There is a recent report about a explosion in the population of anchovies causing feeding frenzy among sea lions:
There are also dolphins and hundreds of sea lions. They are chasing an unexplained explosion of anchovies in the bay. Killer whales showed up to hunt the sea lions. Tourists and scientists have never seen anything quite like it. “There’s easily over 100 to 200 whales in Monterey Bay,” said Nancy Black, a marine biologist and the captain of a whale watching boat. “So this is like, you know, so exceptional we just can’t even believe it.” “Looking pretty good,” she said as she sighted more whales. She says most of the humpback whales should have left for their winter breeding grounds in Mexico but could not pass up this fish feast.
Perhaps the anchovies lost their predators.