In mid-December, when moms were raising pups down south, 700-pound males hauled out onto the Moss Landing Harbor visitor dock. One fell asleep with its face in the water. (Leslie Willoughby Contributed) right).
MOSS LANDING — When baby sea lions are healthy, the curious and bright-eyed creatures sit up on their front flippers and take in the world around them. When humans approach, they skedaddle and leave nothing behind except a fishy, musky smell.
But along the Central Coast, sea lion pups in recent years increasingly have been found stranded — and they’re down to skin and bones. “Sometimes they could barely lift their heads, and they were reluctant to move, even when approached,” said Claire Simeone, a conservation medicine veterinarian at the Marine Mammal Center in Sausalito. “I could see the outlines of their hipbones and their shoulders.”
Even in a good year, a sea lion pup has only a 70 percent chance of reaching its first birthday. But in 2013 only 30 percent survived. And by May of that year, almost 1,500 were stranded along the California coast — up to 10 per day along the Monterey Bay shoreline.
To marine biologists, the deaths were the clearest sign yet that California sea lions, whose numbers skyrocketed for decades, are now smacking up against the limits of their environment.
The stranded pups should have been with their mothers, but the mothers apparently couldn’t get enough nutrition to support them, said Sharon Melin, a researcher with the National Oceanographic and Atmospheric Administration.
One reason was that the California Current, which flows south along the coast, moved farther offshore, making sardines and anchovies less available. Working harder to find food, the moms ate more market squid and rockfish, Melin said, and this change in diet may have reduced the quality of their milk.
The number of pups rescued from Sausalito to San Luis Obispo by the Marine Mammal Center, which has a facility in Moss Landing, jumped from 35 in 2012 to 111 in 2013. And last year that number increased to more than 239.
“We’re seeing another year of low weight and small body size,” Melin said. “We’re telling everyone to brace for more sea lion pups on your beaches.”
Although California sea lions have never been considered endangered, they have been hunted throughout history. Early Californians killed them for food; in the mid-19th century the mammals were hunted for their oil and hides. And from the 1930s to 1950s, they were turned into pet food.
According to UC Santa Cruz scientists, the Montrose Chemical Corp. from 1949 to 1970 manufactured DDT and dumped thousands of tons of the insecticide residue through sewage outfalls near the Channel Islands, the main sea lion breeding area in the U.S. During the late 1960s, scientists found hundreds of premature sea lion pups at the islands, and one year half of all pups died. Tests showed that moms that miscarried their pups had at least eight times more DDT in their tissue than did moms that gave birth to fully developed pups.
Two key events, however, soon improved the sea lions’ fate.
Montrose stopped releasing DDT into the breeding area in 1970, and two years later Congress passed the Marine Mammal Protection Act. The number of pups, which had hovered around 11,000 during the mid-1970s, doubled by 1993 and exploded to 60,000 by 2009, according to the National Marine Fisheries Service.
But the population is now leveling off.
Anticipating more starving pups this winter, the Marine Mammal Center has been ordering medications and training rescue volunteers, Simeone said.
In addition to the pups, the center rescued 180 adult sea lions in 2013 and 420 last year. Some were afflicted by hookworm or another parasite, Toxoplasma gondii, which is carried by cats. Others had contracted diseases such as leptospirosis, a bacterial infection that affects their kidneys. And some were poisoned by a nerve toxin called domoic acid, which is found in increasingly widespread blooms of a particular type of algae, according to NOAA. Sea lions eat fish that eat the algae.
Domoic acid also sickens humans if they eat shellfish that have eaten the toxic algae. When the Marine Mammal Center finds sea lions poisoned by domoic acid, the staff works with health departments to locate the algae and ban people from collecting shellfish nearby.
Marine scientists say that sea lions are the ocean’s canaries in a coal mine. “They tell us so much about the health of the ocean,” Simeone said.
Many fishermen and harbormasters, however, aren’t as enamored with the species.
“If sea lions are around, a salmon sports fisherman doesn’t stand a chance,” said Roger Thomas, the president of the Golden Gate Fishermen’s Association. “A sea lion will tear a fish right off the line and the angler is left with just a head.”
Thomas has been involved in recreational salmon fishing since he started in Monterey Bay in the 1950s. He has observed the sea lion population boom and wonders whether that may be contributing to pup strandings, he said.
At Moss Landing Harbor, the 700-pound mammals cause roughly $100,000 damage each year, said Linda McIntyre, the harbor’s general manager.
Between 200 and 2,000 sea lions vie for dock space around Monterey Harbor, said Harbormaster Steve Scheiblauer. One year they sank five vessels.
When someone tries to get to a boat, the animals usually move out of the way, but they leave vomit and excrement behind. And, he said, because there are so many of them, they are entering places they would ordinarily avoid.
“Most people love the sea lions and want to protect them,” Scheiblauer said. But when he thinks about their future, he said, “I worry that nature will take its course through disease and famine. That would be a tragedy for the animals.”
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The bright pink sea slugs are typically found in Southern California, but have been found moving farther and farther north as ocean temperatures increase, possible due to global warming.
