The effect of bluefish (Pomatomus saltatrix) predation on their prey populations in the Hudson River estuary during the summer and on the continental shelf of the U.S. east coast in the autumn is examined.

Consumption rates of bluefish in both habitats were measured by coupling stomach content fullness estimates with gastric evacuation rate (GER) estimates. The effect of body size, prey type, and temperature on the GER in young-of-the-year (YOY) was examined. Temperature had a highly significant effect on YOY bluefish GER while bluefish body size and prey type did not.

The temporal and spatial patterns of catch-per-unit-effort (CPUE) and gut fullness values were used to infer bluefish movement and feeding chronology, respectively from twelve diel collections of bluefish in the Hudson River estuary in 1992 and 1993. Estimates of consumption rates were made from gut fullness values and gastric evacuation rate data. Bluefish CPUE and gut fullness data suggest that bluefish feed in the nearshore during the day and move offshore and have reduced feeding at night.

Bluefish weights, densities, diet, prey sizes and bluefish consumption rates were used to estimate the loss of YOY striped bass (Morone saxatilis) resulting from YOY bluefish predation. Bluefish show increased preference for striped bass as striped bass density increases. It is concluded that YOY bluefish are important predators of estuarine fish and can have a substantial impact on their recruitment.

The foraging ecology of bluefish on the continental shelf is investigated. Food habits of both spring- and summer-spawned bluefish differ based on size differences. Both YOY and adult bluefish consume a significant amount of prey biomass. The east coast bluefish population consumes a higher biomass of squid and butterfish than is harvested by the commercial fisheries for these species. Our findings suggest that stock assessments for resource species that are prey of bluefish should incorporate variation in natural mortality resulting from variation in bluefish abundance.