Impact of age-0 bluefish (Pomatomus saltatrix) predation on age-0 fishes in the Hudson River estuary: evidence for density-dependent loss of juvenilestriped bass (Morone saxatilis)

We measured bluefish (Pomatomus saltatrix) weights, densities, and prey siz es during the summers of 1992 and 1993 and diets over a 4-year period (1990 -1993) in the Hudson River estuary. This information was used to estimate t he loss of young-of-the-year (YOY) striped bass (Morone saxatilis) resultin g from YOY bluefish predation. We then compared this predation mortality wi th the total loss of striped bass in the system. Data from sampling surveys conducted since the mid-1970's were used to examine relationships between bluefish abundance and striped bass recruitment levels. YOY striped bass, b ay anchovy (Anchoa mitchilli), Atlantic silverside (Menidia menidia), and A losa spp. dominated YOY bluefish diets. There were ontogenetic and interann ual differences in YOY bluefish diets. Bluefish avoided striped bass at low densities but selected for them at high densities, suggesting a density-de pendent feeding response. In the early summer of 1993, bluefish predation a ccounted for 50-100% of the total estimated loss of YOY striped bass. A sig nificant negative correlation exists between the relative magnitude of stri ped bass recruitment and bluefish abundance. We conclude that YOY bluefish are important predators of estuarine fish and can have a substantial impact on their recruitment.