| Summary: | 碩士 === 國立臺灣海洋大學 === 環境生物與漁業科學學系 === 98 === The Japanese spurdog, Squalus japonicus, a bottom-dwelling shark, is one of the by-catch species from bottom trawl fishery in the northeastern Taiwan waters. A total of 770 specimens were collected monthly from Oct. 2008 to Oct. 2009 at Nan Ning fish market, Suao, Yilan County, sample size for males and females were 436 and 334, respectively. All specimens were caught by commercial bottom trawls under the depth >150 m in the waters off Suao (24°34´~24°36´N、121°57´~121°58´E). The range of total length (TL) of males and females were 20.6~59.8 cm and 20.8~69.3 cm, respectively. The maximum likelihood ratio test indicated that there is a significant difference between sexes on weight (TW) –length (TL) relationship and can be expressed as following, TW=0.00230 TL3.18378 (n=436) for males and TW=0.00445 TL3.00312 (n=334) for females. This study used spines to estimate the age and growth parameters. Edge analysis result annual growth rings formation, and opaque band was formed in October. The oldest age of females and males was 22 yrs and 16 yrs, respectively. The age at 50% maturity for female and male was 19.3 yrs and 9.4 yrs, respectively. The best fitted growth equation for S. japonicus is von Bertalanffy growth equation (VBGE). The growth parameters were L∞=80.45 cm, k=0.061 yr-1, t0=-6.64 yrs for females, and L∞=63.66 cm, k=0.111 yr-1, t0=-4.80 yrs for males.
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