Stomachs of 171 muskellunge (Esox masquinongy) ranging in length from 358 to 1270 mm were examined to evaluate fish diet and to estimate through bioenergetics modeling the predatory impact of muskellunge on smallmouth bass (Micropterus dolomieu) in the New River, Virginia. Fifty-five percent of muskellunge stomachs examined contained food. Ninety percent of muskellunge stomachs that contained food contained fewer than six items. Muskellunge exhibited an ontogenetic shift in diet at approximately 800 to 900 mm, changing from a diet consisting primarily of cyprinids to one consisting primarily of catostomids. Smallmouth bass comprised a relatively minor (4% by wet weight) component of muskellunge diet overall, although consumption of smallmouth bass did increase with muskellunge length. At an initial abundance of 100 age-1 fish, muskellunge were estimated to consume 0.18 kg•ha-1•yr-1 of smallmouth bass. In contrast, muskellunge would consume 0.63, 0.31, and 0.43 kg•ha-1•yr-1 of catostomids, cyprinids, and lepomids. Given that muskellunge currently are stocked in the New River as fingerlings (?100 mm), post-stocking survival of muskellunge is probably low (<10%), thus muskellunge predation likely has little overall impact on New River smallmouth bass stocks. In systems where muskellunge stocking is controversial because of possible predatory impacts on other aquatic species, formulating stocking rates based on acceptable losses to muskellunge predation may help to prevent or resolve stakeholder conflicts.
