Murdoch University black bream study project positive for fish and rivers


Student researcher Nathan Beerkens and a young friend release a tagged fish into the river.
Student researcher Nathan Beerkens and a young friend release a tagged fish into the river.

A NEW project tracking black bream throughout the Swan and Canning Rivers is not only giving researchers an insight into the species, but also the health of the waterways.

Murdoch University student researchers Jake Watsham and Nathan Beerkens’ Swan Fish Track study uses acoustic tags to record the bream, one of the rivers’ most coveted fishing species, through the rivers.

Helping to fund the project, a Recfishwest spokesman said preliminary results had given them some interesting information.

“Dedicated fishers would know there are areas where you are more likely to find fish – they can be found as far downstream as Fremantle and well up into the Swan Valley/Guildford reaches and beyond,” he said.

“What the study has helped to prove is that black bream no longer utilise the deeper pockets of water in the middle/upper reaches of the river where oxygen depletion is quite prevalent.

“A number of complex environmental reasons are to blame for this, such as a drying climate limiting freshwater flushing of the river.

“But the accumulation of organic plant matter is also regarded as a cause, resulting from fertiliser nutrient loading leading to algae growth, which dies, sinks, decays and consumes oxygen in the deeper waters, which is hard to replenish.

“The study also showed that fish were spending much more time around complex and woody river banks – such as those lined with trees, snags and natural vegetation – than those which had been cleared and altered.”

The spokesman said “significant improvements” to water quality in the past decade had given them a suitable environment to conduct the study and helped species still recovering from the recent history of poor water quality.

“The findings around directed behaviour to oxygenated waters support continued water quality improvement and fertiliser reduction,” he said.

Mr Watsham said making positive changes in the river needed the combined support of the community, scientists and government.

“If we give back to the river it will give back to us,” he said.

“Reducing the amount of fertiliser we use, improving bank vegetation and resnagging projects will be vital in the sustainable management of the fish in the Swan.”