San Francisco has a serious population problem — huge numbers of sea lions are crowding out the locals, and while the maritime mammals might look cute, some have gotten very aggressive.

After an especially strong breeding season, the sea lions are not only thriving, they are crowding into commercial fishing harbors, and sparking a turf war at public beaches.

"One bumped against me three times, then he went and nipped my little toe," San Francisco swimmer Sarah McCusky told FOX News.

But it's no laughing matter for Bay Area fishermen who complain the thousand-pound mammals are damaging docks and blocking their boats.

"They take over berths and make it difficult for fishermen to get to their boats, and really make it hard for people to do their jobs," Peter Dailey, Deputy Director of the Port of San Francisco, told FOX News.

The Port of San Francisco plans to make the docks sea lion-proof, installing 200-feet of mesh rubber barricade. And if that doesn't work, there are other options.

"There are humane ways you can make their lives miserable. You can be like an noisy neighbor, you can turn on loud music, you can have lights flashing on them, you can hose them down," Dailey told FOX News.

The animals are protected under federal law and as Sarah McCusky points out, they were there first. But she and other swimmers don't feel entirely safe in the water with half-ton carnivores.

"I think it's made us all a little bit more anxious about exactly where we will swim to," McCusky said.

One cause for hope? Crab season starts soon, and scientists say that the arrival of more boats, noise, and dockside activity may pursuade these sea lions to leave on their own.

FOX News' Claudia Cowan contributed to this report.