Researchers Take a Dive in Effort to Save Sea Lions

As populations of the endangered Steller sea lions crashed throughout the Gulf of Alaska and the Aleutian Chain, biologists began worrying about low survival among juveniles.

But the young animals--skittish adolescents that sport up to 300 pounds of muscle and mouths of impressive teeth--were almost impossible to capture on shore for health studies or satellite tagging.

“We were thrashing about in the mid-1990s, trying to figure out a way to catch juveniles because they’re so darned difficult,” said sea lion expert Don Calkins, now based at the Alaska SeaLife Center in Seward. “They tend to stay closer to the water, and they spook so easily.”

Underwater photographer Shane Moore approached Calkins--then a leading sea lion researcher with the Alaska Department of Fish and Game--with what initially seemed like a crazy idea.

“Shane’s an old Wyoming cowboy,” Calkins said. “He said to me: ‘These sea lions just about mob me when I go underwater. I think you could put a lasso around them.’ ”

Calkins and scuba divers with the department’s sea lion project soon confirmed that the young marine mammals were just too curious for their own good. By dangling a herring on a pole, the divers could coax the animals to stick their heads through a noose that allowed them to be hauled to the surface without being harmed. Between 1997 and last spring, 171 young sea lions had been captured for state and federal studies.

More than 100 divers and marine biologists gathered in Seward last month to discuss findings and ideas at the 21st annual Scientific Diving Symposium of the American Academy of Underwater Sciences. The sea lion studies, presented as a narrated video, may illustrate the most dramatic and potentially dangerous version of science diving.

“You’ve got to watch out for the head, especially for those teeth,” Calkins said.

About four years ago, Calkins began working out the method with divers Dennis McAllister and Walt Cunningham. As predicted, they found dozens of youngsters cavorting in the waters near haul-outs, apparently waiting for their mothers to return with food.

“You end up with 20, 30, 50, 100 animals just hanging out,” Calkins said. “So they play around. They’ve got time on their hands, so they’re real curious.”

Fortunately, the massive adult males, which can weigh up to a ton, and the adult females, smaller but still very powerful, were all extremely wary, rarely approaching the divers, Calkins said. “They’re just not interested.”

But the young animals would swim right up, as bold as rambunctious puppies, nipping fins, mouthing gloves.

“They don’t seem to be aggressive,” Calkins said, “just real curious.”

The capture strategy works like this: Two divers sit on the bottom in about 35 feet of water. One holds up a rod baited with herring. The other waits with a rod holding a noose connected to a buoy on the surface by about 45 feet of rope.

The diver with the herring coaxes the sea lion to stick its head through the noose. The other diver tightens the noose and releases the line. Stops keep the noose from strangling the animal or from loosening and falling off.

As the startled sea lion bolts, the divers scramble away. A team in a skiff snatches the buoy, retrieves the line, hauls the sea lion to the surface and puts it into a capture box. Once aboard a research vessel, the animal is anesthetized, allowing biologists to weigh, measure, take samples from and outfit it with a tracking tag. In the end, most animals are released, according to a report by McAllister, Calkins and diver Ken Pitcher.

Since 1997, about eight divers have trained to do the work, now conducted by both state and federal agencies, said Bob Hicks, the dive coordinator at the Alaska SeaLife Center. The 171 animals caught through May ranged from 2 months to 3 years. None died during the capture, though one animal died from an anesthesia-related accident during its exam, the report said.

“It has worked real well,” Calkins said. “There certainly doesn’t seem to be a better way of capturing young-of-the-year and juvenile sea lions.”