Mojarra are members of the Gerridae family of tropical and subtropical saltwater fish. Roughly 40 species are in this family, some of which also occur in brackish water and a few rarely in freshwater. They are small and silvery and have protractile mouths. The upper jaw of the mojarra fits into a defined slot when the mouth is not extended, or “pursed.”

When feeding, the mouth is protruded and directed downward. The dorsal and the anal fins have a sheath of scales along the base, and the gill membranes are not united to the isthmus. The first, or spiny, dorsal fin is high in front, sloping into the second, or soft-rayed, dorsal. The tail is deeply forked.

Most mojarra are less than 10 inches long. They are important for predator species and are used as bait by some anglers. Some species are observed in schools on sandy, shallow flats.

The spotfin mojarra (Eucinostomus argenteus) is abundant in the western Atlantic off the coast from New Jersey to Brazil. It occurs in the eastern Pacific along the coast from Southern California to Peru. The yellowfin mojarra (Gerres cinereus) is common in Florida and the Caribbean.