Guardian: UK Cod Stocks May No Longer Breed In British Waters By 2100, But 3 Cold Winters Good Omen
EDIT
Cod has been exploited for 2000 years, and until the invention of sonars, the stock was thought to be inexhaustible. However, fishermen have long known that the cod's range and numbers changed with temperature. In the 17th century during the "little ice age" the sea was too cold for cod anywhere north of Shetland.
As sea temperatures rise the opposite is happening, cod are happy north of Norway and scientists predict stocks of cod in the Celtic and Irish Seas will disappear by the end of the century.
The most important factor in breeding success is an abundance of food for the larvae and codling as they drift to nursery areas. Cold-water species of plankton are their main food source at this stage. The single most important plankton species has moved its range 600 miles north in response to rising sea temperatures. Warm water species have moved in but cod do not eat them.
So the breeding success of British cod stock is in jeopardy. There is one ray of hope; three cold winters in Britain in a row. If this becomes a trend the North Sea could be cold enough in March for successful breeding.
EDIT/END
http://www.guardian.co.uk/news/2013/mar/03/weatherwatch-british-cod-fishing