Sprinting Salmons Less Likely to Survive Migration

Sockeye salmon that are forced to use fast-moving waters to reach spawning grounds are at risk, a new study suggests.

Salmon often try to burst swim in rapid, turbulent waters. Burst swimming is comparable to sprinting in humans. These fish try to move upstream in fast-flowing waters, a behaviour that utilizes more oxygen than usual swimming methods.

Researchers at the University of British Columbia and colleagues conducted the study. The team tagged salmon with accelerometer transmitters. The device allowed researchers to monitor movements of the fish.

Salmon used in the study were released in the high flows downstream of a dam in southwestern British Columbia. The team then tracked the fish as they navigated the fishway and two lakes to reach their spawning grounds.

"Days after sockeye passed through extremely fast-moving water, we started to see fish dying only a short distance from their spawning grounds," said Nicholas Burnett, a research biologist at UBC and lead author of the study, according to a news release.

Previous research by UBC scientists has shown that burst swimming uses a lot of oxygen and energy. Salmon also accumulate stress metabolites such as lactic acid in blood that can lead to heart attacks.

In the current study, the researchers found conclusive evidence that "sprinting" can affect mortality of wild salmon. Fish tired after burst swimming are more likely than others to die before reaching spawning grounds.

"We now understand how this important but energetically costly swimming behavior can impact the survival of sockeye during their upstream migration," said Burnett in a news release.

The researchers also found that burst swimming taxed female fish than males, showing that female salmons are more vulnerable to environmental stressors during migration.  

The study is published in the journal Physiology and Biochemical Zoology.