Acoustic characterization of biological backscatterings in the Kuroshio‐Oyashio inter‐frontal zone and subarctic waters of the western North Pacific in spring

Abstract

The acoustic characteristics of biological backscattering in the western North Pacific were studied to verify expert knowledge on species composition in the echosigns. The survey was conducted in the KuroshioOyashio inter-frontal zone and the subarctic waters in April 2003. The species composition of backscatterings was identified by using midwater trawl, Isaacs-Kidd midwater trawl and Bongo net. The differences of mean volume backscattering strengths between 120 and 38 kHz (DMVBS 120)38 ) were calculated for the backscatterings. Six types of backscatterings were classified based on the results of net samples and the DMVBS 120)38 . The DMVBS 120)38 of each group was as follows: copepods 13.7-17.3 dB, krill 11.6-15.3 dB, Japanese anchovy )1.6 to 1.1 dB, a myctophid, Diaphus theta )0.8 dB, sand lance 6.1 dB and larvae and juveniles of pelagic and mesopelagic fish )9.6 to )4.0 dB. The results suggest that biological backscatterings in the Kuroshio-Oyashio inter-frontal zone and subarctic waters of the western North Pacific in spring can be characterized by using DMVBS.

Vertical Distribution of Age‐0 Walleye Pollock during Late Summer: Environment or Ontogeny?

“…This frequency difference range also encompasses the frequency difference (120 kHz-38 kHz) values for euphausiids (10.9-16.7 dB;De Robertis et al 2010). Methods used to determine the frequency difference range in the Murase et al (2009) study were based on the copepod species Neocalanus cristatus, which is larger than the Calanus spp. copepods that are typically consumed by age-0 Walleye Pollock during cold years (Coyle et al 2011) in the Bering Sea.…”

“…Zooplankton acoustics.-Because specific algorithms to categorize EBS copepods are lacking, zooplankton (i.e., copepods and euphausiids) were identified following the methods of Murase et al (2009). The 38-and 120-kHz data were resampled into 1-m vertical £ 3-ping horizontal bins; any sample (0.18 m vertical £ 1 ping horizontal) containing an age-0 Walleye Pollock aggregation was excluded from the resample calculation as "no data."…”

“…The 38-and 120-kHz data were resampled into 1-m vertical £ 3-ping horizontal bins; any sample (0.18 m vertical £ 1 ping horizontal) containing an age-0 Walleye Pollock aggregation was excluded from the resample calculation as "no data." Using a ¡90 dB S v threshold, a frequency difference (120 kHz-38 kHz) value was generated for each resampled bin (Murase et al 2009). Bins containing zooplankton were identified using a frequency difference range of 7.1-22.0 dB (Murase et al 2009).…”

“…Using a ¡90 dB S v threshold, a frequency difference (120 kHz-38 kHz) value was generated for each resampled bin (Murase et al 2009). Bins containing zooplankton were identified using a frequency difference range of 7.1-22.0 dB (Murase et al 2009). This frequency difference range also encompasses the frequency difference (120 kHz-38 kHz) values for euphausiids (10.9-16.7 dB;De Robertis et al 2010).…”

Acoustic characteristics of Anchovy schools, and visualization of their connection with water temperature and salinity in the Southwestern Sea and the Westsouthern Sea of South Korea

“…구체적으로 보 면, 멸치의 치어와 성어를 대상으로 한 in situ, ex situ, modeling TS를 구하여 보다 정확한 멸치 자원량 평가에 기 여 하 였 다 (Miyashita, 2003;Sawada et al, 2009;Amakasu et al, 2010). 1990년후반 이후로 남해안, 황해, 일본 주변의 태평양 서북해역을 대상으로 멸치의 공간 적 인 패 턴 과 생 물 량 의 추 정 을 보 고 한 바 가 있 다 (Ohshimo, 1996;Ohshimo, 2004;Murase et al, 2009;Murase et al, 2012). 우리나라에서도 멸치 (Engraulis japonicus)는 생태학적으로도 상업적으로도 매우 중요 한 어종이다.…”