Climate Change and Marine Fish Distributions: Forecasting from Historical Analogy

Analyses of 36 fish and squid species sampled in standardized bottom-trawl surveys of the northwest Atlantic Ocean (1967–present) revealed a continuum of distributional responses associated with seasonal and annual variations in water temperature. Mean and maximum latitude of occurrence of the species were regressed against average surface- and bottom-water temperatures and indices of relative abundance from spring and autumn trawl surveys. Significant (P ≤ 0.05) regression models were fitted for 17 of 36 species from spring and fall survey data. Variations in water temperature were significant in explaining changes in mean latitude of occurrence for 12 of 36 species in both seasons. Maximum latitude distribution responses to interannual differences in water temperatures occurred for pelagic species, including Atlantic mackerel Scomber scombrus and Atlantic herring Clupea harengus. Weighted mean catches of these species shifted poleward by 0.5–0.8 degree of latitude for each 1°C increase in average water temperature, Statistically significant poleward range extensions, associated with warmer water temperatures, occurred for five species in spring surveys and four in fall surveys. Different responses among species to changing thermal regimes of the northwest Atlantic Shelf have important potential consequences for trophic dynamics and fisheries yields of the ecosystem. Species found to be sensitive in distribution to temperature change include primary prey species of some predators that show limited seasonal or annual changes in distribution. Changes in distributional overlaps between some predators and prey therefore are a likely result of shelf warming associated with climate change.