Many, if not all, commercially important species display significant differences in size between the sexes. In some species, one sex enters maturity earlier than the other (e.g. salmonids), in some cases reproduction may start very early in life and occur all year round in captivity (e.g. tilapia). Reproductive status greatly affects individual growth rates as less energy is committed to somatic growth. The ability of a fish farmer to control the ratio of male to female fish, or to produce single-sex stocks has significant economic implications and many positive benefits for the environment. By controlling the number of males to females, the fish farmer can reduce the number of broodstock necessary to obtain a given egg take or increase egg take by rearing mainly females. The sex showing the greatest growth potential can also be selected for; for example, the female turbot can grow to a much larger size than the male. The target may also be to produce a product of great commercial value that only one of the sexes can produce; as with caviar production in the female sturgeon. The selection for sex can also help where there are problems associated with precocious puberty in males, as is the case with salmonid fish such as trout and salmon, and also the sea bass.