Michigan Department of Natural Resources
Fisheries Research Report No.1816, 1974
Survival, Growth, Diet, and Production of Hatchery Trout Stocked in Six Pothole
Lakes in Michigan
Howard Gowing
Abstract.-In the fall of 1965, populations of age-0 and age-I brook trout were established at -three different densities in six Pigeon River lakes, as follows: (1) low-density lakes, 194 fish per hectare, (2) intermediatedensity lakes, 396 fish per hectare; and (3) high-density lakes, 1,335 fish per hectare. There was a direct relationship between total trout density at the outset and the natural mortality rate (q) of the 1965 year class during the first winter after stocking. For the 1964 year class, high densities (125 to 857 fish per hectare) at the outset of the first summer were associated with high natural mortality rates during the summer. Growth in length of the 1965 year class was highest in low-density lakes, intermediate in the lakes of intermediate density, and lowest in high- density lakes. Brook trout stocked at a mean length of 142 mm in November 1965 attained a length of 245 mm in September 1966 after one growing season in the low-density lakes, 218 mm in the intermediate-density lakes, and 173 mm in the high-density lakes. Highest growth rates (g) were achieved in the low-density lakes, and lowest in the high-density lakes. There was an inverse relationship between trout density at the outset of the study, and growth rates (g) of the 1965 and 1964 year classes during the first year. The 1965 and 1964 year classes showed negative growth rates (g) during the first winter in the high-density lakes. Based on the total volume of food observed in the stomachs of trout sampled over a 2-year period, insects made the largest contribution to the diet of trout in all lakes except in West Lost. Crayfish were predominant in trout from West Lost Lake. In three of the lakes containing crayfish, this food type ranked second. Fish, other than trout, ranked second in two of three lakes containing fish. Cladocerans made the third largest contribution in four of the six lakes.