Fecundity (Fish)

Fecundity is the number of eggs a female fish produces in a single spawning event or breeding season, and it is one of the most commercially decisive traits in broodstock selection because it sets hatchery output per female. It is typically estimated gravimetrically by weighing the ovary, subsampling, and counting eggs in the subsample to extrapolate total fecundity, reported as absolute count, relative fecundity per gram of body weight, or per gram of ovary. Values span enormous ranges: a 3 kg Atlantic salmon may carry 7,000 to 12,000 eggs, a carp of similar size 300,000 to 700,000, and a large tilapia only a few hundred mouthfuls of fry. Fecundity scales with body size but also with age, condition, nutrition, and temperature history, so it responds strongly to broodstock management rather than being fixed. High fecundity, however, does not guarantee output: egg quality, fertilization rate, and hatching rate determine how many larvae actually enter rearing. For breeding programs, fecundity curves per female and per family guide selection, mating ratios, and tank planning, and they interact with gonadosomatic index monitoring, egg quality assessment, and induced ovulation schedules. Understanding species fecundity is also essential for modeling effective population size in family selection schemes.