel at velocities greater than 1.0 m/sec was also severely reduced, with a 90% failure rate (Saddlier and O’Connor 1997). Natural light within the tunnel is also severely reduced, which can be a behavioural impediment to fish movement (O’Brien 1999, Thorncraft and Harris 200l0, Fairfull and Witheridge 2003). Recent research has shown that the upstream movement of a range of small native Australian fishes (Australian smelt, unspecked hardyhead Craterocephalus fulvus , bony herring Nematalosa erebi , carp gudgeon Hypseleotris spp.) is adversely impacted by low light intensity (Jones in prep). Several recent studies have also shown that the upstream migration of diadromous galaxiids (e.g. Common Galaxias, Galaxias truttaceus ) through fishways occurs predominantly during daylight (Morgan and Beatty 2006, Zampatti et al. in prep). The installation of ‘windows’ (e.g. steel grating) within barriers such as road culverts to provide light is increasingly incorporated into fish passage improvement works (e.g. Cumberland River at Lorne, Tahbilk Lagoon at Nagambie) in recognition that many species require natural daylight patterns for movement and that darkened areas such as tunnels and culverts create behavioural barriers (Thorncraft and Harris 2000). Although other potential obstacles to fish movement exist in the upper Thomson River (e.g. rapids at Bruntons Bridge, The Gorge), the physical and hydraulic complexity of these natural structures produces low velocity resting areas and reduces the distances travelled between rests at high velocities, thereby enabling the successful upstream passage of fish. In addition, during high flows rapids are ‘drowned’, which also provides important opportunities for fish to move around any obstacles to movement (Baker 2003).

( a) (b) (c)

Figure 2. Upstream (a) and downstream (b) ends of the Horseshoe Bend Tunnel and (c) old river channel.

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4 Restoring connectivity of fish passage for Australian Grayling and other diadromous fish in the upper Thomson River system

Native fish species Restoring fish passage connectivity around the Horseshoe Bend Tunnel along the old course of the Thomson River will enable diadromous fish species, including the nationally threatened Australian Grayling, to move into large areas of habitat upstream. Australian Grayling has declined in distribution and abundance throughout its range due to factors such as barriers to movement and habitat loss and degradation (Backhouse et al. 2008, DEWHAC 2010). A National Recovery Plan for Australian Grayling has been developed by an expert panel to address these threats and includes as a key recovery objective increasing the length of rivers available by facilitating fish passage past barriers (Backhouse et al. 2008). Improved access for Australian Grayling and other diadromous fish would be available to a further 22 km of the Thomson River upstream to the Thomson Dam, 63 km of the Aberfeldy River, and numerous tributary streams, including streams in the Baw Baw National Park. It is recognised that the Thomson Dam will continue to restrict diadromous fish distribution upstream of the dam wall. Nonetheless, a substantial increase in the opportunities for diadromous fish to access the upper reaches of the system will be achieved through restoring fish passage past the tunnel, which supports the need to restore access to rivers for Australian Grayling in accordance with the national recovery plan for the species, and represents an important step toward restoring connectivity and biodiversity of native fish communities in the Thomson River system. The extent to which fish would use the upper Thomson River, or tributaries such as the Aberfeldy River, following the reinstatement of fish passage around Horseshoe Bend Tunnel would depend on a complex range of factors such as flow and habitat conditions, which are likely to vary considerably through time. In the upper Thomson River system, flow in the Thomson River generally exceeds flow in the Aberfeldy River, which might encourage more fish to continue migrating up the Thomson River. On the other hand, the unregulated Aberfeldy River which has a more natural flow regime, generally comprises a large proportion of flow in the upper Thomson River system during high flow periods (i.e. spring – early summer), which represents the key upstream migration period for diadromous fishes in south-eastern Australia (Koehn and O’Connor 1990). The presence of the diadromous Short-finned Eel in the upper Thomson and Aberfeldy rivers is evidence of the upstream colonisation of both stream systems, and also suggests that suitable migration and attraction cues (i.e. flows) exist in both rivers.

Alien fish species Two alien fish species — Brown ( Salmo trutta ) and Rainbow Trout ( Oncorhynchus mykiss ) — have been recorded in the upper Thomson River system. Trout have been implicated in the decline of native fishes worldwide, including galaxiids and Australian Grayling (Crowl et al. 1992, McDowall 2006). Trout are widespread in the Thomson River, including upstream and downstream of Horseshoe Bend Tunnel. As they are already found upstream and downstream of the tunnel, the reinstatement of flows around the tunnel would not result in a range expansion of either species. Allowing additional native fish species upstream into waters containing alien species may increase predatory or competitive interactions, though often the degree of interaction is related to habitat complexity and fish density. Another two alien species, Common Carp (Cyprinus carpio ) and Redfin Perch ( Perca fluviatilis ), are restricted to the mid to lower reaches of the Thomson River around Cowwarr. Habitat conditions in the upper Thomson system (i.e. fast flowing riffle/run habitats) are not considered favourable to the establishment of these species,

12 Arthur Rylah Institute for Environmental Research Client Report Review of diadromous fish distribution in the upper Thomson River system though some individuals may penetrate further upstream. The positive benefits of allowing native diadromous fish species access to a relatively large expanse of upstream habitat, including smaller tributary streams, out-weighs any possible negative impacts from alien species.

