End of grunion season is near, so hurry if you want to see them

Were nearing the end of the time of year when Ventura County residents can witness something only seen on the California coast: grunion runs, when thousands of shimmering, silvery fish flop onto beaches in a nocturnal mating dance.

Even if you don’t plan to harvest any, it’s a spectacle worth seeing.

The small fish make their late-night trek out of the water, riding waves high onto sandy beaches each spring and summer. They’re typically seen on Ventura County beaches starting in late April.

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For four days after a high tide, grunion surf to shore on breaking waves. Females wriggle into the sand tail-first and bury their eggs; then males curve around them to fertilize the eggs. As the next waves wash in, the fish float back to sea.

During the next high tide, about 10 days later, the ocean washes the eggs back into the water, and the baby grunion hatch.

“I call them the original surfers,” said Karen Martin, a professor of biology at Pepperdine University who studies grunion. “They’re the first ones who learned how to ride in on waves.”

The eggs incubate in the sand, where warmer temperatures and higher oxygen levels hasten their development, Martin said. To keep hatchlings from being crushed in their sandy burrows, grunion have evolved an environmentally cued hatching system that’s triggered only when the eggs wash out to sea.

Anywhere from dozens to thousands of fish may show up during spawning season, and lucky late-night beachgoers can view the ritual.

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“It’s a natural phenomenon that doesn’t occur anywhere else in the world,” Martin said.

The grunion runs can be predicted since the tide and moon phases are predictable. According to the California Department of Fish and Wildlife, here’s when you might be able to see some grunion on Ventura County beaches for the rest of this month (the times are very approximate):

• Saturday, Aug. 17, 11:15 p.m. to 1:10 a.m.
• Friday, Aug. 30, 10:15 p.m. to 12:10 a.m.
• Saturday, Aug. 31, 11:15 p.m. to 1:05 a.m.
• Sunday, Sept. 1, 11:50 p.m. to 1:50 a.m.

After that, the grunion aren’t expected to reappear until March or April.

The agency says the times reflect a probable two-hour interval when a spawning run may occur, but that the second hour is usually better. The agency says the best runs are usually on the second and third nights of a four-night period.

Generally, a beach that’s good for surfing also is good for grunion, Martin said.

But the best place is where there isn’t a noisy crowd or a lot of light, she said. For the best experience, hang back and watch quietly.

Grunion fishing is allowed except in April and May. That means that this month, you can harvest them.

But if you do harvest them, here are the rules from the California Department of Fish and Wildlife:

• A California fishing license is required for people age 16 and older.
• Grunion may be taken by hand only; no holes may be dug to trap them.
• There is no bag limit, but take only the fish you can use; it is unlawful and unethical to waste fish.

Still, the grunion runs attract many people who look but don’t touch.

Volunteers with Grunion Greeters patrol Southern California beaches for grunion runs and report their observations on the website grunion.org. The fish hold a special allure, she said.

“They’re somewhat mysterious,” Studer said. “It’s wildlife, so it’s fairly unpredictable. It’s a fish out of water, so right there that’s intriguing. ... To be able to see the life cycle, see the spawning, the fish coming out of the water, the males curling around them, I think, it’s rewarding for people to see that. And a lot of volunteers are motivated by participating in real science and their protection.”

The fish can be found as far south as Baja, and recent warmer waters have allowed the fish to colonize areas up to San Francisco and Tomales Bay, Martin said.

Southern California, however, is ground zero for grunion runs. 

If you go on your own, tread carefully, as sound and vibrations can deter grunion from spawning. Dim your flashlights, or use red lenses to keep the lighting low. Ultimately, grunion sightings depend on being in the right place at the right time, experts said.

“You have to be persistent and lucky,” Martin said. “That’s the best solution.”

From reports by The Star’s Cheri Carlson and Tribune Content Agency