Исследование акустической силы цели японской скумбрии в северо- западной части Тихого океана in situ

Abstract

Significant concentrations of Chub mackerel (Scomber japonicas) were found in 2014 in the area of the Southern Kuril Islands (Northwestern Pacific Ocean (NWPO)). Commercial fishing for Chub mackerel was resumed in the NWPO in 2016. In this connection, exploratory work and acoustic-trawl surveys are carried out to identify distribution and abundance of Chub mackerel in the NWPO. Acoustic abundance estimates of the stock size of Chub mackerel is important for fishing. However, the reflectivity of Chub mackerel is not well understood. Collections of in situ target strength (TS) signals and corresponding fish size measurements for Chub mackerel were obtained as a result of research in the NWPO (2015–2017). The calibrated scientific echo-sounder “EK‑60 Simrad” with two split-beam echo sounders of respectively 38 and 120 kHz was used to collect sonar data. Measurement of the TS of Chub mackerel was conducted at the trawl layer, which corresponds to the trawl opening per the trawling area. The echogram selection process and the filtering process of single targets of Chub mackerel are realize in the “SALTSE” software package (“TINRO”). The dependence of mean target strength (TS, dB) on mean fish length (L, cm) for was estimated as 20 log (L) — 72,8 dB at 38 kHz and as 20 log (L) — 73,6 dB at 120 kHz. The obtained values backscattering strength (Sv) of Chub mackerel in the NWPO are compared with the values Sv of other studies of the reflective properties of Scombridae.