SANTA CRUZ, Calif. -- A high mortality rate for sea lion pups off the California coast has scientists examining several theories that would explain why the pups are starving.

During the past year, the mortality rate for sea lion pups on San Miguel Island off the Santa Barbara coast went from an average of 30 percent to 80 percent.

A few of the theories tossed around include over population, El Nino and ocean upwelling.

"At the time, they weren't exactly sure, but there did seem to be quite a number of emaciated pups ... something going on with the food," said Julie Burrow, of Ano Neuvo State Reserve.

UC Santa Cruz Researcher Patricia Morris said she thinks Mother Nature may not have provided a lot of wind to the Central Coast during the year.

It is the wind-driven water currents that bring nutrient-rich water to the top of the surface and pushes fish and other food sources further off shore. The phenomenon is called curl and coastal upwelling.

"It means there wasn't food coming to shore, and it's the little guys who can't make the long trips way out to sea to get food," Morris said. "It's keeping adult females who are tied to a pup on land. They have to come back and feed that pup. They can't take long trips out to sea."

Other possible causes for the sea lion pup decline including disease, toxins and parasites have all been ruled out.

Morris said that ocean upwelling is just a theory, and it could be a year before the scientific community is able to analyze enough data to find an exact cause.

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