Research finds log booms harmful to B.C. salmon and fish habitats

Two new studies are highlighting what researchers say is the harmful effect of log booms — floating structures that contain logs before processing — on fish habitats in B.C. rivers.

A report from the Pacific Salmon Foundation and the B.C. Conservation Foundation (BCCF), led by the Cowichan Tribes, finds the presence of log booms at the mouth of the Cowichan River caused a 20 per cent reduction in survival rates for adult chinook salmon.

Meanwhile, the lead author of a soon-to-be-published study from the University of B.C. and the Musqueam First Nation says that log booms in the Fraser River have a significant effect on nearby habitat, causing more soil to fall onto the riverbed and fewer invertebrates, which could be food for fish, to spawn.

Researchers say the studies show the need for updated log-boom management practices to help fish thrive, something that is particularly urgent as the warming climate causes river levels to drop and makes life more difficult for salmon.

The PSF and BCCF report studied salmon that had been tagged with transponders, with researchers monitoring how human activity affected their survival.

Jamieson Atkinson, lead author of the BCCF study, said the log booms in the Cowichan River led more seals and sea lions to perch there — which, researchers suspect, caused more salmon to be eaten.

The log booms also exacerbate the problem of low river flows, Atkinson said.

"When river discharge is low, it impacts the ability of fish to move into the river and then increases terminal mortality," he said.

"We need to reassess how log booms are stored in estuaries," he added. "And if they run aground, and they're at mouths of rivers, the best option is to remove them into deeper water or out of the water entirely.

"To see it continuing into 2024, it's time that these changes are made," he added.

Another study, set to be published in the Canadian Journal of Forest Research, looked at the impact of log booms on fish habitat in the Fraser River. It found that the area underneath booms can accumulate wood fibres and bark, and the booms could create oxygen problems for underwater creatures.

UBC forestry professor Scott Hinch, who led that study, said the logs could leach chemicals and toxins that could harm the marine environment.

"They can change plant growth," he told CBC News. "Because of the accumulation of material underneath [them], they can also change the sorts of invertebrates that are growing there.

"These, of course, are the food for the fish."