It may take ten years or more for some bony fishes to become sexually mature. In general, species of a small maximum size begin reproducing at an earlier age than those with a large maximum size. Age and associated size are major factors in determination of adulthood. B. Reproductive modes. In most species of bony fishes, sperm and eggs develop in separate male and female individuals.
Fertilization can be either internal or external.
Males and females may look similar, or they may look very different. A fish may be a sequential hermaphrodite or a synchronous hermaphrodite. Sequential hermaphrodites are born one sex and change sex sometime during the course of life. They are born female, grow into sexually mature females, and have the potential to transform into functional males later in life. In many of the wrasses, sex change correlates with social hierarchy and social behavior.