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頁籤選單縮合
題名 | Mesh Selectivity of Trawl Codend for Japanese Butterfish [Psenopsis Anomala (Temminck & Schlegel, 1844)] off Southwestern Taiwan=臺灣西南海域產刺鯧底拖網網目選擇性 |
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作者 | 蘇偉成; 陳守仁; 賴繼昌; Su, Wei-cheng; Chen, Shou-ren; Lai, Chi-chang; |
期刊 | 臺灣水產學會刊 |
出版日期 | 20091200 |
卷期 | 36:4 2009.12[民98.12] |
頁次 | 頁289-302 |
分類號 | 439.3 |
語文 | eng |
關鍵詞 | 網目選擇性; 底拖漁業; 刺鯧; 尾袋; 臺灣西南海域; Mesh selectivity; Bottom trawl; Psenopsis anomala; Codend; Southwestern Taiwan; |
中文摘要 | 刺鯧(Psenopsis anomala)為西太平洋海域產重要經濟性魚種,在臺灣沿近海小型拖網漁業近年之產量亦呈現穩定狀態。惟其體長、生產量與漁獲尾數/總作業網次數(CPUE)卻逐年下降,因此確有必要對其資源加以管理。本研究利用兩組不同網目規格之三重袋網進行試驗,希望對成熟魚體的捕獲進行管理,以便使未成熟個體有機會繼續成長及發育。本研究在2007年12月至2009年1月於臺灣西南海域使用兩組三重袋網網目,其規格分別為:A組86 mm、75 mm、15 mm;及B組75 mm、60 mm、15 mm,進行9航次,24網次拖網網目選擇性試驗。結果顯示,刺鯧為最主要漁獲魚種,計漁獲刺鯧2,560尾,體長分布主要為150 mm~180 mm間,佔81.5%。以整體漁獲經濟價值考量,75 mm目大袋網可保留約50%之經濟性漁獲重量;60 mm網目則可完全漁獲具經濟效益之體長140 mm以上刺鯧個體。目大86 mm及75 mm之刺鯧50%選擇體長(L50%)分別為253.64 mm及171.60mm,選擇指距(selection span)分別為65.78 mm及28.87 mm,選擇係數(selection factor)分別為2.94及2.28。由以上結果及考量刺鯧之最小性成熟體長顯示,臺灣西南海域底拖網漁業現行20 mm以下之袋網網目應逐步擴大至70 mm,如此將可避免漁獲未成熟刺鯧,並可減少下雜魚之混獲比例。長遠來說,可以幫助資源保育,並改善漁業收益。 |
英文摘要 | Japanese butterfish, Psenopsis anomala, is very important to commercial fishing in the northwestern Pacific. This species has traditionally been a steady catch for bottom trawlers in the coastal waters of Taiwan. However, there has been a decrease in catch size, annual landings, and the catch individual/ total hauls (CPUE) of this species. This trend suggests a better management on this species is urgently needed. This study is to compare the selectivity two two-liner codends each equipped with three sizes of net mesh as a means of limiting catches to mature fish only so that immature ones have more time to develop and breed.To perform this study, we used the two codends to perform a total of 24 hauls during nine cruises off the coast of southwestern Taiwan between December 2007 and January 2009. We counted and measured the fish. One two-liner codend, which we labeled Type A, had three mesh sizes 86 mm and 75 mm codends and a 15 mm cover. The other codend, Type B, also had three mesh sizes 75 mm and 60 mm codends and a 15 mm cover. We caught 2551 Psenopsis anomala with fork lengths ranging from 150 and 180 mm. This fish made up the largest part (81.5%) of our catch. Fifty percent of the whole catch were caught with a mesh size of 75 mm. Japanese butterfish with the fork lengths above 140 mm were caught with a mesh size of 60 mm. Based on our logistic regression analysis, the mesh sizes 86 and 75 mm could catch Japanese butterfish with fork lengths of 253.64 and 171.60 mm. The selection spans (SP) of these two mesh sizes were 65.78 mm and 28.87 mm, and their selection factors (SF) 2.94 and 2.28, respectively. Based on the size of Psenopsis anomala once they reach maturity, the Taiwan government recommendation of 20 mm mesh size for bottom trawling should be changed to 70 mm. This would let the immature Psenopsis anomala escape and reduce bycatch, which would contribute to the conservation our resources and improve income over the long term. |
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