MOVEMENT OF FISHING BOATS WITH FISHING LIGHTS IN THE TSUSHIMA STRAIT IN SUMMER AND FALL USING NIGHTTIME LIGHT SATELLITE IMAGES

Abstract

 As a part of fishery resource management, it is considered to be one of the effective methods to investigate the movement of fishing boats with fishing lights (hereinafter, fishing boats). In this study, I have investigated the movement of fishing boats in the Tsushima Strait in summer and fall using nighttime light satellite images by Suomi-NPP / VIIRS. The fishing boats were distributed like a tongue from the eastern coast of Tsushima to the north off Yamaguchi Prefecture. Comparing the distribution of the fishing boats with the 50m-depth current velocity in the ocean model, the fishing boats were distributed in the stagnant area and its front extending from the east coast of Tsushima to northeast. Although the distribution of the fishing boats is related to the 50m-depth sea temperature in the ocean model, the highest frequency of the sea temperature area where the fishing boats stayed is the 19 °C area in August of 2015, the 22 °C area in September and the 21 °C area in October. The highest frequency of the sea temperature area where the fishing boats were located change with time. On the other hand, since the relationship between the distribution of the fishing boats and the current velocity can be shown dynamically, it is possible to more efficiently estimate the fishing grounds where fishing can be operated by analyzing the current velocity area rather than the sea temperature one.