On the General Features of the Tuna-Fishing Grounds in the Eastern Indian Ocean I : Oceanic and Fishing Conditions in the Western Region of the Sumatra Island

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The following items were clarified, as the results of examining the general features of the tuna fishing grounds ; based on the data of the oceanographical observations made by the "Keiten Maru" (308.03 tons), training ship of the Faculty of Fisheries, Kagoshima University, in the Western region of Sumatra Island, latitude 3°N~4°S, longitude 93°E-96°E, from 1966 to 1968. The results obtained are as follows : 1). In the fishing ground spreading between 94°E and 96°E near the equator there is a remarkable 'line of convergence' and in this region it is possible to observe the local upwelling. 2). In the layer less than 50 m deep, there exists the mixing surface-water with the temperature more than 29.0°C, while in the layer between 50 m and 150 m in depth, there exists a very remarkable thermocline. 3). The water-mass in this region may be divided into four main groups. 4). The proportion of the catch-fish in this fishing-ground was as in the following : the hold of the yellowfin tuna was about 50%, that of the bigeyed tuna and a species of marlin, about 20%, and that of the miscellaneous ones, about 10%, respectively. 5). The depth fit for the tuna to swim was estimated as in the following : in case of marlin, it was the mixed-surface-water, in the yellowfin tuna, the region near the upper layer of the thermocline ; and in the bigeyed tuna, the thermocline or the intermediate layer below the thermocline.
鹿児島大学の論文
1970-12-25