碩士 / 國立臺灣海洋大學 / 環境生物與漁業科學學系 / 97 / Abstract
In this study, we utilized catch and effort of five major fisheries in Gong-Liao waters during 1995~2007 to observe its long term variation of fishery resource in Northeatern Tawian through three fishery approached ecosystem factors, i.e. Mean Trophic Level (MTL), Contribute Trophic Level (CTL) and Fishing-in-Balance (FiB). Meanwhile, to understand the long-term shift of seasonality of migratory species, we used ratio-to-moving-average method to calculate Season Index (SI), and examine seasonality of each species by ANOVA, with which the long term changes of catch, Catch Per Unit Effort (CPUE) and relationship with sea surface temperature for seasonal key species were examed. The results are as following:
1) Except for 2001, the MTL in Kong-Liao capture fisheries during 1995~2007 increased steadily with 0.25 Trophic Level (TL) per decade.
2) The catches and CTL in Kong-Liao capture fisheries during 1995~2007 indicate that Auxis rochei roche (TL=4.1) is the highest contributor to MTL followed by Sarda orientalis (TL=4.2), Loligo edulis (TL=3.5), and Aluterus monoceros (TL=3.5)
3) The FiB index increased year after year since 1995 and peaked in 2006 (=1.16), which suggested that species at high trophic level dominate the catch and may result in unbalanced untilization status.
4) According to the determined seasonality of fish, summer migratory species comprised about 49% of annual catch with the highest value of 88% in 2006. The gradual increase trend of summer/autumn to winter/spring catch ratios may imply a weakened strength of winter migratory species.
5) The CPUE for three key seasonal species were significantly correlated with sea surface temperature except for Aluterus monoceros. The correlations were positive for Sarda orientalis and negative for Auxis rochei rochei and Loligo edulis. Therefore, the monthly fluctuation of temperature during 1995~2007 is one of the most important factors cause alteration of MTL and FiB.
According to the time serials of MTL and FiB indices, the fisheries in Kong-Liao targeting at migratory species showed higher inter-annual variation but without decreasing trend. Such situation suggested that accumulative fishing impact and the sign of “fishing down marine food web” phenomena were not significant. The changes of environment factors from the outer environment were more crucial than fishing itself to the species shift in Kongliao’s fisheries.
Key word: Mean trophic level, Fishing-in-Balance, Seasonal Index, Kong-Liao district
| Identifer | oai:union.ndltd.org:TW/097NTOU5451035 |
| Date | January 2009 |
| Creators | Chu-Yueh Liu, 劉著月 |
| 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 | 101 |
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