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Sea Lions Struggle On San Diego Coast

Katie Schoolov
Sea Lion Pup Strandings Surprises Scientists
Sea Lions Struggle On San Diego Coast
Undersized Sea lion pups are swamping rescue centers along the Southern California Coast and scientists do not know why.

More than 1,300 of the marine mammals have been rescued along the Southern California coast since January. Marine mammal rescue workers have been 10 times busier this year than they were last year.

Seaworld's Rescue Center has helped more than 300 young sea lions since the first of the year. The starving pups were rescued on boardwalks, in stores and, in at least one case, on a La Jolla restaurant's patio. They were in varying states of health. Some are bouncing back. Some continue to languish.

"Just like us, when you don't feel good, you don't always feel like eating. These animals are so severely malnourished, they don't feel like eating either," said Jody Westberg, director the the Seaworld Rescue Center. "Within the first two to three days, they start getting rehydrated, they start getting some of that nourishment that we're providing. They start showing signs of a little bit more activity."

At feeding time, about 40 pups gather for a sardine meal inside a Seaworld enclosure. Some of the pups are fiesty. They are vocal and even spar with other pups as they scramble for scraps. It is a welcome sign for Westberg.

"It means the pups are regaining their health and they're a step closer to returning to the wild," said Westberg. "When we bring them in the most important thing is to get them a physical exam by our veterinary team. Then to rehydrate them and start to provide them nourishment."

Length, weight, sex are all recorded. Blood, fecal and urine samples are taken. Necropsies are performed on the animals that perish. That information is being shared with federal officials. The National Marine Fisheries Service has declared the strandings an unusual mortality event and the agency has put together a panel of researchers to look into the problem.

"Right now, we don't know what that cause is, but the leading hypothesis is that its related to a food issue. That there's a food shortage," said Cynthia Smith of the National Marine Mammal Foundation. "And the animals either aren't able to find the fish that are there, or the fish have moved away, or the numbers have declined."

Hundreds of starving, undersized sea lions have been rescued and even more can be seen along the Southern California coast. Seaworld promises an unlimited capacity to help in San Diego county, but other rescue centers are feeling the strain. Some are turning away all but the most critically ill pups.

Scientists who track sea lion populations are considering several potential causes.

Researcher Mark Lowry examining squid beaks in a lab.
Katie Schoolov
Researcher Mark Lowry examining squid beaks in a lab.

Southwest Fisheries Science Center researcher Mark Lowry regularly visits the Channel islands where the sea lions raise their young. He collects scat samples and examines them for clues about the pinniped's current diet. On a recent day, he put a petri dish under a microscope and examined California market squid beaks.

"Just imagine a parrot beak," said Lowry. "You have an upper beak and a lower beak and they kind of fit into each other"

These squid dominate the sea lion diet, but he expects to find more diversity in that diet this year. Sea lions that are having trouble finding their regular food will broaden their diet to include more sardines, anchovy, and rockfish. Lowry said they will eat what they can find.

That happened during a sea lion pup die-off in 2009, a year when El Nino moved the mammal's food supply away from breeding areas. But this year, there is no El Nino. It is possible that the current population of about 300,000 sea lions is just too large, Lowry said.

"The ability of the environment to sustain a population changes up and down. As so, it's probably dropped down a little bit. And it's affecting the population, at least that's what I think is happening," said Lowry.

Sea lions congregate at the La Jolla Cove, just south of the sweeping La Jolla beach. Older males crowd against each other on the rocky shoreline, but there are also small pups squeezing trying to soak in the sunshine.

Sea lions at La Jolla Cove
Katie Schoolov
Sea lions at La Jolla Cove

It is an unusual scene because pups should be with their mothers on the Channel Islands.

"They shouldn't be weaning until April or May," said Jeff Laake of the National Marine Fisheries Service. He tracks sea lion populations. "They're born out on the Channel Islands, which is 40 to 60 miles off the coast. And they've left early."

If their mothers are having trouble finding food near the Channel Islands, it would be the reason the pups weaned early.

The strandings are not the most worrisome thing about the sea lion situation, said Laake. He said the unusual mortality event has likely already claimed the lives of some 30,000 sea lions pups. That's nearly half of all the sea lion pups born last summer. The normal mortality rate is 15 to 20 percent.

"There was an event in 2009 that occurred in spring when most of the pups are being born and when that happened, it was 80 percent mortality, that cohort. But the public didn't see it because they were so small they actually died out on the islands," said Laake.

Federal officials looking into the situation are still gathering data. They say it may be several months before they can explain the exact cause of the sea lion crisis. Food availability is the leading suspect, but disease hasn't been ruled out.