San Diego, CA

See Thousands of ‘Walking' Fish Storm the Beach in the Dark

Allison Burney
HeatherChappy/Flickr/CC BY-NC-ND 2.0

America is full of surprising creatures that engage in totally unexpected behaviors.

One of those such creatures is the California grunion, a species of fish that lays its eggs on land and “dances” across the beach at night during spawning season. It’s so weird, in fact, that some people still think this phenomenon is a myth!

The only way to find out for sure is to see it for yourself, of course. But that will require an adventurous spirit and a desire to stay up late and head to the beach with nothing but moonlight to guide your way.

To be invited out in the middle of the night to go and watch fish does sound a little ridiculous, but in reality this is the only way to observe this natural phenomenon. — California Department of Fish and Wildlife

While this might sound like a bizarre nightmare to some people, the CDFW says grunion watching has actually become a popular sport in Southern California, with thousands of people lining the beaches, waiting for the action to begin.

If you’re wondering how exciting watching a bunch of fish can really be, apparently, the answer is very—and it’s something unique to California that can only be experienced here!

For starters, grunion are unlike most other fish. They’re one of only a few species in the world that lays their eggs on the beach, and the only fish in California that exhibits this behavior. They’re relatively tiny (only 5-6 inches in length), and have a special relationship with the cycles of the moon, relying on the tides to perfectly time their breeding. They only spawn during a full or new moon, when the tides are at their highest.

In an episode of United States of Animals, National Geographic explains how they accomplish this feat:

When high tide strikes, females ride the tide to the beach and use their tail as a drill to dig themselves into the sand. The males follow, fertilize the eggs, and then flip-flop back to the ocean.

To an observer, it almost looks like the fish are dancing or 'walking' up the beach! A strange sight for sure, but even more interesting is how they can survive out of the water.

Of course, there is an explanation for that, too: they have an unusual ability to “hold their breath.” Grunion can actually close their gills before leaving the water, which keeps oxygenated water in their bodies for short periods of time, enabling them to briefly storm the beach.

But it’s not just the adults that have special gifts. Even the young are equipped with superpowers: they “know” when to hatch! The female buries her eggs just an inch or two below the sand, and the young will fully develop inside the egg before the next high tide arrives (usually around 10 days later). The young will then wait for the tidal conditions to be just right before bursting out of their protective shells and catching a wave out to the ocean to begin their life at sea.

I’m starting to see the fascination with these strange beach-going fish!

If your interest is also piqued, the beaches around La Jolla, California are a great starting place, but there is no “best” spot to see them. Runs occur all over Southern California, but says they prefer “flat, sandy beaches and areas without a lot of flashing light, noise and activity.” This often means the areas near the end of a beach, where there’s less disturbance.

The grunions’ spawning sessions usually only last a couple of hours, so if you don’t want to miss them, your timing is important! The California Department of Fish and Wildlife has a predicted spawning run schedule on their website that lists upcoming viewing opportunities in August.

However, peak spawning season is from late March to early June, so if you don’t catch a glimpse this summer, there will be plenty of other opportunities next spring!

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Freelance writer & proofreader. I love travel, reading, coffee, and exploring nature. On a mission to keep learning, growing, and enjoying this adventure we call life.


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