Fish kills a signal of climate change
As reports continue to flow in about dead fish washed up on the banks of the Pallinup River, the Department of Water and Environment Regulation has warned more fish kills could occur as a result of climate change.
After initial reports of dead fish at Beaufort Inlet last month, DWER has received more reports from campers and commercial fishers from locations along the Pallinup River.
Reports were received from the river mouth to a section 11km upriver.
Poor water quality due to reduced river flows has been a significant factor in other recent fish kills in WA.
“Historically bar-closed estuaries like the Beaufort would have had fish kills in response to seasonal wetting and drying unrelated to land use in the catchment,” DWER said.
“Rainfall and streamflow tracking by the department showed that the 2019 winter season ended with the majority of rivers and streams across the south west land division tracking at below average flows — the driest conditions since 2010.
“Due to the unprecedented nature of this dry season, more fish deaths may occur.”
After investigations into the initial fish death reports at Beaufort Inlet, field tests showed salinity levels were more than double that of seawater.
The water was also quite warm at about 22C, but tested negative for toxic algae.
Because there were no fish in a suitable state for autopsy, none were collected, a DWER spokesman said.
Water testing also revealed nitrogen and phosphorus concentrations above environmental guidelines, however according to DWER, such findings were not unusual for modified ecosystems where the catchment had been cleared for agriculture.
Chris Gunby, who was at the Pallinup River on Friday, said he found “many thousands of dead fish”.
“Some very old and large bream — so this is not a regular event,” he said.
“Some fish have only just died so it may be ongoing.
“The smell of rotting fish is very unpleasant and campers are avoiding the area.”
A report into the state of the Pallinup River and the Beaufort Inlet by the Water and Rivers Commission and Natural Heritage Trust in 2003 showed that the quality of water in the rivers was deteriorating and the inlet was showing signs of extreme nutrient enrichment.
“The Beaufort Inlet is a popular camping and fishing area, requiring a sound management plan if its values are to be adequately protected,” the report said.
“For the river to become a healthier system, an effort to protect and improve the riparian vegetation has to be made ... stock must be largely excluded, weeds controlled and regeneration of trees and understorey species encouraged.”
DWER has urged people to avoid any areas where fish deaths were observed, and to report any sightings as early as possible, to give officers the best chance of understanding and managing the events.
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