A Study of the Lake Trout, Salvelinus Namaycush, in two Algonquin Park, Ontario, Lakes

Abstract

A study was made of the depth distribution, feeding, and growth of the lake trout, Salvelinus namaycush, in Lake Louisa and Redrock Lake, Ontario, in 1947. In the spring the trout were widely dispersed in Redrock Lake but as surface waters warmed to 14° or 15° C. in mid-June they moved into deeper waters. During the summer months the Redrock lake trout concentrated in the lower thermocline and upper hypolimnion while those in Lake Louisa were more widespread. Both populations frequently penetrated the 15- to 20-foot zone in mid-summer up to the 18° C. isotherm. In each lake the smaller trout had a deeper distribution. In both Redrock and Louisa the food was varied in the spring months. Insects, particularly the immature stages, were eaten extensively at this time. During the summer the Louisa trout fed on plankton as there was no other available food. The Redrock trout fed almost exclusively on the yellow perch, Perca flavescens, the distribution of these two species overlapping in the 12° to 18° C. zone. In both lakes a large number of empty stomachs occurred in the early fall. Small trout ate more plankton and insects and less fish than did the larger trout. Food competition and cannibalism were of little importance. Lake Louisa trout grow more slowly than those in Redrock Lake. This difference is correlated with the difference in feeding habits. The Lake Louisa fish have a growth rate similar to other plankton-feeding populations in Algonquin Park while the Redrock trout have growth like that of piscivorous populations. The lake trout of both lakes grow slowly as compared with many growth rates reported for the species. Maturity is reached at age V in both lakes. Variation in year class strength is evident in both Redrock and Louisa lakes.