Giant feral fish are threatening the survival of unique native fish in the rivers of south western Australia.
The world’s largest Pearl Cichlid (a South American species) was recently captured in a Beechboro lake, just north of Perth, and weighed in at nearly a kilo. This fish joins records of the fastest growing goldfish (up to 2kg), and big silver perch and golden perch – all caught in WA fresh waters over the past 12 months.
Dr Stephen Beatty from Murdoch University’s Freshwater Fish Group and Fish Health Unit said there had been a 44 per cent increase in introduced freshwater fish in south-west WA over the past decade. These introduced species now outnumbered native species in the region.
“The Pearl Cichlid was captured as part of an ongoing State Government funded project that aims to understand the species better in order to target eradication action,” Dr Beatty said.
“These fish can enter the river system and are being dumped from aquariums into catchment lakes. They are thriving in these nutrient rich water bodies and can grow much larger than the native fish.
“They compete with native species, and that just adds to the existing threats associated with habitat and water quality decline to put natives under serious pressure."
Dr Beatty said that a dedicated collaborative community campaign was also underway in the south-west to tackle the problem of feral fish in these waterways. This has resulted in more than 10,000 feral fish being removed from rivers over the last year.
"The feral fish monitoring and control program in the Vasse-Wonnerup Ramsar system near Busselton is a federally funded, community based project,” said Dr Beatty.
“It involves the South West Catchments Council, GeoCatch, Shire of Busselton and the State Government Departments of Fisheries, Environment and Conservation, and Water to educate the community to prevent new releases and also target feral fish in local waters for control.”
Researchers from Murdoch’s Freshwater Fish Group and Fish Health Unit have also produced a book and a series of short films to raise awareness about native and introduced aquatic species, thanks to support from SERCUL, Lotterywest and EnvFusion Films.
“The book is a collation of many people’s work in this unique region, and highlights the plight of native fishes and the threat posed by feral aquatic species such as Yabbies and Pearl Cichlids,” said Dr David Morgan, one of the book’s authors.
For more information on freshwater fish including the book and films visit the Freshwater Fish Group website or the Sercul website. Proceeds from the books go to support the freshwater conservation efforts in the region.