Hudson River Fishes and their Environment

<em>Abstract.</em>—Low water temperatures experienced by temperate fish during winter reduce muscle power, resulting in an important limitation to overwintering fishes that may explain why they often seek areas of reduced flow as winter refugia. The Hudson River is a heavily urbanized estuary, and as such, navigation and industrial influences may have particular importance to species seeking to overwinter there. In December 1995 and 1997, we used a mobile hydroacoustic survey, coupled with gill netting and midwater trawling for species identification, to identify the distribution and abundance of key species in the Hudson River. Striped bass <em>Morone saxatilis</em>, white perch <em>M. americana</em>, and bay anchovy <em>Anchoa mitchilli, </em>co-occurred in the lower 25 km of the river. Fish distributions were related to salinity. Striped bass and bay anchovy were found in highest densities in the lower river (Yonkers and Battery regions) and higher salinities. White perch dominated from Yonkers upriver. Acoustic population estimates of striped bass abundance from 1995 (576,110) compared favorably with a wintertime tagging study (949,000), but were grossly underestimated in 1997. Higher salinity in the Battery and Yonkers regions in 1997 may have pushed distributions of striped bass and white perch upriver compared to 1995 sampling and may have led to decreased precision in estimates. This study suggests that key Hudson River fish use much of the lower 61 km of the Hudson River as overwintering habitat.