They’re lounging, biting each other and generally making a ruckus in numbers not seen in more than a decade. And don't even think about stealing their anchovies.

San Francisco’s famed Fisherman’s Wharf district is seeing a surge in sea lions.

First appearing at Pier 39 after the 1989 earthquake, the sea lions have become a well known tourist attraction. The number of sea lions — marine mammals that make loud barking calls and can weight up to a half-ton — crashing at the pier fluctuates over the seasons. On most days more than a hundred can be seen.

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But this week, Pier 39 harbormaster Sheila Chandor has counted more than 1,000 sea lions, and that's the most seen there in 15 years. A huge school of anchovies — a favored food of the pinnipeds — brought them there, Chandor said.

"It's all about the seafood. It's all about the food," Chandor said. "A very good way to put it is they are fueling up for the mating season. It's spring. They are ready to rock and roll down in the Channel Islands, and we're a nice pit stop with some great seafood."

The spike in sea lions is indeed only expected to be temporary. But the barges the sea lions lounge on are designed to hold significant weight, and officials admit this current surge is testing their limits.

Biologists said the number of anchovies in the bay that seems to have attracted extra sea lions this spring is especially high. Chandor said the schooling fish were off the Farallon Islands.

Meanwhile, shops and businesses in the area were hoping the sea lion surge would also result in a tourist shopping spree, attracting more visitors to the area. Sea lion lovers have been flocking to the pier to catch a glimpse of the huge, noisy herd.

"I’ve never seen that many sea lions in one place. I heard about this place, and we came here a few minutes ago, and it’s awesome to see them," said Theresa Simbeck, a visitor from Germany. "It’s very loud, of course, but it’s really nice to see all of them. And it’s funny to watch them fight and relax in the sun."

Big numbers of sea lions have come to their pier in past years, and some 1,700 have previously arrived, Chandor said. It's usually 300 to 400 in winter and up to 700 in spring, Chandor said.