Hatchery-raised salmon too crowded

What is it about?

We investigated if reduced rearing density and increased structural complexity promote development of behavioural skills in brown trout. We reared trout at three densities in tanks with or without structure. We found no effects of structure, but the density effects were very clear. Trout reared at reduces densities were better at finding food and escaping predator attacks, and were also more likely to survive in the wild than were trout reared at conventional hatchery densities.

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Why is it important?

Large amounts of young salmonids are released into rivers and streams across the world to support natural populations. However, conventionally raised fish seem to have problems adapting to their natural environment. This study suggests that a simple change, reducing rearing densities, can increase the quality of hatchery salmonids and their contribution to natural production.