人工魚礁近傍の魚群生態に関する基礎的研究 ＩＩＩ マダイ音響じゅん致漁場におけるマダイを中心とした数種の魚群行動について

Abstract

Experimental fish nursery of Pagrus major using acoustic conditioning had been constructed by Ohita Prefectural Fisheries Experimental Station. Young of Pagrus major were conditioned to feed immediately when the sound started in the feeding net cage, then they were released in Yonozu bay. In the bay, they were fed by an automatic feeder (feeding buoy) subsequently. After seven months, the behavioral characters and community ecology of fishes around the feeder were investigated by direct observation and by some automatic recording instruments. As results, some phenomena concerning the behavior of fishes were found as follows. (1) Around the feeder, fifty-seven kinds of fishes were found and the dominans were Navodon modestus, Parapristipoma trilineatum and Pagrus major. (2) In the daytime, Navodon modestus aggregated beneath the feeder or near the aritificial reefs, and when artificial diet was scatered by the feeder, they clustered beneath the feeder and fed actively. in the nighttime, theyrested at the bottom near the artificial reefs. (3) Parapristipoma trilineatum aggregated around the rocks near the feeder in the daytime, and fed the diet in the nighttime. (4) Pagrus major (16-17cm in total length) came near the feeder only in the daytime and fed at the bottom. (5) It seemed that most of the diet scattered from the feeder was fed on by these three species of fishes, and it was calculated that Pagrus major fed on about 20 percent of all diet scattered.