The signs were unmistakable as sick sea lions turned up one by one on the California coastline.
Some appeared to be unusually sluggish, weak and disoriented. Others displayed what is known as head-weaving behavior, with their snouts upturned as their necks tilted precariously to one side in a seemingly drunken sway. Many of the animals were foaming at the mouth; some were even convulsing from seizures.
Last month, the Marine Mammal Center’s 24-hour rescue hotline was flooded with hundreds of calls reporting sightings of the animals in distress, at one point receiving 144 calls in a single day, Giancarlo Rulli, a spokesperson for the Sausalito center, told SFGATE.
Rulli said that 75% to 80% of those calls were regarding individual sea lions in San Luis Obispo County alone, where the center’s team rescued 25 of the animals that they later determined had been sickened by an outbreak of domoic acid poisoning. Marine mammals can contract the naturally occurring neurotoxin through eating fish such as herring, anchovies and sardines, and once the toxin is in their bloodstream, it can lead to significant heart or brain damage, or even death.
Rulli told SFGATE the Marine Mammal Center was the first to diagnose a case of domoic acid poisoning in a sea lion because of a large outbreak in 1998, and since then has dealt with other outbreaks and mass stranding events on a much larger scale.
“That said, the logistics of transporting these mostly 150-200 pound subadult and adult marine mammals from our field office in Morro Bay to Sausalito — on an expedited timeframe due to their serious health condition — can still be challenging,” he said in an e-mail.
Torple, an adult female California sea lion rescued for domoic acid poisoning in San Luis Obispo County on Sept. 5, 2022, exhibits a common behavioral sign of the disease — head weaving — during rehabilitation at the Marine Mammal Center’s hospital and visitor center in Sausalito. The animal was successfully released back to the wild at Chimney Rock in Point Reyes National Seashore on Sept. 30, 2022.
Bill Hunnewell © The Marine Mammal Center
There is no known cure for domoic acid poisoning, though it can be eliminated through urinary excretion. Once the animals arrived at the Bay Area hospital, the Marine Mammal Center’s veterinary team administered a combination of fluids and non-contaminated fish to help flush the toxin from their systems. Some of the more severe cases also required anti-seizure medications.
“Thanks to the quick action of our teams in responding expeditiously to the sick sea lions and beginning immediate treatment, more than half of the sea lions have already been released back to the wild,” Rulli said, noting that the sea lions were still in rehabilitation at the hospital are on target to be returned to their habitat in the near future.
Experience the heartwarming moment of #MarineMammals returning to the wild wherever you are 🥰 We launched a webcam that shares livestream video from @PointReyesNPS so you can see your support in action 🌊 Text RELEASE to 65179 to be notified when patient releases are visible! pic.twitter.com/Qr7Ch5IZoX
— The Marine Mammal Center (@TMMC) September 29, 2022
Outbreaks of this nature in San Luis Obispo County aren’t considered unusual, especially during this time of year. The Marine Mammal Center has seen mass stranding events of a similar scale in the region three out of the past five years, and rescues anywhere between 60 and 80 sea lions sickened by domoic acid poisoning across its 600-mile response range on any given year.
“Although concerning to see these cases, it did follow a typical pattern of a late-summer spike in domoic acid cases in the region,” Rulli said. “One thing we do know is that the algae (Pseudo-nitzschia) thrives in unusually warm waters off the West Coast — ocean conditions that have become more frequent in recent years as we see the impacts of climate change increase.”
This event was not related to the algal bloom that spread across the San Francisco bay in late August. Sue Pemberton, a curatorial assistant who is also on the marine mammal response team at the California Academy of Sciences, said she had not observed high numbers of animals impacted by domoic acid toxicosis in the Bay Area.
But the bloom of pseudo-nitzschia in San Luis Obispo County did sicken sea lions in Southern California. And while the Marine Mammal Center said the event was not considered unusual in San Luis Obispo County, the Channel Islands Marine and Wildlife Institute called the outbreak “a crisis situation” in Santa Barbara and Ventura counties. A spokesperson for the rescue organization told SFGATE that volunteers came to the aid of more than 262 marine mammals sickened by domoic acid since Aug. 15, some of which required multiple field responses. Most of the affected animals were adult female sea lions, but they also encountered nine male sea lions, two Northern fur seals and one long-beaked common dolphin exhibiting the telltale symptoms of domoic acid toxicosis.
“This was a very difficult time for CIMWI’s all-volunteer team,” the spokesperson said in an email, noting that the organization was fielding 50-100 calls a day. “This strain was potent and much stronger than CIMWI has ever experienced. CIMWI saw more acute symptoms and higher rates of mortality on the beaches and with animals receiving treatment and supportive care.”
California sea lion needle (right) rests in a rehabilitation pool pen during treatment for domoic acid poisoning at the Marine Mammal Center’s hospital and visitor center in Sausalito. The adult female sea lion was successfully released back to the wild at Chimney Rock in Point Reyes National Seashore on Sept. 29, 2022.
Bill Hunnewell © The Marine Mammal Center
Sea lions can be the first animals to be affected by a toxic algal bloom, Rulli said. Because domoic acid can also sicken humans who eat contaminated fish and lead to amnesic shellfish poisoning, a life-threatening condition, the Marine Mammal Center provides data to the state’s public health department so it can closely monitor and issue warnings on seafood.
In the meantime, Rulli said, the center’s scientists are working to investigate the toxic algal bloom’s links with climate change and other environmental factors.
“The past experience of dealing with mass stranding events, including due to domoic acid poisoning, is invaluable and allows us to perform the logistics of the rescue, transport and animal care seamlessly,” said Aliah Meza, operations manager at The Marine Mammal Center’s Morro Bay field office. “Thanks to our dedicated response volunteers in coordination with our veterinary staff, we’re heartened to know that these sick animals are receiving a second chance to return to their ocean home.”