California sea lion below Bonneville Dam
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Questions
and Answers:
Sea lion predation on Columbia River salmon and steelhead
Why are California sea lions a concern on the Columbia River?
In recent years, a growing number of California sea lions in the Columbia River have been preying on endangered and threatened stocks of salmon and steelhead that are protected 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 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. Since then, observers have documented a steady increase both in the number of sea lions at the dam and their level of predation. In 2008, observers reported that 103 sea lions ate more than 4,243 salmon and steelhead in the same limited area below the dam.
Those observations 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.
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.
In April of 2008, they relocated six California sea lions to SeaWorld facilities in Orlando, Florida and San Antonio, Texas, where the animals are all reported to be in good health. However, relocation efforts were suspended after six other sea lions died of stress and heat prostration in cage traps. An investigation by NOAA-Fisheries found that the cage doors fell shut behind the animals while the traps were unattended, but did not determine why the doors closed. The states then suspended plans to remove additional sea lions until March 1, 2009 under an agreement with the Humane Society of the United States, which had challenged those efforts in court.
Will efforts continue to remove California sea lions from the Columbia River?
Yes, the states plan to resume efforts to trap and remove California sea lions in March 2009, because hazing alone has not proven successful in deterring predation. As in 2008, the states’ first priority will be to relocate California sea lions that meet the federal criteria for removal. NOAA-Fisheries is currently working to locate qualified zoos and aquariums to take those animals. However, the states also have the authority to humanely euthanize animals that cannot be placed at a qualified facility or are deemed unsuited for transfer. An interagency Animal Care Committee will oversee the entire removal operation, including the euthanasia of any animals.
Biologists from the Washington and Oregon departments of fish and wildlife also resumed hazing efforts in January to move sea lions away from fish below the dam. The states will also live-trap sea lions to mark them for identification.
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. A population survey conducted in 2006 by the Washington Department of Fish and Wildlife (WDFW) documented 1,200 California sea lions near the mouth of the Columbia River alone.
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 have long been used by wildlife biologists studying 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.
This year, wildlife managers are taking additional precautions to ensure that no animals are inadvertently shut inside the cage traps. Under one new protocol, the trap doors will be locked open to prevent them from closing accidently when the traps are untended. The doors also have been fitted with magnetic locks that require a code to open. In addition, the Corps has updated its surveillance systems at Bonneville Dam to monitor the entire area where the traps are set up.
Will the states’ efforts to protect salmon and steelhead below Bonneville Dam threaten the California sea lion population?
No. Since 1972, when Congress approved the Marine Mammal Protection Act, the West Coast population of California sea lions has been growing at a rate of 5.4 percent to 6.1 percent a year. Today, that population is estimated at over 238,000 animals, which scientists consider at or near the carrying capacity of the ecosystem.
The Marine Mammal Protection Act recognizes that predation by a growing sea lion population can jeopardize salmon and steelhead populations, including those listed under the ESA. The law is specifically designed to help address the imbalance between sea lions and vulnerable fish runs that currently exists in the Columbia River below Bonneville Dam.
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 usually 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 an annual grant of $150,000 from the Pacific States Marine Fisheries Commission to support hazing and sea lion removal below Bonneville Dam. Each state agency has also contributed approximately $15,000 for early-season hazing efforts designed to protect sturgeon in the same area. 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. The Corps also invested more than $3 million to install heavy bars and sonic devices to keep sea lions out of fishways and ladders at Bonneville Dam.
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