The name spotfin mojarra is descriptive of the black spot that appears on the anterior part of the dorsal fin.

When the mouth is closed, the lower jaw is concave, providing another distinctive feature.

The spotfin mojarra has a black spot on the anterior part of the dorsal fin.

[4] Mojarras are tropical species, but a small number of juvenile fish have been found in the Lower Hudson at Bowline Pond and Indian Point.

[4] Eucinostomus argenteus was first formally described in 1855 by Spencer Fullerton Baird and Charles Frédéric Girard with the type locality given as Beesley's Point, New Jersey.