抄録
Some technical consideration were tried on the purse seine fishing in the western water of Kyushu, with special reference to the relationship between catch and three fishing factors; States of nets in operation, current and gathering condition of fish under a fishing lamp.
Present study is based on the data from October 1955 to December 1958. The admissible conclusions are summarized as follows.
1) The average catch of each state of nets in operation is as follows:
Type A……447 boxes Type C……44 boxes
Type B……230 boxes Type D……174 boxes
As a matter of course, the catch of type A is largest. The appearance rate of type A is above 70% in winter and below 50% in early summer.
2) The correlation coefficient of appearance rate of type A to that of favourable condition of current is ρ(X, Y)=0.98. Namely, the state of nets in operation are greatly influenced by current. Consequently, the catch depends on the condition of current greately.
3) The average catch in favourable condition of tidal current is 471 boxes and that in unfavourable condition is 198 boxes. The former is 2.5 times as many as the latter.
4) The gathering condition of fish under a fishing lamp is favourable in the period from summer to early autumn and is unfavourable in winter. The degree of gathering condition of fish under a fishing lamp is closely related to the growth stage of each species. During the period from summer to early autumn, young fishes such as small and medium sardine, jack mackerel and mackerel are superior in number. While in winter, the adult and large sardine is superior.
5) The average catch in the favourable condition of gathering condition of fish under a fishing lamp is 434 boxes and that of reverse case is 260 boxes. The former is 1.7 times as the latter.
6) The average catch in the condition A (three factors are all favourable) is 700 boxes and that in the condition B (one or more of these three condition is unfavourable) is 200 boxes. There have been no case that the catch is less than 200 boxes in the condition A.
7) For the evaluation of fishing grounds by catch, the average catch should be calculated on the cases catching more than 200 boxes.
