A year after more than 1,500 malnourished sea lion pups washed ashore along California beaches, scientists on Tuesday announced a shift in food sources is behind the epidemic.
During a teleconference, scientists from the National Oceanic and Atmospheric Administration (NOAA) revealed there was a shift in the spawning grounds of sardines, which are rich in fat and one of the sea lions' main sources of food.
"The fish populations that sea lions are traditionally feeding off of in Southern California have actually moved to areas further away from those foraging areas for the sea lions," said Justin Viezbicke, the state stranding response network coordinator for NOAA.
Over the last 15 years, the spawning grounds for sardines have moved further and further off shore, scientists said.
By some estimates, the sardines were spawning 60 miles further offshore than previous years.The distance was too far for some sea lion mothers and their pups to reach.'
As a result, scientists said some sea lions fed on less "filling" prey and were not able to nurse their pups adequately.
Scientists also ruled out other factors, including radiation and disease, which some speculated may have contributed to the spike in sea lion strandings.
While not nearly as high as the levels scientists saw in 2013, the number of sea lions pups being brought to rescue centers now is still higher than normal.
As of April, 650 california sea lions have been admitted to rescue centers across California. That's compared to 1,300 admitted last April.
Scientists say a normal level would be about 275 to 300 for the entire year.
The Marine Mammal Care Center in San Pedro had more than 100 animals as of Tuesday and have admitted 300 animals since January.
The Pacific Marine Mammal Center in Laguna Beach is reporting similar numbers.
"This year, it's pretty much a mimic of last year," said Keith Matassa, the center's executive director. "We're concerned again this year because we are seeing an increase number of animals coming into our rehab center. And for the second year in a row, we're into triple digits in-house for patients.
Scientists say their findings are preliminary.