북서 태평양 멸치(Japanese anchovy)에 대한 측면 음향 반사강도 특성

Abstract

Acoustic side-aspect target strength (TS) of living Japanese anchovy (Engraulis japonicus) was measured at 120 kHz during in situ experiments. The data were collected by lowering and horizontally projecting the split-beam transducer into the anchovy school. For analysis and interpretation of the side-aspect TS data, acoustic theoretical model, based on the fish morphology, and dorsal-aspect TS data were used. Total length of the anchovy ranged from 6.6 to 12.8 cm (mean length 9.3 cm). The side-aspect TS distributed between -40 and -55 dB, has an obvious length dependency. The mean side-aspect TS of the anchovy was -47.8 dB, and the TS was about 2 dB higher than mean TS generated from dorsal-aspect measurements. With reference to maximum TS, the results of the side-aspect TS were distributed within the range of the theoretical and dorsal-aspect TS. Apparently these tendency indicates that side-aspect TS measured from the study is useful data. These in situ measurements of side-aspect TS can be applied to improve acoustic detection and estimates of the anchovy, and is necessary to measure with a various frequency and length for making enhance data.