Chronology of Ecological Interactions Associated with the Life‐span of Salmon Supplementation Programs

A temporal context to assess and contain ecological risks associated with salmon supplementation is described in this article. A successful supplementation program has at least four stages: Baseline, Broodstock, Building, and Boundary. These stages can be characterized by the number of target fish (e.g., the species supplemented) that spawn in the wild and hatchery. The type and strength of ecological interactions differ during the four stages of supplementation dynamics. During the Baseline stage, interactions between the naturally produced target species and non‐target taxa (NTT) are likely to be relatively low because of the depressed abundance of the target species. During the Broodstock collection phase, interactions between naturally produced target fish and NTT are reduced but interactions between hatchery produced target fish and NTT are potentially high. Interactions with NTT are likely to be highest during the Building stage because of the high number of hatchery produced target fish released and the increased number of target fish produced in the natural environment. During the Boundary stage, only interactions between naturally produced target fish and NTT occur, but these interactions are likely to be more frequent than during the Baseline stage, particularly if the environmental capacity for NTT has not been improved in proportion to the increase in the target species. The temporal context described indicates that risk assessment and containment should address each of the stages of supplementation dynamics individually and collectively, the time‐span of which could be between 10 and 40 years.