Tuna produce sexually and spawning occurs in two areas, the Mediterranean and Gulf of Mexico within the Pacific in the Atlantic oceans. Female and male spawn in the Gulf of Mexico during April to June. In the Mediterranean, on the other hand, spawning occurs from June to August. Tuna such as bluefin come to sexual maturity at 3 years. Other kinds of tuna reach maturity at 4 to 5 years. Females produce usually over 10 million eggs per year. The eggs have buoyancy and range a great distance on the surface. The larva hatches with a length of 3.0mm. Their heads and jaws are big. Larvae of tuna are very difficult to distinguish compared with others. The weight of young tuna is over 90 to 130 lbs. (40 to 80 kg).
Tuna swim just below the surface of the water, they sometimes appear near the coast. They migrate to the North during spring and summmer and go to the South during the fall.