As the numbers of California sea lions increase at Bonneville Dam, state fish and wildlife agencies are for the fifth year turning to capture and kill techniques to help solve the problem created when the pinnipeds lie in wait for the spring Chinook salmon arriving at the dam.
Some 47 California sea lions captured at the dam were euthanized during the month of April, according to a report ending May 2 by the Oregon Department of Fish and Wildlife, http://www.dfw.state.or.us/fish/SeaLion/.
Another 14 California sea lions were added to a watch list in April and could also be captured and killed in the future.
This is not a new program to rid the river of the sea lions. ODFW and the Washington Department of Fish and Wildlife have been capturing and killing California sea lions since 2012 when they, along with the Idaho Department of Fish and Game, received a letter of authorization from NOAA Fisheries to begin removing and killing the sea lions. They initially asked for authorization in 2008, but a challenge by the Humane Society of the United States delayed the authorization until March 2012.
Since then the agencies have removed 100 California sea lions from the area just below Bonneville Dam. Some 15 were sent to zoos and public displays, while 85 have been euthanized. Seven more died during trapping and handling. In 2015 alone, the agencies removed and euthanized 32 California sea lions.
Removal of the sea lions benefits fish, the agencies say. The states estimate that removals have prevented the loss of 15,000-20,000 salmon and steelhead at the dam since the program began.
Both California (CSL) and Steller (SSL) sea lions are present at the dam, but only the California variety has been targeted. The number of CSLs hit a 2016 peak April 22 when 39 were observed, according to the fourth pinniped report this year by the U.S. Army Corps of Engineers (April 29 Pinniped Report, http://www.nwd-wc.usace.army.mil/tmt/documents/fish/2016/160429_Bonneville_pinniped_update.pdf). The peak for SSLs occurred April 18 when 49 were observed.
A combined (both SSL and CSL) 82 were observed April 22. The 10-year (2006 — 2015) average peak for the combined California/Steller sea lions has occurred at the end of April with 49 animals total.
It’s the California sea lions that are taking the bulk of Chinook salmon. So far they have been observed taking 1,442 Chinook, 46 steelhead and 3 sturgeon, while Steller sea lions have been observed taking 739 salmon, 37 steelhead and 25 sturgeon. The total 2,181 salmon is nearly a two fold increase in just the past two weeks and exceeds the 10-year average of about 2,000 salmon.
However, expanded estimates that include non-daylight and weekend hours when observers are not on duty are even higher. The expanded estimated take by both Steller and California sea lions of Chinook and steelhead combined totals 4,970, exceeding the 10-year average. Last year at this time, the total was 4,420 fish.
On the other hand, catches of sturgeon dropped from the 10-year average consumption, but is similar to the past two years. Estimated consumption of sturgeon through April 29, expanded for non-daylight hours, is 85, the report said.
To put this in perspective, the number of fish passing the dam April 29, the day of the report, was 28,029 spring Chinook salmon and 3,659 steelhead. By May 12 this week, the total rose considerably to 102,902 adult spring Chinook and 5,860 jacks, and 5,824 steelhead (both hatchery and wild).
The three states asked in January for a five-year extension of their authorization to remove and euthanize sea lions at Bonneville Dam under section 120 of the Marine Mammal Protection Act for the lethal removal of “individually identifiable” California sea lions eating salmon and steelhead listed under the federal Endangered Species Act near Bonneville Dam (http://www.westcoast.fisheries.noaa.gov/publications/protected_species/marine_mammals/pinnipeds/sea_lion_removals/sobeck_and_stelle_extension_request_1.27.16.pdf ). The extension requested is through June 21, 2021.
According to a NOAA Fisheries notice, the federal Marine Mammal Protection Act takes into consideration that predation of salmon and steelhead by a growing sea lion population can jeopardize those stocks that are at risk of extinction. . While exclusion gates keep sea lions out of the fishways, other non-lethal hazing using pyrotechnics and rubber buckshot have only a temporary effect. Removal seems to be the most effective means of protecting ESA-listed fish.
State fish and wildlife biologists brand the most problematic CSLs, documenting 79 uniquely branded individual animals — 77 of those had been seen at the dam in previous years.
Non-lethal, boat-based hazing of sea lions by the Columbia River Inter-Tribal Fish Commission began in early March and is continuing three days a week. Dam-based hazing by the US Department of Agriculture also began in early March and is continuing seven days a week. According to the Corps report, hazing has short-term effectiveness and the hazed sea lions quickly return.
The fourth status report was compiled and written by Patricia Madson and Bjorn van der Leeuw of the Corps, covering the period from January 1, 2016 to April 29.