were hit hardest by steller and California sea lions at Bonneville Dam in the
fall of 2017 and the spring of 2018.
of the predation by the pinnipeds at the dam is now by steller sea lions as
their numbers have risen in both spring and fall, while the numbers of
California sea lions is dropping, according to an annual pinniped predation
report by the U.S. Army Corps of Engineers.
7.2 percent of the steelhead run from January through May 2018 was taken by the
predators and 6.8 percent of the winter steelhead run was taken November 2017
through March 2018 (pinnipeds took 11 percent of the steelhead run in 2009). Of
the winter and summer runs of steelhead, steller sea lions took 6.1 percent
while California sea lions took 1.1 percent.
the number of salmonids taken by pinnipeds during the year was lower than in
2017, the number lost is still near the 10-year average, the Corps report says.
the request of NOAA Fisheries, the Corps began sampling during the fall and
winter months (August 15–December 31, 2017) to monitor the growing steller sea
lion presence at the dam in order to evaluate pinniped predation on fall- and
winter-run salmonid stocks. They found that during that period, 3.1 percent of
the coho run was lost to pinnipeds and 1.5 percent of the summer and winter
steelhead run was lost.
report, “Evaluation of Pinniped Predation on Adult Salmonids and Other Fish in
the Bonneville Dam Tailrace, 2018,” was completed January 24, by the Corps’
Portland District, Fisheries Field Unit. Its authors are Kyle Tidwell, Brett
Carrothers, Kristen Bayley, Lindsay Magill and Bjorn van der Leeuw. It is
available at http://pweb.crohms.org/tmt/documents/FPOM/2010/Task%20Groups/Task%20Group%20Pinnipeds/2018%20Pinniped%20Annual%20Report.pdf.
2014 Federal Columbia River Power System Biological Opinion requires the Corps
to monitor the seasonal presence, abundance, and predation activities of sea
lions at Bonneville Dam. Previous annual reports are at http://pweb.crohms.org/tmt/documents/FPOM/2010/Task%20Groups/Task%20Group%20Pinnipeds/.
were to all species of salmonids. During the spring (Jan. 1 to June 2) 3
percent of all salmonids in the dam’s tailwater succumbed to sea lions. That’s about
3,112 fish. Breaking that down, 2.9 percent of the chinook salmon run and 0.04
percent of the lamprey run were lost, in addition to the steelhead losses.
a comparison, sea lions took 0.4 percent of the total salmonid run in the
spring of 2002 and that rose to 4.3 percent during the low-flow year of 2015
and 5.8 percent in 2016.
all salmonid losses to the predators during the spring (3,112), some 2,368 were
consumed by steller sea lions – that’s 2.3 percent of the run – and 746
salmonids by California sea lions (0.7 percent of the run).
lamprey were also hit by the sea lions, with a total of 58 consumed. Steller
sea lions consumed 20 of those, while California sea lions ate 38.
in the fall (Aug. 15 to Dec. 31) for all salmonids were 892 fish, 1.2 percent
of salmonids at the dam. That includes 0.7 percent of the chinook salmon at the
dam, as well as the losses to coho and steelhead. This was during a period when
an estimated 426,162 total salmonids passed Bonneville Dam. In addition, 238
white sturgeon were taken by the sea lions, all 2 feet to 4 feet in length.
fall chinook salmon were taken in mid-September, while steelhead depredation
was heaviest in late-August and early-December. Coho were the predominant prey
from mid-October through mid-November.
observers during the fall period documented weekly predation estimates of as
much as 27 percent for chinook, 53 percent for steelhead and 48 percent for
coho relative to the number of fish passing the dam during a specific week.
levels of consumption are a direct result of the increasing presence of
predatory SSLs at BON and the growing population of BON-habituated SSL,” the
report says. “Columbia River salmonids now contend with quasi-resident SSL
predators that have increased in abundance and predatory impact.”
number of steller sea lions in the spring was 4.7 percent higher than last year
and 4.8 percent higher than the 10-year average. The number of California sea
lions dropped by 27.1 percent from last year and by 23.9 percent of the 10-year
near record low runs of ESA-listed winter and summer steelhead and small run of
ESA-listed spring Chinook Salmon that passed Bonneville Dam this sampling
season had to swim past high numbers of SSLs, however numbers of CSLs are
slightly lower than past years,” the report says. “Our estimates show that in
general: CSL abundance and fish consumption are down, SSL abundance and fish
consumption are up, and the total number of salmonids killed this year by both
species of pinniped, although lower than previous years, is similar to the ten
documented increasing trends in White Sturgeon predation that are of concern,
and identified that ESA-listed winter steelhead are being impacted by prolonged
SSL presence and predation,” the report continued.
