臺灣東部海域正鰹 (Katsuwonus pelamis) 之性比與性成熟研究

       正鰹 (Katsuwonus pelamis) 為熱帶性鮪類，也是臺灣東部海域重要經濟性漁獲之一。本研究主要目的在探討臺灣東部海域正鰹性比組成及性成熟體型，所得之研究成果將可提供該魚資源評估模式建議之基礎參數及擬定漁業管理策略之參考依據，達該魚種永續利用之目標。於2020年1月至2020年12月間，按月於臺東縣新港魚市場採集正鰹樣本。總計採得358尾正鰹生殖腺樣本 (雌魚183尾；雄魚175尾)，樣本體長 (尾叉長fork length, FL) 範圍介於31.0–74.5 cm；體重 (round weight, RW) 介於0.6–8.7 kg。雌雄總性比無顯著性的差異，雌魚樣本之生殖腺成熟指數 (GSI) 介於0.50–2.46，在4–6月有一個成熟高峰存在，雄魚GSI月別變化平均值範圍為 0.12–2.28，在5–7月有一個成熟高峰存在。經由組織學觀察所得卵巢生殖發育階段屬於產卵階段為3–8月，產卵比例最高的季節為4至7月，雌魚性成熟之最小體長為42.5 cm；雄魚為40.0 cm。雌魚達50%性成熟體長為51.5 cm；雄魚為53.4 cm。

       Skipjack tuna (Katsuwonus pelamis) is a tropical species that has been historically exploited off the coast of Taitung (eastern Taiwan). The objective of this study will be used as biological input parameters for stock assessment and management strategy evaluation, furthermore to sustainable resource utilization. Samples were collected monthly from the Shinkang fish market of Taitung from January to December 2020. A total of 358 individual samples were collected (fork length ranged between 31.0 and 74.5 cm, and round weights ranged from 0.5 to 8.7 kg). The sex ratio for monthly and total samples was generally 1:1. The monthly female gonadosomatic index ranged from 0.50 to 2.46 and peaked from April to June, whereas the monthly male GSI ranged from 0.12 to 2.28 and peaked from May to July. According to histological observations of gonad variations, the greatest proportion of mature females was collected from March to August and peaked from April to July. The estimated 50% length-at-maturity (Lm50) was 51.5 cm for females and 53.4 cm for males.