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Assessment of the impacts of depredations from cetaceans and sharks on longline fishery in the southeastern waters of Taiwan
|Authors: ||Kuan-Yu Su|
|Contributors: ||NTOU:Institute of Marine Affairs and Resource Managemen|
Cetacean;Shark;Depredation;Longline;General Linear Model
|Issue Date: ||2011-11-23T03:25:58Z
|Abstract: ||本研究針對12艘台東新港延繩釣樣本船於2009年10月起至2010年12月止，所填報的31本漁撈日誌（總投繩作業649次）進行分析，以瞭解鯨豚及大型鮫類咬食對東南部海域延繩釣漁業之影響。鯨豚及大型鮫類破壞率(damage rate)分別為19.26%及11.56%；尾數咬食率(depredation rate in number)分別為2.21%及0.51%；重量咬食率(depredation rate in weight)分別為3.23%及0.47%；咬食指標(depredation index)分別為每千鉤被咬食0.93和0.22尾。鯨豚及大型鮫類主要咬食的物種為鬼頭刀及黃鰭鮪。以漁獲量推估台東新港延繩釣漁業被鯨豚及大型鮫類咬食損失金額分別為台幣1,339萬元及178萬元，各佔總收益的4.5%及0.6%。東新港延繩釣漁業受鯨豚咬食之影響因子，利用二項式泛線性模式(Binomial GLM)分析結果顯示破壞率與目擊鯨豚、鬼頭刀、黃鰭鮪和長鰭鮪漁獲尾數及鬼頭刀漁獲尾數與季節間的交互作用呈現顯著關係；而尾數咬食率及咬食指標透過泛線性模式(General Linear Model)分析後，與鬼頭刀漁獲尾數及水深呈現顯著關係。|
The depredation impacts of cetacean and sharks on longline fisfery in Xinkang, Taitung were evaluated based on the 31 logbooks from 12 sampling vessels with a total of 649 operations in the southeastern Taiwan water from October 2009 to December 2010. The impacts caused by cetacean are more serious than those by large sharks in the longline fisheries off southeastern Taiwan waters. The damage rates of cetacean on the longline fisheries estimated to be 19.26% and shark equal to 11.56%, respectively. The depredation rates of cetacean were estimated to be 2.21% in number and 3.23% in weight, which were both significantly higher than those of sharks which are 0.51% in number and 0.47% in weight. The depredation indexes were estimated to be 0.93 and 0.22 per thousand hooks for cetacean and sharks, respectively. Our analysis indicated that cetacean and sharks preferred dolphinfish and yellowfin tuna. The economic loss due to depredation of longline fisheries were estimated by combining logbooks and yield and sale records of longline fisheries in Xinkang. Annual economic loss in Xinkang due to depredations of cetacean and sharks are estimated to be 13.39 and 1.78 million NT dollars, respectively. The economic loss caused by depredations from cetacean and large sharks occupied 4.5% and 0.6% of total revenue of longline fisheries in Xinlang, respectively. The General Linear Models (GLM) were used to analyze the influences of the environmental factors, sightings of cetacean, catch compositions and fishing types on the cetacean depredation. The results suggested that only catch in number of dolphinfish and depth had statistically significant impacts on the cetacean depredation for longline fisheries in Xinkang.
|Appears in Collections:||[海洋事務與資源管理研究所] 博碩士論文|
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