Water Assessment Aquatic Ecology Report Series Status of fish communities and observations on South Esk freshwater mussel ( Velesunio moretonicus ) populations in the Macquarie River catchment upstream of Lake River July 2009 ISSN: 1835-9523 Report No. WA 09/02 Water Assessment Branch Water and Marine Resources Division Department of Primary Industries, Parks, Water and Environment Copyright Notice: Material contained in the report provided is subject to Australian copyright law. Other than in accordance with the Copyright Act 1968 of the Commonwealth Parliament, no part of this report may, in any form or by any means, be reproduced, transmitted or used. This report cannot be redistributed for any commercial purpose whatsoever, or distributed to a third party for such purpose, without prior written permission being sought from the Department of Primary Industries, Parks, Water and Environment, on behalf of the Crown in Right of the State of Tasmania. Disclaimer: Whilst DPIPWE has made every attempt to ensure the accuracy and reliability of the information and data provided, it is the responsibility of the data user to make their own decisions about the accuracy, currency, reliability and correctness of information provided. The Department of Primary Industries, Parks, Water and Environment, its employees and agents, and the Crown in the Right of the State of Tasmania do not accept any liability for any damage caused by, or economic loss arising from, reliance on this information. Preferred Citation: DPIPWE (2009). Status of fish communities and observations on South Esk freshwater mussel (Velesunio moretonicus ) populations in the Macquarie River catchment upstream of Lake River. Water Assessment Aquatic Ecology Report Series, Report No. WA 09/02. Water and Marine Resources Division. Department of Primary Industries, Parks, Water and Environment, Hobart, Tasmania. Contact Details: Department of Primary Industries, Parks, Water and Environment Water Assessment 13 St Johns Avenue, New Town Phone: 03 6233 6833 Web: www.dpiw.tas.gov.au Email: [email protected] Cover Page Images: Top: Goldfish ( Carassius auratus ). Bottom left: Macquarie River at Delmont Rd, November 2008. Bottom right: Lake Leake, February 2009. The Department of Primary Industries, Parks, Water and Environment The Department of Primary Industries, Parks, Water and Environment provides leadership in the sustainable management and development of Tasmania’s resources. The Mission of the Department is to advance Tasmania’s prosperity through the sustainable development of our natural resources and the conservation of our natural and cultural heritage for the future. The Water and Marine Resources Division provides a focus for water management and water development in Tasmania through a diverse range of functions including the design of policy and regulatory frameworks to ensure sustainable use of the surface water and groundwater resources; monitoring, assessment and reporting on the condition of the State’s freshwater resources; facilitation of infrastructure development projects to ensure the efficient and sustainable supply of water; and implementation of the Water Management Act 1999 , related legislation and the State Water Development Plan. Fish and freshwater mussels in the Macquarie River catchment Summary This assessment of fish communities and South Esk freshwater mussel ( Velesunio moretonicus ) populations was undertaken in the area of a proposed water management plan (WMP) for the Macquarie River catchment, Tasmania, which will encompass the Macquarie River and all of its tributaries upstream of the Lake River confluence. Under the proposed WMP for the area, water resources are to be managed in five Water Management Regions (WMRs): Upper Macquarie River, Lower Macquarie River downstream of Elizabeth River, Blackman River, Elizabeth River and Isis River. During 2007-2008, sampling of fish communities and freshwater mussel populations was undertaken across 25 sites in the catchment (23 riverine sites, and Lake Leake and Tooms Lake) using several methods including visual observations, electrofishing and netting techniques. Where suitable historical data were available, data collected during the recent surveys were compared to historical data to examine temporal changes in fish communities and mussel populations in the Macquarie catchment. This work provided a comprehensive overview of the status of fish communities and the current distribution of V. moretonicus in this region. Additionally, information regarding predation by great cormorants ( Phalacrocorax carbo ) on mussels, and fish-host preferences of V. moretonicus larvae (glochidia) was also gathered. Nine fish species were recorded in the catchment, including four native fishes