Blacksaddle Toby

Canthigaster valentini organize themselves into harems dominated by one mature territorial male and containing one or more territorial females. There may also be some immature individuals of either sex present in the dominant male's territory. Each female has her own respective domain within the territorial male's. Bachelor males, males who are sexually mature but do not inhabit a territory of their own with females, are either wanderers or live near another social group. These social groups, though male dominated, were found to be defined by the female fish living within the male's territory. Whenever a mature female dies or is in any way removed, the mature male's territory shrinks to include only the domains of the living females. When a male is removed, females remain territorial, though a bachelor male will most likely takeover any territory left undefended by a territorial male.

Canthigaster valentini are gonochoric, approximately half of the population being male and the other half being female, distinguishable by external characteristics. Dominant males breed exclusively with the females in their territory and maintain territorial boundaries. C. valentini's eggs are demersal, attached to algae on coral rubble. Females can lay anywhere between fifteen and over 800 eggs at a time every four to ten days depending on the season. Spawning generally occurs between 8:00AM and 3:30PM year-round. After eggs are laid, no parental care is required because eggs are unpalatable and, thus, reasonably safe from predation. It was found that predatory fish would rarely attempt to eat the eggs of C. valentini and when eggs were ingested they would be quickly egested.