マダイ音響馴致漁場における魚群の行動について

Abstract

Experimental ?? nursery of Pagrus major using acoustic conditioning had been constructed by Ohita Prefectural Fisheries Experimental Station. In a previous paper, the behavioral characters and community ecology of fishes around the feeder were reported seven months after Pagrus major had been released. After an additional twelve months, behavior of Pagrus major and some other fishes were investigated by direct observation, by some automatic recording instruments and by all the day observation using echosounder and some instrument. 1. Around the feeder, fifty-six kinds of fishes were found and two-thirds of them were the same species as previously observed. 2. Number of fishes was seen to have increased compared to the previous observation. The dominant fishes were Navodon modestus, Parapristipoma trilineatum, Pagrus major, Apogon semilineatus and Trachurus japonicus, as in the previous observation the former three kinds of fishes were the dominants. 3. Navodon modestus and Parapristipoma trilineatum were almost the same size as in the previous observation. Pagrus major had grown up from 16-17 cm to 25-30 cm in total length, but their number had decreased to about one-fourth. 4. In the daytime, Pagrus major swam at the bottom layer or rested on the bottom. When the feed was scattered by the feeder, they clustered just beneath the feeder and fed actively at the bottom layer and sometimes rose to the midwater layer. In the nighttime, they rested at the bottom.