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Analysis on the trends in growth pattern and fishing exploitation of dolphinfish in the eastern waters off Taiwan
|Authors: ||Chen, Chia-Chi|
|Contributors: ||NTOU:Department of Environmental Biology and Fisheries Science|
dolphinfish;eastern waters of Taiwan;growth parameters;length-frequency;biological reference points
|Issue Date: ||2020-07-02T07:40:35Z
|Abstract: ||本研究係以2003年至2016年間於台東縣新港魚市場所量測記錄鬼頭刀(Coryphaena hippurus)之尾叉長(fork length)資料，採用ELEFAN體長頻度分析法並擬合von Bertalanffy成長方程式估計台灣東部海域鬼頭刀之成長參數，以分析雌雄別鬼頭刀歷年之成長趨勢變動。根據估計所得之歷年成長參數，本研究再配合歷年漁獲量資利用漁獲曲線法及單位加入生產量分析進一步估計歷年全死亡率、自然死亡率、漁獲死亡率及相關之生物參考點，作為對台灣東部海域鬼頭刀資源狀態變動分析之參考依據。 根據歷年體長頻度顯示雌雄別每年皆分別在11月以及7月有加入群，且體長推移情形也不大相同，因此本研究分別針對兩加入群進行探討，區分為11至翌年6月之秋季加入群以及7至10月之夏季加入群，並以雌雄別分開探討。研究結果顯示台灣東部海域1至6月漁獲對象多為零歲以及一歲鬼頭刀，7至10月則以一歲鬼頭刀為主。根據歷年之成長分析結果顯示，雌性鬼頭刀之體長有小型化的趨勢。在死亡率估計方面，雄性鬼頭刀之自然死亡率會略大於雌性鬼頭刀，秋季加入群之漁獲死亡率亦略大於夏季加入群，整體之開發率在近十年則有增加的趨勢，且平均開發率雌魚會大於雄魚。單位加入生產量分析結果顯示，雌性鬼頭刀之歷年漁獲死亡率在過去有較大的機率會大於F0.1之生物參考點。|
To analyze the historical growth pattern of male and female dolphinfish (Coryphaena hippurus) in the eastern waters of Taiwan, the growth parameters were estimated using ELEFAN with von Bertalanffy growth curve based on the length-frequency data (fork lengths) sampled in Hsinkang fish market, Taitung County from 2003 to 2016. According to the estimation of the growth parameters over the years, this study also estimated the total mortality, natural mortality, fishing mortality and biological reference points of the dolphinfish over the years using the catch curve method and yield per recruit analysis as a reference for the exploitation trend of dolphinfish in the eastern waters of Taiwan. The length-frequency distributions over the years show that there are two recruitments in November and July every year, and progress of the length distributions are obviously different between these two groups. Therefore, the analyses of this study were conducted based on the assumption of two groups, which divided into the autumn recruitment group from November to next June and the summer recruitment group from July to October, with different genders, respectively. The results show that the catches from January to June mainly consist of 0 and1 year-old dolphinfish, and the catches from July to October mainly consist of 1 year-old dolphinfish. The results of growth analysis indicate that the body lengths of females tend to be smaller in recent years. In terms of mortality estimation, the natural mortality for male dolphinfish is slightly higher than female dolphinfish, and the fishing mortality for the summer recruitment group also a little higher than that for the autumn recruitment group. The overall exploitation rate increased in the past decade, and the average exploitation rates for females are larger than that for males. The results of yield per recruit analysis reveal a higher chance that the fishing mortality rate for female exceed the reference point of F0.1.
|Appears in Collections:||[環境生物與漁業科學學系] 博碩士論文|
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