California sea lion pups generally stay with their mothers for their first six months to one year of life. But unseasonably warm water, like that found in “the blob” five years ago, can make it hard for sea lion mothers to find food for their offspring, leading to pups stranded on local beaches. NOAA Fisheries is monitoring a new warm water event that could be affecting sea lion populations.
From 2013 to 2015, scientists observed an unusually warm pocket of water in the northern Pacific where temperatures spiked as high as six to seven degrees above average. In response, marine food webs went haywire and record numbers of starving baby sea lions and seals were stranded along the California coast as their mothers struggled to feed them.
Most California sea lions migrate to the Channel Islands off the coast of Ventura County to breed every year. Because of their proximity to the mating grounds, southern California rescue organizations such as the Pacific Marine Mammal Center and Sea World San Diego often notice problems with pups earlier than the rest of the California coast. These organizations have already reported early rescues of sea lion pups that could be connected with the blob-like conditions.
NOAA Fisheries is monitoring everything from pup weights in the Channel Islands, the health of adult sea lions and ocean temperatures to try to get ahead of any problems.
“We’re paying very close attention to all of those indicators,” says Cara Field, medical director at The Marine Mammal Center whose Monterey Bay Operations rescues animals from Monterey and Santa Cruz counties. During the 2015 blob, The Marine Mammal Center rescued more than 1,000 stranded pups.
Even so, local temperatures are still well below the record blob temperatures, says Francisco Chavez, senior scientist at the Monterey Bay Aquarium Research Institute. “This [event] doesn’t look to be as big of a beast as the other ones,” says Chavez. “But only time will tell.”
This year’s warming waters are part of a larger trend that has continued to develop over the last decade, says Chavez. Though he says scientists don’t know what specifically is causing the dramatic oscillations in ocean temperatures, they are still investigating the underlying causes.
In the meantime, marine life continues to experience the consequences of a changing climate.
When people start noticing stranded sea lion pups on their beaches, “that means there’s a bigger problem in the ocean,” says Field. Sea lions are a “sentinel species” because they eat a lot of the same fish that humans do. “Our lives are all intertwined together with the health of the ocean… and [sea lions] have a lot to tell us about what’s happening in the ocean,” says Field.
