Sea temperature rise is causing fish species in the North Sea to shift their ranges northward in latitude and/or deeper to find colder waters. The North Sea waters have warmed by 1.1 degrees Celsius over the past 30 years.

• Perry, Allison L. et al. "Climate Change and Distribution Shifts in Marine Fishes." Science 308(5730): 1912 -1915 (24 June 2005). Science Express on 12 May 2005 at www.sciencemag.org

Of the 36 species examined in the North Sea (including exploited and non-exploited species), two-thirds were found to be migrating to cooler waters. The "center" of species populations moved from nearly 50 kilometers (km)  to more than 400 km north, while southern boundaries moved from over 100 km to more than 800 km north. Species that shifted their distributions the most were smaller and had faster life cycles than those species that did not shift. Because species are shifting at different rates and amounts, the authors expect their results to have implications for commercial fisheries; some of the northern waters to which fish are migrating are already among the most over-fished in the world.

Implications: Changes in North Sea fisheries, already under stress from over-fishing, are likely to accelerate with climate change. Fisheries may need to shift to smaller and more adaptable species, as the effects of climate change continue to disrupt marine ecosystems, and as fish populations depart for cooler waters and interact with new marine species. On economic grounds alone, this could have huge implications: the North Sea fishery is valued at billions of dollars a year. Of equal significance is the clear indication that climate change has already begun to interfere with large-scale marine habitats.