SalmonScape is an interactive mapping application designed to display and report a wide range of data related to salmon distribution, status, and habitats. The data sources used by Salmonscape include stream specific fish and habitat data, and information about stock status and recovery evaluations

Questions and Answers
Sea lion predation on Columbia River salmon and steelhead

Why are California sea lions a concern on the Columbia River?

Since 2002, California sea lions in the Columbia River have been taking a significant toll on endangered and threatened stocks of salmon and steelhead listed for protection under the federal Endangered Species Act (ESA). Sea lion predation occurs throughout the lower river system, but the problem is especially acute below Bonneville Dam where returning salmon and steelhead congregate as they prepare to move up the dam’s fish ladders to spawn upstream. Sea lions also prey on mature sturgeon below Bonneville Dam, and on listed salmon and steelhead runs in the Willamette River and other tributaries to the Columbia River.

What salmon and steelhead runs are at risk from sea lion predation?

Thirty-two wild salmon populations bound for the upper Columbia and Snake rivers are vulnerable to predation by sea lions immediately below dam. The population of greatest concern is the Upper Columbia spring chinook run, which is listed as “endangered” under the federal Endangered Species Act (ESA). Snake River spring/summer chinook, listed as “threatened” under the ESA, are also highly vulnerable to predation by sea lions feeding immediately downriver from Bonneville Dam. Other ESA-listed salmon and steelhead populations passing through the lower Columbia River when sea lions are feeding include lower Columbia River chinook, lower Columbia River steelhead, middle Columbia River steelhead, Snake River Basin steelhead, upper Willamette River chinook and Upper Willamette River steelhead. All are listed as “threatened” under the ESA.

How do fish managers know that California sea lions are preying on these runs?

Each year since 2002, the Army Corps of Engineers has stationed observers with spotting scopes and along the deck of Bonneville Dam to record the number of salmon and steelhead consumed by sea lions between January and May when ESA-listed runs are present. In 2002, they observed 31 sea lions consume 448 salmon and steelhead in the tailrace area, which extends about one-quarter mile below the dam. The following year, they observed 104 sea lions consume 2,329 salmon and steelhead in the same area. The Corps issues regular reports of its observations in months when California sea lions are present.

Those records are just one indication of the level of sea-lion predation on Columbia River salmon and steelhead.  Another estimate, based on California sea lions’ metabolic needs, suggests that 100 animals feeding in that area consume at least 13,000 salmon each spring. That estimate applies to predation only in the tailrace of Bonneville Dam; it does not consider predation that has been observed farther downriver in the lower Columbia River or its tributaries.

How many California sea lions have been removed from the lower Columbia River under federal authorization?

From 2008-12, wildlife managers for WDFW and ODFW removed a total of 54 California sea lions in the Columbia River. Thirty-eight were euthanized by lethal injection and 11 were successfully placed in zoos and aquariums where space was available. The remaining five died during capture activities.

Are sea lions native to the Columbia River?

California and Steller sea lions have roamed the Pacific coast for centuries, but were not seen entering the Columbia River in significant numbers until the 1980s.  Steller sea lions, the larger of the two species, are now present at the mouth of the Columbia River year-round, but California sea lions spend their annual breeding season at rookeries off the coast of southern California and Mexico.  In fall, thousands of adult males and juveniles return north to forage for food along the west coast of North America.  A 2006 survey conducted by the Washington Department of Fish and Wildlife (WDFW) estimated there were up to 1,200 California sea lions and 1,000 Steller sea lions in the lower Columbia River. 

Since the early 1980s, California sea lions have been moving in increasing numbers farther and farther up the Columbia River – first to the Astoria area, then to the Cowlitz River and on to Bonneville Dam, 145 miles from the river mouth.  In recent years, California sea lions have been reported above Bonneville Dam, with occasional sightings in Drano Lake and McNary Pool. 

Like California sea lions, Steller sea lions have been observed feeding below Bonneville Dam in recent years, but their primary prey is white sturgeon rather than salmon and steelhead.  In 2008, the U.S. Army Corps of Engineers observed 17 Steller sea lions consume 606 sturgeon in the tailrace below the dam, which represented 98 percent of the predation documented by sea lions on sturgeon that year.  By contrast, California sea lions accounted for 96 percent of the predation on salmon and steelhead that year.

What steps have been taken to deter sea lions from preying on salmon?

Each spring since 2005, boat-based "hazing" teams from the Washington Department of Fish and Wildlife (WDFW), and the Oregon Department of Fish and Wildlife (ODFW) and the Columbia River Inter-Tribal Fish Commission have attempted to drive sea lions away from salmon and steelhead congregating below Bonneville Dam. Using "seal bombs" (underwater firecrackers), rubber buckshot and other non-lethal measures, those crews have worked with USDA Wildlife Services hazing teams and the Army Corps of Engineers to move sea lions away from fish gathered below the dam. While hazing often interrupts their feeding, California sea lions usually return to the area within a few hours after the hazing teams depart.

In March 2008, NOAA-Fisheries authorized Washington, Oregon and Idaho to remove individual California sea lions documented as preying on salmon and steelhead below the dam. The five-year authorization, granted under Section 120 of the Marine Mammal Protection Act, allows the states to use lethal or nonlethal measures to remove California sea lions that 1) can be identified by markings, 2) have been hazed to discourage them from predation and 3) have been documented feeding on salmon and steelhead below the dam. Steller sea lions are not subject to removal by the states, because they are listed as threatened under the federal Endangered Species Act.

