Captured Sea Lions Swing Back
by Cassandra Profita
ODFW expands branding program to target nuisance pinnipeds
Most California sea lions swim into Astoria's East Mooring Basin from the Columbia River before hauling out on the O dock for all to see.
But earlier this month six sea lions arrived in a horse trailer after being captured below Bonneville Dam in a trap set by the Oregon Department of Fish and Wildlife.
The ODFW's sea lion branding program, which historically has done its trapping in Astoria, has expanded its reach to target the nuisance sea lions that haul out below Bonneville Dam, where they feast on fragile salmon runs passing through the fish ladders. A new trap has been set up to catch sea lions below the dam on the Washington side of the river. The U.S. Army Corps of Engineers, Washington Department of Fish and Wildlife and National Oceanic and Atmospheric Administration are helping with the effort.
The program caught its first six pinnipeds below the dam last week, trapping them in a cage similar to the ones in Astoria and then using a crane to load them one by one onto a reconfigured horse trailer to be trucked back to the East Mooring Basin for branding and tagging.
Satellite tracking devices have shown the pinnipeds could be back up at the dam again in less than 48 hours, said Matt Tennis, a marine mammal researcher for ODFW who leads the branding program in Astoria. However, so far the six sea lions captured last week - five California sea lions and one Stellar sea lion - are still stationed in the estuary.
Tennis said many sea lions make the trip from Astoria to Bonneville all the time. In fact, historical data show one of the California sea lions captured last week had made four trips between Astoria and Bonneville in 2004 and three such trips in 2005.
As ODFW workers trucked the six captive sea lions to Astoria, one pinniped tagged with a tracking device was making his way down the river at a slightly slower pace. He left Bonneville at 8 p.m. April 3, and arrived in Astoria at 1 p.m. April 5.
According to ODFW spokesman Rick Hargrave, the capture and removal of sea lions from Bonneville Dam will ensure the peskiest pinnipeds get identified and properly marked. Practicing the procedure is also important for officials who may be called upon if the National Oceanic and Atmospheric Administration approves a section 120 lethal removal of certain sea lions from the Bonneville Dam area.
A proposal to euthanize 80-100 sea lions at Bonneville Dam is under way and has completed the public comment period; a task force is being formed to study the option in detail before any approvals are made. The sea lions have reportedly become a nuisance to wildlife officials and a potential threat to endangered salmon swimming through the fish ladders.
"We have a bunch of bad actors," said Hargrave. "The reason we brand them is to figure out who the routine visitors are. They will be the ones targeted if we do get approved for the lethal option. We also want to make sure we know how to do it. If the section 120 process ever gets to the point where they approve the lethal option, we'll have to trap them," he said.
Experts have estimated sea lion predation at Bonneville reduces salmon runs by 2 to 3 percent. Hargrave said that percentage is based only on the takes at the dam, not the 147 miles from the mouth upriver.
"We don't know how many they're getting before they get up here," he said. "That's a definite concern."
Gary Soderstrom, president of the Columbia River gillnetters' Fisherman's Protective Union, said his group supports the lethal removal of the sea lions at Bonneville. He said the sea lions have become accustomed to the methods now used to deter them from feasting at the fish ladders, and they will find their way back to the dam if they are relocated.
"They're an extremely intelligent animal," said Soderstrom. "They've been using the river boats and hazing them for several years now and they've learned just to laugh at them. You're not dealing with sheep."
The California sea lion population has reached 300,000 individuals and scientists believe it is near carrying capacity. However, they are still protected under the Marine Mammal Protection Act, which prevents wildlife agencies from using typical population control methods.
"We don't want to kill everything," said Soderstrom. " We just want things back into a balance."
The branding program tracks the sea lions' movements within the Columbia River system and beyond. Two of the sea lions captured at Bonneville last week were already marked: One was C443, which means it was first branded on the Columbia River; another was branded in San Miguel, Calif. Tennis and his team branded three new sea lions, C643, C644 and C655, and released a 1580-pound Stellar sea lion that was too big to fit in the branding cage. All six sea lions were released into the East Mooring Basin.
As the effort to capture and mark the sea lions at Bonneville continues, there's no telling how many sea lions at Bonneville will be delivered to Astoria's O dock. Tennis said it would be a "slow, tedious process" trying to get the sea lions back into the transport cage after being branded, which is why the program does not truck the sea lions farther away from the river and the dam.
April through May is prime time for the California sea lions to be feasting in the Columbia River, he said. They stop in on their way south to breeding grounds in California in the spring and then come back on a northward migration in late August and September.
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