Survival of Marked Lake Trout in Lake Manitou, Manitoulin Island, Ontario

Abstract

Lake trout (491 in all), Salvelinus namaycush, planted as yearlings in Lake Manitou in 1952 were tagged at age VII when taken in trap nets during spawntaking operations. At the same time 259 native adult trout of unknown age were also tagged. In spawntaking operations in subsequent years tag numbers were noted for tagged fish recaptured and the fish returned to the lake after normal spawntaking. Both groups were estimated to have suffered a decrement of 25% per year. The lake trout planted were given a distinctive fin clip on planting so that comparisons of recaptures of tagged and untagged planted fish permitted estimates of the survival of the total plant. The mean annual mortality rate from the time of planting was also estimated at 25%. Trout planted later appeared to have suffered a similar mortality rate. Observations on planted lake trout of known age indicated that the peak age for first spawning in females was age VI. There is no predation by sea lamprey in Lake Manitou.