Wednesday, 18 January 2012

Ecological disaster as 300,000 farmed salmon lost?

Over 300,000 farmed salmon have been 'lost' by Meridian Salmon when 12 salmon cages broke loose in Shetland on Christmas Day.

A spokesman for Meridian said “It’s important to make a distinction between fish loss and fish escape. Over 300,000 adult Atlantic salmon were involved in the incident, but it remains unclear whether an escape of live farmed fish did occur or whether the fish died during the incident.”

Which means that there is a strong possibility that 300,000 farmed salmon are swimming about in the North Atlantic creating havoc in the marine ecosystem.

Why we need to be worried

When farmed salmon escape they can interact with wild salmon causing significant changes in the wild salmon stocks during ten salmon generations (about 40 years). In rivers with a high number of escaped farmed salmon it appears that the population is gradually dominated by the offspring of farmed and hybrids of salmon. Even after many decades without new escapes, it is possible that these populations will be dominated by descendants of escaped farmed fish.

Other consequences:

• Farmed fish have lower genetic variation than wild fish.

• Farmed fish hybridise with wild fish.

• The fitness of wild populations is reduced by immigration of farmed fish.

• Escaped farmed fish destroy, and compete with wild fish for spawning beds.

• The progeny of escaped farmed fish out-compete wild fish in the competition for resources in the river, both as fry and as parr.

• Farmed salmon increase the hybridisation between salmon and trout

• The size and fitness of the populations of salmon stocks will be reduced if the percentage of farmed salmon continues to be high.

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