サウ海の鮪漁況と海況について

概要

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We made some researches on the relations between the fishing conditions of tuna and general oceanographical conditions, comparing the fishing season of Summer with that of Winter. The results obtained were as the following. 1. Fishing rate per 100 hooks amounted to 6.4 in Summer and to 7.4 in Winter. 2. In the case of Yellow-fin tuna the percentage of fish caught in Winter was 52.5 and in Big-eyed tuna the percentage was 16.7 0, and that in Summer was 63.9 and 2.3 respectively. And from this fact it was elicited that the fluctuation of Big-eyed tuna catch in Summer was irregular. 3. The body length composition of Yellow-fintuna showed the varying range of 100-160 cm ; the most general standard of size of the fish lay within the range of 130-150 cm; and a greater number of large-sized fish was found in Summer than in Winter. 4. The sex ratio of Yellow-fin tuna was about 692 in Winter ; 57.1 in Summer (both in the case of male). The almost all the fish caught in both seasons were found to be near the state of Ripenning. 5. The optimum temperature for catch was found to be 20°-23°C in Winter ; 23°,--25°C in Summer. 6. Oceanographical and astronomical conditions in Winter and those in Summer showed different appearances; having quite intimate relations with the fishing conditions respectively.