SoCal’s ‘sex-crazed fish party’ — the grunion run — may be facing difficulties

One of nature’s most unusual mating rituals takes place right here in Southern California — the grunion run. Masses of sardine-like fish ride the tides onshore to mate in one of the late spring and early summer’s most epic wildlife displays. But this may soon become a thing of the past. In recent years, grunions have seen a decline in their population.

I became curious about the runs after seeing a flyer advertising a  ‘sex-crazed fish party’ at night on Venice beach. Tim Rudnick, the flyer’s author, is a long-time Venice resident and has been organizing grunion-run parties for 22 years. He operates the Venice Oceanarium and throws these parties as a way to get people to care about the environment. 

 “The grunion just excite the hell out of you," Rudnick said. "You feel like you're in a wild, wild environment. You never see the city the same again after that.”

The party began at 10:30 p.m., as a few hundred people trickled in. The beach was completely dark, except for a few flashlights, white stars and the distant rainbow colors of the Santa Monica Ferris wheel. 

All these people came to witness one of SoCal’s most impressive natural events. If you’ve never seen a grunion run, here’s what happens: Female grunions ride the tide onto the shore and then use their tail as a shovel to dig themselves into the sand until they are sticking straight up, like an asparagus shoot.

Then the males — or "sex-crazed fish," as Rudnick describes them — come onshore. They wrap themselves around the females and release their milt or sperm to fertilize the eggs she’s just laid. Then they males and females all scurry back out to sea. What makes these runs so spectacular is they can happen in the thousands — covering entire beaches with these squiggly tide surfers.

Rudnick hoped this year’s run would be a big one, but as the hours passed by there were no signs of fish.

Karen Martin,  a professor at Pepperdine University and one of the world’s leading experts on grunion, said she has some ideas as to why a lot of fish are not showing up. Looking at long-term survey data for the California coast, she has seen a decline in grunions over the last three to four years. The culprit? In large part, it could be climate change.

“The grunion are not only going to be affected by changing ocean temperatures but they also can be affected by changing air temperatures, because they spawn on beaches,”Martin said.

Ocean temperatures were affected by warmer air in 2016 in 2015, which were two of the hottest years on record. Loss of habit caused by rising sea levels could also be affecting the grunion.  Another big way they’re losing the sandy beaches they need to spawn is due to people building sea walls to protect ocean property or damning rivers that bring natural sediment to beaches.  Grunion are an important food source for the halibut, sea bass, dolphins and sea lions.

People saw a few fishes here and there, but this year’s Venice grunion run party was a bit of a dud. Benjamin Kay, a marine biology professor at Santa Monica College and Santa Monica High School, brought a group of students out to see the run.

“Yeah, I’m a little bummed," Kay said. "I told all my students it would be a spectacle, and we saw like four fish. ... But that’s the way it is, you know, it’s a little bit like fishing.”

The lack of fish at this year’s Venice party could be due to climate change, but it can be hard to predict when and at which beach the fish will run on.  They also might have been scared away by all the people, lights and sounds. 

If you want to see a grunion run for yourself or learn more about the fish, check out the California Department of Wildlife's grunion page.