Sardines moving offshore are not to blame for the high number of California sea lion strandings in Southern California.
Southern California has seen an unusually high number of sea lion pup strandings over the past couple of years. The heightened number of (stranded) animals closely mimics last year’s crisis when over 370 marine mammals came ashore in 2013 in need of medical attention, the Pacific Marine Mammal Center in Laguna Beach said in a press release on May 1, 2014.
The National Oceanic and Atmospheric Administration (NOAA) considers a marine animal as stranded when it is on the beach, dead or alive, or in need of medical attention while free-swimming. In 2013, the strandings were high enough for federal officials to call for an “Unusual Mortality Event” in Southern California.
In a teleconference with the press on May 6, 2014, Sarah Wilkin of the Marine Mammal Health and Stranding Response Program said that sardines have moved farther offshore. Wilkin indicated that sardines may contain more fat and nutrition than other fish, which nursing mothers need for their pups, intimating the sardines were partially to blame for the sea lion pup strandings.
But, information provided by NOAA shows sea lion sardine consumption declined between 2005 and 2010 in the Channel Islands, indicating sardines are not even a favored meal. In fact, market squid is a sea lion’s most frequently consumed food, not sardines, according to NOAA graph shown on the left.
Sea Lions will dine on anything seafood. Sam McClatchie, La Jolla oceanographer for Southwest Fisheries Science Center, said, “The sea lions are opportunistic feeders and so you shouldn’t get too fixated on the idea that all they’re feeding on is sardines because that’s not correct.”
With respect to the claim that sardines have higher fat content that nursing mothers need, that’s seal poop. Here’s the fat content per 100 grams of the fish sea lions commonly consume:
Sardines 1.5 grams of fat
Market Squid 1.38 grams of fat
Salmon 13 grams of fat
Anchovies 9.71 grams of fat
After a year of research, the National Marine Mammal Stranding Network (created under the Marine Mammal Health and Stranding Response Program consisting of over 100 organizations partnered with NOAA Fisheries Service to investigate marine mammal strandings) does not seem to know why we are seeing a heightened number of sea lion pup strandings, or at least, they aren’t telling us.
The number of California sea lions along the west coast has been increasing since the early 1970s. The U.S. sea lion population size is approximately 300,000. Between 50,000 to 60,000 pups are now born each year. Sea lion populations cannot grow without limit and eventually are often limited by the available rookery space and food resource, NOAA said in an email on May 14, 2014.