US Army Corps of Engineers
Portland District Website Website

Sea Lion Management

Columbia River salmon, steelhead and white sturgeon face serious threats from California and Stellar sea lions. Since the 1990’s, sea lions have consumed tens of thousands of migrating salmon and steelhead, many from threatened and endangered runs protected under the federal Endangered Species Act (ESA).


Sea Lion Monitoring and Observation Program

Columbia River salmon, steelhead and white sturgeon face serious threats from California and Steller sea lions. Since the 1990’s, sea lions have consumed tens of thousands of migrating salmon and steelhead, many from threatened and endangered runs protected under the federal Endangered Species Act (ESA).

The federal Marine Mammal Protection Act (MMPA) of 1972 specifies the actions state fish and wildlife management agencies can take to manage California and Steller sea lions. Recognizing that predation by a growing sea lion population can jeopardize salmon and steelhead stocks at risk of extinction, the US congress amended the MMPA in 1994 to allow States to apply for limited lethal removal authority under a narrow set of circumstances (Section 120 of the MMPA).

In March 2008, fish and wildlife agencies in Washington, Oregon, and Idaho received federal authorization under Section 120 of the MMPA to remove California sea lions that have been observed preying on salmon and steelhead below Bonneville Dam. The federal authorization allows wildlife managers to use lethal measures to remove sea lions that meet specific criteria, although the states’ first priority has been to relocate them to zoos and aquariums.

Removal of problem sea lions has proven to be the most effective means of protecting fish from predation. While exclusion gates keep sea lions out of the fishways, other non-lethal deterrents such as pyrotechnics and rubber buckshot fired at them have only a temporary effect. Wildlife managers from Washington and Oregon and federal and tribal partners have been chasing sea lions away from the area immediately below Bonneville Dam for over a decade.

The California sea lion population along the West Coast is no longer considered at risk and has exceeded its “optimum sustainable population” with the current population at an estimated 300-330,000 individuals, up from less than 75,000 individuals when the MMPA was adopted in 1972. This means removing the relatively few sea lions necessary to reduce the immediate risk to salmon and steelhead at Bonneville Dam will have no impact on the California sea lion population. Of note, all of the sea lions that migrate north of California are males.

Steller sea lions, as a species, are split into separate distinct population segments between the east and west coasts of the Pacific ocean. The Stellers in the Columbia River are from the eastern segment and are currently exceeding 42,000 animals. They were recently delisted from the ESA and down-regulated as not depleted; they could be managed similar to California sea lions if the State wildlife agencies elect to do so. Current salmonid predation by Steller sea lions match the levels of predation California sea lions were having when the States requested Section 120 authority.    

Sea lions (especially Steller sea lions) often target sturgeon of spawning age; unlike salmon, sturgeon spawn multiple times in their lifetimes, meaning several generations are lost. In recent years, the number of white sturgeon being consumed by Steller sea lions has declined significantly, but the number of spring chinook eaten by Steller sea lions has increased. The Corps' pinniped monitoring team has documented an increase in the number and duration of stay of Steller sea lions at Bonneville over the last 10 years. 

The consequence of inaction

There has been an unprecedented effort among Northwest states, federal agencies, tribes, and private citizens to protect and recover salmon and steelhead. These efforts equate to hundreds of millions of dollars invested annually and billions over the past decades. The ongoing imperiled status of these fish is not only costing the region millions in direct investments, but also in opportunity costs associated with lost fisheries, restricted power generation, and constraints on land and water use. If predation by sea lions at these environmental pinch points is not addressed there is a high risk that these investments will fail and additional fish runs will be disappear.

The pinniped monitoring program was developed to fulfill requirements set forth in the 2000, and 2008 Federal Columbia River Power System Biological Opinion. This Biological Opinion outlines operational criteria for dams in order not to jeopardize the continued existence of fish species listed as threatened or endangered under the Endangered Species Act (ESA). The Corps’ efforts remain focused on keeping sea lions out of the fishways and working with tribal, federal and state partners to find a solution to a difficult problem.

On January 27, 2016, the states of Oregon, Washington, and Idaho submitted a request to NOAA Fisheries to extend the letter of authorization granted on March 15, 2012 under Section 120 of the MMPA to permanently remove CSL at Bonneville Dam that were having significant negative impacts on the recovery of ESA-listed Chinook salmon and steelhead stocks. The States did not request any changes or modifications to the terms and conditions of the 2012 Letter of Authorization (LOA). The requested extension was approved on July 7, 2016 for an additional five years. To date, more than 200 CSL have been removed under the initial authorization from 2008. The Corps will continue to satisfy the Biological Opinion requirements by supporting the efforts of the states and tribes to manage this complex issue. This includes collecting the fish predation and abundance data, consolidating those data in bi-weekly and annual reports, and supporting the non-lethal hazing efforts at the project.
In 2016 the USACE pinniped monitoring team documented the second highest number of pinnipeds (149 individual California Sea Lions, and 54 Steller Sea Lions) at the Bonneville Dam tailrace. The estimated inclusive Salmonid consumption rate by both species of pinnipeds in observation area was 8,969 or 5.5 percent of the adult salmonid run at Bonneville Dam from Jan. 1 through May 31. This is the second highest level of predation recorded to date. The monitoring program has evolved through the years and continues to more accurately quantify and describe the interactions of pinniped and fish using advanced technology and rigorous statistical design. The program is currently operational this year and has been monitoring sea lions on project since August, 2017.

Since 2008, several groups have opposed NOAA Fisheries’ decision to allow the states of Oregon, Washington, and Idaho trap and euthanize specific California sea lions listed as known repeat offenders.  These groups have staged protests and attempted to disrupt hazing and trapping operations at Bonneville Dam.  The Corps has been largely successful in referring media and public comment to the agencies directly involved with trapping. 

Cooperating Agencies

The role of the Corps is to track the number of individual pinnipeds and their predation on salmon, steelhead, lamprey and sturgeon; evaluate the effectiveness of various predation deterrence activities; and keep sea lions out of the dam’s fish ladders. Science-based management of the sea lions below Bonneville Lock and Dam is a contentious issue and requires collaboration with the National Oceanic and Atmospheric Administration (NOAA), Oregon and Washington Departments of Fish and Wildlife, Pacific States Marine Fisheries Commission (PSMFC), Columbia River Inter-Tribal Fish Commission (CRITFC) the United States Department of Agriculture (USDA) and various special interest groups.