This is a specimen of Melanorhinus microps, however, iNaturalist does not yet have this species in its list of species. It was taken from the surf near Isabela, PR.
Several thousand in groups along the west and northwest shore of Eel Pond.
The Neotropical silversides are a family, Atherinopsidae, of fishes in the order Atheriniformes. About 104 species in 13 genera are distributed throughout the tropical and temperate waters of the New World, including both marine and freshwater habitats. The familiar grunions and Atlantic silverside belong to this family.