Scientists seek cause of sea lion pup die-off
LOS ANGELES — Hundreds of starving sea lion pups are washing up on beaches in Southern California, overwhelming rescue centres and leaving scientists scrambling to figure out why.
At island rookeries off the coast, 45 per cent of the pups born last June have died, said Sharon Melin, a wildlife biologist for the National Marine Fisheries Service based in Seattle. Normally, fewer than one-third of the pups would die.
It’s got so bad in the past two weeks that the National Oceanic and Atmospheric Administration declared an “unusual mortality event.” That will allow more scientists to join the search for the cause, Melin said.
Pups are normally weaned from their mothers in April.
Even the pups that are making it are markedly underweight, Melin said.
The most recent pups weighed at the breeding area on San Miguel Island were about 16.8 kilograms, Melin said. They should weigh up to 26.7 kilograms by now, she said.
Melin said she doesn’t know how the pups are making it to the mainland, but they must be using currents and swimming.
“That’s a long way, and they are very small,” she said. “They don’t have a lot of fat, and the water is pretty cold. They are often dehydrated, which is typical with emaciation. It puts them in pretty bad condition.”
Those landing on the mainland may have been looking for food if their mother stayed out foraging too long, Melin said.
Live sea lion standings are nearly three times higher than the historical average, said Jim Milbury of the National Marine Fisheries Service, part of NOAA.
Between Jan. 1 and March 24, 948 pups were rescued, Milbury said. The bulk of those were in Los Angeles County, which had 395, followed by San Diego, Orange, Santa Barbara and Ventura counties, he said. Last year, only about 100 pups needed saving during the same period.
At the Pacific Marine Mammal Care Center in Laguna Beach, there were 139 animals being cared for Friday. Of those, 131 were sea lion pups, said spokeswoman Melissa Sciacca. She said the centre has treated more than 220 sea lion pups so far this year, while the centre treated 118 in all of 2012.
Southern California rescue facilities have become so crowded they have had to start sending pups to Northern California, said Jeff Boehm, executive director at The Marine Mammal Center in Sausalito, which was caring for 30 starving pups.
Scientists were performing tests to determine if the problem is food availability, disease or both.
Biologists knew last spring that this year’s supply of anchovies and sardines could be limited, Boehm said.
“These two species of fish are an extremely important part of California sea lions’ diets, and females simply may not have been able to nurse their young sufficiently, resulting in abandonment, premature weaning and subsequent standings,” he said.
There has been no sign of adult female mortality, Melin said.