Diet and Daily Ration of Bay Anchovy in the Hudson River, New York

Abstract

Along the U.S. Atlantic coast, bay anchovy Anchoa mitchilli form an important component of estuarine and coastal food webs. The combination of its trophic position and abundance makes the diet and ration of this fish important in the study of estuarine systems. Diet and ration have been studied in this species in the middle and southern parts of its range, but information is lacking for the northern parts. Therefore, this study sought to quantify the diets and daily ration of bay anchovy on a seasonal basis within the Hudson River, New York, estuary. Diets of bay anchovy in the Hudson River were similar to those reported in other parts of their range. Bay anchovy ate mostly copepods, barnacle Balanas spp. nauplii, and mysid shrimp Neomysis americana. Mysids were seasonally important, contributing up to 81% (by weight) for adult fish in August. No differences were detected in diet composition or prey length between age-0 and adult bay anchovy within months, but age-0 fish did have an estimated ration up to 2.7 times as high as that of adults. The adult ration ranged from 0.061 g per gram of body weight per day in May to 0.252 g g⁻¹ d⁻¹ in August. The ration of age-0 fish ranged from 0.449 to 0.684 g g⁻¹ d⁻¹ in August and September. The daily ration of bay anchovy was higher than reported for the mid-Chesapeake Bay. This was surprising, as the Hudson River fish are older and larger than those studied in the Chesapeake Bay and physiological allometry indicates that larger individuals should have lower specific rates than smaller ones. This counterintuitive finding suggests that food availability was higher in the Hudson River than in the Chesapeake Bay studies.