Using Voyage Data Recorder and Logbooks Data to Explore the Fishing Pattern of longline Fisheries in the Coastal Water of Taiwan
延繩釣漁業為我國重要漁業，佔沿近海漁業總產量的10%。本研究利用2010年間，在臺灣沿近海作業之24艘CT0~CT4(CT0為5噸以下、CT1為5噸以上未滿10噸、CT2為10噸以上未滿20噸、CT3為20噸以上未滿50噸、CT4為50噸以上未滿100噸)延繩釣漁船的航程記錄器(Voyage Data Recorder，VDR)資料共554 航次，分析其作業模式。結果顯示，延繩釣漁船依噸級別之不同，會有不同之作業船速，其中CT0~CT3噸級鮪延繩釣漁船作業之船速分別在2.37節、3.76節、3.45及3.27節以下;而CT0~CT4噸級雜魚延繩釣漁船作業之船速，則分別在2.82節、3.80節、3.31節、5.62節及5.91節以下，且以前述所訂之船速加上一倍標準差為基準，在此基準以上為非作業、以下為作業。結果顯示，超過80%之作業航跡在此基準內。利用VDR 資料判別作業狀態時，大於CT2 漁船建議至少以每60分鐘資料為最佳選擇；CT1以下的船則以3分鐘為標準，若是想了解投繩、揚繩之間的區別，大於CT2漁船必須使用每30分鐘的資料。作業位置差距方面，CT0、CT1、CT4的船在VDR作業眾數和漁獲日誌資料平均相距小於3.5浬，CT2、CT3的船在VDR作業眾數和漁獲日誌資料平均相距超過5浬。在影響漁獲量的因子部分，以努力量、季節、噸級別、作業時間、投繩平均速度、揚繩平均速度、漁獲位置經、緯度為因子，使用一般線性迴歸，結果顯示，鮪延繩釣的漁獲量與季節、努力量、揚繩平均速度以及作業時間相關，而雜魚延繩釣的漁獲量與漁獲位置經、緯度及作業時間相關。鮪延繩釣夏季的捕獲量高於其他季節，而雜魚延繩釣在西部漁獲量高於東部、北部高於南部。本研究建議判斷延繩釣作業速度時，以投繩速度加一倍標準差的速度為分界，以上為非作業，以下為作業。本研究利用VDR資料得知漁船作業速度、作業時間、作業地點，可與漁獲日誌進行對照，得到較準確的資料，提供漁政單位作為管理之用。
Longline fishery is one of the most important fisheries of Taiwan,
which were accounted for over 10% of total catch. For understanding the fishing pattern of Taiwanese coastal longline fisheries, 554 trips data collected from 24 vessels Taiwanese coastal longline fishing CT0~CT4 vessels (CT0 is less than 5 tons, CT1 is for more than 5 tons less than 10 tons, CT2 is for more than 10 tons but less than 20 tons, CT3 is for more than 20 tons but less than 50 tons, CT4 is for more than 50 tons but less than 100 tons) were used to analysis of fishing pattern of these vessels. The results showed the fishing speed were 2.37 knot, 3.76 knot, 3.45 knot, 3.27 knot for CT0 to CT3 pelagic longline fishing vessels, respectively. For bottom longline fishing vessels, the fishing speed were less than 2.82 knot, 3.80 knot, 3.31 knot, 5.62 knot, and 5.91 knot for CT0 to CT4, respectively. Use this speed add a standard deviation as indicator can distinguish fishing and steaming, the accuracy was more than 80%. Regarding the appropriate time intervals, it is suggested that vessels larger than CT2 vessels interval should use 60 minutes interval. For those smaller than CT2, 3 minutes interval would be appropriate. For position, both of pelagic and bottom longliners showed the average fishing position difference of CT0, CT1, CT4 fishing vessels were less than 3.5 nautical miles between VDR and logbook data. However, the average fishing position difference were more than 5 nautical miles for CT2 and CT3 fishing vessels. Regarding the linear regression function of catch, fishing effort(number of hooks), season, tonnages, fishing time, speed, catch position(latitude and longitudes) were used as independent variables. Tuna longline catches
were correlation to season, fishing effort, average hauling speed and fishing time for tuna longline fisheries. The fishing position and the fishing time are correlated to catch of bottom longline catch. It showed tuna longline has high catch in summer, and bottom longline has higher catch in western than eastern, higher catch in north than south waters of Taiwan. This study suggests that average setting’s speed add a standard deviation could be defined as the fishing speed of longline fisheries. This study showed VDR data could be used to understand the fishing area, fishing time, and fishing speed, and further be applied to compare with the logbook and get useful information for management purpose.
