Stock structure of yellowtail flounder off the northeastern United States

An interdisciplinary study incorporating geographic patterns of abundance, geographic variation in growth and maturity, morphometry, and genetics suggests that yellowtail flounder Limanda ferruginea on the principal U.S. fishing grounds should be managed as separate stocks despite genetic homogeneity. Significantly different patterns of abundance and biomass over time suggest two harvest stocks of yellowtail flounder with a boundary on southwest Georges Bank. Geographic patterns of size and proportion mature at age indicate two phenotypic stocks of yellowtail flounder, with a boundary on northern Georges Bank. With respect to current U.S. management units, southern New England yellowtail form a separate harvest stock than Georges Bank yellowtail, and Cape Cod yellowtail are a separate phenotypic stock than those on Georges Bank or off southern New England. However, no apparent differences between samples from southern New England and Mid Atlantic, or between samples from Cape Cod and Gulf of Maine were found in any of the analyses. Morphometric analysis showed sexual dimorphism and significant difference between yellowtail from U.S. waters and those sampled off Newfoundland, but little morphometric variation among samples from U.S. areas. Collaborative genetic analysis also found little variation among U.S. samples. Yellowtail flounder resources off the U.S. appear to be a single genetic stock, but significant variation in life history attributes and different patterns of abundance over time suggest that yellowtail flounder off the northeastern U.S. should be managed as three stocks: Cape Cod-Gulf of Maine, Georges Bank, and southern New England-Mid Atlantic.