Comparison of hatchery-reared lake trout stocked as fall fingerlings and as spring yearlings in Lake Ontario

We made 16 paired releases of lake trout Salvelinus namaycush of four year classes (1979–1982) at five locations to compare survival and growth of hatchery-reared fish stocked as fall fingerlings (FF) and as spring yearlings (SY). Comparisons were based on fish at ages 2–8 recovered with bottom trawls, with gill nets, and from anglers' catches. Mean lengths and weights were greater for SY than for FF at all ages, and SY attained sexual maturity at an earlier age than FF. The survival of FF may have been affected by average size at stocking and by the severity of the weather during the first winter after stocking. Survival ratios of SY to FF lake trout from stocking to age 2 ranged from 1.32:1 to 6.80:1, and a ratio of 2.41:1 was considered to be typical. Stocking cost per 1,000 fish was US$21.76 for FF and $35.45 for SY. Under the most cost-effective hatchery regime for producing lake trout (the maximum number of SY plus some FF to fully utilize hatchery space and personnel year round), rearing cost per 1,000 fish was estimated to be $235.41 for SY and $38.75 for FF.