Chilling out

Climate warming has forced the distribution of several fish stocks in one of Europe's major fishing grounds many kilometres north or to greater depths to find cooler waters, according to a study by climate change scientists. The distribution of major fish species, including cod and haddock, has shifted in response to an average 1 o C rise in the temperature at the bottom of the North Sea over the past 25 years. In the same period, more exotic southern species have encroached on North Sea waters and established themselves. The shift in fish populations has profound implications for fisheries, which have already driven stocks to record lows, the researchers say. Researchers at the University of East Anglia and at the Centre for Environment, Fisheries and Aquaculture Science in Lowestoft studied fisheries data gathered from 1977 to 2001 and looked at the relative abundance of catches. They also examined records of sea temperatures, general climatic patterns, the effects of the Gulf Stream and the abundance of prey species. The researchers studied a number of bottom-living species in the North Sea which comprises a group with varied biogeographical origins and distribution patterns. They determined the centres of abundance for each species in terms of mean latitudes and depths, and the boundary latitudes for those species that have either a northerly or southerly range limit in the North Sea. The team found that almost two thirds of 36 species had shifted their distributions in line with the rise in sea temperature. According to the study, published in Science (DOI: 10.1126/science.1111322), the change in species distributions in the North Sea varied from 48 to more than 400 kilometres over this period. Of the 21 species that changed distribution, 15 changed latitude and 13 moved further north. Two species were revealed to move south, but the authors believe these can be explained by local details. A new study of fisheries data from the North Sea reveals that many fish species have changed their distribution towards cooler waters over the past 25 years as sea temperatures rose which may have major implications for climate warming on fisheries. Nigel Williams reports. Sea change: North Sea catches are changing not only as a result of the severe fishing pressure, but also because of climate change. Many traditional species are moving to cooler waters and more exotic species are turning up.