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A study on the fluctuation of the mean trophic level of set-net fishery landings in the coastal waters of Hualien during the period 1995-2005
|Authors: ||Sian-Yu Chen|
|Contributors: ||NTOU:Department of Environmental Biology and Fisheries Science|
Set-net fishery;Species composition;Mean trophic level (MTL);Fishing-in-balance (FiB) index
|Issue Date: ||2011-06-30T08:23:04Z
|Abstract: ||本研究利用1995~2005年間，花蓮縣崇德海灣-東益發定置網漁場及七星潭海灣-朝金定置網漁場歷年現場漁獲紀錄資料，配合各漁獲魚種營養位階(TL)指標值，推估此二定置網漁場之平均營養位階(MTL)與漁獲平衡指數(FiB)的變動趨勢，同時結合衛星遙測表水溫之資料，來探討其MTL與水溫變化間之關聯性。其結果分述如下： 一、根據1995~2005年東益發及朝金定置網漁場歷年漁獲交易記錄顯示，此二漁場分別發現有115及124種魚類，其中以洄游群性魚類，如圓花鰹(TL=4.1)、矛尾翻車魨(TL=3.9)、扁花鰹(TL=4.3)、鬼頭刀(TL=4.4)、紅尾圓鰺(TL=3.6)、白腹鯖(TL=3.1) 及齒鰆(TL=4.2)等有較高之漁獲量。 二、由1995~2005年間MTLy之變動顯示，此二定置網漁場之MTLy自1998年起至2005年間均有下降之趨勢，其下降幅度約為每年0.017~0.023之間，且漁獲魚種營養位階(TL)小於4的漁獲比例，亦自1998年起亦有逐年增加之勢。 三、根據1995~2005年FiB指數之變動顯示，此二定置網漁場並未達食物網向下過度利用之情形，但此二漁場之FiB指數均自2002年起逐年下降中。 四、由此二定置網漁場年別MTLy與年平均SSTy之變動關係顯示，其MTLy與SSTy之間有顯著的正相關，另由月別MTLm與平均月別SSTm之變動亦顯示，二者之間有顯著的正相關，亦即在低水溫時期，此二漁場之漁獲魚種傾向於低TL之現象。 綜上可知，花蓮東益發及朝金定置網漁場自1998年起，其MTL及FiB均有下降之趨勢，亦即高營養位階魚種之漁獲比例逐年減少，而此一現象顯示，本省東部定置網漁業資源之食物網結構，有逐年弱化之情形。|
In this study, the mean trophic level (MTL) and the fishing-in- balance (FiB) index of set-net fishery landings from Dongyifa and Chaojin set-net fishing grounds in the coastal waters of Hualien during 1995 and 2005 were estimated using the trophic level of all fishery resources. We also analyzed the relationship between MTL and SST in these two fishing grounds. The results were summarized as follows: 1. A total of 115and 124 species were found by the landings from Dongyifa and Chaojin set-net fishing grounds during 1995 and 2005, respectively. The analysis of landings by fish group showed that the main fishing species were the pelagic group species in these two fishing grounds, such as Auxis rochei rochei (TL=4.1), Masturus lanceolatus (TL=3.9), Auxis thazard thazard (TL=4.3), Coryphaena hippurus (TL=4.4), Decapterus kurroides (TL=3.6), Scomber japonicus (TL=3.1) and Sarda orientalis (TL=4.2). 2. The annual MTLy of both fishing grounds showed a stepwise decline from 1998 to 2005, and the percentage of the landings of species ofTL<4.0 also declined during the same period. The MTLy decreased at a rate between 0.017 and 0.023. 3. The fluctuation of FiB index in these two fishing grounds suggested that the “fishing down marine food web” phenomena were not significant during 1995 and 2005. However, the FiB index wasstepwise declined since 2002. 4. The correlation analyses suggested that the relationship between MTLy and SSTy, and between MTLm and SSTm were positive significant. To sum up, the ecological indicator of MTL and FiB showed that the landings of set-net fishery in the eastern coastal waters were decre- ased since 1998. While, the structure of food pyramid for the set-net fishery were weaken even more.
|Appears in Collections:||[環境生物與漁業科學學系] 博碩士論文|
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