By: Victoria Moorwood
Sea lion pups in Southern California have faced unusually high mortality rates during the past five years. Between 2013-17, sea lion pups were found to be extremely emaciated, dehydrated and underweight, according to the National Oceanic and Atmospheric Administration (NOAA). This issue continues to impact sea lion pups in San Diego, although a recent trend of improvement has just begun to surface.
Sea lion pup strandings occur when a pup is separated from its mother when she leaves the shore to look for food. Strandings are caused when it takes the mother an unusually long time to find food and the babies venture off by themselves, often unsuccessful. From 2013-17, hundreds of dying, starved and sick pups washed ashore, stranded and in desperate need of help.
NOAA labeled the issue an Unusual Mortality Event (UME) from 2013-17, which is defined by the Marine Mammal Protection Act as an unexpected stranding that incurs a significant amount of death and demands an immediate response. Strandings peaked in 2015, at around 4,000, from January to June. Strandings decreased to around 1,000 in 2017, which is a 75 percent decrease.
Matthew Pim, a kayak tour guide at La Jolla Kayak, remembers the strandings around La Jolla Cove clearly.
“I remember there were like 200 pups that got stranded and needed to be re-nourished by SeaWorld and those are the ones that are all tagged,” he said. “There’s a lot of babies and you can see their ribs on occasion, meaning they’re not getting food.”
Rescue and rehabilitation efforts have been a major contributor to producing more healthy pups, although the cause of recent natural improvements is still unknown.
Several rescue and rehabilitation programs exist in San Diego, through SeaWorld, the San Diego-based National Marine Mammal Foundation and The Marine Mammal Center.
Jordyn Degroote, a volunteer at The Marine Mammal Center, rehabilitated pups during the Unusual Mortality Event in 2015 and has continued to see results of both rehabilitation efforts and continued population struggles in La Jolla, such as premature births and starvation.
“They’re still doing research to find out why so many sea lion pups, specifically, stranded,” she said. “We’ve gotten a lot of answers, but stressors that the sea lions don’t need to go through are definitely something that can be avoided.”
Degroote said environmental factors, such as trash and the decrease of fish, combined with tourism and a lack of public education about sea lions contributed to the strandings.
NOAA’s investigation found that higher deaths were likely caused by a lack of sea lion prey, specifically sardines, that only impacted Southern California coasts. However, the exact cause of the food shortage is still under investigation.
Jennifer Cull, animal care and training supervisor at the National Marine Mammal Foundation (NMMF), said the root of recent improvement hasn’t been clearly defined yet, but changing weather patterns could be a factor.
Cull and NOAA both said that the extreme number of pup deaths were likely caused by a combination of natural elements that seemed to all hit the population at the same time. Warmer water can cause algae blooms that can increase levels of toxic algae, which are then eaten by fish. This, combined with San Diego’s recent warm water climatic changes, called “El Niños,” can lead to a decrease of fish and a smaller food supply for sea lions.
“They don’t really know why it’s been transcending out of it,” Cull said. “The fish were moving further off the rookeries because of a few things: there’s an algae bloom, warmer waters—and that just goes with the whole global warming—and the El Niños.”
Although NMMF and NOAA research points to heating waters and changing weather patterns, some members of the La Jolla community believe that more is behind the depletion of fish than just environmental factors.
John Leek, a member of the La Jolla Parks and Beaches Committee, has spent years tracking the rates of rehabilitated sea lion pups released back into the ocean.
He agrees that the stranded pups are suffering due to a lack of food, but blames NOAA for what he believes to be the underlying cause: overpopulation.
“The real problem was, and still is, a federal program run amuck that has created an ecological disaster all over the West Coast,” Leek said.
He said that through their fishing regulations, NOAA has allowed California sea lions to reach a population size that outweighs their environments’ carrying capacity. Before the peak of strandings in 2015, there were complaints about too many sea lions in La Jolla.
Leek also doesn’t believe that the sea lion population is bouncing back as robustly as NOAA reports.
“So many died off that there is now some carrying capacity, so starvation will not quite happen for a few more years,” he said.