STARVED BY THE SEA? Mass die-offs in the Pacific are sending the emaciated bodies of seabirds, seals, and sea lions ashore from California to Alaska.
Last Monday, I went looking for death. Technically, I was on a biweekly wildlife survey of San Francisco’s Thornton Beach. I was tagging along with Kirsten Lindquist, head of Beach Watch, a shoreline monitoring program created by the Greater Farallones National Marine Sanctuary. As we neared the water, California and mew gulls stood on glistening wet sand and small flocks of sanderlings twisted and turned in unison over the crashing waves.
There was no hint of doom, but in recent months this and many other Pacific Coast beaches have become sandy graveyards for thousands of common murres. “Two weeks ago, we found 80 dead murres here,” Lindquist said as we set off down the beach with another volunteer. “I have no idea what we’ll find today.”
Common murres—black-and-white fish eaters sometimes mistaken for penguins—breed on the rocky cliffs of the Farallon Islands about 27 miles off the California coast. This past summer, beachcombers began reporting dead and weakened murres on shores from Northern California all the way up to the Gulf of Alaska. In September alone, Beach Watch volunteers found some 1,500 murre carcasses—six times the average, and four times the average during an El Niño, when more murres die (more on that below).
As we followed the shoreline, our eyes scanning for sodden feathery bodies, Lindquist told me that murres aren’t the only marine animals in the region suffering declines of late. In fact, they’re the fourth Pacific Coast species to experience a mass mortality event in the past year.
Cassin’s auklets were the first casualties. These seabirds began washing up on beaches between Northern California and Alaska in record numbers late last year. Just as the auklet die-off began to ebb in January, dead pinnipeds (seals, sea lions, and walrus) started appearing. Since then, more than 3,000 famished sea lion pups and 80 emaciated Guadalupe fur seals—a threatened species—have come to shore in California.
The majority of animals have been young and severely malnourished, and in the case of the seabirds, dead. “We’re seeing ribs, hips, spines. They really look like walking skeletons,” said Jody Westberg, a member of the SeaWorld Rescue Team, which is helping to rehabilitate some of the seals. Similarly, most of the seabirds Beach Watch volunteers have found are “feather and bone,” said Lindquist. Any live murres that wash ashore are sent to rehab centers, such as International Bird Rescue, which has treated more than 460 birds since the die-off began and released dozens back into the wild (they usually treat only 10 murres per month this time of year).
While no one knows what exactly is causing the strandings and die-offs, experts are certain they have something to do with the weirdly warm Pacific waters that have persisted off the West Coast since last year, starting with “the blob,” a huge expanse of mild water, and magnified by a current El Niño event. The sea temperature is now several degrees higher than normal.
The tepid temps have attracted strange visitors, including swarms of hundreds of thousands of red tuna crabs, which invaded Southern California beaches in June, and tropical bluefin tuna, which showed up earlier than usual this year. “What we’re seeing is very different from what we normally see in fall,” says Russell Bradley, the Farallon Islands program manager for the conservation organization Point Blue. “I counted 25 brown boobies—that’s unbelievable. And a blue-footed booby. October in the Farallons looked more like Baja than Northern California.”
While these tropical guests may be enjoying their stay, the warm water—which is much less nutrient-rich than the cold water that typically wells up from the Pacific’s depths—can spell big trouble for some local species.
Cassin’s auklets and common murres, for example, have suffered more than other seabirds. Auklets are among the few seabirds that feed exclusively on lipid-packed, cold-water-dwelling copepods and krill—tiny crustaceans that warm waters may have driven away or far too deep for auklets to find.
Common murres face a similar challenge. In late summer, the birds are rendered temporarily flightless. Adult murres undergo a “catastrophic molt” and their chicks can’t fly yet, so the birds must dive and swim for their food. Unfortunately, experts believe the warm water has caused the fish they eat to become more spottily distributed and may be forcing them into lower ocean depths—too deep for the molting adults and chicks to reach. (The layer of warm surface water off the Farallons in September extended to a depth of about 100 feet). “Birds that end up in a bad location with limited resources at this time of year are screwed,” says Jaime Jahncke, director of Point Blue’s California Current group and an expert in marine food-web dynamics.
As for pinnipeds, difficulty finding food may have contributed to the strandings, but biologists have identified another culprit: domoic acid, a neurotoxin produced by a massive and persistent algal bloom in the Pacific that has been made worse by warm waters.
Experts expect some animal mortalities during El Niño years. Previous murre die-offs, for example, have coincided with warm water events in the past, but none have been as deadly as this one. “We’re going into this El Niño with very different conditions than the conditions were in 1982 or 1997,” says Bradley. “We’ve never seen anything like this. There are so many unknowns.”
As for Lindquist and her beachcombers, they’re collecting a dwindling number of murre bodies. Last week’s survey on Thornton Beach turned up a single dead murre—an emaciated adult whose new flight feathers hadn’t fully grown in. It was a dramatic decline from the 80 that had been found two weeks before. “Maybe it really is coming to an end,” Lindquist said.
Even if this episode is over, however, she knows another will follow. Given how strange sea conditions have been as of late, experts like Lindquist are wondering not if, but when.