They can lay between 1000 and 4000 eggs about 3 to 4 inches beneath the sand, as the males fertilize the eggs. Nearly two weeks later when the spring tides return, the eggs hatch, completing a remarkable life cycle. Evidently, the young fish need the wave action to break loose from their shells.
Nobody knows how the grunion can so precisely time the tidal cycle. These fish seem to spend most of their life near the coast in about 15 to 60 feet of water and can live up to four years. John Steinbeck of Tenera Environmental told me that he has found grunion as far north as San Francisco, but they are most abundant from Morro Bay southward. It's interesting to note that grunion found in the Gulf of California spawn during daylight.
The grunion season is closed through May, but you can observe them. The next expected grunion run along the Central Coast starts on the night of May 6, right after high tide at 10:22 p.m. for about a two-hour period. The second hour is usually better.
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