Evidence for atmosphere-ocean forcing of yellowtail flounder (Limanda ferruginea) recruitment in the Middle Atlantic Bight

We investigated the relationship between large-scale climate variability (the North Atlantic Oscillation, NAO), continental shelf hydrography, and year-class strength of yellowtail flounder (Limanda ferruginea) in the Middle Atlantic Bight. Using long-term environmental time series (1963-98), dominant winter NAO phase in the northeast region of the United States was correlated with local air temperature records from Block Island, Rhode Island (December-March). Air temperature also influenced the characteristics of a pool of remnant winter cold water on the continental shelf, such that negative NAO winters produced a colder-than-average summer cold pool, and vice versa. Smoothed data sets of L. ferruginea recruitment over the 36-yr period (using Southern New England VPA and hindcast data) were highly correlated with the NAO and air temperature, highlighting the influence of multi-year variability. Although less robust, the relationship with the NAO remained significant after removing equal-but-opposite long-term linear trends from the series. Surprisingly, recruitment and cold pool bottom temperature were only marginally correlated. Data from independent 2-m beam trawl and submersible sampling in the region (1994, 1996-2000) indicated a strong relationship between the abundance of recent settlers and cold pool temperature; however, this pattern was often modified by subsequent changes in cold pool stratification (fall overturn). These results underscore the dynamic role thermal habitats play in the lives of early stage benthic fishes. For yellowtail flounder, the generation of recruitment variability represents one endpoint of a complex interaction between large-scale phenomena (climate) and more localized, event-scale features (cold pool).