Steller sea lion predation on white sturgeon in the waters below Bonneville Dam this year has continued its rapid growth and in the process left fish and wildlife managers with a problem for which there are really few answers.
Over the past few years populations of white sturgeon in the lower Columbia River have been slumping. Fishery managers estimate the abundance of legal-size fish (38-54-inch fork length) has declined from averages of 131,400 during 1998-2007 and 91,100 during 2008-2010 to a projection of 77,000 this year.
Concerns have forced the states of Oregon and Washington to cut the lower river harvest allocation from 40,000 in 2009 to 24,000 in 2010 to 17,000 in 2010.
The lower river population has to this point been considered robust and not in need of protections under the Endangered Species Act. Thirteen salmon and steelhead stocks, bull trout, Kootenai River white sturgeon in north Idaho and other Columbia River basin fish species are ESA listed.
“White sturgeon aren’t listed, and hopefully they won’t get listed,” said Charlie Corrarino, Oregon Department of Fish and Wildlife Conservation and Recovery Program manager.
From Jan. 7 through Feb. 23 the Stellers had been observed taking 1,136 white sturgeon compared to the previous record -- 1,100 last year for the entire winter-spring season. In 2010 observers atop the dam noted that 676 sturgeon had been taken through Feb. 24.
Research has been ongoing since 2002 at the dam, which is owned by the U.S. Army Corps of Engineers, to evaluate the behavior of marine mammals that swim up the Columbia to feast on, primarily, salmon and white sturgeon. The observations begin in January and continue through May when most, if not all, of the Steller (SSL) and California (CSL) sea lions have left for the Pacific about 146 river miles downstream.
The study was launched because of concern about the impacts of California sea lions on ESA-listed spring chinook salmon and steelhead stocks. Around the start of the century the dam workers and fish and wildlife officials began to notice an increase in CSLs making the trip to Bonneville to feed mostly on spawning salmon that mill around below the dam in search of a passage route – the fish ladders.
The SSLs likewise discovered an all-you-can-eat banquet, white sturgeon that have in recent years congregated literally in the thousands in areas below the dam to idle through the winter.
The vast majority of the salmon take is by CSLs, and the vast majority of the sturgeon take is by SSLs.
The number of SSLs seen visiting the dam each winter-spring has climbed steadily: Zero in 2002 to 3, 3, 4, 11, 9, 39, 26 and then doubled to 75 different animals last year. And last year’s record could be surpassed. Already researchers have documented at least 34 different individual SSL’s since Jan. 7, compared to 21 through Feb. 24 a year ago.
Observers have also seen SSL’s prey on 508 fish of unknown species, as compared to only 100 by this time last year.
“It is likely that at least 90 percent of the unknown fish caught by Steller sea lions were sturgeon,” according the Oct. 25 weekly status report prepared by Corps researchers Robert Stansell, Bjorn van der Leeuw, and Karrie Gibbons. “The Steller sea lions are catching many of the fish at the downstream range of our viewing area, making fish identification very difficult.”
A record daily high of 122 fish were observed caught by SSLs on Jan. 11. Most sturgeon caught are in the 2- to 4-foot-long range.
“Few fish are passing the count stations (1,024 steelhead, 8 Chinook) since January 1, slightly less than last year. Total salmonid catch to date (96 expanded by interpolating for weekends) is less than last year (138) but similar to 2009 (82), mostly by Steller sea lions,” the report says.
Through early this week only 3 CSLs had been spotted at the dam. A total of 89 CSLs were identified at the dam last year and the number has ranged from 54-104 since 2002. The numbers of California sea lions at the dam typically starts to build as the numbers of spring chinook salmon arriving at the dam mount. Peak spring chinook counts at the dam are usually in late April to early May. A total of 12 chinook had been counted in the dam’s fish ladders through March 1.
Federal, state and tribal entities have over the years attempted to “haze” the sea lions with cracker shells, seal bombs and other pyrotechnics and well as acoustic devices but have had little success at reducing predation.
The states of Idaho, Oregon and Washington sought and received authority under Section 120 of the Marine Mammal Protection Act to trap and permanently remove, to zoos and aquariums or by lethal means, CSLs that had been observed eating salmon and the dam. Section 120 provides an option for removing pinnipeds that are having a “significant” impact on listed stocks.
A total of 40 CSLs, which are not ESA listed, were removed over the past three years. But late last year the U.S. Court of Appeals for the Ninth Circuit ordered that the lethal removal authority decision by NOAA Fisheries be vacated. NOAA Fisheries is now mulling whether it can, or should, correct the flaws noted by the appellate court panel and issue a new decision.
Section 120 is not an option for attempting to control SSL predation on the unlisted white sturgeon. And the big pinnipeds’ appetite for listed salmon does not likely reach that significant threshold as required in the MMPA. Last year the CSLs’ observed salmonid take was 3,276; the SSLs’ was 634. In its ruling the Ninth Circuit said that NOAA had not adequately explained how the CSLs impact on protected salmon were significant while deeming larger hydro and harvest impacts not significant.
Meanwhile the states have launched research under MMPA permits to trap SSLs, mark for identification purposes and “put instruments on them so we can track their foraging behavior,” said Robin Brown, the ODFW’s Marine Mammal Project leader and a veteran of more than 30 years of pinniped research. A total of eight were trapped and marked last year, and this year’s permit allows the trapping of 20.
A few Steller sea lions continue to be observed hauled out inside the Bonneville powerhouse two corner collector outfall at times, but none have been seen this year using three traps deployed below the dam, the research report says.
