Characterization of 2N and 3N freshwater rainbow trout strains for better lake stocking strategies

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Recreational fishing in Canada provides more than 4.9 billion dollars in economic activity both directly through fish culture and license sales and indirectly through the promotion of tourism. Most of Canada's popular fishing lakes are stocked annually with various species of fish, particularly rainbow trout, from hatcheries to mitigate the impacts of intense fishing activity on natural, wild fish populations. However, most of these stocking programs, particularly in British Columbia experience very high stocking mortality rates, particularly in triploid fish. Triploidy is a means of creating non-reproductive fish, which have the benefit of eliminating the exchange of genetic material between stocked fish and wild populations. In British Columbia alone, the Freshwater Fisheries Society of BC (FFSBC) stocks over 5 million trout a year (~2.5 million as triploids) into > 900 lakes and in some cases up to 70% of the fish introduced into a lake die within days or weeks of stocking. The precise reasons for these high death rates are not known, but there is evidence that variation in lake chemistry and stocked/wild fish competition may both be important contributors to this high mortality. FFSBC has access to many different types (called strains) of trout for stocking programs, but the overall performance and competitiveness of these different strains or the effects of creating triploids on survival and performance under different environmental conditions are not known. This grant will characterize the performance and environmental tolerance of various strains of trout and examine the effects of selective breeding between strains on the overall performance of diploid and triploid trout. The goal of this research partnership is to work toward understanding why triploid fish do not perform well in natural environments compared with their diploid counterparts. The long-term goal of this partnership is to develop a triploid fish with superior performance and low mortality rates could save the FFSBC more that 1.8 million dollars a year and help revitalize recreational fishing in British Columbia and Canada.