Alameda, Calif. ? Michael Schiff stalked down a long beach at 1 a.m. and scanned the shallow water for a mystery fish lost for about 150 years.

“I know they’re here, but they’re very shy,” whispered Schiff, a volunteer on a scientific survey team. “Shine a light on them and they swim away, but they’re hard to see without it.”

Suddenly, several small fish glimmered silver in his flashlight beam, squirming and slithering to escape.

The grunion, a famous fish in Southern California, is back in San Francisco Bay.

Or at least people once again are finding them.

The six-inch long, silver bellied fish which lives only in the ocean waters off California and Baja California went missing in the Bay Area after being netted and identified in the 1850s.

In Southern California, meanwhile, the grunion’s unusual mating habits made it a cultural icon, as much a part of surfside lore as the Beach Boys.

Unlike all but a few fish species, grunion leave the water or swim to its edge to spawn.

The ocean fish mass together on high tides during new and full moons. Then they swim, surf and flop to shore to deposit their eggs in the sand before washing back to sea.

Hollywood comedians make jokes about the grunion’s clumsy trysts. People crowd around Southern California beaches late at night to witness the moonlit summer spectacle.

Some people even scoop them up, cook and eat them.

In the Bay Area, though, the fish faded into oblivion.

“It’s a mystery what happened to them,” said Karen Martin, a Pepperdine University biology professor. “I think the fact that they’re there in San Francisco Bay is pretty remarkable. It’s like they’re coming home.”

The grunion began popping up in state fish netting surveys in 2001, and also in studies of fish dropped near nests of terns at Alameda.

The Bay population is smaller than that in Southern California, but enough to surprise and delight Martin, a grunion expert.

She and her allies organized teams of volunteers called Grunion Greeters to do grunion counts this summer at Crown Beach in Alameda.

The teams had to look hard but they found grunions spawning.

Their discovery means that grunions live in the Bay, and are not rootless wanderers trying to reconnect with their Malibu and Huntington Beach cousins.

“It’s important they’re not coming from elsewhere,” said Kathy Hieb, a state marine biologist. “The big question still is: ‘Where have they been all this time?”‘