Fish facts: Silver perch
Fish facts: Silver perch.
Its closest relative is, however, Welch’s grunter (Bidyanus welchi), which was first encountered by Europeans in 1861 from Coopers Creek and is native to the drainages of Lake Eyre and the Barcoo, Diamantina and Georgina Rivers.
In contrast, silver perch were first described by Europeans in 1838 from the area between the Gwydir and McIntyre Rivers, where they were called bidyan by the Aboriginal people of the area, hence their scientific name.
This species has also been introduced into the Lake Eyre Basin as well as several impoundments and coastal river systems of south-eastern Queensland, New South Wales and south-western Western Australia as part of restocking efforts.
Adult silver perch are omnivorous, feeding on a variety of small prey including zooplankton, insect larvae, molluscs, crustaceans and worms as well as algae.
In many parts of their range the amount of algae in the diet tends to increase with fish size.
Most of the adult fish tend to move upstream in a short spawning run period between November to February, while immature fish may move upstream over a longer period between October to April.
Recent constructions of native fish friendly fishways on several weirs have improved this situation along the middle and lower reaches of the Murray River, but silver perch populations remain endangered in many other regions due to a myriad of factors including siltation that reduces spawning habitat and survival of silver perch eggs and larvae, diversion of eggs and larvae into irrigation water, cold water pollution from dams, and introduced diseases.
Female silver perch grow to a larger size than males, reaching a maximum size of around 45 cm and 7-8 kg.
Maximum age is at least 17 years for river fish and 27 years for fish in impoundments.