|Climate change and deepening of the North Sea fish assemblage: a biotic indicator of warming seas|
|Dulvy, N.K.; Rogers, S.I.; Jennings, S.; Stelzenmüller, V.; Dye, S.R.; Skjoldal, H.R. (2008). Climate change and deepening of the North Sea fish assemblage: a biotic indicator of warming seas. J. Appl. Ecol. 45(4): 1029-1039. dx.doi.org/10.1111/j.1365-2664.2008.01488.x|
|In: Journal of Applied Ecology. British Ecological Society: Oxford. ISSN 0021-8901, more|
Climatic changes; Demersal fisheries; Introduced species; Life history; Temperature effects; ANE, North Sea [gazetteer]; Marine
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1. Climate change impacts have been observed on individual species and species subsets; however, it remains to be seen whether there are systematic, coherent assemblage-wide responses to climate change that could be used as a representative indicator of changing biological state.
2. European shelf seas are warming faster than the adjacent land masses and faster than the global average. We explore the year-by-year distributional response of North Sea bottom-dwelling (demersal) fishes to temperature change over the 25 years from 1980 to 2004. The centres of latitudinal and depth distributions of 28 fishes were estimated from species-abundance–location data collected on an annual fish monitoring survey.
3. Individual species responses were aggregated into 19 assemblages reflecting physiology (thermal preference and range), ecology (body size and abundance-occupancy patterns), biogeography (northern, southern and presence of range boundaries), and susceptibility to human impact (fishery target, bycatch and non-target species).
4. North Sea winter bottom temperature has increased by 1·6 °C over 25 years, with a 1 °C increase in 1988–1989 alone. During this period, the whole demersal fish assemblage deepened by ~3·6 m decade−1 and the deepening was coherent for most assemblages.
5. The latitudinal response to warming was heterogeneous, and reflects (i) a northward shift in the mean latitude of abundant, widespread thermal specialists, and (ii) the southward shift of relatively small, abundant southerly species with limited occupancy and a northern range boundary in the North Sea.
6. Synthesis and applications. The deepening of North Sea bottom-dwelling fishes in response to climate change is the marine analogue of the upward movement of terrestrial species to higher altitudes. The assemblage-level depth responses, and both latitudinal responses, covary with temperature and environmental variability in a manner diagnostic of a climate change impact. The deepening of the demersal fish assemblage in response to temperature could be used as a biotic indicator of the effects of climate change in the North Sea and other semi-enclosed seas.