Distribution, Abundance, and Survival of Age-0 Muskellunge in Upper St. Lawrence River Nursery Bays

Abstract

Distribution, abundance, and survival of age-0 muskellunge Esox masquinongy were evaluated at 10 bays in the Thousand Islands section of the St. Lawrence River over a 7-year period, 1990–1996. Muskellunge fry (24 mm) identified with thermal or oxytetracycline otolith markers were stocked in 1990–1992, 1994, and 1996, and fin-clipped fingerlings (76 mm) were stocked in the bays in 1994 and 1996. Success of the stockings was evaluated to examine the feasibility of enhancing bays that have natural reproduction (natural) and establishing populations in unused bays (restoration). Most age-0 muskellunge were found in shallow habitats (<1.5 m), and success of capture by seining decreased with increasing water depth. Estimates of age-0 abundance by mark–recapture and catch–area were not significantly different. Population density ranged from 0 to 42 muskellunge/ha of nursery habitat, and no significant differences were observed between natural (18.8 fish/ha) and restoration bays (20.5 fish/ha). For all years combined, 67% of fish in natural bays originated from fry stocking, compared with 74% in restoration bays. No significant difference in contribution to age-0 abundance by origin (fry, fingerling, wild) was observed between natural and restoration bays. No stocking occurred in 1993 and 1995, but wild age-0 muskellunge were captured in 9 of 10 bays. The presence of wild muskellunge in 4 of 5 restoration bays indicated that these bays were incorrectly characterized as lacking natural reproduction. Survival of stocked fry was relatively low (0–3%), compared with survival of fingerlings (0–35%), but stocked fry contributed more to abundance (over 50%) than wild or fingerling sources. Due to its success, fry stocking should be reconsidered as a useful management tool for enhancing and restoring muskellunge populations.