Southern Pygmy Perch (Murray-Darling Basin lineage)  |  

Nannoperca australis Murray-Darling Basin lineage

Status: Vulnerable on the EPBC Act list

The Southern Pygmy Perch-MDB is a small, laterally compressed fish which grows to a maximum size of 85 mm. Southern Pygmy Perch-MDB differ from the closely related Nannoperca obscura (Yarra Pygmy Perch) by having a smooth, non-serrated lower edge of the preoribital bone. Morphologically, Southern Pygmy Perch-MDB appear the same as other lineages of Southern Pygmy Perch, and range in colour from cream to gold-orange to greenish-brown mottling on its back and sides, to a silver white belly. Fins are generally clear to dusky, but for males turn bright red to black in the breeding season.

Government evidence of impact of climate change:

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  • Australian Government, Conservation Advice, Nannoperca australis Murray-Darling Basin lineage

    While climate change doesn t directly cause bushfire; it has caused an increase in the occurrence of extreme fire weather and in the length of the fire season across large parts of Australia since the 1950s (CSIRO 2020).
    Climate change has driven longer; more intense fire seasons and an increase in the average number of elevated fire weather days; as measured by the Forest Fire Danger Index (FFDI) (CSIRO 2020).
    Bushfire seasons of this intensity and scale are likely to increase as a result of climate change (CSIRO 2020). 3.2 Changing rainfall Suspected Freshwater ecosystems are particularly patterns current vulnerable to climate change because they are and future isolated and fragmented within a terrestrial landscape (Morrongiello et al.; 2011).
    Surface water; which determines the quality and availability of aquatic habitat; depends heavily on rainfall and temperature regimes which are predicted to drastically change under climate change predictions (Carpenter et al.; 1992 Hobday Lough 2011).
    Extreme events such as storms (and associated floods) and droughts are projected to rise in frequency and or intensity under climate change (Aldous et al.; 2011 Hobday Lough 2011).
    Given that remaining Southern Pygmy Perch MDB populations are isolated and fragmented; there is a high likelihood that severe impacts will occur to the species as a result of changing rainfall patterns driven by climate change.
    Bushfire can adversely affect stream habitat by increasing water temperature; altering water chemistry (Lyon O Connor 2008); and creating sediment ash runoff slugs that can form in waterways following rainfall on burnt areas (Lyon O Connor 2008 Alexandra Finlayson 2020).
    It has been proposed that restoration work in streams degraded by sand slugs may be better directed toward restoring refuge habitat (deep pools and backwaters) rather than focussing on residential habitat (addition of wood timber structures) to increase the resilience of species such as Southern Pygmy Perch MDB to drought and flood (Bond Lake 2005). 1.4 Changes to flow Suspected River regulation throughout the Murray Darling regimes past; Basin; which has involved the construction of current thousands of dams; weirs and other structures and future in catchments and along waterways (Lintermans 2007) have greatly influenced natural flow regimes.
    Median runoff is predicted to decline by up to 12 and flood frequency is predicted to decrease (Balcombe et al.; 2011).