California Sea Lion Strandings

Written by on April 3, 2013 in Marine Life, Seals, Sea Lions & Sea Otters

UPDATE Apr 21 — 

Scientists still don’t know for sure why these sea lions are continuing to beach themselves in California, but they have a theory. Many think it has to do with “some weird oceanic phenomenon” that is blocking the pups’ food source. Since it is not an El Niño year and there is no evidence of a toxic algal bloom or infectious disease outbreak, this seems to be the only explanation.

Last week, several articles were published regarding the sea lion deaths in Southern California. Here’s a summary of the situation so far:

California sea lion adult and pup.

California sea lion adult and pup. Photo credit: NOAA.

For reasons still unknown, hundreds of starving California sea lion pups have washed up on beaches from San Diego to Santa Barbara.

In a normal season, less than a third of sea lion pups born at rookeries off the coast of Southern California would die. This year, 45 percent of pups born in June have died, leading the National Oceanic and Atmospheric Administration (NOAA) to take “the extraordinary step of declaring an Unusual Mortality Event.”

As of March 24, 948 pups have beached themselves along the coast since the beginning of the year. This is nearly three times higher than the annual average. Rescue facilities are quickly overcrowding and many are forced to send new pups to rescue centers up north. Unfortunately, this trend is expected to continue and even increase through April.

The most likely causes include food availability or disease. Scientists have suggested that the supply of anchovies and sardines (staples in the sea lion diet) may be limited this season. If this is the case, it could have affected the sea lion mother’s ability to nurse her pups, causing her to abandon them.

A sea lion pup is typically weaned from its mother in April and before that time, the mother usually only leaves to find food. It’s possible the sea lion pups went in search of their own food if their mothers were gone too long.

“We’re working quickly to respond to this crisis,” said National Marine Mammal Foundation (NMMF) researcher Dr. Stephanie Venn-Watson in a statement. “The NMMF’s focus is to help save the lives of these malnourished sea lions and at the same time help our colleagues determine what’s causing this alarming increase in stranded pups.”

We’ll keep you posted as the situation progresses.

California sea lions underwater.

California sea lions underwater. Photo credit: NOAA.

To learn more, check out these articles:

Copyright © 2013 by Marine Science Today, a publication of Marine Science Today LLC.

About the Author

About the Author: Emily Tripp is the Publisher and Editor of She holds marine science and biology degrees from the University of Miami's Rosenstiel School of Marine and Atmospheric Science and a Master of Advanced Studies degree in Marine Biodiversity and Conservation from Scripps Institution of Oceanography. When she's not writing about marine science, she's probably running around outside or playing with her dog. .


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