Marine biologists investigating cause of sick sea lion pups

Marine biologists are at a loss as to why an unprecedented number of sea lion pups are turning up near death along Southern California's coastline.

Since the beginning of the year, some 1,400 young California sea lions were admitted to rehabilitation centers across the state, according to Sarah Wilkin, the marine mammal stranding coordinator for the National Oceanic and Atmospheric Administration. Wilkin said that figure is five times the normal rate of beached pups for this time of year.

"Nobody was quite prepared for the scope of this," said Wilkin. "The major common factor for all these stranded pups is that they're coming in emaciated, dehydrated, basically starving. They have been unable to find enough food to sustain themselves."

As to why they are not getting enough of the fish they need for both nutrition and hydration is still unclear. But what is clear to marine biologists is this beaching epidemic only affects the young. Most of the sick sea lions were born last summer.

"The pups can't dive as deep," said Wilkin. "They can't travel as far so they might be more impacted in even just a slight change in the distribution of prey."

NOAA has taken an extraordinary step by declaring this an "unusual mortality event" to receive additional funding for rehabilitation and research.

"The numbers speak for themselves," said David Bard with the Marine Mammal Care Center at Fort MacArthur in San Pedro, Calif. "As far as the underlying causes, anything that I can tell you would be a guess."

Typically, Bard's facility receives between 50 and 80 animals in the first quarter of the year. So far in 2013, it has treated more than 400.

"What we started seeing since January is animals coming in at roughly half the weight that they should be," said Bard. "You can see their shoulder blades, you can see their spines."

SeaWorld San Diego reports similar figures. Spokesperson Dave Koontz said its rehab facility has treated more than 300 animals in 2013, a number that also includes elephant and harbor seals. Koontz says that's more in the first four months of 2013 than in 2011 and 2012 combined.

Wilkin says the NOAA is working with fishery scientists and oceanographers to pinpoint the exact cause. Besides food shortages, they are also exploring other theories including exposure to biotoxins, disease and human pollutants. They are even looking into possible radiation contamination from Japan's Fukushima nuclear power plant meltdown following the 2011 tsunami.

But regardless the reason, Wilkin said this could be a sign of something more troubling in the waters off the coast of California.

"We consider marine mammals usually as sentinels," Wilkin said. "By investigating causes that are impacting them, we do a lot of times get information that in turn can impact us. We eat a lot of the same fish species. We are using the oceans for similar ways so what we learn from them does play into our health."

Early findings indicate that the year has been relatively neutral in regards to ocean conditions, including temperature, according to Wilkin. So far, the California seal lion pup is the only marine mammal being affected in such a way.