The influence of Gulf Stream warm core rings on recruitment of fish in the northwest Atlantic

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Abstract
The a priori hypothesis that entrainment of shelf water by warm core rings reduces recruitment of marine fish stocks through offshore transport is tested. Weekly satellite images for 1973 through 1986 are used to generate time-series of the positions and numbers of warm core rings and the locations of the shelf-slope front from the mid-Atlantic Bight [North Atlantic Ocean] to the Grand Banks. These data are combined with estimates of the timing of the spawning and the duration of larval stages to create stock-specific annual indices of ring activity and shelf-slope front variability. There is evidence that increased warm core ring activity reduces recruitment in the 17 groundfish stocks examined, with the exception of cod from Georges Bank. A similar analysis of 7 pelagic stocks and one shellfish stock showed no consistent evidence that warm core rings reduced their recruitment; however, the recruitment data for many of these pelagic species are less reliable than for the groundfish stocks.