Bluefin tuna form spawning aggregations. Males and females synchronously produce eggs and sperm (milt), resulting in mating among many individuals at the same time. This is also called broadcast spawning.

Mating System: polygynandrous (promiscuous)

Bluefin tuna migrate to either the Gulf of Mexico or the Mediterranean and form spawning aggregations. Females lay up to 10 million eggs each spawning period. Males fertilize the eggs as they are produced by the females. Water temperatures during spawning are 24.8°C to 29.5°C in the Gulf of Mexico and 18.9°C to 21.1°C in the Mediterranean.

Bluefin tuna become sexually mature between the ages of 4 and 8 years.

Breeding interval: Bluefin tuna breed once yearly.

Breeding season: Breeding occurs from April to June in the Gulf of Mexico and June to August in the Mediterranean.

Range number of offspring: 10,000,000 (high) .

Range gestation period: 1.5 to 4 days.

Average gestation period: 3 days.

Range age at sexual or reproductive maturity (female): 4 to 8 years.

Average age at sexual or reproductive maturity (female): 5 years.

Range age at sexual or reproductive maturity (male): 4 to 8 years.

Average age at sexual or reproductive maturity (male): 5 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); broadcast (group) spawning; oviparous

No parental care is provided for the young.

Parental Investment: no parental involvement; pre-fertilization (Provisioning)