碩士 / 國立臺灣海洋大學 / 環境生物與漁業科學學系 / 96 / Abstract
Shuangxi River is an important river in the northeastern Taiwan. During 2004-2008, Taipei County adopted two step fishing prohibition measures to protect the environment and creatures in the river. In order to know the change of the creature between prohibited and non-prohibited river sections (Shuangxi and Gongliao), we selected Eriocheir japonica as the target species by which the efficiency of the prohibition measure were examed. Meanwhile, the differences of four indicators in the two river sections, including abundance, sex-ratio, ages composition and body length, were also compared.
According to the data collected through trap sampling, we found that the female compositions of Eriocheir japonica on three age stages (1~2yrs；2~3yrs；3+yrs) were different, especially on the stage of 2~3yrs. The monthly changes of female numbers on 2~3yrs in the Shuangxi section were higher than that of the Gongliao section. Besides, the test of independent on each age stage indicated that the 2-3yrs female crabs were significant (P＜0.05), which imply that the two step fishing prohibition has resulted in different abundance of certain cohort. However, the difference in abundance, sex-ratio and body length were not statistically significant. Such phenomenon may be due to its catadromous characteristics that can cause inter-annual variability of abundance. The 2~3 year-old crab group was considered as the residential stock (prior to catadromous migration stage), so we can easily found the difference between Shuangxi and Gongliao. The other overall indicators (abundance, sex-ratio and body length) were blurred by the frequent migration and no significant differences were found between the two river sections.
The present fishing prohibition policy in Shuangxi River did not singnificantly increase abundance of Eriocheir japonica, which may be not crucial to its conservation. Therefore, in addition to the fishing prohibition measures, there should be more approaches if we want to conserve it more efficiently. In this thesis we also proposed a few supplementary measures for a better conservative effectiveness.
| Identifer | oai:union.ndltd.org:TW/096NTOU5451039 |
| Date | January 2008 |
| Creators | Tzai-Shun Hsieh, 謝再順 |
| Contributors | Hsueh-Jung Lu, 呂學榮 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 92 |
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