碩士 / 國立臺灣海洋大學 / 環境生物與漁業科學學系 / 99 / Gongliao, on the northeastern coast of Taiwan and with oceanic and ecological complexity, is one of the most important fishing villages of the New Taipei City. According to satellite data, the sea surface temperature (SST) of Gongliao area has increased 0.64℃since 1980. In addition to the influence of global warming, the intensity and location of upwelling and front zone have also fluctuated. Consequently, the catch species, fishing period, and environment of the habitat were varied. These changes have not been studied scientifically. The present study aims at investigating major fish species caught by the marine fisheries in the Gongliao area, including both migratory and benthic species. Based on Sea Surface Temperature Anomalies (SSTA) and fishery data during 1995-2010, this study used time series analysis and t-test to study the effects of climate change on fishery resources in Gongliao. The results were summarized as follows:
1. The time series of the total fish catch in Gongliao indicated that the average catch increased from 2,218 tons per year in 1995 to 2002 to 6,087 ton per year in 2003 to 2010. During the same periods, catch of Auxis rochei rochei in total fish catch was increased from 0.08% to 13% and in the meantime catch of Scorpaenodes littoralis in total fish catch was decreased from 12% to 3%, representing the two most significantly fluctuating species.
2. According to the catch composition of anchovies and the satellite SST of the Gongliao area, the influence of China Coastal Current has been diminished due to the global climate change and the recruit amount of Engraulis japonicus during spring fishing season decreased. The catch of E. japonicus in total fish catch was 91.5% during 1995 to 2000, but decreased to only 17.1% in 2001 to 2010. Contrarily, the catch composition of warm-water species, Encrasicholina spp., gradually dominated in the total fish catch as a consequence of the strengthening process of Kuroshio. In the fall fishing season, species of the genus Encrasicholina comprised of up to 94.5% of the total fish catch and gradually replaced Engraulis japonicas as the dominant species in the Gongliao fishery..
3. As indicated by the catch composition of the stick-held dip net fishery during 1995-2010, the dominance of Loligo edulis (decreased from 18.9% to 1.2%) in total catch was replaced by Auxis rochei rochei (increased from 28.8% to 82.4%). The Loligo edulis fishery mainly operated in the northern areas while the Auxis rochei rochei fishery was in the coastal water of Gongliao. Therefore, this is an indication that in the Gongliao areas the change of composition of phototactic fish in summer and warm-water fish gradually expanded northward to replace the cold-water species.
4. Based on the time series analysis during the period of 1995-2010, the catch of Sarda orientalis was highest in 2002, with 4,584 kg/household, and decreased thereafter since 2003. It is suspected that the climate change has caused the decrease in larval anchovy and flying fish roe in the area and then indirectly caused the decrease in Sarda orientalis, which feed on larval anchovy and flying fish.
5. The change in sea condition, in particularly the El Niño phenomenon would affect on the catch of Japanese eel. The distance of the Kuroshio Current from Taiwan would be related to the catch of Japanese eel. The shortest distance happened during 1999-2000, only 11.37 nautical miles, while the catch of Japanese eel was the highest (152,000 fish caught). The longest distance occurred in 2010, 18.14 nautical miles from Taiwan, while only 9,500 fish were caught.
6. There were significant difference between mullet and milkfish catches in typhoon and non-typhoon ( t =2.99, 2.74; P=0.006, 0.01, respectively) periods, which suggested that the catch of mullet and milkfish increased significantly after typhoons.
7. According to the shift of cold and warm regimes in the Gongliao area, the water temperature during warm periods was 0.3℃ higher than the average value (1995-2010), while in cold periods was 0.3℃ lower than the average. The catches of many species were periodically alternated in response to the physical regime shift, including the catches of Gelidium spp., Kyphosus cinerascens, Dentex tumifrons, Scorpaenodes littoralis, Auxis rochei rochei, Scomber spp., and Seriola dumerili. Generally, the catch of Gelidium spp., Kyphosus cinerascens, Dentex tumifrons, and Scorpaenodes littoralis were higher during the warm period and lower during the cold period while the catches of Auxis rochei rochei, Scomber spp., and Seriola dumerili were on the contrary.
To sum up, the short- and long-term changes in resources showed that both the catches of migratory and benthic fishes were affected by the sea water warming and extreme climate events. As the ocean current changed, the catch was alternated. Consequently the bait species decreased, the catch in cold and warm period alternated, and eventually impacted on the transition of fishery resource structure and, therefore, the income of fishermen.
| Identifer | oai:union.ndltd.org:TW/099NTOU5451026 |
| Date | January 2011 |
| Creators | Chu-Chen Cho, 卓菊貞 |
| Contributors | Kuo-Tien Lee, 李國添 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 113 |
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