Timing of fish movement The upstream migratory period of diadromous fishes in south-eastern Australia encompasses an extensive time frame (Koehn and O’Connor 1990), although the migration of different species from marine habitats into lower freshwater reaches of rivers is concentrated around late spring – early summer (Sloane 1984, Gehrke et al. 2002, Raadik et al. 2001, Zampatti et al. 2003). In the Thomson River, fish must first migrate various distances within the , then up the system before they enter the Thomson River itself, before moving upstream through the lowland section to the gorge section commencing at Cowwarr Weir. During migration over this distance, some species may move at different speeds and some movements may be continuous or erratic, so the timing of diadromous fishes reaching the upper Thomson River system upstream of Cowwarr Weir is unclear. Environmental flow recommendations have been developed for the Thomson River which include providing flows for fish passage (Earth Tech 2003, TMEFT 2004). In particular, low flow freshes have been recommended in the period December to April to provide localised fish movement in the upper reaches. A continuous low flow has also been recommended between December to April (Earth Tech 2003, TMEFT 2004). Given the uncertainty about the timing of diadromous fishes reaching the upper reaches, a continuous low flow along the channel of the Thomson River around the Horseshoe Bend Tunnel for upstream may be more effective in facilitating upstream fish passage than short-duration peak flows. The flows provided need to be of sufficient depth to allow for localised fish passage but also to provide refuge. A depth of >0.4 m has been recommended in the environmental flows determination for the Thomson River (Earth Tech 2003) as being the minimum water depth for fish habitat.

Recent research has shown that adult Australian Grayling undertake downstream spawning migrations to the lower reaches of rivers around April–May, coinciding with rises in flow or ‘freshes’, followed by return upstream migrations (Koster and Dawson 2010a, b). Similarly, adult Tupong migrate downstream to the sea for spawning around May–August, coinciding with relatively high flows (Koster and Dawson 2009, Crook et al. 2010). Providing freshes is therefore recommended during April–August to facilitate the downstream (and return upstream) migration of some adult diadromous species. High flow freshes (i.e. >800 ML/d) have been recommended in the period May–November as part of the environmental flow recommendations for the Thomson River (Earth Tech 2003, TMEFT 2004).

Regulating flow through Horseshoe Bend Tunnel Flow rates are one of the important factors limiting the upstream movement of fish. Although flow rates through the tunnel could be reduced, there are other impediments to fish movement through the tunnel, such as steep gradients, sudden drops in height and lack of light. Consequently, altering flow rates alone would have little effect on fish migration. In contrast, the natural river channel of the Thomson River around Horseshoe Bend provides greater opportunities for fish movement because of the complexity of flow patterns (riffle, run, pool, glide, etc.) which provide opportunities for fish to move over short or long distances at a time, aswell as areas of useable resting and foraging habitat.

Arthur Rylah Institute for Environmental Research Client Report 13 Review of diadromous fish distribution in the upper Thomson River system

Fish stocking The recruitment of diadromous fishes relies on complex migrations from freshwater environments to the sea and vice versa. Given that most diadromous fish species in the Thomson River are only short-lived (e.g. Australian Grayling: 2–5 years, Common Galaxias: 1–2 years), if diadromous fish species such as Australian Grayling were irregularly stocked upstream of the tunnel they would persist for only a short period and would not be able to develop self-sustaining populations in the upper reaches unless the critical migration pathway between fresh water and the sea was restored.

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5 Conclusions and recommendations

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, but would naturally also be found in the upper reaches of the system if they had access. The presence in the upper Thomson River system of the diadromous Short-finned Eel, Long-finned Eel and lampreys, which are capable of climbing over barriers, 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 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. A major barrier to fish passage into the upper reaches of the Thomson River systems is the Horseshoe Bend Tunnel. Opportunities for fish to migrate through the old river channel are limited, with flow in the channel estimated to occur only about 3% of the time. Migration of fish through the tunnel would also be impeded by steep gradients, sudden drops in height and excessive water velocities. A lack of natural light in the tunnel poses a further impediment to fish passage. Restoring fish passage connectivity around the Horseshoe Bend Tunnel along the old course of the Thomson River will enable diadromous fish species, including the nationally threatened Australian Grayling, to move into large areas of habitat upstream.

The following recommendations are made based on the findings of this study:

• Restore fish passage connectivity along the old course of the Thomson River around Horseshoe Bend Tunnel. The environmental flow recommendations developed for the Thomson River should be used as a basis for determining the flows required for fish passage. Given the extended migratory period and uncertainty about the exact timing of diadromous fishes reaching the upper Thomson River system, providing a continuous low flow for fish migration may be more effective in facilitating upstream fish passage than short-duration peak flow events. Providing ‘freshes’ is recommended during April–August to facilitate the downstream (and upstream return) migration of adult diadromous species, although for Australian Grayling the key period for adult migration is April–May. It is recommended that the environmental flow recommendations developed for the Thomson River be used as a guide for water depth (e.g. > 40 cm).

• Design and implement a long-term monitoring program to assess the re-establishment of diadromous fishes. This should include pre-intervention and post-intervention monitoring in the upper Thomson River, Aberfeldy River, tributaries, and the mid reaches of the Thomson River near Cowwarr, to provide an indication of fish migration into the system.

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