Utilization Mechanism of Fisheries Information in Far-seas Skipjack Purse Seine

在远洋鳕鱼围网渔业中，为了发现鱼类，人们在渔场的定位上做了大量的工作。本研究的目的是对渔场鱼类探测的决策因素--渔业信息的利用情况进行分析，评估渔场内的鱼类数量，以及围网渔船转移到其他渔场时的态度和行为理论。信息可以分为两类：宏观方面和微观方面。鱼类探测的宏观方面是指利用与其他船只的无线电通信来定位渔场，记录自己过去的巡航记录，以及与无线电浮标相连的漂流木材的位置定位。在微观方面，从桥上或鸟巢观察可以有效地发现海比…的群体更多的RD。在这种情况下，在接近海鸟聚集的位置后，进行声纳扫描以评估鱼量，以确定捕捞作业的适宜性。在无线电通信的有效性和探鱼的导航方法方面，还收集了数据以供进一步分析，并从围网捕获率的角度考察了船只尺寸的影响。新版《船舶大小吨位计量单位》实施后，对太平洋中部海域的远洋围网渔船规定小于351GT，大于等于200GT。根据新的测量单位，改型后的船只倾向于配备更大的鱼舱，这可能会影响围网渔船的操作理论。以静冈县野津港的渔获量数据为例，分析了重新建模对渔获量的影响与船舶行为的关系。改型后的渔船具有更大的鱼舱，作业次数、作业天数和巡航天数增加，而每次作业和每次拖曳的渔获量没有变化。在渔获量条件较好的情况下，随着年巡航次数和年渔获量的增加，对船舶尺寸有改型的影响。由于驾驶台上的双筒望远镜观测发现，驾驶室附近的振动可能会导致对鱼的探测能力降低。通过对新建围网的振动测试，认为该船的振动不会影响观测能力。较少

In the far-seas skipjack purse seine fisheries, the numerous efforts are made on the locating of fishing ground, for the purpose of fish detection. The aim of this research project is the analysis on the utilization of fisheries information which is the decision factor for the fish detection in the fishing ground, and the evaluating of the fish amount, as well as the theory for attitude and behavior of purse seiner on moving to another fishing ground.The data on the fisheries information was collected by means of the on-board survey during the cruise of porse seiner. The information could be divided into two categories; macro and micro aspects. The macro aspects for fish detection mean the locating of fishing ground by use of radio communication with other vessels, the records of own past cruise and the position locating of the drifting timbers attached with the radio buoy. In the micro aspects, the observation from the bridge or crow's nest is effective to find out the flock of sea bi … More rds. In this case, after approaching to the position of sea birds flocking, the sonar scanning is conducted to evaluate the fish amount so as to decide the propriety of the fishing operation. On the effectiveness of radio communication and the navigation method for the fish detection, the data were also collected for the further analysis.The influence of the vessel size was also investigated, from the view point of catchability of purse seiner. After the enforcement of the new version for the tonnage measuring unit of vessel size, the far-seas skipjack purse seiner was regulated to be less than 351GT, and greater than or equal to 200GT, in the central area of Pacific Ocean. According to the new measuring unit, the re-modeled vessels are tended to be equipped with the larger fish-hold which may affect the operation theory in the purse seiner. With the catch data obtained at Yaizu port of Shizuoka Prefecture, the influence of re-modeling on the catch amount was analyzed in relation to the vessel's behavior. The re-modeled vessel with the larger fish-hold increased the number of operations, operating days and cruising days, while no change was observed on the catch amount per operation and per hauling as well. The effect of remodeling in vessel size was obtained as the increase of the yearly cruising number and yearly catch amount in the case of good catch condition.Concerning the fish detection by the binoculars observation on the bridge, the vibration near the wheelhouse may result into the lower ability for fish detection. According to the measurement of the vibration for the newly built purse seiner, the vibration of this vessel is considered not to affect the observation ability. Less