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UncertaintyHow effectively can undesirable impacts of predation be ameliorated by management actions including hydrosystem operations, habitat modifications and predator population control?
Sources ISAB/ISRP 2016-1: Uncertainties Review
NPCC Fish and Wildlife Program 2014
Criticality Level Priority
Rationale Predators respond behaviorally, ecologically, and evolutionarily to foraging opportunities, such as those created by hydroelectric dams that modify the migratory corridors of juvenile and adult salmon, and the release of large concentrations of naïve hatchery-reared smolts. Contemporary predator populations are probably supported to some degree by the relatively constant annual releases of about 140 million salmon and steelhead from hatcheries. The feasibility and cost effectiveness of predator control programs are questionable except in relatively restricted areas where prey are especially vulnerable and predator impacts are concentrated (e.g., near bird colonies and tailraces). Benefits of reducing smolt mortality due to piscivorous birds and fish might be largely lost through density dependent (i.e., non-additive) mortality at later life stages (ISAB 2015-1; see Programmatic Comment 5). Such compensatory effects are less likely later in life, and predation during upstream migration is likely to have more impact on adult abundance than an equivalent rate of predation at earlier life stages. Predator control programs can also have counter-intuitive and unintended consequences for both the target populations and other predator and prey species.

last updated: Jan 27, 2016