沿岸底延縄漁業における釣獲の日周変化

抄録

The present paper describes the variation of catch set-line fisheries with special reference to the operation time, analysing the results of experimental fishings conducted at Sagami Bay in 1979 and 1980. The diel variation of hooking rate (Total catch/hook) was obtained, showing higher values at dawn and dusk, and lower values in the daytime as well as at night. Catch composition, however, was different in each fishing operation time. The diel variation of hooking rate was discussed for each species, so that several patterns of its variation could be classified. One is the nocturnal, that indicated the high values of hooking rate at night, for brown hakeling Physi-culus maximowiczi, bermuda catfish Promethichtys prometheus, and common Japanese conger Conger myriaster. The other is the diurnal and divided into two further types: The hooking rate of silvergray seaperch Malakichthys griseus was high at dawn and/or dusk, the same was true for Japanese bluefish Scombrops boops and Hilgendorf saucord Helicolenus higendorfi. While, pacific pomfret Brama japonica showed high values of hooking rate in the daytime.