Kokanee or Sockeye: Balancing Conflicting Objectives through an Assessment of Density Dependent Processes

Alouette reservoir, 50 km from Vancouver, was created by the impoundment of two lakes in 1928. Following dam construction, anadromous sockeye salmon became stranded, establishing a resident kokanee population which are now the focus of a directed recreational fishery. Following impoundment, the reservoir underwent oligotrophication due to blockage of anadromous nutrients, disrupted littoral productivity and large changes to the hydrograph. In partnership, the province and BC Hydro committed to nutrient restoration of the reservoir in 1999, which immediately resulted in an increase in growth and abundance of kokanee salmon. After the restoration of the kokanee population, an experimental spill over the dam caused some juvenile kokanee to smolt, resulting in the return of sockeye two years later for the first time in almost 100 years. This new twist has led to an unintended trade-off between fish and agencies: maximize kokanee production, which are supported by provincial jurisdiction and the provincial staff who run the nutrient restoration program, or support/enhance the sockeye smolts/returns, which are supported by federal jurisdiction and local stakeholders. This work will utilize a 15 year dataset to determine the strength of density dependence at various life stages and will evaluate tradeoffs associated with various management actions.