碩士 / 國立臺灣海洋大學 / 環境生物與漁業科學學系 / 104 / Abstract
Set-net fishery is one of the most important and representative fisheries in the coastal water off the Ilan county. In the present study, we have investigated the fluctuations of ecosystem for coastal fisheries in the water off the Ilan county using catch data from setnets respectively located in the coastal water off Shi-Chen, Dong-Ao, and Nan-Ao of the Ilan county during 2010-2015. Catch species of setnets were investigated by the analysis of species composition. Mean trophic level (MTL) and contribute of trophic level (CTL) of each catch species were further analyzed and estimated. Major results from this work were described as follow:
1.Catch species from 3 indivual sentnet comprised 47 families and 115 species, 70 families and 151 species, 70 families and 146 species, respectively. In total, catch species of all these 3 setnets comprised 86 families and 197 species. The diversities of catch species mainly resulted from the catch of coral reef fish species, comprising 35 families and 96 species.
2.Pelagic fish species accounted for >60 % of total weight of catch. Among these pelagic species, Katsuwonus pelamis (TL=4.4), Auxis thazard (TL=4.3), Sarda orientalis (TL=4.3) respectively ranked the first, second and third in terms of total weight of catch.
3.In spring, K. pelamis, S. orientalis, A. thazard, Decapterus maruadsi and Sphyraena barracuda accounted for the majority of catch. In autumn, Trichiurus lepturus, K. pelamis, S. orientalis, Scomberomorus niphonius and Tylosurus crocodilus accounted for the majority of catch. In winter, S. orientalis, T. lepturus, A. thazard, S. niphonius, Scomber australasicus and Masturus lanceolatus accounted for the majority of catch. Additionally, all these seasonal target species had relatively higher CTL.
4.Results from the fluctuation of annual catch and MTL for these three setnets during 2010-2015 indicated that a downtrend in annual catch and an uptrend in annual catch of fish species with relatively lower TL (< 4).
Taken together, MTL of all these 3 setnets have decreased since 2010 and catch of fish species with high TL continued to drop annually, indicate that those marine food chains required for fisheries resource have been weakened annually.
Key words：Set-net fishery, Species group, Mean trophic level(MTL), Yilan bay
| Identifer | oai:union.ndltd.org:TW/104NTOU5451015 |
| Date | January 2016 |
| Creators | Lin, Yi-Chieh, 林奕潔 |
| Contributors | Liao, Cheng-hsin, 廖正信 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 79 |
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