OpisthonemaOpisthonema is a genus of herrings, the thread herrings, found in tropical waters of the Western Hemisphere. They get their name from a filamentous nature of the last ray of the dorsal fin. Currently, five species are in this genus.SpeciesOpisthonema berlangai Berry & Barrett, 1963 Opisthonema bulleri Opisthonema libertate Opisthonema medirastre Berry & Barrett, 1963 ''Opisthonema oglinum''