Bull trout binge feed on migrating juvenile sockeye salmon

What is it about?

Juvenile sockeye salmon ("smolts") migration from rearing lakes to the ocean. Recent telemetry research on the Chilko (British Columbia) population has identified small clear rivers as an area of poor survival, and bull trout have been observed to congregate at the lake-river edge to feed on smolts. We use stomach contents of bull trouts to assess feeding rates on sockeye smolts. Virtually all stomach contents were smolts, and feeding rates were high, often exceeding theoretical daily maximums.

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Why is it important?

We found that bull trout target and feed upon migrating sockeye smolts, a newly-identified predator-prey relationship. Bull trout consumption was very high relative to other studies and laboratory-established daily maximums. Therefore bull trout appear to be "binge-feeding" on smolts, and the smolt outmigration may be an important source of energy and growth for bull trout. We also provide evidence that fish can regularly exceed theoretical daily maximum consumption rates when food is plentiful.