沿岸底延縄漁業における漁具の浸漬時間の影響〔沿岸底延縄漁業の釣獲機構に関する研究-1-〕

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Effects of immersion time in coastal set-lines have been studied through six pairs of simultaneous operations conducted on the same ground of Sagami Bay. Using ordinary fishing methods the first operations were conducted around sunrise, and the second ones were set after sunrise and hauled in the afternoon, overlapping the two sets so as to elongate the duration of immersion time. Comparing the nature of the catch between the first and second operations, the first yieded a higher proportion of the targeted demersal fishes than the second. Hooking rate as a function of immersion time with each operation showed variation divided into two phases. A steady decline occurred in a comparatively short duration followed the setting of fishing gear. Thereafter, it changed into a slight tendency to increase with longer immersion times. Moreover, the incidence of damage to gear and of attacks by predators increased linearly with immersion time.