The common silver-biddy (Gerres oyena), also known as the blacktip silver biddy, Darnley Island silverbelly, longtail silverbiddy, oceanic silver biddy, shining silver-belly or slender silver belly,[3] is a species of mojarra native to marine and brackish waters of coastal waters of the Indian Ocean and the western Pacific Ocean.

It inhabits estuaries, coastal waters and lagoons.

This species is important to local commercial fisheries.

[2] Based on the seasonal reproductive cycle of the species, ovary development of the females occurs from March to September, while the testes development of the males occurs between March and August.

For both sexes, the maximal development occurs during April and May.