碩士 / 國立高雄海洋科技大學 / 漁業生產與管理研究所 / 106 / The smooth hammerhead shark, Sphyrna zygaena, a top marine predator, is one of the most important species of the Taiwanese offshore commercial shark fisheries. However, very little is known about the stock status of the species. Currently, the per-recruit models have been applied to many elasmobranch populations which lack sufficient catch, effort, and abundance index data to conduct a full stock assessment. In these situations, such methods may provide the best available description of population status because they can be used to estimate biological reference points (BRPs) or indicators of population status. To understand its population dynamics, the present study applied the Per-recruit models to estimate BRPs, and evaluated the impact of uncertainties associated with natural mortality, by using a sensitivity analysis. The analysis of BRPs showed that the sex specific current fishing mortality (Fcur) was lower than the corresponding BRPs of F0.1 for males but higher than F0.1 for females. Furthermore, results of the spawning-per-recruit (SPR) analyses indicated that the current SPR (SPR12%) was substantially lower than target (SPR35%) and threshold (SPR30%) levels. This finding implies that the female smooth hammerheads stock in the Northwest Pacific Ocean is over-exploited under current fishing conditions. Any possible increases in fishing mortality should, therefore, be closely monitored to ensure sustainable utilization of the stock.
| Identifer | oai:union.ndltd.org:TW/106NKIM0451011 |
| Date | January 2018 |
| Creators | YEN, MING-CHIH, 顏銘志 |
| Contributors | TSAI, WEN-PEI, 蔡文沛 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 46 |
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