From 2008-10, wildlife managers for WDFW and ODFW removed a total of 40 California sea lions that met the federal criteria for removal below the dam.

Will the states continue to remove California sea lions from the Columbia River?

That is not yet certain. In November of 2010, the Ninth Circuit Court of Appeals rejected NOAA-Fisheries’ rationale for authorizing the states to use lethal measures to remove California sea lions that prey on fish protected under the federal Endangered Species Act. The states will only resume removing California sea lions from the Columbia River if the federal agency renews their authorization to do so.

How do the live traps work? 

Sea lions naturally haul out of the water and rest on structures such as jetties and docks. They will also haul out into floating cages, which are used by wildlife biologists to capture these animals. In a typical operation, a biologist leaves the door to the trap open until one or more animals are inside, then trips the door shut. 

Precautions are taken to ensure that no animals are inadvertently shut inside the cage traps. Doors to the traps are locked open to prevent them from closing accidently when the traps are unattended. The Corps has updated its surveillance systems at Bonneville Dam and monitors the entire area where the traps are set up. 

Have the state’s efforts to remove California sea lions been effective?

There are some positive signs, but it is too soon to assess the success of the states’ efforts. The good news is that the number of California sea lions feeding in the tailrace area has declined from a high of 104 animals in 2003 to 39 in 2012. The percentage of protected salmon and steelhead runs consumed by California sea lions has also declined in recent years, although that trend is partly due to larger salmon runs in recent years. Run timing and river conditions also affect predation rates, complicating an assessment of the states’ efforts.

Will the removal of specific California sea lions from the Columbia River impact the overall sea lion population?

No. California sea lion numbers have grown rapidly since the 1970s and the species is now at “carrying capacity” – near the highest level the environment can sustain – according to wildlife biologists. The U.S. population of California sea lions is estimated at some 300,000 animals, all on the Pacific coast. By comparison, the overall Pacific coast population of California sea lions was 10,000 in the 1950s. An aerial survey conducted in 2011 by the Washington Department of Fish and Wildlife documented over 2,000 California sea lions on the South Jetty at the mouth of the Columbia River alone.

Why can't sea lions be relocated to other natural areas?

Previous efforts to relocate sea lions to other waters have been largely unsuccessful, because sea lions often return to the site where they were captured. The experience with sea lions at the Ballard Locks in Seattle in the late 1980s is a prime example:  In 1988 and 1989, resource managers captured 39 California sea lions that had been foraging at the Ballard Locks and transported them to the outer Washington coast near Long Beach, where they were released. Within a few weeks, 29 of those animals returned to the Locks to resume preying on salmon and steelhead.

The result was much the same the following year, when resource managers transported six California sea lions back to their breeding area off the coast of southern California. Three of those animals returned to Puget Sound within 45 days and a fourth was sighted in the Columbia River. Sea lions captured at Bonneville Dam and relocated to the Oregon coast and the lower Columbia River have also returned to the dam within a short period of time.

What would happen if California sea lions were allowed to continue foraging in the lower river?

Left unchecked, California sea lions could undermine the recovery of threatened and endangered Columbia River salmon and steelhead. For some stocks, recovery efforts have been under way for decades, and funded with billions of dollars in public investment.

Previous experience with California sea lions at Seattle’s Ballard Locks demonstrates the risk these animals can pose to vulnerable fish stocks. From the early 1980s through the mid-1990s, resource managers tried a variety of methods to deter sea lions from preying on Lake Washington winter steelhead. Those efforts were unsuccessful, and sea lion predation continued until the run was effectively destroyed.  Today, Lake Washington winter steelhead remain at critically low levels and the population is not expected to recover. With sea lion numbers and predation increasing on the lower Columbia River, fish managers fear some Columbia and Snake River stocks could meet the same fate.

Are other impacts to ESA-listed salmon and steelhead being addressed?

Yes. There has been an extraordinary and growing effort in this region to protect and recover salmon and steelhead populations.  Sport and commercial fisheries on the Columbia River are specifically designed to target hatchery-produced fish and spare threatened and endangered stocks.  In most cases, wild salmon and steelhead must be released, and fishing seasons are managed to hold incidental mortality rates for those fish within strict federal limits.

Meanwhile, recovery plans are being developed in every watershed to restore important habitat, improve dam passage survival and reform hatchery programs to assist wild fish populations.  Northwest citizens have supported restoration efforts, and borne the costs, because of the importance of salmon to our heritage, their cultural value to Native Americans and the economic value of salmon to Washington’s fishing communities.

How much does it cost to protect salmon and steelhead from sea lions below Bonneville Dam?

Washington and Oregon fish and wildlife departments have each received annual grants of $100,000 to $150,000 from the Pacific States Marine Fisheries Commission to support hazing and sea lion removal below Bonneville Dam. In past years, each state has also contributed approximately $15,000 for early-season hazing efforts designed to protect sturgeon, but the Columbia River Inter-Tribal Fish Commission has assumed this responsibility.

The Army Corps of Engineers provides approximately $150,000 per year to document predation, haze sea lions and conduct fieldwork related to sea lion predation. This is in addition to the Corps’ $3 million investment to install heavy bars and sonic devices to keep sea lions out of fishways and ladders at Bonneville Dam.