More Than 1,000 Sea Lions Gather at San Francisco’s Pier 39, the Largest Group in 15 Years

Visitors to San Francisco’s Pier 39 are often greeted by a familiar cacophony of barks, splashes and blubber-splats from the city’s iconic sea lions. But last week, that chaos hit a new level as more than 1,000 sea lions were counted congregating by the pier, the largest such gathering in 15 years.

The massive herd of sea lions has entertained residents and tourists alike. Large crowds have come to watch the mammals lie in the sun, while others have tuned into the pier’s live stream.

“It’s really a phenomenon,” Sheila Chandor, the Pier 39 harbormaster, tells SF Gate’s Andrew Chamings. “There are also a huge number of pelicans and a lot of anchovy in the bay. It’s like a National Geographic photograph right now.”

A large amount of food nearby—mainly schools of anchovies and herring—is the primary reason so many sea lions have gathered this year, officials say. The small fish seem to be concentrated near the Farallon Islands west of San Francisco.

Sea lions first began gathering at the pier in Fisherman’s Wharf in 1989, and their congregations soon numbered in the hundreds. The herd reached a record high of 1,701 individuals in fall 2009, but within weeks, the animals mysteriously vanished. Sea lions also completely disappeared for a brief period in 2014.

These yearly variations likely come as sea lions follow food—from spring to spring, fish populations move across different regions, and the sea lions’ presence has fluctuated accordingly. While the number of fish in the area has remained relatively stable, marine heatwaves in recent years have caused fish to become more concentrated, per the Guardian’s Maanvi Singh, which can affect where the mammals will gather.

Lately, the number of sea lions has bounced between 300 and 400 in the winter, and roughly 700 in spring, Chandor tells the Associated Press’ Haven Daley. The large amount of sea lions at Pier 39 this season might signal a strong population and ecosystem.

“[California sea lions’] population kind of reflects the health of the ocean,” Adam Ratner, the director of conservation engagement at the Marine Mammal Center, tells NPR’s Emma Bowman. “So, seeing big numbers of California sea lions is obviously a great thing.”

The animals won’t stay at the pier for too much longer, though, as they’ll soon move south down the California coast to the Channel Islands for birthing and mating season. According to the National Oceanic and Atmospheric Administration, female sea lions give birth from May to June and are ready to mate again after just three to four weeks. Breeding season usually ends in August.

Sea lions’ migration isn’t devoid of threats. Boating incidents, pollutants and net entanglement are some of the greatest risks to the species. And on shores—including Pier 39—harassment from humans is a worsening problem. According to a report from the Marine Mammal Center released last month, 30 percent of the sea lions, seals and otters taken into the California facility in 2023 were victims of harassment by humans or dogs.

The Marine Mammal Center advises leaving at least 50 yards of space between humans and sea lions on a beach—an act of respect that will allow both species to coexist.

“I bet a number of these guys are frequent visitors to Pier 39,” Dan Costa, an evolutionary biologist at the University of California, Santa Cruz, tells the Guardian. “Probably it’s one of their favorite places, and they keep coming back for the good food. And these sea lions are probably thinking, ‘Oh, look at all those tourists!’”

“It’s such a fabulously exciting visual right now,” Chandor tells SF Gate. “When they’re together in these kind of numbers, they energize each other. They’re just all fat and happy.”

Christian Thorsberg | READ MORE

Christian Thorsberg is an environmental writer and photographer from Chicago. His work, which often centers on freshwater issues, climate change and subsistence, has appeared in Circle of Blue, Sierra magazine, Discover magazine and Alaska Sporting Journal.