Impacts of Morphological Characteristics on Target Strength of Chub Mackerel (Scomber japonicus) in the Northwest Pacific Ocean

Chub mackerel ( Scomber japonicus ) is an important commercial fish in the Northwest Pacific Ocean. Accurate target strength TS underpins acoustic stock assessment but of S. still poorly understood. In this study, Kirchhoff-ray mode (KRM) model was used to estimate and its relationship with sound wave frequency morphology. The results revealed that values varied pitch angle shifts, impact on scattering being greater at higher frequency. This less because 38 kHz has been for biomass these resources. At frequencies kHz, 70 120 200 greatest a range -10° 0°, which related swim bladder tilt. There were almost no differences between estimated using measured distributions universal distribution. When N [-3°,4°], average body length 12.04–22.17 cm four -48.88 dB, -49.14 -49.75 dB -48.55 respectively. regression intercept b 20 –body equation -73.27 -73.56 -74.18 -73.46 Variation 0–300 m depth about 10 dB. simulated broadband spectrum shows characteristics individuals different 0–250 kHz. These could be identification echograms provide reference