Document ID: chunk:federal_register_of_legislation:F2019L00106:body:0:p43
Version: federal_register_of_legislation:F2019L00106
Segment Type: other
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Character Range: 114431–117343

Australia (Koehn 2005; Davies et al., 2012). European carp disturb native fish habitats by raising turbidity and destroying submergent macrophytes (Roberts et al., 1995; Roberts & Sainty 1996; Villizi et al., 2014). European carp larvae feed upon similar prey items as larvae of two other species of native fish, Murray cod and golden perch (Tonkin et al., 2006), so it is possible that the same competition exists for Macquarie perch. Large carp were observed trailing groups of Macquarie perch in spawning habitats in the Mitta Mitta River upstream from Lake Dartmouth, and were video filmed filtering gravel (Tonkin et al., 2009). These behaviours could suggest feeding on Macquarie perch eggs, however, gut analysis of six individuals did not reveal any eggs (Tonkin et al., 2009). These samples were kept pending future investigation using genetics (Tonkin et al., 2009).
Eastern gambusia (Gambusia holbrooki), native to the Gulf of Mexico, were introduced to Australia in the mid-1920s to control mosquito larvae (Cadwallader & Backhouse 1983; Lloyd & Tomasov 1985; Arthington 1991). The fish was distributed widely around Australia during World War II to military camps. It is now found widely across the Murray-Darling Basin (Lintermans 2007). Although there are no direct studies on the impacts of Eastern gambusia on Macquarie perch, they are known to harass and impact other species of fish through fin-nipping and eat fish eggs and juveniles (Koehn & O'Connor 1990a;b; Bayley & Li 1992; Arthington & McKenzie 1997), and have been observations have been made of fin-nipping on native southern pygmy perch (Nannoperca australis) (Tonkin et al., 2011), thus may similarly impact juvenile Macquarie perch.
Targeted removal of the introduced species redfin and European carp in Seven Creeks during September 2014 has contributed to an increased abundance and successful recruitment of Macquarie perch within this waterway (ARI unpub. data, cited in ARI pers. comm., 2017). The impact of introduced fish species on Macquarie perch is likely to have been significant and has contributed to the widespread decline of the species. If introduced fish species such as salmonids, redfin, eastern gambusia and European carp continue to increase in numbers and proliferate in areas where Macquarie perch live and breed, the species will decline further and recovery will be extremely difficult.

6.2.3 Barriers to fish movement
Human made structures such as dams, weirs and regulators are known to impede migration and prevent completion of life cycles of freshwater fish species (Cadwallader 1978; Faragher & Harris 1994; Thorncraft & Harris 2000; Gilligan et al., 2005), such as the Macquarie perch. Instream barriers can prevent fish moving between spawning and feeding areas as well as interrupting gene flow and fragmenting fish populations (Lintermans 2013c; NSW DPI 2013a). The fragmented range of Macquarie