As reported earlier, fish populations may adapt and change in response to significant fishing pressure. Researchers are now suggesting that the genetic make-up of cod in the Atlantic Ocean might be changing, since cods genetically predisposition to seek out shallower waters are more likely to end up in nets or on fishing lines, while deep-dwellers are more likely to survive and reproduce.
If the current over-fishing of shallow living cod is not put to an end, evolutionary biologist Einar Árnason and his colleagues believes the genetic variant found in shallow-living cod will be lost all together. If the deep-water cods do not spread into the shallows, and Árnason doubts they will since they are adapted to deep water conditions, the shallows may be become devoid of cod within the next 10 years. This will decrease the size of the total cod population and will also force the fishing industry to either give up cod fishing altogether or switch to expensive deep-water trawling.
Árnason and his colleagues have studied cod populations off the coast of Iceland, where fish stocks are still in fairly decent condition compared to the severely depleted populations found in the western Atlantic. In their study, the researchers examined how the genotypes of Icelandic cod have changed between 1994 and 2003.
It was already known that cod living in the Icelandic shallows have a different variant of the pantophysin I gene than the cods found at much larger depts. In their study, Árnason and his colleagues found that the shallow-water variant of pantophysin I is becoming increasingly rare; a change which they attribute to the fact that most Icelandic cod fishers work in shallow waters near the coastline using lines and nets instead of carrying out deep-water trawling.
Árnason and his team also found that Icelandic cod are reaching sexual maturity at a younger age and at a smaller size than before. This is discovery is a chilling revelation for Icelandic fishermen and conservationalists alike, since that was exactly what happened in Newfoundland waters before that cod population crashed completely.
The study has been published in the journal PLoS ONE