Research conducted by the Department of Water and Environmental Regulation has found good numbers of fish and crayfish in the Collie River, despite the river suffering from low water levels throughout the year.
Department of Water and Environmental Regulation researcher Emma Christie presented the findings of the department’s Healthy Rivers program that examined conditions at 10 sites along the river to the shire council’s Weeds and Waterways Advisory Committee in August.
The study found that all seven expected native species to the river – freshwater cobbler, marron, gilgie, western minnow, nightfish, western pygmy perch, and blue spot goby – were present.
A spokesperson for the Department of Water and Environmental Regulation said the communities of fish and crayfish in the river were at the expected levels.
“Generally, fish and crayfish communities were good, with all species expected in the system being found and successful breeding in several locations,” the spokesperson said.
“We found high numbers of western pygmy perch in Duderling Pool and freshwater cobbler in a site at Quinns Road.
“The presence of all seven expected species, and high abundances at two sites, suggests the ecosystem is able to support the native species via a range of habitats, water quality conditions and food sources.
“We found juveniles at eight of the 10 sites – this is particularly important as it shows that the fish and crayfish can move through the system to access necessary areas required for breeding, nursery and foraging.”
Weeds and Waterways Advisory Committee member Ed Riley said he was particularly concerned about the results from Duderling Pool (more commonly known as Bucks Hall Pool).
“The most disturbing but not unexpected results were recorded in … the Bucks Hall Pool where no gilgies were found and only the odd marron,” he said.
“There were low numbers of native fish and the presence of the introduced gambusia came as no surprise as salinity and water temperature were high with poor pH levels.”
The department spokesperson said Duderling Pool was suffering from “a number of threats to the pool ecology, including catchment conditions and reduced rainfall due to climate change.”
The spokesperson said the department had been undertaking management actions to address the pool’s salinity issues, while the Myalup-Wellington Project may also help in removing some of the highly-saline water before it reaches the pool.