碩士 / 國立海洋大學 / 漁業科學學系 / 89 / A total of 34,366 specimens of the bigeye thresher shark, Alopias superciliosus, collected at Nanfanao fish market from 1989 to 1999 were analyzed by using MULTIFAN to estimate the parameters of von Bertalanffy growth function (VBGF) and age composition. The parameters of VBGF for this species were estimated as follows: growth coefficient (K) ranged from 0.080 yr-1 to 0.098 yr-1, asymptotic precaudal length (L∞) ranged from 233cm to 248cm and age at zero length (t0) ranged from -4.3 yr to -3.4 yr. Mean age at capture seemed decrease in recent year. Instantaneous total mortality rate (Z) ranged from 0.26 yr-1 to 0.48yr-1, natural mortality rate (M) being 0.154yr-1, and exploitation rate (E) ranged from 41% to 68% for 1989-1999. Yield-per-recruit was estimated to be 18.9kg and the maximum potential yield-per-recruit was 20.9kg for 1999, exploitation rate, therefore, is only 10.6% left to develop. Spawning per recruit ranged from 4% to 30% for 1989-1999. In order to achieve the standard of SPR% of 30%, the E values must be decreased to 38%. Further more catch-per-unit-effort (CPUE) from 1995 to 1999 is decreasing gradually. In this study, it is suggested that fishing mortality rate for the bigeye thresher shark in the northeastern waters off Taiwan should be properly decreased to 0.096yr-1.
Keywords: Alopias superciliosus, Stock assessment, MULTIFAN,
Yield-per-recruit, Spawning stock biomass per
recruit
| Identifer | oai:union.ndltd.org:TW/089NTOU0451012 |
| Date | January 2001 |
| Creators | Wen-Lung Juang, 莊文龍 |
| Contributors | Kang-Ming Liu, 劉光明 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 70 |
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