The California grunion is a member of the Atherinidae family of fish known as silversides. It is an important forage species for predator fish; in season, large numbers of anglers gather on the beaches to ﬁll buckets with grunion that are undergoing a remarkable spawning ritual in the sand.
IdentificationThe California grunion has an elongate body and head that are more or less compressed. The mouth is small, and the scales are small, smooth, and firm. Its coloration is bluish-green above and silvery below; a bright silvery band tinged with blue and bordered above with violet extends the length of the body.
Size/AgeThe maximum known size of grunion is 7.5 inches. The life span is usually 3 years, with some individuals surviving 4 years.
Life history/BehaviorThe most rapid growth takes place during the ﬁrst year, at the end of which they are 5 inches long and capable of spawning. The spawning behavior of grunion is one of the more unusual among all marine ﬁsh. Females, accompanied by one to eight males, swim onto the beach with an incoming wave, dig themselves into the sand up to their pectoral ﬁns, and lay their eggs.
The males wrap themselves around the female and fertilize the eggs. With the next wave, the ﬁsh return to the sea. Thus, the spawning process is effected in the short period of time between waves. Most females spawn from four to eight times a year, and thousands of the ﬁsh may be along the beach at a time.
Spawning takes place from early March through September and then only for 3 or 4 nights following the full moon, during the 1 to 4 hours immediately after high tide.