Document ID: chunk:federal_register_of_legislation:F2019L00106:body:0:p55
Version: federal_register_of_legislation:F2019L00106
Segment Type: other
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Character Range: 146854–150005

frequency and/or intensity under climate change (Aldous et al., 2011; Hobday & Lough 2011). As are extreme fire weather events, with the resultant greater risks of secondary water pollution and sedimentation (Morongiello et al., 2011).
Tonkin et al. (2017b) suggests that most remnant populations of Macquarie perch, which are now predominantly isolated within small tributary systems characterised by highly variable flows, face a heightened risk of poor recruitment periods, particularly under climate change predictions. Extreme flow events during the spawning period in these areas are likely to negatively impact upon recruitment frequency and adult survival (Tonkin et al., 2017b).
With predictions for longer and more severe dry spells as a result of climate change, drought impacts are likely to further stress freshwater fish populations in southeastern Australia (Crook et al., 2010). Reductions in run off due to climate change will further fragment freshwater habitats and fish populations, leading to reduced 'fitness' (Balcombe et al., 2011). Climate change, coupled with the impacts of existing land and water use, could further significantly change freshwater ecosystems in the Murray-Darling Basin unless on ground conservation actions are undertaken (Pittock & Finlayson 2011). Additional declines in water quantity and quality will have an adverse impact on existing freshwater ecosystems (Pittock & Finlayson 2011).
The general effects of climate change on freshwater systems will likely be increased water temperatures, decreased dissolved oxygen levels, and the increased toxicity of pollutants (Ficke et al., 2007). Generally, Australian freshwater fish are predicted to be impacted by climate change by increased rates of habitat loss and fragmentation, surpassing of physiological tolerances and the spread of introduced species (Morongiello et al., 2011). Water temperatures are especially important to freshwater fish as all are exothermic, hence body temperatures are identical to environmental temperatures (Ficke et al., 2007). Increased water temperatures are likely, on average, to decrease dissolved oxygen levels, given that cold water has the potential to hold more dissolved oxygen than hot water (Ficke et al., 2007). Macquarie perch are particularly vulnerable to local extinction under climate change scenarios given the species already fragmented range (Morrongiello et al., 2011). Some introduced fish species are likely to benefit from warmer temperatures, habitat degradation and increased modification of natural flow regimes, whereas others will be detrimentally affected by increases in flow ephemerality, disturbance and the surpassing of physiological tolerances (Booth et al., 2011; Morrongiello et al., 2011).
Freshwater fish in the Murray-Darling Basin have been particularly affected by the changes to flow regimes and biological connectivity associated with water-resource development and climate change will place further stress on these species (Balcombe et al., 2011). However, there is some thought that climate change may potentially benefit Macquarie perch in the southern Basin, as increased