Blue tangs generally mate in large resident aggregations over sandy patches between reefs. These fish seem to prefer locations 6 to 10 m deep with reasonably strong currents to sweep the fertilized eggs to sea. Mating readiness is indicated by color changes in the adults, who change from a uniform deep blue to pale blue on the front half of the body and dark blue on the rear half of the body. Courting females and a small number of males break off from the aggregation and release gametes at the water's surface in a behavior called a "spawning rush." Often, spawning rushes are not successful and are broken off by the female. Pair spawning is limited to small populations.
Mating System: polygynandrous (promiscuous)
Prior to a spawning aggregation, small groups of fish travel from nearby reefs before forming schools of over one-hundred individuals. Although spawning aggregations typically occur every day at a given location, they are often restricted to less than 20 individuals. The largest spawning occurs in the late afternoon three to eight days following the full moon in the winter months. However, the exact variables contributing to spawning aggregations are still unknown. It is likely that offshore currents, moon phase, predator abundance, and light levels all play a role in predicting spawning aggregations. Generally, spawning aggregation sites are also used by Acanthurus bahianus and members of the genera Scarus and Sparisoma. Sexual maturity is reached after one year.
Breeding interval: Breeding occurs once or twice a year.
Breeding season: Breeding occurs year-round, but more often during winter.
Average time to hatching: 24 hours.
Average age at sexual or reproductive maturity (female): 1 years.
Average age at sexual or reproductive maturity (male): 1 years.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sequential hermaphrodite (Protandrous ); sexual ; fertilization (External ); oviparous
Parental care is absent in this species.
Parental Investment: no parental involvement; pre-fertilization (Provisioning, Protecting: Female)