Foraging habits of bluefish, Pomatomus saltatrix, on the US east coast continental shelf

After spending summer months in estuaries, spring- and summer-spawned young -of-the-year (YOY) bluefish, Pomatomus saltatrix, migrate out to continenta l shelf waters of the Mid-Atlantic Eight in early autumn. Adult bluefish ar e found on the continental shelf throughout summer and fall. Both juveniles and adults have high food consumption rates and are generally piscivorous. To determine principal prey types on the shelf, dietary analyses were perf ormed on YOY and adult bluefish collected from National Marine Fisheries Se rvice autumn bottom trawl surveys in 1994 and 1995. Both spring- and summer -spawned YOY bluefish diets were dominated by bay anchovy. However, the sig nificantly larger size of the spring-spawned cohort was associated with the consumption of other prey species such as squid, butterfish, striped ancho vy, and round herring. Summer-spawned bluefish were significantly smaller i n 1995 than in 1994; diet and prey size comparisons suggest that body size had a dramatic influence on the amount of piscivorous feeding in the summer -spawned cohort. Adult bluefish diet was dominated by schooling species suc h as squid, butterfish, and clupeids. Cannibalism was virtually nonexistent . Daily ration estimates of YOY bluefish on the shelf(4-12% body wt/d) were similar to estuarine estimates in late summer. It is estimated that during the month of September, YOY bluefish in aggregate consumed 6.0 to 6.8 bill ion bay anchovies in 1994 and from 2.2 to 5.3 billion in 1995. The effect o f this predatory loss on population dynamics of bay anchovy and the fish co mmunity on the continental shelf is unknown.