Feeding strategies of young-of-the-year muskellunge from two large river ecosystems

We analyzed stomach contents from 674 young‐of‐the‐year (age‐0) muskellunge (Esox masquinongy) sampled in New York waters of the St. Lawrence and upper Niagara rivers to (1) describe diets and document use of nonnative prey, (2) examine the feeding strategy (generalized versus specialized) and the importance of different prey types, (3) evaluate temporal patterns in feeding strategy and prey importance, and (4) determine how prey length related to muskellunge length and whether this relationship differed among prey types. Banded killifish Fundulus diaphanus , native cyprinids, and tessellated darters (Etheostoma Olmstedi) were the most important prey numerically and by weight in the St. Lawrence River. Native cyprinids, banded killifish, and darters (Etheostoma spp. and Percina spp.) were the most important prey in the Niagara River, but nonnative cyprinids were more important by weight than darters. Muskellunge from both rivers exhibited a specialized feeding strategy, with individuals specializing on different prey types. The muskellunge feeding strategy and the prey types of greatest importance were consistent among years and among months within years. The relationship between prey length and muskellunge length differed among prey types: as muskellunge length increased, lengths of laterally compressed, spiny prey increased at a slower rate than did the lengths of fusiform prey. Mean prey length as a proportion of predator length declined with increasing muskellunge length in the St. Lawrence River but was constant in the Niagara River. In the St. Lawrence River, prey length as a proportion of predator length decreased for all prey types except cyprinids, for which length was a constant proportion of predator length. Our results can be used to guide evaluations of prey fish assemblages at muskellunge nursery sites and to prioritize sites as candidates for protection, restoration, or use as stocking locations.