PORTLAND, Ore. -- A sea lion was found dead Tuesday in the Columbia River, near the Interstate Bridge, just two days after the bodies of six sea lions were found in open traps on the Columbia River and appeared to have been shot.

The body of the sea lion found Tuesday in the Columbia River near the Interstate Bridge.

The cause of this death was not known. A passerby saw the floating animal and alerted authorities, who towed the body to a river patrol office. The investigation will be turned over to the Oregon Department of Fish and Wild Life, Oregon State Police and NOAA.

“It is an unusual location, it could be natural causes, who knows?” said Dep. Travis Gullberg with the Multnomah County Sheriff's Office.

Also Tuesday, the Humane Society of the United States has reached agreement with state and federal governments that blocks killing or permanent removal of the sea lions iuntil early 2009.

In return, the Humane Society will drop its appeal in federal court against the U.S. Commerce Department and the governments of Oregon and Washington, Sharon Young, the society's field director of marine issues, said Tuesday.

Army Corps: Sea lion shooter got on restricted island

The deaths of the six other sea lions are under investigation after the bodies of the federally protected animals were found Sunday.

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The Army Corps told KGW Monday that they believe the shooters gained access to Cascades Island, a restricted area which is part of the Bonneville Lock and Dam complex.

Necropsies revealed Monday that no bullets were found in the animals, but the rounds likely went right through them since they found what were believed to be entry wounds.

The carcasses of four California sea lions and two Steller sea lions were found Sunday about noon. On Monday, the Humane Society announced they were offering a $5,000 reward for anyone with information leading to arrests in the shooting.

A tip line was set up at (206) 853-1964. The discovery came one day after three elephant seals were found shot to death at a breeding ground in central California.

 Details: More on elephant seals

All three species are federally protected by the Marine Mammal Protection Act. But Steller sea lions are also protected under the Endangered Species Act, authorities said.

Oregon and Washington state are trapping some California sea lions to keep them from eating salmon at Bonneville Dam, just east of Portland.

Seven California sea lions were trapped starting April 24 after the 9th U.S. Circuit Court of Appeals approved their capture. One died during a medical inspection before transfer to a Sea World park. Only one of the animals was destined for relocation, officials said.

Trapping operations will be suspended during the investigation, said Rick Hargrave, Oregon Department of Fish and Wildlife spokesman, who was at the scene.

 Comment: Your reaction to shooting deaths

The six animals found dead Sunday appear to have been shot by somebody on the Washington state side of the Columbia during the night, according to Brian Gorman, regional spokesman for National Marine Fisheries Service, or NOAA Fisheries, in Seattle.

Two California sea lions and one Steller sea lion each were found in two open cages next to each other on the river, he said.

The area was being treated as a crime scene by state and federal agencies, Gorman said.

A small group of activists waved signs near Bonneville Dam to protest the sea lion trapping Monday and expressed outrage over the recent shooting deaths.

 More: Protestors

Oregon and Washington have been granted federal authorization to capture or kill up to 85 sea lions a year for five years at the base of the dam, where they feed on endangered salmon headed upriver to spawn.

Fishermen and American Indian tribes have pushed to protect the salmon and remove the sea lions, by lethal force if necessary, forcing a delicate balancing act by the federal government.

"We're really shocked," said Sharon Young, society spokeswoman, who learned about the deaths from a reporter.

"We're a nation of laws and we should expect people to abide by them," Young said.

"The cruel shooting of defenseless sea lions left vulnerable in government traps should mark the final chapter in this sad story of blaming sea lions for salmon declines in the Northwest," said Michael Markarian, The HSUS' executive vice president. "The agencies must investigate aggressively and halt the entire trapping program immediately."

Investigators will try to determine if there is any link between the animals killed Sunday on the Columbia and the elephant seals killed Saturday near San Simeon on the central California coast, Gorman added.

Both state and federal law enforcement officials are investigating the crime, which can carry penalties of up to $20,000 and one year in federal prison for each animal protected under the MMPA, and up to $50,000 and one year in prison for each animal protected by the ESA.

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