It's a Marathon, Not a Sprint: Sprinting Salmon Less Likely to Survive Migration

It's a marathon, not a sprint; this phrase is truer than most for sockeye salmon. Scientists have found that fish which essentially "sprint" to their spawning groups through fast-moving waters are less likely to survive than those who take it a bit easier.

When salmon encounter turbulent, fast-moving water, they need to move upstream with "burst swimming." This is similar to sprinting in humans, and essentially involves the fish working harder in order to make headway against fast waterways. In previous research, scientists have found that burst swimming requires extra oxygen and energy, creating a buildup of stress metabolites like lactic acid in the blood.

"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, the lead author of the new study, in a news release.

Burst swimming is actually more common in places where there are high flows caused from dams. Scientists examined salmon after they passed through fast flows and compared them to those who chose to swim a bit more slowly through these sections. In the end, the researchers found that burst swimming had a greater impact on female fish, which supports the idea that female salmon are more sensitive to environmental hardships during migration.

"We now understand how this important but energetically costly swimming behavior can impact the survival of sockeye during their upstream migration," said Burnett. "Our work demonstrates how important it is for salmon to have easy access around obstacles in the river."

The findings reveal a bit more about salmon migration and show what kind of management strategies may be necessary to boost salmon populations in the future. By creating less fast flow areas, managers can ensure that salmon are more easily able to migrate to spawning grounds without dying in the process.

The findings are published in the journal Physiological and Biochemical Zoology.