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Today, it’s just as exciting to watch these elusive fish emerge from the sea at midnight. With the light of the full moon dancing on the water, the silvery grunion surf the waves and sinuously skim up the beach. During a large run, thousands of grunion shimmer brilliantly in a silver lining along the surf. Coming ashore to spawn on a full or new moon, the grunion arrive after a high tide with such regularity that the time can be predicted a year in advance. Completing its life cycle out of water, the 5-6 inch female vertically drills herself into the sand and deposits her eggs. Males surround her and curl around her body to discharge their milt and fertilize her eggs. This process only takes about 30 seconds but the run usually lasts from 1 to 3 hours. As quickly as they arrive, the high tide recedes and the fish return to the sea. Thousands of fish disappear in an instant. The unique sight of this unparalleled reproductive event often leaves observers bewildered.
March 4th 9:50pm marks the official beginning of the grunion run season. Runs last from March to August with April and May being “closed season†months when no catching of grunion is permitted. During “open season†grunion may be caught only by hand and with a state fishing license. Grunion have been protected since 1927 by CA Department of Fish and Game. Endemic to southern California and northern Baja, California Grunion (Leuresthes tenuis) have a narrow distribution ranging from Point Conception in California to Punta Abreojos in Baja, Mexico. Making this the only place in the world you will see this exceptional fish. 90% of the population reside off the coasts of Los Angeles, Orange and San Diego, with some of the largest runs in Orange County.
After the female lays her eggs, she wriggles to free herself and pops out of the sand and returns to the ocean. Safe from the waves, the eggs incubate in the moist sand during the lower tide levels. In about 10 days, the eggs hatch during the next high tide series and are washed back into the sea. Grunion spawning is an amazingly precise feat in sync with tidal cycles. Along our coast we have two high tides, the higher of the two occurs at night. Grunion only spawn on these higher tides and only after the tide has receded. This allows the eggs to be safe from subsequent waves that would wash them away. There are only 3 to 4 nights following the highest tide that spawning conditions are right and it is these nights that grunion spawn.
I’ve been a “Grunion Greeter†volunteer since 2002 through Pepperdine University and Scripps. I have witnessed runs with thousands of fish piled inches high and have also seen the animals that appear for the feast. The elegant Yellow Crested Night Heron and the odd looking guitarfish are two. Anyone can become a Grunion Greeter after attending a workshop designed to teach data collection skills and introduce you to the grunion. The Greeters monitor local beaches and collect data for two hours and submit this information online at www.grunion.org
. The data are used for researchers conducting studies on these remarkable fish and to ensure protection of incubating eggs. The 2007 project will contribute to a 3 year study funded by NOAA, National Fish and Wildlife Association, and CA Sea Grant College to test whether grunion may be useful as environmental indicators. As a fun activity with friends and family or a scientific study to aid research and conservation, witnessing a grunion run is an intriguing encounter that only occurs here.
For more information on grunion:
http://arachnid.pepperdine.edu/grunion
/
2007 Grunion Greeter workshops in your area:
http://arachnid.pepperdine.edu/grunion/volunteer.htm
2007 expected Grunion Runs (open & closed seasons):
http://www.dfg.ca.gov/mrd/gruschd.html#runs
CA Dept. of Fish and Game grunion information:
http://www.dfg.ca.gov/mrd/grnindx3.html
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