Silver perch are an elongate fish with a laterally compressed, oval-shaped body. They have a pointed head and snout and a relatively small mouth with equal jaws and narrow bands of very fine villiform (needle-like) teeth. The spiny dorsal fin is moderately high and strong and merges with the soft dorsal fin without a distinct notch or break. The tail is slightly forked. Very large specimens assume a slightly disproportionate appearance with a strongly humped forehead, strong lateral compression and a more distinctly pointed, almost beak-like head and snout. Silver perch colouration varies based on water clarity (darker colouration is associated with clearer water) but specimens are generally a dusky bronze or green colour on the back, with silvery-grey flanks and a white belly. On some specimens dark edges to the scales create a subtle cross-hatched or checkered appearance on the flanks.
Silver Perch, Bidyan |
Status: Critically Endangered on the EPBC Act list
Government evidence of impact of climate change:
Australian Government, Conservation Advice, Bidyanus bidyanus
However; King et al. (2008) demonstrated that silver perch spawning in the Murray River in the Barmah Millewa area; as measured by drifting eggs and larvae; increased significantly compared to the two preceding years during a prolonged; sizeable spring summer flood event that was substantially enhanced with environmental water allocations.
King et al. (2008) demonstrated increased spawning of silver perch and other native fish can be achieved by environmental flows that aim to mimic components of natural flood events.
For example; in 2009 2010; 154 gigalitres of Commonwealth environmental water was delivered to environmental assets in the Murray Darling Basin; while in 2010 2011 more than 387 gigalitres of delivered water aimed to capitalise on the ecological benefits of high rainfall and increased river flows experienced across the Basin and support the ecological recovery of riverine and wetland communities following years of extended drought (Australian Government; 2010 2011).