Thursday, June 9, 2011

Fishing May Result in Smaller Alaskan Salmon

According to research published on, fishing has driven evolution of smaller Alaskan salmon. A study by Neala Kendall at the University of Washington in Seattle sorted through data from canneries on the size and age at maturation of the sockeye (Oncorhynchus nerka) fished from five fisheries in Bristol bay, Alaska, since 1943.

The researcher found that the fish had become 14 millimeters shorter on average. Moreover, the number of fish that spent two rather than three years in the ocean before returning to fresh water to spawn increased by 16 per cent.

Fishing for the largest sockeyes is the likely culprit, says Kendall, because fishing targets larger fish. Many of these are breeding females, and removing them from the population also eliminates their eggs. Body size is a heritable trait, so the genes within those eggs – some of which are associated with late maturing and large body size – are also lost.

According to the study, fishing-induced evolutionary changes could also explain why the population of Atlantic cod (Gadus morhua) in the southern Gulf of St Lawrence has been unable to rebound since the fisheries there collapsed almost three decades ago. As with sockeye, cod fishers harvested the largest fish, including breeding females.

The lucrative Bristol bay sockeye industry brought in $5 billion between 1950 and 2008. According to Ms. Kendall, if current trends continue, the fishery could become less profitable.

Kendall presented her findings at the second International Marine Conservation Congress in Victoria, British Columbia, Canada, last month.


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