Some fish in particular Chondrichthyes, such as sharks, but also some Osteichthyes as the coelacanths have internal fertilization and are viviparous. A small minority of fish is ovoviviparous. The majority of fish species has separate sexes, therefore, there are males and females . Among the Teleostei, however, some species are hermaphroditic. Among the serranidae especially is present hermaphroditism synchronous, in which the gonads of male and female are developed simultaneously and in very rare cases it is possible to self-fertilization, while in other fish gonads develop in later times sequential hermaphroditism and is sex reversal.
If the fish is born male, and finally becomes female, you have the proterandry, if the opposite happens you have the proteroginia . The proterandry is present in about 8 families, including bream and pomacentridae, the proteroginia is much more widespread, being present in about 14 families, including wrasses and serranidae.