(CBS News ) LAGUNA BEACH, Calif. - In California, young sea lions are in danger of starving to death and it is not clear why.
"I'm going on a rescue right now," said Peter Wallerstein talking on his cell phone while in his truck. "'I've already rescued two sea lions."
Wallerstein can barely keep up with the distress calls. His sea mammal rescue operation has already saved 240 California sea lion pups this year.
"Not much energy left in this guy," he said about one particular sea lion. Almost all were dying from starvation.
"We found them seven miles up the flood control channel, found them under a car, and we don't really know why," he said.
On average, about a hundred sea lions are rescued in Southern California during the winter. But 700 have been picked up over the last three months.
"They're very sick," said Keith Matassa, who runs the Pacific Marine Mammal Center in Laguna Beach. His team is nursing 115 sea lions back to health.
"A normal sea lion at this age -- 8 to 9 months old -- should be around 60, 70 pounds," said Matassa. "We're seeing them come into our center at 20 to 25 pounds, and really they look like walking skeletons."
Sea lions depend on herring, sardines and other small fish found close to California's coast.
Sarah Wilkin is a marine biologist with the National Marine Fisheries Service. Asked why it has reached this point, she said: "We're looking at whether the prey that these animals should be eating just isn't available to them for some reason, and that could be because there's less of it or because it's moved and it's not accessible."
It can take four months of care before the animals are strong enough to be released back into the Pacific.
"This is the ultimate gift watching an animal come in as a walking skeleton," said Matassa, "and watching it run off the beach...and just head out where it should be."
Scientists worry they'll find even more starving sea lions in the weeks ahead. April and May are usually peak months for sea lion rescues.