Anadromous Fish Predation Strategies, Actions, and Metrics

Predator Management Strategies

• Redistribute avian predators
• Reduce fish predation
• Monitor and reduce marine mammal predation

Predator Management Control Actions
Predators consume large numbers of juvenile salmon and are a major cause of mortality of ESA-listed fish in the Columbia River system. There are four predators that have significant impacts on anadromous fish. Caspian terns and double-crested cormorants, which eat large numbers of migrating fish, have enjoyed population increases over the last two decades in the Columbia River estuary and are also present in the mid-Columbia region. Among fish, northern pikeminnow are voracious consumers of juvenile salmon and steelhead. California sea lions are known to consume substantial numbers of adult chinook salmon and steelhead below Bonneville Dam, while Steller sea lions and harbor seals consume smaller amounts.

Federal and state agencies are cooperating in efforts to reduce predation on listed species. Programs to redistribute Caspian terns in the estuary, drive away and block sea lions from Bonneville Dam fish ladders, and reduce the northern pikeminnow population through a sport-reward program have been successful in reducing the loss of adult and juvenile salmon to predation. BPA is one of three agencies with responsibilities for predator management within the FCRPS, along with the U.S. Bureau of Reclamation and the U.S. Army Corps of Engineers. Efforts continue to control specific predators and improve survival of juvenile fish.

Predator Control Actions

• The Corps and BPA will initiate studies to investigate the effects of non-indigenous piscivorous predation on the survival of juvenile salmon, especially as predators prepare for the fall and over-wintering months.
• BPA is increasing the reward structure for the Northern Pikeminnow Management Program (NPMP) to achieve further reduction of pikeminnow predation on listed salmon and will also use an incentive-based approach to test site-specific removals of northern pikeminnow and other non-indigenous fish predators.
• The Corps will implement the Caspian Tern Management Plan to reduce tern predation on juvenile salmon in the Columbia River estuary.
• The Corps and BPA are continuing and expanding our research efforts to monitor and evaluate the effects on juvenile salmon of Caspian tern redistribution.
• The Corps and BPA will initiate studies to investigate the regional double-crested cormorant population and potential management measures to disperse that population.
• The Corps continues to employ deterrent actions to reduce avian predation on juvenile salmon near the dams.
• The Corps installs sea lion exclusion devices (SLEDs) at all main adult fish ladder entrances at Bonneville Dam on an annual basis.
• The Corps and BPA continue to support land and water-based harassment efforts to keep sea lions away from the area immediately downstream of Bonneville Dam.
• The Corps and BPA continue to support efforts to monitor sea lion abundance, distribution, predation rates and the effectiveness of deterrent actions.

• Report on the change in annual predation rates and the estimated resulting change in annual juvenile salmonid survival rates.