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Topic: Genetic impacts of escaped fish


Farmed salmon that escape are one of the biggest environmental challenges facing the Norwegian aquaculture industry. That is because some of the escaped fish manage to spawn with wild salmon, affecting the genetic makeup of wild populations.

Do escaped salmon survive?

The proportion of fish that survive long enough to spawn after escaping depends on the time of year and their life stage when they escape. If a farmed fish escapes in the early part of production or just before reaching sexual maturity, it is more likely to survive and reach the spawning grounds. Fish that escape in between those ages will have bigger problems with learning to catch food and avoid predators, for instance, so fewer of them survive.

Is the genetic makeup of wild salmon affected?

It has been demonstrated that escaped farmed salmon have affected the genetic makeup of wild salmon populations in many Norwegian rivers. Regular monitoring is carried out to review this situation.

Does it matter that the genetic makeup is affected?

The salmon in each river are adapted to the environment in that particular river. If the population’s gene pool changes as a result of escaped farmed salmon spawning in the river, they may become less well adapted. It has been shown that “hybrid” salmon are less likely to survive than wild salmon.

Escaped cleaner fish

The cleaner fish that the aquaculture industry uses to eat sea lice can also escape and hence affect local populations.