Columbia River salmon and steelhead face a serious threat from sea lions that have learned to consume these fish at predation hotspots such as dams, fish ladders, and natural pinch points in the river and its tributaries. Since monitoring began in the early 2000s, sea lions at Bonneville Dam have consumed thousands of migrating fish each year, many from runs listed as threatened and endangered under the federal Endangered Species Act (ESA).
The federal Marine Mammal Protection Act (MMPA) recognizes that predation by a growing sea lion population can jeopardize salmon and steelhead stocks at risk of extinction. After a multi-year effort to haze sea lions away from fish below the dam, NOAA Fisheries concluded that non-lethal measures, by themselves, were not sufficient to curb the growing levels of predation.
Since receiving federal authorization to conduct lethal removals of California sea lions in 2008, Washington, Oregon, and Idaho state wildlife managers have removed an average of 19 California sea lions annually. Despite these measures, consumption of salmon and steelhead by sea lions below Bonneville Dam continued to increase as Steller sea lions became established in the 2010s. In response, Congress passed a new law in December 2018 to provide state and tribal resource managers greater flexibility to manage sea lions.
This new law gave states and tribes approval to expand their sea lion removal efforts -- including removing Steller sea lions for the first time -- on a portion of the Columbia River and tributaries. Since this permit was issued in 2020, resource managers have lethally removed sea lions from Bonneville Dam each spring and fall. These efforts have begun to show signs of success, with sea lion presence and abundance at the dam beginning to decline and tens of thousands of salmon estimated to have been saved as a result of these removals.
Future work will focus on Washington’s tributaries, particularly the Cowlitz and Lewis rivers, to identify predation hot spots and mitigate impacts of sea lions to fish runs of concern through targeted lethal and non-lethal management. The Kalama River may be considered if emerging issues are identified. The Department has been working with co-managers to request additional appropriations to expand removal efforts within these tributaries.
Details of the new MMPA Section 120(f) permit
As of early 2025, the current permit is pending an extension, which would allow the remainder of authorized lethal removals to be used.
In December 2018, the president signed into law legislation that gives state and tribal resource managers more flexibility to manage sea lion predation on Columbia River fish populations.
The legislation allows the National Marine Fisheries Service (NMFS) to approve permits for Washington, Oregon, and several area tribes that streamline the removal process for a designated number of sea lions from a portion of the Columbia River and adjacent tributaries each year.
In August 2020, NMFS approved an application allowing WDFW and partners to expand their program to lethally remove sea lions preying on threatened and endangered salmon and steelhead in the Columbia River basin.
The expanded removal program gives wildlife managers more flexibility to remove sea lions by:
- Expanding the sea lion removal area both above and below Bonneville Dam, from River Mile 112 near the I-205 bridge to McNary Dam, and from adjacent tributaries.
- Allowing the removal of Steller sea lions as well as California sea lions.
- Not requiring the stringent procedures to qualify sea lions for removal as the current permit (i.e. identifying individuals by markings, previously hazing them, and documenting predation on salmon or steelhead).
The expanded scope of removals means managers from WDFW, as well as state and tribal partners, will now conduct operations for much of the year, instead of the four to six weeks of the previous federal permit.
Frequently asked questions
Why are sea lions a concern on the Columbia River?
Since 2002, 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). Predation by sea lions 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 in the Columbia River?
Thirty-two wild salmon populations bound for the upper Columbia and Snake rivers are vulnerable to predation by sea lions immediately below dams. 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 sea lions are preying on these runs?
Every 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 California sea lions consume 448 salmon and steelhead in the tailrace area, which extends about one-quarter mile below the dam. In 2017, by comparison, they documented 156 individual sea lions consuming an estimated 5,384 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 observed farther downriver in the lower Columbia River or its tributaries.
Are sea lions native to the Columbia River?
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 two species native to Northwest waters, 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, 60,000 to 80,000 adult males and juvenile California sea lions return north to forage for food along the west coast of North America. In recent years, surveys conducted by the Washington Department of Fish and Wildlife (WDFW) and Oregon Department of Fish and Wildlife (ODFW) estimated there were up to 2,000 – 3,000 California sea lions and 1,000 Steller sea lions in the lower Columbia River near Astoria.
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. Until 2008, their primary prey was white sturgeon, consuming 1,800 of them in the tailrace below the dam within view of observers from the U.S. Army Corps of Engineers. By spring 2018, it was estimated that Steller sea lions below the dam were eating more adult salmonids than those consumed by California sea lions.