to Tasmania (short- finned eel ( Anguilla australis ), common galaxias ( Galaxias maculatus ), river blackfish (Gadopsis marmoratus ) and southern pymgy perch (Nannoperca australis )) and five alien species (goldfish (Carassius auratus ), rainbow trout (Oncorhynchus mykiss ), redfin ( Perca fluviatilis), brown trout (Salmo trutta) and tench ( Tinca tinca )); however, it is likely that G. maculatus and G. marmoratus are not indigenous to the region. The species composition of the fish communities in all WMRs, other than the Blackman River WMR, were similar, with the native A. australis and N. australis , and alien P. fluviatilis , S. trutta and T. tinca being common in all four WMRs. Native (but potentially not indigenous) G. maculatus and G. marmoratus , and alien C. auratus were uncommon and only found in 1-2 WMRs. Based on backpack electrofishing data, alien species accounted for significant proportions of the total catches in lowland (27%) and upland (49%) riverine sites. Perca fluviatilis , S. trutta and T. tinca were the dominant alien species, with P. fluviatilis and T. tinca being more prolific in lowland reaches and S. trutta in upland reaches. Overall, the species compositions of the fish communities in the catchment during 2007-2008 were similar to historical records for the region, although the distributions and abundances of some species appear to have changed in recent years. Flows in rivers in the region during the study were relatively low and had been so for some time prior to the study (the last major floods in the catchment occurred in 2005, and, generally, flows in rivers in the catchment have been relatively ii Fish and freshwater mussels in the Macquarie River catchment low since 1990). These recent low-flow conditions appear to have allowed some species which prefer still or slow-flowing habitats ( N. australis , P. fluviatilis and T. tinca) to extend their distributions. These conditions may also have assisted the upstream dispersal of an alien pest species ( C. auratus ) in the lower Macquarie River system upstream of Lake River; an area where it has not previously been recorded. Additionally, the distribution and abundance of populations of an alien species that was previously wide-spread and valued by recreational anglers ( S. trutta ) has declined recently. This is likely to be due to low flows in the catchment causing poor recruitment and unfavourable environmental conditions for this species. Similarly, in recent decades, flow conditions appear to have influenced the distribution of the endemic V. moretonicus in the Macquarie catchment upstream of Lake River by dewatering some reaches where mussels previously occurred. This species is now restricted largely to the lower reaches of the Macquarie River where habitats are relatively deep, and flow conditions are relatively stable due to flow regulation. Velesunio moretonicus were found in dense aggregations in run habitats at some sites in the lower Macquarie River; however, the viability of populations in the catchment is unknown and requires further investigation. Velesunio moretonicus glochidia were found on only two fish species, native A. australis and alien T. tinca , with A. australis having a much higher prevalence of parasitism compared to T. tinca . Furthermore, larger-sized individuals of both species appeared more likely to be parasitised. Fish that were parasitised by glochidia were mostly collected from sites where adult V. moretonicus were recorded, but at two sites, Isis River at Isis Road and Macquarie River at Tooms Lake Road, no live adult mussels were observed. This study has shown that, in recent times, broad-scale changes have occurred in fish communities in the Macquarie catchment and that the distribution of the endemic freshwater mussel V. moretonicus in this region may also have reduced. Both of these alterations to the ecosystems of the Macquarie River system appear to be associated primarily with flow regime alterations; however, in some instances, landscape degradation (e.g. removal of native riparian vegetation; nutrient enrichment of soils, hence waterways, etc.) is likely to have caused compounding impacts. Prolonged periods of reduced flows or unseasonal flow patterns (due to dry climatic conditions and/or water use), similar to those which have recently occurred in the catchment, are likely to impact on fish communities and freshwater mussel populations. Such conditions are likely to allow alien pest fishes to further extend their distributions and continue to restrict colonisation of V. moretonicus in areas it previously occupied. Seasonal flow variability and adequate baseflows in all rivers in the region are critical to the long-term viability of fish and mussel populations. Proactive management