碩士 / 國立高雄海洋科技大學 / 漁業生產與管理研究所 / 97 / Abstract
This study, which takes Changchun Set-net Fishing Ground at the northeastern coast and Manfong Set-net Fishing Ground at the southwestern coast of Taiwan as its objects of study, aims to explore and analyze catch data in logbook of the two water areas where Set-nets are installed, and their operation year catches from 2001 to 2007; and to find out the differences and variations of Catch Per Unit Effort (CPUE), Catch Species Composition, Fishing Seasons, Fishing Conditions of the Set-net fishing grounds in the two fishing sites. The results are excerpted as follows:
1. The CPUE of Changchun Set-net Fishing Ground is always higher than that of Manfong’s . Whereas Changchun Set-net Fishing Ground has two peak catch seasons, which are November to December and March to June respectively; Manfong Set-net Fishing Ground has only one peak catch season, which is March to June.
2. The reason why both the diversity index and the homogeneity index of Manfong Set-net Fishing Ground are higher than those of Changchun’s lies in that it has more dominant species in its species composition; furthermore, the production differences among the dominant species in Changchun Set-net Fishing Ground are quite large.
3. The first dominant species which have the largest production in the previous years in Changchun Set-net Fishing Ground and Manfong Set-net Fishing Ground are Auxis rochei and Seriola quinqueradiata respectively. Furthermore, the second and third dominant species in Changchun Set-net Fishing Ground are Masturus lanceolatus and Mola mola, and Tylosurus acus melanotus and Megalaspis cordyla in Manfong Set-net Fishing Ground respectively. The cumulative productions of the top three dominant species in Changchun Set-net Fishing Ground and Manfong Set-net Fishing Ground account for 49.4% and 26.8% of the average yearly catch, and thus have a great impact on the bumpiness or scantiness of the yearly catch of the fishing grounds.
4. Changchun Set-net Fishing Ground has a higher catch because of the broad continental shelf in its vicinity, its inlet topography which makes the current mild and sufficient sunlight exposure which promotes the growth of food microorganisms. Furthermore, as the net gears are installed in the vicinity of places where the contour line changes abruptly (i.e. the so-called fish route or reefs), and outside leader net has been installed, large schools of pelagic migratory fishes can be effectively guided into the Set-net. Moreover, net gears are less subject to deformation because the water area where they are installed is smooth and the average current speed is lower than 0.4 knot 99 % of the time. It is judged that the good catch can be mainly contributed to the above-mentioned advantageous conditions.
5. The reasons why Manfong Set-net Fishing Ground has a relatively lower catch may lie in that the net gears are installed in places where the contour line changes smoothly, the net gears are installed relatively shallow, and no outside leader nets have been installed. Thus, large schools of pelagic migratory fishes can not be guided into the Set-net effectively. Moreover, the current in the water area where the nets are installed is relatively strong the average current speed is higher than 0.4 knot 14 % of the time and thus the net gears are subject to deformation.
| Identifer | oai:union.ndltd.org:TW/097NKIM8451008 |
| Date | January 2009 |
| Creators | Shih-Ming Chiang, 姜士明 |
| Contributors | Huoo-Yuan Jenq, 鄭火元 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 135 |
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