North Pacific albacore mature at roughly 5-6 years of age (approximately 85 cm in length). Peak spawning of albacore in the Pacific Ocean is generally believed to occur in subtropical waters centered around 20o N and 20o S latitude. It is assumed that the North Pacific albacore stock spawns from March through July on grounds located in the western and central Pacific Ocean. There is some information, albeit limited, that albacore may spawn multiple times in a year. Albacore are believed to be pelagic spawners that broadcast their gametes in open water, often near the surface, with fertilization being external. Estimates of female fecundity (number of eggs) range from 0.8 to 2.6 million eggs per spawning (roughly 100,000 eggs per kg of body weight). Eggs are approximately 1 mm in diameter and remain buoyant by an enclosed oil droplet. Eggs develop rapidly, with hatching occurring in 24 to 48 hours. The early life history of albacore is not clearly understood at this time, but very young albacore (larvae and juveniles in their first year of life) are believed to remain relatively close to the spawning grounds and eventually, congregate in waters south and east of Japan prior to beginning their first migration.