CBS News correspondent John Blackstone reports Hedley Prince has been trying for months to stop sea lions taking over a dock used by fisherman and pleasure boaters.
Prince has good reason to worry. He's seen what's happened a little further down Fisherman's Wharf, at Pier 39.
"I've never seen so many," said Sarah Nahn, a tourist. "And there's like a boom in the population."
Marine Mammal Act
Pier 39, San Fran's Premier Bay Attraction
Sea Lion Mystery
In 1950 there were only about 10,000 sea lions on the West Coast. Today their population is estimated at 300,000. Pier 39 alone is home to some 1,500 - up from the few dozen that moved in there in 1990.
The noisy invaders have proved such a hit with tourists, Pier 39 merchants have done nothing to chase them away.
But for others on the bay, sea lions have become a nuisance - demanding constant vigilance. All along the West Coast, fishermen complain about their big appetite for already dwindling salmon.
Even though they're trespassing, the law is on their side. The marine mammal protection act makes it illegal to even bother these guys.
"If we were being infested by slime eels, people wouldn't care what we did to them," said Prince. "But because these things are cute, whiskers, big brown eyes - we're pretty limited in what we can do."
What he has done, is put up some barriers to discourage the sea lions.
But in the battle against these blubbery beasts, it's a small victory along an ever more crowded shoreline.