About Gerres oyena (Forsskål, 1775)
Common silver-biddy, scientifically named Gerres oyena, has multiple other common names including blacktip silver biddy, Darnley Island silverbelly, longtail silverbiddy, oceanic silver biddy, shining silver-belly, and slender silver belly. It is a species of mojarra that is native to marine and brackish coastal waters of the Indian Ocean and western Pacific Ocean, where it lives in estuaries, coastal waters, and lagoons. This species grows to a maximum total length of 30 cm (12 inches), though most individual Gerres oyena do not exceed 20 cm (7.9 inches) in length. It is an important species for local commercial fisheries. For this species' seasonal reproductive cycle, female ovary development takes place from March to September, while male testes development occurs between March and August. The maximum level of gonad development for both sexes happens in April and May. Calculations using the gonadosomatic index show the minimum standard length (SL) at sexual maturity is 89.7 mm for females and 81.4 mm for males. The standard length at which 50% of individuals are sexually mature is 104 mm SL for females, and 92 mm SL for males.
