Why are so many sea lion pups starving? Scientists find the answer off the Central California coast

An emaciated and sick sea lion pup at the Marine Mammal Care Center in San Pedro in 2013. New research blames a lack of nutritious fish off California’s central coast for the rise in starving pups in Southern California. (Mark Boster / Los Angeles Times)

Government scientists say there’s a simple explanation for the surge in starving sea lion pups along the Southern California coast: Their mothers can’t find enough nutritious food.

The high-fat, high-calorie fish species that female sea lions prefer to eat have been harder to come by in their usual hunting waters around the Channel Islands breeding colonies, according to researchers from the National Oceanic and Atmospheric Administration. As their preferred sardines and anchovies became less plentiful, they’ve had to settle for rockfish and market squid instead.

The decline in sardines and anchovies and corresponding increase in less nourishing fish explains 81% of the change in sea lion pup weights between 2004 and 2013, the NOAA scientists reported Tuesday in the journal Royal Society Open Science.

California sea lions have had a precarious existence since the late 1800s, when humans began hunting them for their fur, meat and oil. Many of them also became casualties of fishing operations. By the 1970s, the number of sea lions had dwindled to around 50,000, experts estimate.

The animals’ fortunes began to change in 1972, when President Richard Nixon signed the Marine Mammal Protection Act. With federal protection, the population of Zalophus californianus grew about 5% per year, reaching 340,000 in 2014.

Hunger drove sea lion pups ashore in Southern California in record numbers in 2013. These rescued pups were cared for by the Marine Mammal Care Center at Fort MacArthur in San Pedro. (Irfan Khan / Los Angeles Times)

That progress hasn’t always been steady. In El Niño years, anchovies and sardines became scarce and sea lions switched to rockfish, squid and hake. Previous studies have found that when sea lion mothers eat more rockfish and squid (as determined by analyzing their scat), the pups they nurse have lower body weights.

A team from NOAA’s Fisheries Service wondered whether the effects were limited to El Niño years.

To find out, they needed to know where pregnant and nursing sea lions liked to hunt. They estimated a likely foraging range based on the movements of six female sea lions from San Miguel Island that were tagged by researchers in the 1990s. The data from those tags showed they liked to hunt off the California coast between Big Sur and Malibu.

Next they had to figure out what kinds of fish were available in those waters. For more than 30 years, researchers from NOAA’s Southwest Fisheries Science Center have been taking a census of young rockfish and other fish species in central California. Data for the area they needed was available from 2004 to 2014.

Finally, they looked up the average weight of 14-week-old sea lion pups from San Miguel Island for each year between 2004 and 2011. During that period, the average weight ranged from 14.8 kilograms to 20.9 kg for female pups and from 17.5 kg to 23.6 kg for male pups.

The pattern they found was clear: When sardines and anchovies were abundant and rockfish and squid were scarce, sea lion pups weighed more. Conversely, when rockfish and squid were plentiful and sardines and anchovies were not, sea lion pups weighed less.

The NOAA scientists weren’t able to study the “composition or quantity” of milk produced by sea lion mothers, so they couldn’t make a direct link between the types of fish in the sea and the nutritional value of their milk. Still, the results amount to “compelling evidence” that the pups are starving because their moms can’t produce enough milk for them, the scientists wrote.

At least 375 sea lions have stranded themselves on Southern California beaches so far in 2016, according to NOAA. The study authors said this trend could continue for quite some time.

“We expect repeated years with malnourished and starving sea lion pups,” they wrote.

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Port commissioner wants to sue the feds over sea lions

Commissioner Bill Hunsinger wants the Port of Astoria to go after the federal government regarding sea lions.

Port of Astoria Commissioner Bill Hunsinger said the agency should do something — potentially litigation — against the federal government regarding California sea lions in the Columbia River.

“Somebody has to be first, and I think it’s time for the Port of Astoria to be first at something,” Hunsinger said, after adding sea lions to the agenda of Tuesday’s Port Commission meeting.

Hunsinger, a commercial fisherman, said the agency needs to do something before the smelt start running early next year. The small, oily eulachons are a popular diet for male California sea lions migrating by the thousands north between breeding seasons, along with endangered salmon runs and anything else seasonal and abundant.

The pinnipeds have been showing up in the Columbia in increasing numbers, including more than 2,300 counted in March at the Port’s East End Mooring Basin. The Port has said the sea lions, which can weigh up to 1,000 pounds, are causing extensive damage to docks and preventing slips at the basin from being rented to boat owners. Hunsinger estimated 143 prospective customers are waiting to get a slip at the West End Mooring Basin, where sea lions have not congregated, while the east mooring basin remains empty, except for two docks near the breakwater with mostly commercial vessels.

“I don’t know why we have to provide those sea lions a home,” Hunsinger said, adding the National Oceanic and Atmospheric Administration should help the Port solve the problem or compensate the agency for the damage caused by the animals.

Sea lions were protected by the Marine Mammal Protection Act in 1972, when their population was as low as 25,000. Current estimates have the population at more than 300,000 along the entire West Coast. NOAA oversees protection of sea lions through the National Marine Fisheries Service.

The Port’s attorney, Tim Ramis, said the idea sounds like a novel first-time effort, and that he would look into the options.

Executive Director Jim Knight said the most effective barriers tried by NOAA were rolled steel that keeps sea lions from jumping on docks. He estimated the barriers could cost the Port $450,000 to $500,000.

“It’s a daunting number,” he said, adding the Port may need to find an alternate solution.

Raise the bar

Robin Brown, Marine Mammal Program Leader for the Oregon Department of Fish and Wildlife, said he has worked on the sea lion issue with the Port for decades.

About 15 years ago, Brown said, he helped the Port create drawings of 1.5-inch galvanized steel pipes elevated nearly 2 feet above the edges of the docks, a strategy he said has worked in various ports in the Puget Sound region.

“To do the East End Mooring Basin, you’re talking about $15,000 to $20,000,” Brown said. “The marinas in Puget Sound have done that, and they have been effective.”

Brown said a shortage of prey in California, a growth in the sea lion population and stronger runs of smelt and salmon are driving the sea lions into the Columbia River. He said it is a problem the Port will have to deal with for decades.

“Really, the only way to deal with it is to make the investment for some significant and solid barriers,” Brown said, adding marine mammal problems are near the bottom in funding priorities for NOAA.

Starving sea lions

Sharon Melin, a wildlife biologist with the Alaska Fisheries Science Center, said she recently found California sea lion pups in their San Miguel Island rookeries averaged 26 pounds, more than 30 percent less than usual and the lowest average weights in more than 40 years of monitoring. The starvation points to their mothers’ difficulty in foraging because of unseasonably warm waters driving prey farther offshore. Mothers and young tend to stay closer to their California rookeries.

Melin said the expectation is for the large die-offs and strandings of the last couple of years to continue with El Niño conditions.

“For the most part, this doesn’t affect the males as they tend to migrate out of the area in late August and remain north of San Francisco through most of the winter and spring,” she said.

Both Melin and Brown said the seasonal availability of prey will determine where and how many sea lions aggregate.

Read the original post: http://www.dailyastorian.com/