유영자세각에 따른 정어리(Sardinops sagax)의 음향산란강도 추정에 관한 연구

Abstract

Sardines (Sardinops sagax) represent a globally significant fishery resource with considerable commercial value. As sardine catches have consistently increased in recent years, understanding their distribution and fluctuations has become essential for effective resource management and ongoing monitoring. Acoustic survey methods, a critical approach for monitoring fishery resources, necessitate knowledge of the inherent Target Strength (TS) of marine organisms. Among the factors influencing target strength estimation, the swimming tilt angle plays a particularly significant role. Consequently, comprehending how target strength varies with changes in swimming tilt angle is vital. This study employed the Kirchhoff-ray mode (KRM) model to estimate target strength and examine variations in the swimming tilt angle of sardines under flowing water conditions. Swimming tilt angles were measured at flow velocities of 30 and 50 cm/s. The KRM model was utilized to estimate target strength for 17 sardine samples (total length: 13.0–24.6 cm) across four frequency bands (38, 70, 120, and 200 kHz). Results indicated that the normalized mean target strength was moderately elevated when the swimming tilt angle slightly decreased (e.g., -2°). Conversely, when the swimming tilt angle exceeded 5° or when the standard deviation was high, the normalized mean target strength tended to decline. These findings underscore the significance of swimming tilt angle as a critical factor influencing target strength.