Predation by Age-0 Bluefish on Age-0 Anadromous Fishes in the Hudson River Estuary

We examined the diets of 374 age-0 bluefish Pomatomus saltatrix collected in the Hudson River estuary from July to October 1989. Fish were the primary prey, accounting for 96–99% of the diet by weight. Anadromous fishes, including striped bass Morone saxatilis, blueback herring Alosa aestivalis, American shad Alosa sapidissima, and Atlantic tomcod Microgadus tomcod, constituted a large portion of the diet of bluefish of all sizes. There was a positive linear relationship between prey size and predator size, Small and medium-sized bluefish consumed mostly bay anchovies Anchoa mitchilli, striped bass, and white perch Morone americana, whereas the largest bluefish primarily preyed on Atlantic tomcod. Bluefish fed opportunistically on the most abundant prey (bay anchovies, striped bass, and white perch) but larger bluefish exhibited a preference for Atlantic tomcod. We also detected an ontogenetic shift in prey type that may have been determined by changes in the size and relative abundance of prey that occurred as the season progressed. Predation by age-0 bluefish may represent a substantial source of mortality for age-0 anadromous fishes in the Hudson River estuary.