To provide a yellowtail cultured fish that is hard to get thinner after the opportune time of a genital organ, and is superior in durability.SOLUTION: A breeding method of yellowtail cultured fishes comprises the steps of: obtaining larvae of the yellowtail fishes by artificially collecting eggs after breeding yellowtail fishes for at least 2-months, under an adjustment breeding environment where at least one of a day length condition and a water temperature condition is adjusted； starting the breeding from the obtained larvae of the yellowtail fishes, and making the yellowtail fishes grow up； obtaining a male individual having GSI of 0.5% or more and 10.0% or less or a female individual having the GSI of 0.5% or more and 4.5% or less in the genital organ opportune time, and obtaining the yellowtail cultured fishes having the obesity index of 18 or more and the weight of 3.5 kg or more in opportune time； and obtaining the yellowtail cultured fishes having the obesity index of 17 or more and the weight of 3.5 kg or more and having the GSI lower than a numerical value at the genital organ opportune time, after the genital organ opportune time from the obtained opportune time yellowtail cultured fishes. The yellowtail cultured fishes obtained by the breeding method are provided.SELECTED DRAWING: None【課題】生殖器官の成熟期後に痩せにくく、持続性に優れたブリ属養殖魚の提供。【解決手段】日長条件及び水温条件の少なくとも一方が調整された調整飼育環境下で、ブリ属魚類を少なくとも２ヶ月間飼育してから、人工的に採卵して、ブリ属魚類の仔魚を得ること、得られたブリ属魚類の仔魚から飼育を開始し、ブリ属魚類に成育させること、生殖器官成熟期に、ＧＳＩが０．５％以上１０．０％以下の雄個体又はＧＳＩが０．５％以上４．５％以下の雌個体であって、肥満度１８以上及び体重３．５ｋｇ以上の成熟期ブリ属養殖魚を得ること、得られた成熟期ブリ属養殖魚から、生殖器官成熟期後に、肥満度１７以上及び体重３．５ｋｇ以上であって、ＧＳＩが生殖器官成熟期での数値よりも低いブリ属養殖魚を得ることを含むブリ属養殖魚の飼育方法；当該飼育方法により得られたブリ属養殖魚。【選択図】なし
