POPULATION-DYNAMICS OF BROOK TROUT (SALVELINUS-FONTINALIS) DURING MAINTENANCE LIMING OF AN ACIDIC LAKE

Maintenance liming of an acidic lake in the Adirondack Mountains of New York state (Woods Lake) was conducted three times over a 5 yr period in an attempt to establish a self maintaining brook trout population. Various strains and age classes of marked brook trout were stocked annually and the population was inventoried semi annually to evaluate survival, growth, and reproductive success. The Woods Lake brook trout population was dominated by young, stocked fish throughout the maintenance liming period of 1985-89. Based on spring emergent fry trap catches and fall trap net cathces of unmarked fish, only one naturally produced year class (1986) was successfully recruited to the Woods Lake brook trout population. Low annual survival rates (< 20%) of juvenile trout were observed throughout the study period. Although initial growth rates and condition of young trout were satisfactory, increased intraspecific competition for food resulted in declining growth rates and condition of older age classes. Fall standing crops of brook trout remained at relatively low levels of 6 to 10 kg ha-1 and both production per unit biomass and growth efficiency decreased over the 5-yr. Repeated whole lake liming and limited spawning habitat improvement were not sufficient to sustain brook trout natural reproduction in Woods Lake. Low productivity, marginal spawning habitat quality, and low survival rates of stocked trout in Woods Lake resulted in the failure to establish a self maintaining, productive brook trout population in Woods Lake.