Rockfish was a commercially important fish specie in marine ranching areas in Korea. To estimate density and biomass of rockfish using acoustic method, target strength (TS) information is required on the species. This study measured TS dependence on tilt angle and size on 14 live rockfish individuals at 38, 70, and, 120 kHz by ex-situ measurement (tethered method) and acoustic scattering model (Krichhoff ray mode, KRM). The swimbladdered angle ranged from 18 to 30˚ (mean ± s.d. = 26 ± 4˚ ). The mean TS for all individuals was highest -35.9 dB of tilt angle -17˚ at 38 kHz, -35.4 dB of tilt angle -25˚ at 70 kHz, and -34.9 dB of tilt angle -22˚ at 120 kHz. The ex-situ TS-total length (TL, cm) relationships were TS38kHz = 20log10(TL) - 67.1, TS70kHz = 20log10(TL) - 68.6, and TS120kHz = 20log10(TL) - 69.9, respectively. The model TS-total length (TL, cm) relationships were TS38kHz = 20log10(TL) - 66.4, TS70kHz = 20log10(TL) - 67.0, TS120kHz = 20log10(TL) - 67.0. The two measurements between the ex-situ TS and KRM model for TS-tilt angle and fish size were found to be significantly correlated.

• 윤은아 | Euna YOON
• 김기선(전남대학교 해양기술학부) | Kiseon KIM (School of Marine Technology, Chonnam National University, Yeosu 59626, Korea)
• 이인태(전남대학교 해양기술학부) | Intae LEE (School of Marine Technology, Chonnam National University, Yeosu 59626, Korea)
• 조현정(전남대학교 해양기술학부) | Hyeon-Jeong JO (School of Marine Technology, Chonnam National University, Yeosu 59626, Korea)
• 이경훈 | Kyounghoon LEE Corresponding author