This study used hydroacoustic method to identify the vertical and horizontal distribution of Antarctic silverfish in the Ross Sea, Antarctica. In February and December 2018, Antarctic silverfish was detected up to 250 meters, and was mainly distributed in water depths of 20 to 30 meters. The horizontal distribution of Antarctic silverfish was mostly undetected in February, and December showed a relatively stronger distribution than that of February. Antarctic silverfish is characterized by their distribution near sea ice.

We explored the frequency response of krill target strength (TS) to understand the Antarctic krill (Euphausia superba) and ice krill (Euphausia crystallorophias) using the stochastic distorted-wave Born approximation (SDWBA) model. The results showed that the distribution of orientation and the fatness factor could significantly impact on the frequency response of TS. Krill TS is clearly depended on acoustic properties, which could affect to estimate the biomass of two krill species. The results provide insight into the importance of understanding TS variation to estimate the Antarctic krill and ice krill biomass, and their ecology related to the environmental features in the Southern Ocean.

In this study, the target strength for multi-frequency (38 kHz, 120 kHz, 200 kHz) of juvenile silverfish (Pleuragramma antarcticum) was estimated using by the KRM (Kirchhoff-ray mode) model. The body shape of the silverfish was described by a picture and the body length of nine individuals ranged in 1.8 cm to 8.8 cm. The maximum TScm according to the total length for the constant term (b20) was – 92.93 dB at 38 kHz, – 86.63 dB at 120 kHz, and – 85.89 dB at 200 kHz, respectively. The averaged TScm according to total length for the constant term (b20) was – 100.0 dB at 38 kHz, – 93.0 dB at 120 kHz, and – 106.9 dB at 200 kHz, respectively.

Recently, wideband acoustic technology has been introduced and started to be used in fisheries acoustic surveys in various waters worldwide. Wideband acoustic data provides high vertical resolution, high signal-to-noise ratio and continuous frequency characteristics over a wide frequency range for species identification. In this study, the main characteristics of wideband acoustic systems were elaborated, and a general methodology for wideband acoustic data analysis was presented using data collected in frequency modulation mode for the first time in Republic of Korea. In particular, this study described the data recording method using the mission planner of the wideband autonomous acoustic system, wideband acoustic data signal processing, calibration and the wideband frequency response graph. Since wideband acoustic systems are currently installed on many training and research vessels, it is expected that the results of this study can be used as basic knowledge for fisheries acoustic research using the state-of-the-art system.