Conservation management of southern pygmy perch (Nannoperca australis) in NSW, in the context of climactic extremes and alien species

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    Abstract Small freshwater fishes have been reported to have an extinction risk greater than or equal to that of their larger counter parts. This may be due to certain traits many small freshwater fishes possess, such as: limited geographic range, relatively poor dispersal and movement capabilities, specialized habitat requirements, and vulnerability to predation, especially by alien fishes. This is appears to be the case in Australia, with 77.7% of freshwater fishes listed as threatened being of small body size: only 63.4% of the total number of freshwater fish species are small-bodied. Southern pygmy perch, Nannoperca australis, is one of these species: its range has dramatically declined in recent decades, particularly within New South Wales, and it is listed as threatened in that state and in Victoria. The overall aim of this study was to determine the current abundance and distribution of southern pygmy perch within NSW, assess impacts contributing to its decline and provide tools and advice for future management. The specific objectives were to 1) examine temporal and spatial changes in the distribution and abundance of the southern pygmy perch population in Coppabella Creek, southern NSW, under extreme climatic conditions; 2) evaluate the suitability of marking and tagging techniques to aid in conservation and management of southern pygmy perch in NSW and elsewhere; and 3) examine the relationship between the abundance and distribution of southern pygmy perch populations within NSW relative to the distribution and spread of alien fish species, and evaluate these finding in relation to the current and future management and conservation of southern pygmy perch.The distribution and abundance of southern pygmy perch within Coppabella Creek, a small tributary of the Upper Murray River, were dramatically impacted on by extreme climatic events, a prolonged drought (1996-2010) followed by flooding (2010, 2011 and 2012). While there was significant drying of pools and loss of fish during the drought, the fish persisted within refuge sites. However, following flooding, there were catastrophic declines in the both the abundance and the distribution of the species. Fish collected declined from 2375 individuals across 6 sites during the drought to only 4 individuals at 2 sites after the floods. During the drought, the distribution of this species covered 28 of the 34 km of Coppabella Creek. After flooding, that distribution reduced to 5 km. The abundance and distribution of the alien common carp (Cyprinus carpio), by contrast, dramatically increased after flooding: the species advanced a further 8.8 km upstream, and collections increased by more than four times. I tested two quick and cost-effective methods for the marking of southern pygmy perch: 1) calcein for the mass or batch marking of juvenile fish; and 2) visible implant elastomer (VIE) for the marking of individuals or cohorts. The calcein marking showed similar results to those achieved in previous studies, with 100% detection rate with the higher (1%) concentration of calcein at 114 days, and no significant impacts on growth or mortality. Whilst there was no significant impact on growth or mortality with VIE tags, the tagging location proved problematic. Two of the tag locations (dorsal and anal) had substantial tag rejections and hence detectability problems, with only the caudal peduncle being identified as viable tagging location. I also explored relationships between the presence/absence of southern pygmy perch and alien species, by sampling multiple sites in three small tributaries of the Murray River, Coppabella, Mountain and Blakney''s creeks. Generalized liner mixed model analysis found that, overall, the presence of southern pygmy perch was significantly related to the abundance of common carp. Unlike the results of other studies, where redfin perch (Perca fluviatilis), brown trout (Salmo trutta) and gambusia (Gambusia holbrooki) were found to h
    Original languageEnglish
    QualificationMaster of Philosophy
    Awarding Institution
    • Charles Sturt University
    • Humphries, Paul, Co-Supervisor
    • Watts, Robyn, Co-Supervisor
    • Gilligan, Dean M., Co-Supervisor, External person
    Award date16 Nov 2015
    Place of PublicationAustralia
    Publication statusPublished - 2014


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