TONS OF FISH ON THE BEACH: A CALIFORNIA GRUNION RUN, Guest Post by Caroline Hatton

Grunion run on a Southern California beach

My friend and fellow children’s book author Caroline Hatton took all the photos in this post in April 2009 at Cabrillo Beach in San Pedro, California, when she enjoyed this free outdoor activity.

On special nights, along the Pacific coast from southern California to Baja California and from about March to August, multitudes of little fish come out of the water onto sandy beaches. This fish, the California Grunion (Leuresthes tenuis), is one of only a few in the world known to spawn on land.

Every fourteen nights or so, the full moon and new moon pull tides to their highest levels. During the following four nights, as the high-tide mark gradually moves back down the beach, lucky observers may witness the wonder of a grunion run. (Note: full moon, August 3, 2020; new moon, August 18, 2020.)

California Grunion (Leuresthes tenuis, up to 7 inches or 19 cm long)

Shortly after the tide has peaked in the middle of the night, lone male grunion surf onto the beach. If no one spooks them, and they make it back out to sea safely, more fish appear on the sand.

The trick is to stay away from the edge of the water until lots of fish arrive, or else any human presence, footstep vibrations, voices, or flashlights will likely scare the scout fish away. Even stray cats know to sit back and wait for dinner. Soon the number of fish on the beach reaches into the thousands, squirming, leaping.

Female California Grunion laying eggs before the next ocean wave brings males.

By now females swim and wriggle far up the sand. If males have followed a female, she digs into the soft slush with her tail.

Female California Grunion laying eggs a few inches deep and male contributing milt to fertilize them.

As she lays her eggs a few inches deep, males crowd around her and let their sperm or milt flow down along her body, fertilizing the eggs. Done mating in about thirty seconds, the males scurry back down to the water. She twists and jerks herself free and rides the next wave back to sea.

Eggs in a hole made by a female California Grunion.

Once the lovefest is in full swing, nothing can make it stop, so observers can finally approach. Even though the fish are acutely alive, there’s nothing fresh about their smell. The ocean water is packed so thick with fish, the inside of breaking waves glows like silver. “Fish soup” comes to mind.

Every few waves, one bigger one litters the sand with a mess of frenzied fish, and the next big wave rinses them all off the beach. In the few quiet seconds when no wave is crashing, the flip-flopping fish bodies can be heard slapping softly. Night herons glide over the edge of waves, land to grab fish, and take off with a beakful.

Grunion orgy

In April 2009, I walked among the fish—after overcoming mild repulsion for the unsettling, demonic throngs writhing and the nauseating smell. I took slow-motion steps with extreme care, sinking to my ankle bones in soft slush. Fish flopped on and off my naked toes, so light, so gentle, enchanting after all. But then I thought, Why is it slimy? Because of whatever coats fish that makes them slippery, plus what all the males are delivering—not an attractive foot bath.

I was glad my sense of taste was left out, even though California Grunion is edible. But frozen fish sticks are easier to catch, don’t require a fishing license, and are said to taste much better.

The falling tide deposits several inches of sand, which protect the eggs from the hot drying sun and hungry bird beaks. The eggs mature within ten days. Sea water reaches them for the first time during the next, highest night tides at their peak. The waves stir the eggs and make them hatch, then sweep the larvae out to the open ocean.

The timing of grunion runs is critical. Eggs laid as tides ebb remain undisturbed long enough to be ready to hatch. The wrong date or time and rising tides would likely wash the eggs away too soon.

As amazing as grunion is, it is not the only fish that crawls out of the water and doesn’t die: eels, mudskippers, and lungfish spend even more time on land. Grunion is not the only sea creature to spawn in rhythm with the phases of the moon: many algae, corals, and fishes do so too. And grunion is not the only fish to gather by the thousands to spawn: in special spots along the Atlantic or Pacific coast of North America, silversides and capelins pile up in shallow shore waters.

Humans, including Native Americans, have long caught and eaten grunion. To stop the grunion population from dwindling, in 1926 the California Department of Fish and Game began to close the fishing season from April through June. Grunion numbers went back up, so since 1948 the closed season has been shortened to April-May. Waiting on the beach, hoping to see grunion run is a spring tradition and a tourist attraction in Southern California. Friends of mine who have tried over a dozen times have yet to see it happen. I was lucky to watch grunion run twice, out of only a few tries over the years.

FOR MORE INFO

Online videos, more numerous than the fish on the beach, make it possible to watch a grunion run without getting wet and cold.