Survival, Growth, Reproduction, and Diet of Brook Trout (Salvelinus fontinalis) Stocked into Lakes after Liming to Mitigate Acidity

Abstract

Brook trout (Salvelinus fontinalis) were stocked into two previously acidic (pH 4.5–5.2) Adirondack Mountain lakes, Woods Lake and Cranberry Pond, following liming in June, 1985. Age 0+ Temiscamie × Domestic hybrid brook trout were stocked at 200∙ha−1 with one-half of the fish selected for presumed acid tolerance. Age 1+ Temiscamie strain brook trout were also stocked at 50∙ha−1. Liming increased pH to well above 7 and alkalinity to over 200 μeq∙L−1. Growth and condition of stocked fish were good while water quality conditions remained suitable. However, in Cranberry Pond, which reacidified 6 mo after liming, both growth and survival declined dramatically. Much of the population loss was due to emigration. Annual survival in Woods Lake averaged 35 and 25% for the age 0+ and 1+ fish, respectively. Initially large invertebrates made up most of the diet for stocked fish. These taxa were replaced by zooplankton within a few months. Limited natural reproduction was associated with low velocity groundwater inflows and high acidity in tributary streams. Fry emergence from artificial spawning substrates placed in Woods Lake peaked well after snowmelt inflows which produced toxic conditions in littoral areas.