Evolution induced by commercial fishing may explain why the bodies of Alaska's sockeye salmon have shrunk by 5 percent since the 1940s. A study by the University of Washington in Seattle sorted through data from canneries, focusing on the size and age at maturation of the sockeye (Oncorhynchus nerka) from five fisheries in Bristol Bay, Alaska, since 1943. The fish have become, on average, 14 millimeters shorter and were 16 percent more likely to spend two instead of three years in the ocean before returning to fresh water to spawn. Because body size is a heritable trait, the study finds the likely cause is evolution because fishermen generally target larger fish. If current trends continue, the lucrative Bristol Bay sockeye industry could become less profitable in time.
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