Grunion are two fish species of the genus Leuresthes: the California grunion, L. tenuis, and the Gulf grunion, L. sardinas.

What does grunion in English mean?

grunion in American English

(ˈɡrʌnjən) noun. a small, silvery food fish, Leuresthes tenuis, of southern California, that spawns at high tide in wet sand.

Why is it called a grunion run?

Conveniently, the grunions' mating habits make them very easy to catch. That's why you'll find many organized events called “grunion runs”, in which all people 16 years and older, with a valid fishing license, are allowed to come to the beaches and grab as many grunion as they wish (if under 16 no license is required).