CLIMATE-CHANGE AND MARINE FISH DISTRIBUTIONS - FORECASTING FROM HISTORICAL ANALOGY

Analyses of 36 fish and squid species sampled in standardized bottom-t rawl surveys of the northwest Atlantic Ocean (1967-present) revealed a continuum of distributional responses associated with seasonal and an nual variations in water temperature. Mean and maximum latitude of occ urrence of the species were regressed against average surface- and bot tom-water temperatures and indices of relative abundance from spring a nd autumn trawl surveys. Significant (P less-than-or-equal-to 0.05) re gression models were fitted for 17 of 36 species from spring and fall survey data. Variations in water temperature were significant in expla ining changes in mean latitude of occurrence for 12 of 36 species in b oth seasons. Maximum latitude distribution responses to interannual di fferences in water temperatures occurred for pelagic species, includin g Atlantic mackerel Scomber scombrus and Atlantic herring Clupea haren gus, Weighted mean catches of these species shifted poleward by 0.5-0. 8 degree of latitude for each 1-degrees-C increase in average water te mperature. Statistically significant poleward range extensions, associ ated with warmer water temperatures, occurred for five species in spri ng surveys and four in fall surveys. Different responses among species to changing thermal regimes of the northwest Atlantic Shelf have impo rtant potential consequences for trophic dynamics and fisheries yields of the ecosystem. Species found to be sensitive in distribution to te mperature change include primary prey species of some predators that s how limited seasonal or annual changes in distribution. Changes in dis tributional overlaps between some predators and prey therefore are a l ikely result of shelf warming associated with climate change.