Age and Growth of kwangtung skate, Dipturus kwangtungensis in the Northeastern Waters off Taiwan

• Main Author: 陳婧綺
• Other Authors: Shoou Jeng Joung
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/21995356118335908767

碩士 === 國立臺灣海洋大學 === 環境生物與漁業科學學系 === 97 === The kwangtung skate, Dipturus kwangtungensis, is the by-catch of trawl fishery in northeastern Taiwan waters and it is regarded as trash fish due to its low economic value. The specimens of kwangtung skate were collected from Dashi fish market of Yilan County. Determined from vertebral band count on 422 specimens (230 female and 193 male) and verified with length-frequency analysis of 1,438 specimens (761 female and 677 male) and all were collected from 30-200m depth by commercial trawlers. Translucent and opaque bands on vertebral centra were demonstrated to be formed once a year via centra edge analysis. The vertebral centra can be counted up to 13 for both sexes.The parameters of Gompertz growth equation estimated from vertebral band counting were are the followings: asymptotic total length (L∞)= 90.0 cm, growth coefficient (k)=0.12 yr-1, age at zero length (t0) =4.92 yr-1 for females; and L∞=75.4 cm, k=0.16 yr-1,t0=3.29 yr-1 for males. The ages at maturity were estimated to be 13 and 11 yr old for females and males, respectively. Length-frequency analysis supported our vertebral ageing estimates. The parameters of von Bertalanffy growth equation estimated from caudal thorn band counting with Ford-Walford plot were L∞=98.4 cm, k=0.13 yr-1 for female and L∞=92.6 cm, k=0.12 yr-1 for male. In conclusion, the Gompertz growth equation derived from vertebral band counting can best describe the growth up the kwangtung skate.