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.
To learn more, visit the Columbia Basin Fish and Wildlife Program Web site at
www.cbfish.org. The site provides
access to the current portfolio of projects designed to protect and rebuild fish
and wildlife populations affected by federal hydropower development in the Columbia
Report on the change in annual predation rates and the estimated resulting change
in annual juvenile salmonid survival rates.