The hope is to trap 10 to 20 per year and, with the followup monitoring, build a data base chronicling the SSLs’ residency time in the river, their feeding habits, movements and other attributes.
The SSL trend is exactly following the trend set by the CSL. Until the past 10 yearsago, few of the pinnipeds were seen upriver, much less all the way up at the dam. But in recent years the populations of both species that move inland during the late winter and spring has increased.
Brown said of the 1,200 or so CSLs marked since the late 1990s, 1,000 at Astoria, Ore., near the river mouth, only about 10 percent of them have been seen upriver.
The SSL research was launched to build a baseline of information on the animals, much like has been done for the CSLs, to help inform potential management actions to reduce the fish-pinniped interactions.
With building numbers of SSLs in the area below the dam, it is possible that their predation on salmon could grow to significant levels that would allow control actions under the MMPA’s Section 120, if the species was delisted. Oregon and Washington last year jointly requested the NOAA Fisheries Service delist the eastern population of SSLs, which live and breed along the coast from southeast Alaska down to central California.
“We don’t want that to happen,” Brown said of the prospect of significant SSL predation on salmon. But the state agencies want to be prepared when and if any management options emerge.
“Maybe someone in Congress will step up and realize we need more management tools,” Brown said.
The arrival of the first CSL at the dam last week is the latest since 2004. Stansell and Brown say that might be a sign that the removal program has had an impact.
“It’s got to be due to the removal program,” Stansell said of the late appearance of CSLs. In past years arrivals began as early as in January.
Brown said that last year’s removals in particular were animals that had a history of arriving early to begin their pursuit of salmon.
* States Seek Delisting Of Steller Sea Lions; NOAA To Decide By Aug. 30 Whether Warranted
The states of Oregon and Washington on Aug. 30, 2010, petitioned NOAA Fisheries to delist the eastern “designated population segment” of Steller sea lions. Two days later, the state of Alaska submitted a similar petition.
The eastern DPS, in a range extending from Cape Suckling in southeast Alaska east to British Columbia and south to California along the coast, is listed as threatened under the ESA. The average weight for an adult male is 566 kilograms or about 1,226 pounds and 263 kg (580 pounds) for females with maximum weights of about 1,120 kg (2,470) and 350 kg (772) respectively.
In a 90-day petition finding issued Dec. 13, NOAA Fisheries found that the petitions presented substantial scientific or commercial information indicating that the petition action “may” be warranted. Comments on the finding were accepted through Feb. 11.
The federal agency is now amidst the ESA process of determining whether or not delisting is indeed warranted. That decision is due by Aug. 30, one year from the date of the receipt of the first petition.
If NOAA Fisheries decides the delisting is warranted, another public comment period would ensue. Then the agency would take the information gathered through the process and launch into the development of a “final rule” – the actual listing determination.
The process will be exhaustive scientifically, according to Lisa M. Rotterman, Steller sea lion coordinator for NOAA Fisheries’ Protected Resources Division, Alaska Region. As coordinator of the species’ status review and petition review processes Rotterman said she is conscious of the need to make an unbiased evaluation.
“We want to make sure we have a very valid scientific reason” if it is decided the eastern DPS is to be delisted, or if it is decided it is not, she said. Rotterman said at this point the jury is still out.
“We’ve gotten quite a few comments and a wide variety of opinions about what we should do,” Rotterman said. They include comments and information from states, tribes, fishing groups, conservation groups, animal rights groups and others.
The states say that 30 or more years of steady growth has lifted the eastern population to a level at which they are no longer in danger.
“We believe that, based on your review of this material and additional information others can provide, the Department of Commerce and NOAA Fisheries will find that the EDPS of Steller sea lions from central California through southeast Alaska has recovered to healthy and sustainable levels of abundance, faces no significant threats as defined under the law and no longer meets the criteria for listing as a threatened species under the federal Endangered Species Act,” the Oregon-Washington petition concludes.
The states note that a revised Steller recovery plan completed by NOAA Fisheries in 2008 reports that the EDPS has been increasing by 3.1 percent or more per year for the 25-year period ending in 2002 and has continue growing at the rate, more than doubling for the southeast Alaska, British Columbia and Oregon population. In 2002 the total EDPS population was estimated to number from 46,000 to 58,000. Much of the turnaround resulted from the near elimination of predator control kills and commercial harvest.
A 2007 study concludes that the “population is now probably as high as it has been in the past century,” the Oregon-Washington petition says.
The Stellers gained protection from commercial exploitation with passage of the Marine Mammal Protection Act in 1972.
The states’ petition said that “none of the potential threats to recovery of sea lions identified in the recovery plan (predation, harvest, killing, human impacts, entanglement in debris, parasitism, disease, toxic substances, climate change, reduced prey biomass or quality, disturbance, or any cumulative effect of a combination of these factors) appear to be significant sources of mortality for EDPS sea lions, nor do they seem likely to prevent the continued population growth of the EDPS in the foreseeable future.”
“The recovery of the Eastern Steller sea lion DPS is an ESA success story and a good example of government and non-government agencies and other stakeholders working together to develop and implement conservation actions to recover a species from significant declines,” the Alaska petition says. “We offer our assistance in the delisting process. It is important to prioritize this delisting to document this ESA success story and accurately reflect the healthy status of this Steller sea lion DPS.”
“The Eastern DPS of the Steller sea lion is clearly not in danger of extinction now, nor is it likely to be in danger of extinction in the foreseeable future. Consequently, the State of Alaska respectfully requests that NMFS take immediate action to remove the Eastern Steller sea lion DPS from the threatened list under the ESA.”