report said that, just as Upper Willamette River winter steelhead are at risk
due to pinniped predation, so too are the steelhead at Bonneville Dam.
and wildlife managers need to take action to ensure the continued existence of
steelhead, and other threatened and endangered anadromous fish species. This
should entail a review of the current CSL management plan, and the development
of an equitable SSL management plan,” the report says.
than the Corps’ monitoring program (this report includes fall 2017 through
spring 2018), the Corps collaborates with state, tribal, and federal agencies
charged with managing fish and pinniped species. Since 2008, the states of
Oregon, Washington, and Idaho have implemented a pinniped removal program at
the dam under section 120 of the Marine Mammal Protection Act to permanently
remove predatory California sea lions that are having significant negative
impacts on the recovery of ESA-listed chinook salmon and steelhead stocks, the
report says. The Columbia River Inter-Tribal Fish Commission also collaborates
with the program with its boat-based hazing efforts, and the U.S. Department of
Agriculture provides dam-based hazing.
the number of pinnipeds at the dam during the fall months (August through
December) has generally been on the rise with none in August and September
2011, but 10.8 and 13.2 respectively by 2017. In October 2011 some 2.4
pinnipeds were observed on average, rising to 14.8 by 2017. There was a spike
in the low-flow years of 2015 and 2016 to 22.5 and 26.6. November 2011 saw 4.9
and in 2017, the number was 18.5. December 2011 saw 7, but by 2017 the average
number had risen to 16.4.
the 2017 fall period, just 3 individual California sea lions were observed at
the dam, but 36 individual steller sea lions were present. This proportion of
California to steller sea lions in the fall has been typical since 2011, and,
in fact, the first California sea lion hadn’t shown up at the dam until Nov. 2,
92 California sea lions were marked and authorized for removal at the dam
during the spring period: 27 were actually removed in 2018. The highest level
of removal was in 2016 when 57 were removed. 2008 was the first year for
removal under a MMPA Sec. 120 permit: 11 were removed.
lions are protected under the federal Marine Mammal Protection Act. California
sea lions in the U.S. are not listed as endangered or threatened under the
federal Endangered Species Act. The most recent population estimate for the sea
lions in the U.S. was 296,750 animals in 2016.
that will allow the lethal removal of more California sea lions, as well as
steller sea lions, from the Columbia River was signed into law by President Trump
in December. The Endangered Salmon and Fisheries Predation Act amends the
existing Marine Mammal Protection Act of 1972 by giving more flexibility to
remove sea lions that prey upon threatened and endangered salmon and steelhead
in the Columbia River. The bill also lists white sturgeon as a protected
species. Oregon, Washington, Idaho and CRITFC have said they will apply for a
MMPA Sec. 120 permit to begin removing steller sea lions at Bonneville Dam.
addition, a MMPA Sec. 120 permit was given to the Oregon Department of Fish and
Wildlife last year to lethally remove up to 93 California sea lions from
Willamette Falls on the Willamette River near Portland in order to protect from
predation by the mammals the runs of wild winter Upper Willamette River
steelhead and spring chinook. ODFW has lethally removed five California sea
lions in the past two months.
CBB, January 11, 2019, “With New Permit, Oregon Begins Lethally Removing Sea
Lions At Willamette Falls To Protect Steelhead,” http://www.cbbulletin.com/441999.aspx
CBB, December 14, 2018, “Legislation Awaiting President’s Signature Would Allow
Significant Increase In Killing Of Salmon-Eat,” http://www.cbbulletin.com/441918.aspx
CBB, November 20, 2018, “Oregon Plan To Euthanize Sea Lions At Willamette Falls
Approved By NOAA Fisheries,” http://www.cbbulletin.com/441816.aspx
CBB, March 16, 2018, “Corps Report: Pinniped Predation Consumed 4.7 Percent Of
Salmonids In 2017 In Bonneville Tailwater,” http://www.cbbulletin.com/440368.aspx
January 19, 2018, “West Coast California Sea Lion Population Has Rebounded;
Meets Marine Mammal Protection Act Goal,” http://www.cbbulletin.com/440111.aspx
December 1, 2017, “Recovery Of West Coast Marine Mammals Dramatically
Increasing Consumption Of Chinook Salmon,” http://www.cbbulletin.com/439896.aspx