This report summarizes the activities and progress for the fourth year of a Habitat Conservation Fund project comparing the survival of alkaline rainbow trout strains from Stump and Green lakes, to that of a non-alkaline strain from Pennask Lake, introduced into high pH lakes. From 1992 to 1994, Lake 5567 received annual stockings of one-year-old rainbow trout progeny from Stump, Green and Pennask lakes brood fish. Till Lake was also stocked with these strains since 1992.
After three years of sampling fish stocked in 1992 into Lake 5567, cumulative catches of Stump and Green lakes strains through October 1994 showed recovery rates of over 32% of the original number released, compared to 18% for the Pennask strain. After two years of sampling for fish released into Lake 5567 in 1993, cumulative catches for Stump and Green strains were 36% and 43%, respectively, compared to 28% for the Pennask strain. The 1994 release, sampled only after the first summer, showed similar recoveries of age 1+ fish for all strains (16.0 to 19.8%). Cumulative samples from three sampling periods in Till Lake have yielded a total of 129 Stump, 80 Green, and only 15 Pennask fish.
In short term survival studies, Pennask strain rainbow trout fingerlings held in net pens in alkaline Till, Valentine, and Johnson lakes had lower survival rates than the alkaline strains from Green and Stump lakes. In Till and Valentine lakes, the Stump strain had the best survivals. In Johnson Lake, the Green Lake strain had by far the best survival; 86.7% compared to 31.0% for Stump and 11.7% for the Pennask strain.
Net pen experiments with age 0+ kokanee in alkaline Stump Lake suggest that a difference in time of stocking of a two or three week period, in spring, could affect initial survival rates in high pH lakes.
Godin, Theresa I., Tsumura, Kanji; Mathias, Karin L.. 1994. Alkaline Lakes Enhancement: Habitat Conservation Fund Progress Report (1994-95). Ministry of Environment, Lands and Parks. Fisheries Project Report. RD42