Malnourished and dying California sea lion pups are likely to be seen again in high numbers on California beaches this winter and spring. Scientists with the National Oceanic and Atmospheric Administration have been monitoring sea lion rookeries on the Channel Islands and have found the lowest weights in pups in 41 years of recorded history.
“We’re preparing for higher than normal numbers, because the information that’s coming from the islands, from the scientists, are saying that the pups are the smallest that they’ve really ever been,” said Justin Viezbicke, stranding coordinator for the National Marine Fisheries Service in California.
Since January 2013, starving California sea lion pups have been washing up on beaches at alarmingly high numbers. The cause is believed to be a wide swath of abnormally warm water that has depressed the number of sardines in typical hunting areas. Sardines are important food sources for nursing mothers.
Viezbicke said strandings on the mainland could be high, because many pups are continuing to survive in the rookeries. When they leave, they’re not able to forage successfully and end up washing ashore on mainland beaches. Those strandings could begin occurring in late December and early January.
“If that’s similar to what we were having last year, where the pups are good enough to get off the island but not overall healthy enough to last within the system that they’ve got because of their situation, then we’re anticipating seeing higher than normal strandings again this year,” Viezbicke said.
The “blob” of warm water that has extended for thousands of miles into the Pacific Ocean from the West Coast has cooled in recent months. That would normally be a good sign for returning sardines. However, Nate Mantua, a research scientist with NOAA Fisheries, said the strong El Niño is likely to warm up the water near the coast again.
“It’s expected to have stronger and stronger influences on ocean currents and weather patterns off the West coast that are likely to keep it really warm for the next few months,” Mantua said. “That means that the marine food webs are still going to be disrupted near shore and really around those rookeries.”
Additional factors could complicate the care of sea lions. Another unusual mortality event has been declared for Guadalupe fur seals, a threatened species of seal that began stranding in abnormally higher numbers last January. Viezbicke said the protected status of the fur seal requires more space and isolation for animals receiving care. That could reduce the capacity facilities have to care for California sea lion pups.
“It’s a little bit more challenging space-wise, when you add other species,” Viezbicke said.
Adding to that challenge is the lingering domoic acid in ocean waters after a record toxic algal bloom that stretched from Southern California up into Alaska. The neurotoxins dumped into the water from the bloom can persist for months and concentrate in the flesh and viscera of shellfish.
Viezbicke said adult sea lions and fur seals needing treatment could further complicate care, since pups cannot be safely housed with adults.
Despite the multiple consecutive seasons of strain on young California sea lions and the subsequent low survivorship, scientists said the overall population remains healthy at around 300,000 individuals.
“At this time, the health of that population remains really good and really strong and much better than it was just a few decades ago,” Mantua said.
Viezbicke said scientists will continue monitoring the population in coming years.
“If it keeps happening, there will be concerns, but with a robust population of 300,000 animals, the reality is that it’s not a population concern at this point, but it’s something that we’re definitely keeping an eye on,” Viezbicke said.
Despite the overall wellbeing of California sea lions, the sight of starving sea lion pups will be difficult for many beachgoers. People who do encounter sea lions or fur seals they believe are suffering should not approach the animals but should contact the Marine Mammal Stranding Network at 1-866-767-6114.
Viezbicke said even so, the public should be aware that with the limited capacity to help the animals, many will not be able to receive care.
“You really want to temper the public’s expectations in those scenarios, because we understand that there’s concern, but the reality is we can only take so many animals in. And that’s really for the better of those animals that are currently in the facilities,” Viezbicke said. “It’s more of a quality thing.”