A number of recent scientific papers have identified fishing induced evolution as contributory factors in the decline of some fish stocks - the Grand Banks off Newfoundland being one fishery so affected. despite a complete moratorium on cod fishing on the Grand Banks the stocks there have failed to recover - at all.
One reason for that is a big change in the physiology of the remaining stock, research shows that the new stock mature at three years whereas before - when the stock was huge, fish did not become sexually mature until aged six years. Small fish are able to escape or avoid trawls, as a result, through natural selection, it is the smaller fish that survive in larger numbers and in turn produce smaller fish capable of reproducing at an earlier age scientists say.
According to a New Scientist article (Turbo-evolution shows cod speeding to extinction) - Fishing is causing cod to evolve faster than anyone had suspected it could, fisheries scientists in Iceland have discovered. This turbo-evolution may be why the world's biggest cod fishery, the Grand Banks of Newfoundland, crashed in 1992 and has yet to recover. A second article (Catching only big fish leads to small fry) provides evidence that targeting the most mature fish has a greater effect in depleting stock levels through adversely affecting fecundity and viability. On the North coast of Cornwall, lobstermen are thinking that large, mature female lobsters would be better returned to the water - berried or not - so as to best create the greatest chance for maintaining the fecundity and viability of the stock.
What has done more damage to the Western hake stock? - landing large catches of big mature females or landing of 'cigarillos' or pin hake?
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