The Role of the Okanagan Basin Fish-and-Water Management Tool in Boosting Sockeye Production

Record breaking returns of sockeye salmon in 2009 and 2010 marked the culmination of a remarkable turnaround for populations of this species in the Columbia River Basin. The sockeye salmon aggregate in the Columbia is composed of just three populations of this species originating from Redfish Lake in Idaho, Wenatchee Lake in Washington State and Osoyoos Lake in British Columbia. Although all three of these populations have exhibited recent-year increases in returns relative to their multi-decadal averages, Okanagan sockeye salmon have accounted for more than 75% of the aggregate return since the year 2000 and accounted for no less than 295,000 of the roughly 386,000 sockeye adults that passed Bonneville Dam in the summer and fall of 2010. Media and management agencies have engaged in a wide range of speculation about the causes for the resurgence of these sockeye populations. Here we review the recent history of stock management and restoration efforts focused on Okanagan sockeye in both the U.S. and Canada to identify the factors associated with its spectacular increase in total production. Our results indicate that a combination of intentional management actions and fortuitous events have enabled Okanagan sockeye salmon to rebound to levels at or above their historic maximum. The actions and events involved include: (1) rejection of historic escapement objectives that capped total production far below the carrying capacity of freshwater spawning and rearing environments, (2) development and operational deployment of the FWMT decision support system to facilitate “fish friendly” water storage and release decisions where the latter have greatly reduced density-independent losses of sockeye eggs and fry to flood-and-scour or drought-and-desiccation events, (3) FWMT enabled identification and mitigation of rearing habitat reductions for juvenile sockeye due to oxygen-temperature “squeeze” conditions in Osoyoos Lake, (4) supplemental production from recent year introductions of hatchery-origin sockeye fry into Skaha Lake and (5) improvements in juvenile fish-passage in the Columbia River combined with a coincidental return to survival-favourable conditions for southern sockeye stocks in coastal marine waters. Taken together, our results serve as encouraging evidence of the potential resilience of wild salmon populations and the great strides that are possible when agencies, industry and resource users on both sides of the Canada-U.S. border set aside their differences to work towards a common objective such as salmon restoration.