Economic Evaluation of Lake Enrichment Strategies for British Columbia Sockeye Salmon

Previous research has shown that, in some stocks, there can be a large (up to 22%) decrease in body weight of sockeye salmon Oncorhynchus nerka when large numbers of conspecifics are present in the Gulf of Alaska. This observation led to a hypothesis that may allow fisheries managers of British Columbia sockeye salmon to maximize the net economic benefits from enhancement efforts. Specifically, sockeye salmon enhancement efforts could be restricted to year classes that smolt in years when total smolt abundance in the ocean is low, resulting in faster growth and larger‐than‐average adult body sizes and biomass of catches. Lake enrichment is an appropriate enhancement method to manipulate smolt abundance. A “pulsed enhancement strategy” (deliberate variation in the number of sockeye salmon juveniles produced each year) was compared with an “annual enhancement strategy” (constant annual juvenile production) for four British Columbia stocks of sockeye salmon (Babine Lake, Chilko Lake, Owikeno Lake, and Stellako River), by means of a simulation model containing biological and economic components. Extensive sensitivity analyses showed that annual enhancement produced greater net economic benefits than pulsed enhancement under most conditions. However, plans to start fertilizing large, remote sockeye salmon lakes in British Columbia will greatly increase fertilization costs. With such high costs, pulsed enhancement could lead to the greatest economic benefits.