SPAWNING GRUNION

      From March to August, with a peak in April to June, hundreds of thousands of seven-inch, silvery fish called grunion wash out of wavelets along sandy beaches in southern California to Baja California in Mexico to spawn.  These slender, streamlined fish spawn at night in wet sand at high tide levels, for a few nights in a row, every two weeks, under a full or new moon.  Whole beaches at the high water line shimmy and wiggle with the many thousands of grunion piled on each other and ready to spawn. 

     Each little fish flops around on the wet sand just up from the foamy surf.  Each female looks for a place to dig into the sand with her tail, and, eventually, does, straight down about five inches, until only her gills and head is above the sand.  Then she releases her many tiny eggs into that hole she dug, while one or more males wrap themselves around her and eject sperm into the hole, which seeps down and fertilizes the eggs.  

     As each grunion finishes its reproductive duty, it flops back into the wavelets with a wiggle and flip of its tail and is gone into the ocean again.  And as it does, the exiting fish meets grunion riding incoming wavelets and flopping onto the beach ready to spawn.

     Grunions' unique way of spawning reminds me of how horseshoe crabs spawn.  The crabs, which are not crustaceans, but related to scorpions and spiders, crawl up on wet sand at the high tide mark to spawn during a full or new moon.  Eggs of both these species are buried in the sand at the high tide line, making it a bit difficult for birds and other creatures to find and ingest them, although some eggs of each kind are consumed while being deposited in the sand.  The eggs of both species are warmed by sunlight shining on the sand and will hatch in two weeks during the next high tide that washes the young into oceans or estuaries. 

     Adult grunion eat zooplankton and other small critters in the Pacific Ocean.  And, in turn, many grunion are ingested by gulls, herons, brown pelicans, crabs, larger fish and other creatures associated with beaches and oceans.  

     Though small, grunion are big in spawning drama, and as a keystone species with many creatures that eat them.  Their reproductive ways are interesting to watch on beaches during spring and summer. 

       

           

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