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.
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.
https://www.latimes.com/california/story/2022-06-09/photos-never-been-to-a-grunion-run-come-along-with-us Photos: Join us for a grunion run, a SoCal beach tradition