Survival of Atlantic Salmon Fry Stocked at Low Density in the West River, Vermont

Fry of Atlantic salmon Salmo salar stocked at low density (32/100 m2; ±0.7, SE) in the West River, Vermont, produced underyearling and yearling parr densities of 13.5 ± 0.8/ 100 m2 and 5.9 ± 0.5/100 m2, respectively. Survival of fry stocked at low density to underyearling and yearling part- was 42 ± 2.5% and 19 ± 1.3%, respectively. Density of underyearling part produced from fry stocked at low density was not significantly different from the 10.6 ± 1.5 parr produced from fry stocking at high density (mean, 117 ± 16.5/100 m2). However, the 4.0 ± 0.8 yearling part-/100 m2 produced was significantly lower at high stocking density. Survival to underyearling and yearling parr at high stocking density was 11.6 ± 2.0% and 4.6 ± 1.0%, respectively, both significantly lower than survival rates at low stocking density. Thus, low-density stocking produced equal or greater densities of parr with much higher survival rates. Estimated smolt production from low-density fry stocking (with the assumption of a part—to-smolt overwinter survival rate of 65%) was about 4.0 smolts/100 m2; this is equivalent to a fry-to-smolt survival rate of 13%. Results from stocking fed and unfed fry were similar, except fed fry were more likely to produce yearling smolts. Managers of restoration and enhancement programs with limited broodstock, eggs, or incubation space should be able to produce more smolts by stocking fry at lower densities over wider areas without affecting per-unit-area smolt production.