It is fact that the Atlantic cod has, for many centuries, sustained major fisheries on both sides of the Atlantic. However, the North American fisheries have now largely collapsed. In a study conducted by the University of Iceland and Marine Research Institute in Reykjavik it is mentioned that possible mechanisms of the collapse of fisheries was due to fisheries-induced evolution. It is said that cod fishing is of highest intensity in shallow water in Iceland and it selects against genotypes of cod adapted to shallow water.
The study reveals a significant difference in Darwinian fitness (relative survival rate) between shallow-water and deep-water adapted cod. The shallow-water fish have only 8 percent of the fitness of deep-water fish. This difference can lead to rapid elimination of shallow-water fish in only a few generations with drastic effects on the population and the fishery.
Einar Arnason, professor of population genetics and lead author, opined that there is no direct targeting of specific genotypes. Instead the intense selection results from the interaction of fish that select their habitat by genotype and fishermen choosing to fish in the preferred habitat of the fish. It is said that this study further supports the hypothesis of an imminent collapse of Icelandic cod due to the intense fisheries-induced selection. The cod fishery at Iceland is one of the world’s few remaining cod fisheries. The study appears to have met all criteria for concern that this fishery is threatened.
