Studies on Underwater Sounds Produced by Japanese Horse Mackerel Trachurus japonicus in Net Pens at Culture Grounds in Innermost Kagoshima Bay

Abstract

The differences between swimming and feeding activity of recorded underwater sound in summer and winter produced by Japanese horse mackerel in a net pen were analyzed using the one-third octave band method. The small and big-sized fish show the same curve patterns under swimming and bait-eating activity in summer, but in the term of the maximum and minimum level frequencies, it seems slightly different. The swimming sound curve pattern in summer was same as in winter, but there were some different patterns in bait-eating sound. The two respective records obtained simultaneously on the inside and outside of net pen when swimming activity were same in regard to the pattern and sound level, but the records when bait-eating activity were different.