I) As regards Nisikurasawa Keddle Net (Fig. 1) by which yellowtail have been most abundantly caught of all fishing grounds in Suruga Bay, the daily catches of yellowtail and bluefin tuna and their younger fishes were examined in the seasons of yellowtail Jan. ?? May of 1921, '22, '25, '28, '29, '30 and '31 and in the summer months, June ?? July, of 1922 and '30.
i) Averaged total catches and averaged centers of the fishing seasons of the most important fishes, yellowtail and young bluefin tuna, are given as follows: ??
ii) The durations of abundant catch and scarce catch of yellowtail and young bluefin tuna appear somewhat periodically (Fig. 2 and 3).
II) The numbers of fish in daily catches and the possibility of occurrence of the catch on each day of normal year being defined, the catches at Sigedera and Nisikurasawa Fishing Grounds were studied with the results summarized in the following lines: -
i) At Sigedera, the primary fluctuation of a period of 130 days is noticed in the daily catches of young bluefin tuna in the duration spreading over about 20 months, 0- to II-age fish, in normal year (Fig. 4) and there exist also the secondary fluctuations of about 20 dayperiod as shown in the text-figure; it is very remarkable in its most abundant season.
ii) The above-mentioned secondary fluctuations are also noticed in the daily catches in the most abundant season of normal year of Nisikurasawa (Fig.5) preceding those of Sigedera by about one month.
iii) Though the catch of adult yellowtail at Sigedera (Fig. 6) are very scarce in contrast with its abundance at Nisikurasawa (Fig. 7), its younger fish being rather abundantly caught at the former (Fig. 6).
The fishing seasons of the adult and young are different respectively at both fishing grounds.
III) Together with some other fragmental records of the catches of many keddle nets along the coast of Suruga Bay in 1930, the following conclusions were obtained.
i) The day of the most abundant catch of each fishing ground became later toward east along the northern coast of the bay and the total catch during the whole duration and the catch on the day of the most abundant catch were smaller toward the east in 1930 (Table 3),
ii) The fishing seasons were nearly the same in the fishing grounds along the northern and western coasts of the bay but the intervals of abundant catch and scarce catch seemed to take place alternately in the two districts.
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