Along San Diego shores, the grunion are spawning once again. These small silver fish swarm the beaches on the waves at night and bury their eggs in the sand. It is a phenomenon unique to southern California and the northern Baja coast, and if you’ve never tried to find them, you’re in for a treat.
Grunion expert Dr. Karen Martin, Biologist and Executive Director at Pepperdine University’s Grunion Greeters Project spoke with Patch about the “look but don’t touch” season.
“This is usually the best time to see the grunion run because the fish should not be disturbed,” Martin says. “Grunion are running all along the SoCal coast to Santa Barbara.”
If you want to try your luck, most flat, San Diego sandy beaches should see grunion action at night. Check ahead with your local lifeguards, as some beaches are closed after hours, she says.
The female grunions will be vertical, having dug themselves tail-first into the sand. The males will be swimming around them. Photo: Julianne Steers, courtesy Grunion.org
What happens at a grunion run?
The grunions beach themselves to lay eggs and stick around while the males fertilize them. Yes, they are making little grunions while you watch.
“The female digs in—tail first —to lay their eggs, around 3,000 at a time. The males will wrap around the females and fertilize their eggs,” Melissa Studer of the Grunion Greeters project said in an interview with BBC Earth Unplugged. Roughly 10 to 14 days later, the eggs will hatch, allowing the next generation to swim off with the tide. The grunion spawns at age 1 and have a life span that ranges from two to four years, according to the project.
Each female will spawn only once a season, while the males will return in the tides, multiple times a night, Studer says. Burying the eggs in the sand gives the species an added chance for survival.
The grunion spawn during the highest tide of the month from as early as March and as late as August, but April through June tends to be their most active period.
During the spring, grunion are protected, officials remind, and cannot be “fished or gathered.”
While many spectators come out to witness the egg-laying event, with scores of fish flopping on the shore, remember that in the spring you can look but can’t touch.
“April is observation-only,” according to the California Department of Fish and Wildlife. Starting April 12, the observation of the grunion will continue nightly through May 29.
The forecast, put together by the California Department of Fish and Wildlife, shows expected grunion runs for 2021— view the whole schedule here— begins between 10:30 and 11 p.m. and lasts until well after 1 a.m.
Though the department of fish and wildlife does not suggest the “best beach to view the grunion run,” they do suggest asking your local lifeguards during the season.
Where is best to see the grunion run in San Diego County?
There is no “best” spot, according to Martin.
“As we say, only the fish know where they’ll show up on any given predicted spawning night,” Martin says. “However, they do prefer flat, sandy beaches and areas without a lot of flashing light, noise and activity.”
The largest runs occur in southern CA, but smaller runs can occur farther north.
“Conditions at each beach are constantly changing, so we cannot recommend a specific beach in your area,” she says. “Beach curfews vary between municipalities, so we advise you to look into local regulations before heading out.”
If you choose a beach that meets the general criteria, Martin suggests staying away from crowds and noise.
“The grunion are less likely to run in an area with a lot of disturbance,” she says.
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