Hudson River Fishes and their Environment

<em>Abstract.–</em>Bay anchovy are the most abundant fish found along the U.S. Atlantic coast. This coupled with trophic position and importance to piscivores makes them ecologically vital. However, the anchovy’s small size renders them vulnerable to impingement and entrainment at industrial water intakes. Therefore, knowledge of anchovy spatial distributions relative to such intakes is critical to understanding anthropogenic effects on this species. To evaluate the distributional ecology of bay anchovy in the Hudson River Estuary we conducted seasonal hydroacoustic surveys to define regional density and total abundance of larval, juvenile, and adult anchovy in the river from 1996–1998. Adults concentrated in the lower river during prespawning periods, utilizing the lower 50 km during spawning. Adults dispersed within the river and then emigrated during fall and winter. Larvae and juveniles were in highest densities upriver of spawning locations, with a downriver shift in density distribution during fall. Few juveniles overwintered in the river. Abundance of all stages peaked in spawning season, 1997, when abundance of adults, juveniles, and larvae were estimated at 150 million, 3 billion, and 5.5 billion individuals, respectively. Distributional patterns suggest a panmictic population that includes the Hudson River Estuary and nearby coastal areas, but with possible age segregation. These findings suggest population impacts to anchovy within the River may be distributed on a more regional than a local scale.