A Night with the  Moonlight Dancers

Grunion, a small fish that lives off the coast of California and does something almost no other fish does: it comes out of the ocean at night to lay eggs on land. More info

Instead of staying in the water, grunion come out of the ocean at night to lay their eggs on sandy beaches. This amazing event is called a grunion run. During a grunion run, hundreds or even thousands of fish ride the waves onto shore, wriggle into the wet sand, and quickly bury their eggs before slipping back into the sea. These runs happen on warm spring and summer nights, usually during high tide and under the glow of the moon. Because the timing has to be just right (tides, temperature, and moonlight all working together), grunion runs are rare and exciting to witness, especially in places like Alameda where you might catch a glimpse of this magical nighttime event right in your own backyard.

How Humans Can Help

Now connect it to conservation actions. What can kids and families do to protect grunion and other shoreline creatures?

Grunion runs are a special event we can enjoy, but they only continue if we help protect them. 

When observing a run, families should stay quiet and avoid using bright lights. If you need light, use a red-light flashlight or headlamp (you can even cover a flashlight with red cellophane), since its longer wavelengths are less noticeable to the fish and won’t disturb their spawning. It’s also important not to walk or dig in the sand during grunion season, because eggs are hidden just beneath the surface. 

Leaving natural items like seaweed and driftwood in place helps protect those eggs from drying out or being washed away. Keeping our coastal waters clean and free of pollution also supports healthy habitats for grunion and other marine life. You can even help by spreading the word, teaching friends and family about grunion so more people understand how to be respectful beach visitors. 

In Alameda, the East Bay Regional Park District’s Crab Cove hosts grunion search events from April through September, offering a great chance to learn and observe responsibly. Grunion are also protected under California law, which means they can’t be collected without a fishing license, another way to ensure their populations stay healthy.

What Grunion Teach Us

Even though they are small, grunion have a big story to tell. Their life cycle is closely tied to the rhythms of the tides and the phases of the moon, showing us how animals use natural timing to survive. By coming onto land to lay eggs, they create a rare connection between ocean and shore, supporting a wider ecosystem. Scientists study grunion to better understand ocean health, since changes in their behavior or population can signal shifts in coastal environments. Their eggs and hatchlings also provide food for birds, fish, and other shoreline animals, meaning many species depend on the same beaches. In this way, grunion remind us that even the smallest creatures play an important role in the web of life.

The Grunion’s Message

Grunion may be tiny, but their message is powerful: healthy beaches matter. By protecting shorelines, keeping them clean, quiet, and natural, we’re not just helping one fish, but an entire community of marine and coastal life. When we care for these spaces, we make sure future generations of animals and kids can continue to experience the wonder of a grunion run under the moonlight.

The grunion may be small, but their story makes a big splash.