The Oregon Department of Fish and Wildlife will soon begin hazing sea lions below the fish ladders at Willamette Falls in an attempt to reduce predation on federally protected salmon and steelhead during migration to the upper reaches of the Willamette River and its tributaries.
California sea lions have long been drawn to the falls in springtime to feed on chinook salmon and steelhead but in recent years their number has grown, raising fears about impacts on fish listed under Endangered Species Act.
Already three of the big marine mammals are hanging out below the Willamette Falls fishway “and are actually feeding on winter steelhead,” said Tom Murtagh, ODFW fish biologist in charge of the sea lion hazing project. The winter steelhead have begun to climb over the fishway on their way to spawning grounds upriver; the year’s chinook run will begin arriving at the falls in the coming weeks. The fish pass up and over ladders built at Pacific Gas and Electric’s T.W. Sullivan hydroelectric project.
The sea lion count last year climbed to as many as 13 with from 10-13 at the dam daily from March into June.
Even without the predation, the number of winter steelhead has “dropped to the point that we have concerns,” Murtagh said. The winter steelhead counts have been, for the most part, in a downward spiral since the early 1970s except for a brief rebound in the early 2000s. The 2008 count was 4,915 and was followed by the second lowest count on record, 2813, in 2009.
Passage in 2010 totaled 7,300 fish and represented nearly 40 percent of the total Columbia River return.
A pilot program was launched last year to see whether sea lion hazing could be effective in moving these animals away from Willamette Falls and, as a result, reduce fish mortality. The hazing with cracker shells, seal bombs (submersible noise makers comparable to an M80 firecracker) and other noisemakers will begin next week and take place five days a week between dawn and dusk through April 30.
The hazing effort will be conducted between Willamette Falls and the Interstate 205 Bridge about a mile downstream by a boat crew of three. Another hazer will work on the ground near ladder that is at the dam on the west shore in West Linn southeast of Portland. The falls are about 26 miles upriver from the Willamette’s confluence with the Columbia River.
The hazers aim to move California sea lions away from the falls where salmon and steelhead tend to stall and congregate before entering fish ladders, which makes them an easy target. When flows are at higher levels the turbulence below the fish ladders increases and seems to confuse the fish.
“It takes a while for the fish to figure out where they want to go,” Murtagh said.
No hazing will occur downstream of the I-205 Bridge, and sea lions will not be killed or harmed.
“Our purpose is not to harm the sea lions or move them off the river entirely, our intent is to move these animals away from ESA-listed fish that are congregating at the fish ladders waiting to swim upstream,” Murtagh said.
The hazing operation is being conducted under the authority and consistent with policies set in the Marine Mammal Protection Act. Additionally, predation of listed salmon and steelhead by California sea lions below Willamette Falls has been identified as a concern in the Draft Upper Willamette River Salmon and Steelhead Recovery Plan.
The hazing effort last year did seem to be effective in chasing the pinnipeds away from the ladder area.
“It’s good as long as you’re on the water,” Murtagh said.
Passage of wild winter steelhead at Willamette Falls since 2001 has averaged 8,100 fish annually, but has had a wide range of from 2,800 up to 16,000 fish.
Prior to fish ladder construction, only spring chinook and winter steelhead traveled above the falls, aided by higher water in late winter and spring. Historically, spring chinook spawned in the Middle Fork Willamette, McKenzie, South Santiam and North Santiam Rivers. By the 1950s, dams on all the major tributaries above Willamette Falls blocked more than 400 stream miles that were originally important spawning and rearing grounds.
Summer steelhead, fall chinook and coho salmon have been introduced above the falls over the years and now return in relatively small numbers.
The native Willamette winter steelhead stock is a late run, passing Willamette Falls from February through May. Spring chinook move through the Willamette Falls ladder between March and July, spawning in September and October.
The Upper Willamette chinook salmon “evolutionarily significant unit” was first listed as threatened on March 24, 1999. Following a status review that threatened status was reaffirmed on June 28, 2005. The ESU includes all naturally spawned populations of spring-run chinook salmon in the Clackamas River and in the Willamette River, and its tributaries, above Willamette Falls, Oregon, as well as seven artificial propagation programs:
The Upper Willamette steelhead “designated population segment” was listed as a threatened species on March 25, 1999, and that threatened status was reaffirmed on Jan. 5, 2006. The DPS includes all naturally spawned anadromous steelhead populations below natural and manmade impassable barriers in the Willamette River and its tributaries upstream from Willamette Falls up to and including the Calapooia River.
Meanwhile over on the Columbia, Steller sea lions that started arriving in the fall have begun once again to gorge themselves on white sturgeon in the waters below Bonneville Dam, according to Robert Stansell of the U.S. Army Corps of Engineers.
The estimated sea lion sturgeon harvest increased from a single catch (2005), to 315 (2006), and 467 (2007) and by 2010, the expanded white sturgeon consumption estimate below the dam had risen to 1,879, according to research at the dam conducted by the Corps. That catch is almost exclusively by Steller sea lions, even though California sea lions also make the 146-mile trip from the Pacific Ocean to the dam.
Stansell said that the predation on white sturgeon, which cluster in areas below the dam in winter, is at this early stage ahead of last year’s pace.
So far this year since researchers began daylight observations there have been an average of 12.5 Steller sea lions present per day through Feb 2. That compares to 8.7 per day and last year and considerably fewer Stellers in previous years.
The number of individual sea lions, including California and Steller species, observed at Bonneville Dam during the winter-spring season has increased from an average of 83 per year between 2002 and 2007 to 123.7 per year for the past three years, according to the Corps’ research report, “Evaluation of Pinniped Predation on Adult Salmonids and Other Fish in the Bonneville Dam Tailrace, 2008-2010.” This is primarily due to an increase in the presence of Steller sea lions (averaging 5.0 per year before 2008 and 46.7 from 2008 to 2010). A total of 75 different Steller sea lions were observed at the dam. The research has been ongoing since 2002, when zero Stellers were observed.
So far this year the Stellers have been observed taking an average of 2.2 steelhead per day, last year compared to 1.9 last year and 2.1 in 2009.
The Steller sea lions have been catching on average 34 white sturgeon per day so far this year compared to 24 last year when a record number of the big fish were observed taken by sea lions. The average through Feb. 2, 2009 was 15, according to totals compiled by the Corps research crew.
No California sea lions, which focus on salmon, have arrived at the dam so far this year, Stansell said.