The influence of size on striped bass foraging

Abstract

Striped bass Morone saxatilis is an abundant piscivorous fish in estuaries and coastal systems along the US Atlantic coast and has also been stocked into systems in California and the continental US. Despite the widespread distribution of striped bass and their relative importance as a predator in these systems, little is known about how relative size of prey affects their prey capture success. This study measured the capture success and handling times of striped bass fed live shiners Notropis atherinoides and N. chrysocephalus and the results are expressed in terms of size (prey-to-predator size ratio, PPR). Striped bass capture success declined with increasing PPR. It was best described (p < 0.01) by the equation: attack success = 0.861-1.82PPR. Handling time (h) increased with increasing PPR (p < 0.01) and was described by the equation: h = 0.339e(11.9PPR). Comparison of prey profitability curves showed that the relative size of prey suggested as most profitable (mass/time) was similar to that found in the stomachs of wild striped bass in Chesapeake Bay from 1990 to 1992. The peak in frequency of PPR from stomachs occurred at PPR = 0.12 (mean PPR = 0.14) and was identical to the peak in profitability from model results (PPR = 0.12), although both the diet PPR and model profitability distributions were skewed towards larger relative prey sizes. Comparison of the results of this study with a similar study for small bluefish suggests that profitable prey sizes for striped bass overlap with those of much smaller bluefish.