Grunion are known for their unusual mating ritual wherein at very high tides, the females come up on to sandy beaches where they dig their tails into the sand to lay their eggs. The male then wraps himself around the female to deposit his sperm, and for the next 10 days the grunion eggs remain hidden in the sand.

What is so unusual about grunion?

A unique feature of the grunion's breeding biology results in its spawning on particular nights during the warm months, just after the highest tide. ... The eggs are actually laid in the sand on the beach during a full or new moon when the tide cycle is at its peak (spring tide).

Why do Grunions spawn on the beach?

Grunion reproduce by coming completely out of the water to lay their eggs on sandy beaches. Shortly after high tide, af- ter the new or full moon, sections of these beaches may be covered with thousands of fish dancing about on the sand. Some of the largest, most consistent grunion runs occur in Orange County.