Fish display an astonishing variety of reproductive modes, ranging from parthenogenesis in the molly Poecilia formosa to permanently attached parasitic males in the deep-sea fish Haplophryne mollis. Similarly, fecundity ranges from 300 million eggs per year in Mola mola to a few live born offspring, e.g., in many sharks (Lagler et al. 1977). Parental care may be absent, as in many pelagic fishes, or involve various kinds of nest guarding or mouthbrooding. This variety implies that constraints to the ability of fish populations to reproduce themselves will also take different forms. Knowledge of reproduction is therefore important for proper management and conservation of fish species.

Information on reproduction in FishBase is assembled in three tables: REPRODUCTION, MATURITY and SPAWNING. The REPRODUCTION table documents the general mode and the type of reproduction that apply to the species throughout its range. The MATURITY and SPAWNING tables, on the other hand, present information on the size and age at first maturity and spawning of different populations of the same species, occurring at different localities. These tables are described below.