Regional climatic warming drives long-term community changes of British marine fish

Climatic change has been implicated as the cause of abundance fluctuations in marine fish populationsworldwide, but the effects on whole communities are poorly understood. We examined the effects ofregional climatic change on two fish assemblages using independent datasets from inshore marine (EnglishChannel, 1913–2002) and estuarine environments (Bristol Channel, 1981–2001). Our results show thatclimatic change has had dramatic effects on community composition. Each assemblage contained a subsetof dominant species whose abundances were strongly linked to annual mean sea-surface temperature.Species’ latitudinal ranges were not good predictors of species-level responses, however, and the samespecies did not show congruent trends between sites. This suggests that within a region, populations of thesame species may respond differently to climatic change, possibly owing to additional local environmentaldeterminants, interspecific ecological interactions and dispersal capacity. This will make species-levelresponses difficult to predict within geographically differentiated communities.