Increasing stocking success in alkaline lakes in British Columbia: characterizing the factors that affect high pH tolerance in rainbow trout

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Recreational fishing is a popular and economically important activity in Canada, generating more than $8 billion in both direct and indirect economic activity, which amounts to about five times the economic impact of the commercial fishery in Canada. In British Columbia alone, ~400,000 freshwater anglers are drawn to BC lakes annually contributing $546 million in direct benefits to the province's economy and $411 million in indirect and induced economic impacts. The Freshwater Fisheries Society of BC (FFSBC) supports this important activity by stocking BC lakes with over five million trout each year. But mortality following stocking can represent a substantial economic cost to the FFSBC. Stocking trout into alkaline (high pH) lakes results in particularly high mortality. At present, about one quarter of the lakes stocked by the FFSBC have high pH, and the number of these high pH lakes, and their pH levels, have been increasing over the last few decades. The primary goal of this research partnership is to help the FFSBC improve the survival of stocked fish in high pH lakes. This research will help the FFSBC decide whether to attempt to selectively breed a pH tolerant strain of trout, or whether to invest in infrastructure to alter the rearing conditions in the hatchery in ways that could increase the high pH tolerance of existing strains of trout. As a component of this work, we will also explore the genetic basis of variation in tolerance of high pH and the effects of environmental factors on high pH tolerance, contributing to an improved understanding of the mechanisms involved in pH tolerance in fish. Improving survival of stocked fish in high pH lakes could save the FFSBC more that $1.8 million each year, provide additional opportunities for BC anglers, and support an important economic activity in British Columbia.