Photos: Join us for a grunion run, a SoCal beach tradition

Sex on the beach is best in the dark. Greenion knows that. Every spring and summer, a few days after the full moon or new moon, the small, silvery fish wash ashore to spawn by the thousands on Southern California’s beaches.

Like the annual return of swallows to San Juan Capistrano or California’s gray whale migrations off the coast, grunion runs remind us that wildlife survives in a sprawling metropolis. Although unknown to many, grunion runs are a local fixture. Coastal Native Americans once relied on them for food. In the 1960s, Frank Zappa wrote and recorded an instrumental song called “Grunion Run,” which featured the sounds of a guitar plugged into a fuzz box.

On a recent night, about 100 visitors to Cabrillo Beach in San Pedro voyeured the mating dance that takes place just after high tide. It unfolds like clockwork. In a moment the beach is empty. Then a wave crashes, depositing the squirming fish on the wet sand to lay and fertilize countless eggs before retreating back to sea.

A line of people along the beach raise flashlights to spot fish.

Beachgoers use flashlights to illuminate Grunion spawning at night on Cabrillo Beach in San Pedro.

(Luis Sinco / Los Angeles Times)

Basically, females dig nests with their tails and lay eggs in the sand. Up to eight males attempt to mate with each female by curling their bodies around them. Milt flows through the female’s body to fertilize the eggs. Throughout the night more Grunion slide up the beach and merge over the surf line.

How the Grunion know when to run remains a mystery. It could be the pull of the tides or the position of the moon. The eggs develop over 10 days and hatch on the next high tide. Most juveniles are consumed by other fish and shorebirds higher up the food chain.

The fish are unique to southern California and northern Baja. They are essentially scented. Most nights the law only allows you to watch the fish. Open nights are held during the season and those with a valid fishing license can hand-catch an individual limit of 30 fish. Beach erosion and coastal development are threatening the fish’s spawning habitat, although experts say the species currently appears viable.

The next Grunion run is expected to take place on June 16th in San Pedro.

A bunch of squirming grunion

Thousands of Grunion meander around Cabrillo Beach during their nightly spawning ritual.

(Luis Sinco / Los Angeles Times)

A man photographs a mass of grunion

Flashlights illuminate thousands of Grunions spawning on Cabrillo Beach. Each female can lay thousands of eggs, which usually take around 10 days to hatch.

(Luis Sinco / Los Angeles Times)

A mass of grunion washed ashore

Thousands of Grunion meander around Cabrillo Beach. The females use their tails to dig a nest in the wet sand and lay thousands of eggs.

(Luis Sinco / Los Angeles Times)

People shine grunion with flashlights.

People watch the Grunion run at Cabrillo Beach, one of the best places in Southern California to watch a run. Guided programs are offered by the Cabrillo Beach Aquarium.

(Luis Sinco / Los Angeles Times)

Beachgoers kneel to watch a Grunion run in San Pedro.

Beachgoers watch the Grunion wash ashore. While the females dig nests, the males try to mate by wrapping their bodies around them.

(Luis Sinco / Los Angeles Times)

People shine flashlights on crowds of grunion on the beach.

Beachgoers watch the Grunion wash ashore. The small, silvery fish are unique to southern California and northern Baja.

(Luis Sinco / Los Angeles Times) Photos: Join us for a grunion run, a SoCal beach tradition

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