Pier 39 threw a party on May 21 to celebrate the 20th anniversary of their infamous sea lions’ arrival in 1990. It was the second celebration planned for the pinnipeds this year – but this time the guests of honors decided to show up.

Back in January (the official anniversary month), the sea lions had taken off for better fishing grounds, leaving their dedicated docks at Pier 39 virtually empty. So there wasn’t much to celebrate.

But in the past month, the number of the playful sea mammals has been rising, much to the joy of both tourists and Pier 39 merchants alike. Instead of the few dozen seen on the docks from December to March, there are now a couple of hundred each day.

Why they left at the end of last year is still a mystery. Experts don’t know for sure what tempted them away, but a record number of starving yearlings found stranded on Northern California beaches last year hinted that the food supply had shifted away from the Bay Area. Larger numbers of sea lions were seen in Oregon and Monterey Bay, where food supplies were greater.
Neither does anyone know why the creatures are returning now, nor how many will eventually set up camp again on the docks. A few hundred animals are far below last year’s record number of 1,700, but the “infestation” (as it was originally termed) in 1990 started with only a few hundred as well. K-Dock had just been renovated and there was a large herring run that year, creating prime conditions for the sea lions looking for a location to haul out for their rest periods.

“We had a perfect storm of sea lion deliciousness,” said Sheila Chandor, who has been harbormaster at Pier 39 since before the sea lions’ arrival.

So have the perfect conditions returned? Only time will tell.

“The fact that people cared that they left is the real story here,” said Jeff Boehm, executive director of The Marine Mammal Center, which monitors the health and safety of the sea lions at Pier 39.

And indeed they cared. News stories aired around the world about the mystery of the missing mammals. While the commercial fishing fleets, that have to compete with the ravenous carnivores for a limited fish supply were not sad to see them depart, the tourist destination that has become synonymous with the barking, fish-breathed hordes felt the loss more deeply.

So at least tourists and Pier 39 tenants were happy to celebrate the 20th anniversary, even if it was a few months late, with cupcakes, beverages and party hats – plus a new iPhone interactive game created especially for the sea lions. The object of the Pier 39 Sea Lion Game is to save the sea lions from predators and pollution in the Bay and bring them back to Pier 39. It’s competitive (just like the sea lions) and whoever saves the most sea lions each day can win a pair of tickets for RocketBoat, the high-speed water adventure. The game can be downloaded from the iPhone App Store, or you can find more information at www.mapiz.com.

You can love them or leave them, but you can’t ignore them – and it looks like the Pier 39 sea lions are back for the crowds to adore.