Not only are salmon runs diminishing in the Pacific Northwest, the fish themselves are also shrinking, according to several recent studies. A study conducted at five Washington hatcheries revealed size decreases from 11 percent to 27 percent over a 12-year period, reports the Seattle Post-Intelligencer. That means some salmon that used to average 6 pounds now typically weigh only 4.5 pounds. Researchers at British Columbia’s Simon Frasier University say the smaller salmon have lower survival rates and fewer offspring, since smaller fish tend to produce fewer eggs and dig poorer nests. Scientists say hatchery fish also out-compete native fish for food in the ocean, while another cause for the decline in size might be net-fishing techniques that target larger fish. Such methods amount to a kind of unnatural selection, where the smallest, rather than the fittest, survive. The studies add evidence for those seeking fishery reform: “It points a finger at our overall policy for salmon fishery management,” says biologist Brian Bigler.
This article appeared in the print edition of the magazine with the headline Shrinking salmon.
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