Rainbow trout
Global production of rainbow trout, "Oncorhynchus mykiss", requires over 3 billion eggs per year. This number is met because of broodstocks which undergo selection and conditioning in hatcheries. Trout have been reared artificially for over 80 years. Rainbow trout broodstocks are commonly manipulated to delay maturation and spawning time in order to provide eggs regularly and optimise supply. Artificial selection has favoured larger fish due to evidence of correlations between fish size and fecundity.