Abstract
It is important to use acoustic echo data to observe schooling characteristics of fish. The echoes should be different due not only to acoustic specifications of the echo sounder such as pulse duration and beam width, but also to fish schooling characteristics such as depth and distribution density. The echo envelope characteristics are examined through a computer simulation for the purpose of recognizing schooling pattern of fish. The envelopes of two fish schools were simulated in the same acoustic and geometric conditions. One school (S-school) is constituted of small size fish with 12±5cm of body length and 15 fish/m3 of distribution density, and the other one (L-school) is with 30±3cm and 4 fish/m3. Both are layer-shaped schools with the same thickness. In order to examine the characteristics of echoes, the simulated echo envelopes are analyzed using amplitude histogram and amplitude spectrum. The schooling difference is reflected to some extent in the spectrum and the amplitude distribution. It is considered that the characteristics of envelopes are worth studying on schooling pattern dependence on species, circumstances, and environment for the purpose of species identification and behavioral studies.
