Along the beaches of Southern California, on certain nights of the month in spring and summer, you can watch thousands of silvery fish throw themselves onto the beach to spawn.
What is a Grunion?
The fish known as California Grunion, scientific name Leuresthes tenuis, are members of the silverside family. They’re silvery in color, almost translucent, and shimmer with blue and green highlights in the light.
These fish are famous all throughout California for their nighttime, high-tide mating ritual. They swim up onto the beaches in astounding numbers, arriving as the incoming waves break on the shore, in order to lay and fertilize their eggs. Sometimes there are so many grunion spawning, the beach looks like a shimmering silver carpet.
Observing a grunion run is something of a rite of passage in Southern California. Standing on a beach in the dark, waiting for masses of wriggling silver fish to appear on the beach is an exercise in patience — and sometimes the fish don’t even show up at all.
But when they do show up, they hit like a lightning strike. One moment a wave breaks on the beach with nothing but water, sand, and seaweed. But then the next wave hits the beach and, as it recedes, the beach is filled with flopping and squirming silver fish.
The grunion season runs for about six months — from March through August — for about eight days each month (although the runs in August tend to be quite small to nonexistent). This ritual usually takes place a few days after a new moon (when it’s very dark) or a few days after a full moon (where there’s a fair amount of light.) As such, Grunion Runs are relatively easy to predict.
Grunion runs always happen at night. They can start as early as 9:00 PM or as late as Midnight or even 1:00 AM. The runs tend to happen over four days, with the second and third night usually being the most abundant.
The California Department of Fish and Wildlife maintains a schedule of anticipated times for grunion runs at the Grunion Page. The times given are for Cabrillo Beach and the Los Angeles Harbor. San Diego runs tend to be about five minutes earlier, and grunion runs around Santa Barbara are approximately 25 minutes after the posted times.
There are two seasons for grunions — open and closed. During the closed season (April, May, and June) you can only observe (and photograph) the fish. But during the open season (March, July, and August), anyone is free to catch up 30 grunions each night.
During the open season, attendance at the runs tend to be busier. Many people carry a large bucket or two to hold their catch. You’re supposed to catch them by hand, although some people use their buckets to scoop the fish up right out of the surf.
Keep in mind, if you want to catch some grunions yourself, anyone 16 years and older must have a California fishing license ($17.54 for a one-day license, $27 for two days, or $54 dollars for the season).
The open season can be intense. The grunion are light averse (they tend to swim on down the beach if they see flashlights on shore), so the people who have come to the beach to harvest grunion often get angry at those with flashlights who just want to see the fish. Many fishermen will use red-light headlamps to give them enough light to see the grunion without scaring the fish away.
Grunion Mating Dance
After swimming ashore, a female grunion will dig a hole in the sand with her tail and wriggle down inside, leaving just her head poking out of the sand. Once she’s in place, she starts laying eggs — as many as 3,600 at a time.
Once she starts laying, the male grunions flop over to her, curl around her, and release their milt (a fancy word for fish semen) against the female’s body so it can flow down into the hole to fertilizing the eggs. Competition for females can be fierce, with a dozen or more males wrapped around a single female. But sometimes the connection can be more intimate.
Once fertilized, the eggs develop in the sand over the next ten days and hatch during the next high tide cycle. It’s not easy for a infant grunion in the ocean — many are eaten by bigger fish or other oceanic predators. But grunion life is a numbers game, and enough survive to adulthood to continue the spawn cycle. It takes about a year for a grunion to reach maturity. They can live for up to five years, though this is rare. Most don’t make it past three years.
How to see a Grunion Run
There are many places along the coast of California to see a grunion run, but one of the most popular places is at Cabrillo Beach, adjacent to the Cabrillo Marine Aquarium.
The trick is the grunions run at night, and the parking lot for the beach closes at 10:30. We’ve been down there when people have gotten locked inside the gates. But parking in the area can be hard to come by, especially during the fishing season. If you arrive early enough, you can probably snap up a spot along Stephen M. White Drive (near the Stephen M. White Statue). Otherwise you can try your luck on Pacific Avenue, across the street from the Air Force Base.
But the grunions perform their mating dance on many of Southern California’s beaches.
- 3800 Stephen M White Dr, San Pedro
- GPS Coordinates: 33.709166, -118.282814 [ Google Maps ]
- what3words: ///unfunny.tasters.whoops
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