Who Killed the Sea Lions?

Sitting in the turbulent waters below the Bonneville Dam on the Columbia River, east of Portland, Ore., 15-foot-square floating platforms surrounded by 8-foot-high fencing lay in wait, designed to trap sea lions. Last Saturday night, as usual, the manually triggered traps were open; fish and game representatives had permission to capture 61 California sea lions and had to wait until one of them was inside the cages. When biologists next checked the traps, around 11:30 Sunday morning, two were closed, six sea lions were dead, and the authorities had a bizarre whodunit on their hands.

Federal and state officials descended on Bonneville, initially operating under the assumption that someone had shot the marine mammals (two endangered Steller sea lions and four California sea lions, only one of which was on the list of 61) with a high-powered rifle at close range. But Wednesday the mystery deepened: investigators conclusively determined that the animals were not killed by gunfire. Only one sea lion had puncture wounds, which were consistent with bite marks, and the metal fragments found in soft tissue near the neck of two of the other animals could have been from old wounds. Federal officials now say they're not even sure there were humans involved in the deaths, or whether the traps might have sprung by accident. What happened at Bonneville last weekend seems less and less clear.

Stoking the mystery is the resentment toward sea lions that is palpable among salmon fishermen in the Pacific Northwest these days. The salmon run dwindled drastically this year, causing officials to cut short the fishing season. In that climate, fishermen are none too favorably disposed to the population of California sea lions that regularly sift the waters downstream of Bonneville Dam in the hope of feasting on a tasty Chinook. Steps were taken to clear the pesky sea lions out. After nonlethal measures to ward off the persistent marine mammals proved ineffective, the states of Washington, Oregon and Idaho petitioned for and were granted authority to remove the 61 most troublesome California sea lions—lethally, if necessary. Though the Humane Society of the United States filed suit challenging the states' move, and the Ninth Circuit Court of Appeals stayed any action to kill the creatures, the states began to trap some of the sea lions in preparation for a transplant to zoos and marine parks where they would be offered them a new home. Authorities put the trapping program on hold on Sunday.

On Tuesday the Humane Society announced that it had reached a compromise with the government: in exchange for dropping its appeal against part of the lawsuit, the feds and states would suspend all trapping until at least next February.

Investigators are tight-lipped about how they're going about solving the puzzle. Army Corps of Engineers spokesman Matt Rabe told NEWSWEEK his agency had turned over documents and possibly videotapes from security cameras at the scene, but Brian Gorman, spokesman for the National Oceanic and Atmospheric Administration, said Friday that no videocameras had been trained on the traps. Bonneville's "critical features"—the spillway, powerhouses and fish ladders—hadn't been compromised, Rabe said. But the government will be reviewing its security measures in the wake of the incident to see if improvements are needed.

Gorman said NOAA investigators will try to determine how the gates were opened and are now awaiting tissue samples from the dead animals, which will indicate whether they were somehow poisoned—though it's not at all clear how that could have happened, he said.

If foul play was involved, the perpetrators figured out a way to slip past security at a federally controlled dam that has taken extra safety precautions in the aftermath of 9/11. If they gained access to the traps by land, they would have had to sneak around a gate manned by a guard. If they came by boat, they'd have had to navigate the turbulent waters coming off the dam itself, which would require skilled seamanship. "We have two mysteries," Gorman said. "How did the animals die, and how did the gates get closed?"

Investigators haven't ruled out some natural event or accident. One theory is that a drop in water levels below the dam could have put enough tension on the ropes to get the traps to close by themselves. But that scenario is a "stretch," Gorman said, because an agitated batch of trapped sea lions on one platform would likely have caused those on the other to jump into the water. It's possible that, once trapped, the sea lions could have overheated. But it wasn't a particularly hot day, Gorman said, and sea lions are known to spend several hours in the hot sun without any problem.