Age and growth of shortfin mako (Isurus oxyrinchus) in the south Atlantic Ocean

• Main Authors: Wu, Pei-Wei, 吳培瑋
• Other Authors: Joung, Shoou-Jeng
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/fnh58f

碩士 === 國立臺灣海洋大學 === 環境生物與漁業科學學系 === 104 === The shortfin mako（Isurus oxyrinchus）is an epipelagic species distributed in temperate and tropical seas. Growth band pairs were counted on sagittal slice vertebral centra by using a X-ray method.The specimen collected by observers in Taiwanese longline fisheries is used for age and growth analysis. Between May 2011 to Aug. 2014, 140 female and128 male were captured in south Atlantic（0°22´ N - 38°53´ S, 49°06´ W - 12°47´ E）. Marginal increment analysis indicated that annual opaque band formed during October. Applied the Likelihood ratio test, the von Bertalanffy growth function between female and male revealed which in south Atlantic was significant different（P<0.05）. von Bertalanffy with size at birth parameters estimated as following estimates: L∞ = 392.7 cm FL、k = 0.0367/yr for female; L∞ = 327.9 cm FL、k = 0.0484 /yr for male. From age 1 to 4, the growth rate of males is larger than that of females, thereafter, females showed a significantly larqer growth rate compared to females. Maximum length observed was reached at age 35 and 313 cm FL for female, and age 21 and 250 cm FL for male.