SURVIVAL, DISTRIBUTION, AND ION COMPOSITION IN 2 STRAINS OF BROOK TROUT (SALVELINUS-FONTINALIS) FRY AFTER EXPOSURE TO EPISODIC PH DEPRESSIONS IN AN ADIRONDACK LAKE

Brook trout (Salvelinus fontinalis) fry are susceptible to high mortal ity in acidified waters because of their low tolerance to acidic condi tions and the potential occurrence of this life stage with episodic ac idification associated with snowmelt. Prior to snowmelt, equal numbers of Assinica and Temiscamie strain fry were placed into enclosures. Tw elve days after stocking, no consistent differences between strains we re observed in survival, distribution, or ion composition. No fry of e ither strain survived in enclosures placed in shallow water (pH 4.8; 0 .7 m depth). Fifty to 100% of fry of both strains survived in enclosur es placed in deep water (pH 6.3; >2.0 m depth). Fry survival in long e nclosures that extended from shallow to deep water was 80-99%. Within long enclosures, both strains were recovered in higher densities from middle and deep sections of the enclosures than from shallow sections. High fry survival and non-random distributions in the long enclosures indicated that both strains were able to avoid lethal, nearshore wate rs during spring snowmelt by moving to deeper water.