What steps have been taken to deter sea lions from preying on salmon?
Washington Department of Fish and Wildlife (WDFW), and the Oregon Department of Fish and Wildlife (ODFW), Idaho Department of Fish and Game (IDFG), Columbia River Inter-Tribal Fish Commission (CRITFC), Army Corp of Engineers and USDA Wildlife Services (WS) have worked together to use various non-lethal tools 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, CRITFC boat crews work with WS dam-based teams to haze 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 extension, granted under Section 120 of the Marine Mammal Protection Act, allowed 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. The states' federal permit, which was renewed in 2016 for another five years, did not authorize removal of Steller sea lions. Under new authorization issued in 2020, the states and tribes were issued a permit that gives wildlife managers more flexibility to remove sea lions by:
- Expanding the sea lion removal area both above and below Bonneville Dam, from River Mile 112 near the I-205 bridge to McNary Dam, and from adjacent tributaries.
- Allowing the removal of Steller sea lions as well as California sea lions.
- Not requiring the stringent procedures to qualify sea lions for removal as the current permit (i.e. identifying individuals by markings, previously hazing them, and documenting predation on salmon or steelhead).
As of early 2025, the current permit is pending an extension, which would allow the remainder of authorized lethal removals to be used.
How many California sea lions have been removed from the lower Columbia River under federal authorization?
From 2008-19, wildlife managers for WDFW, ODFW, and IDFG removed a total of 219 California sea lions that met the federal criteria for removal below the dam. 191 were euthanized by lethal injection, 15 were placed in zoos and aquariums, and 7 died accidentally in capture traps. From October 2020 to Fall of 2024, 98 Steller sea lions have been removed at Bonneville Dam, along with 84 California sea lions. Three Steller and 14 California sea lions were also removed at Willamette Falls in the same timeframe.
How do the sea lion 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 accidentally 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 sea lions been effective?
The states’ efforts have not completely eliminated predation below Bonneville Dam, but they have reduced the number of sea lions feeding on salmon and steelhead each year. Wildlife managers estimate that more than 50,000 adult salmonids have been saved from predation by sea lions as a direct result of the states’ efforts at Bonneville Dam and Willamette Falls. Most of these savings are attributed to the expanded authorizations that began in 2020, which allowed the removal of larger Steller sea lions that remain in the Columbia River system for extended periods, consuming salmonids throughout the fall, winter, and spring. Since these management efforts began, both the average number of sea lions and the duration of their stay in the Columbia River and its tributaries have decreased.
At Willamette Falls in Oregon, sea lion removals have substantially reduced the probability of extinction for winter steelhead runs. In 2017, before removals began, increasing predation rates led to an 89% probability that at least one of three steelhead runs (North Santiam, South Santiam, or Molalla) would go extinct in the next 100 years. Several years of lethal removals at Willamette Falls greatly reduced the number of sea lions and brought predation rates down from an estimated 33% of returning adults in 2017 to under 2% in 2023. As a result, the probability of quasi-extinction for one of these runs within the next 100 years decreased to less than 10%. While this case represents a particularly extreme instance where a small number of sea lions were consuming a large proportion of especially vulnerable steelhead runs at a defined predation hotspot, a similar analysis for spring Chinook passing Bonneville Dam showed a 1.5% average reduction in quasi-extinction probability across all runs, highlighting the effectiveness of sea lion removals in supporting salmon recovery in the Columbia River.
Will the removal of specific 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" – the highest level the environment can sustain – according to wildlife biologists. The U.S. population of California sea lions is currently estimated at approximately 300,000 animals, all on the Pacific coast. In the 1950s, the U.S. population of California sea lions estimated at 10,000 animals. The eastern population of Steller sea lions is also estimated to be at or near carrying capacity, with an estimated 70,000 animals.
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, most 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. ODFW saw a similar outcome when they transported sea lions from Willamette Falls to the Oregon coast in 2018.
What would happen if sea lions were allowed to continue foraging in the lower river?
Left unchecked, 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 without intervention.
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.
Elsewhere in Washington, WDFW and partners continue to evaluate pinniped populations and predation on other salmon and steelhead stocks in Puget Sound and coastal waters, and explore potential deterrence and management measures. Wildlife managers are making efforts to expand their understanding of the impact of seals and sea lions in these ecosystems, including additional legislative funding to help facilitate statewide pinniped management efforts.
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.