The Venice Oceanarium: The Grunion Are Running

By Tim Rudnick

Last month, June 3, the Venice Oceanarium presented its 16th annual grunion party. Six to seven hundred hearty Venetians made their way to the beach at 10:30pm to watch these amazing fish come out of the waves to spawn. Young kids played in the surf and waited for the first of the grunion to appear. Older folks just watched. The night was moonless, but the darkness only increased the mystery of these fish.

No other fish in the world does what they do. Grunion hunting is a waiting game. At first only a few grunion appeared – two to four with each wave. The night was cool, so those not prepared for an ocean evening left early. Those who stayed began to see the numbers increase. Within an hour, 30 to 40 grunion started to “run” our shore. The excitement swelled as people began to observe the mating rituals. Many folks left at this point.

But the real reward came forty-five minutes later, just before midnight. At that time the shore became a virtual carpet of fish. Thousands and thousands of fish – everywhere glistening in the dark night. For those who waited, the night ended in a crescendo.

And how does the Venice Oceanarium know exactly when the grunion are going to run? How can they predict it six months ahead of time?

The grunion run four to six times a month from March to August. They run on the high tides of the month, usually after a full or new moon. Therefore, it is easy to predict with a simple tide calendar!

It is during these tides that the ocean climbs highest on the shore. This wet sand offers the perfect conditions for the female grunion to lay their eggs. The following tide, the next night, falls short of this wet sand where the eggs have been deposited. The fertilized eggs remain in their wet sandy womb for two weeks. When the water returns in the next high tide the eggs are ready to hatch and re-enter the ocean. Millions of young hatchlings fill the waters and stimulate the waiting schools of grunion to come onshore and continue the life cycle.

How do the first fish know just when to come ashore? Natural Selection! The fish that didn’t lay their eggs just at the high tides had their eggs washed away too early to be hatched and were eliminated from the gene pool.

The Oceanarium selects the dates for its parties very carefully. Usually the grunion are running at odd hours like 2:00 in the morning on a Tuesday or Thursday night. Obviously this is not a good time for a party. The Oceanarium has a party when the grunion run around 10:00-10:30 on a weekend. That usually happens only once or twice a year.

When the Oceanarium started having these grunion parties, hardly anyone knew the grunion ran in the middle of the city, at Venice Beach. Since then, the Oceanarium has put the Venice grunion on the map. This is important and was the main reason why the Oceanarium chose to do these parties. By identifying the presence of grunion in Venice, the Oceanarium emphasizes the importance of having a dark and quiet beach at night. And it makes the argument to keep the lights of the developing beach-front dim on the shore.

The next grunion runs will take place July 3 11pm-1am and July 4 12-2am. After that they will run again July 16 10:30pm-12:30am and July 17 11pm-1am, but these last two days are late in the season and the grunion turnout is expected to be low. For more information visit the Oceanarium’s website at

Categories: Science/Technology, The Beach

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