CalCOFI 1407NH Cruise Data. In California Cooperative Oceanic Fisheries Investigations (CalCOFI): Acoustic and Trawl Data

Acoustic backscattering data were collected between stations using a hull-mounted Simrad EK60 split-beam echo sounder equipped with five frequencies (18, 38, 70, 120, and 200kHz). The EK60 was calibrated before each cruise using the standard sphere method (Foote et al., 1987). Pulse length was set to 1.024ms with a ping rate of 0.5s_1. Beam angles were 71 for the 38kHz transducers and111 for the 18 kHz. Power for both 18 and 38kHz transducers was 2kW. As the three highest frequencies did not reliably penetrate to the depth of the daytime deep scattering layer (DSL) at the vessel transit speed (10knot), they were not used in this study. Acoustic data were processed and noise removed using Echoview software. Nautical area scattering coefficient (NASC) was calculated over 100m distance segments by 5m depth intervals. See Davison et al. (2015a) for further details of acoustic data analysis methods.

本研究在各测站之间采集声学背散射数据，所用设备为搭载5个工作频率（18、38、70、120及200 kHz）的船壳安装式Simrad EK60分裂波束回声测深仪。该EK60设备在每个航次前均采用标准球体法完成校准（Foote等，1987）。其脉冲长度设置为1.024 ms，脉冲重复速率为0.5 s⁻¹。38 kHz换能器的波束角为7°，18 kHz换能器的波束角为11°。18 kHz与38 kHz换能器的发射功率均为2 kW。由于在船舶航行速度为10节时，三个最高频率的声波无法可靠穿透至日间深层散射层（DSL）的深度，因此本研究未采用这三个频率。声学数据通过Echoview软件完成处理与噪声剔除。研究以100米距离段与5米深度间隔为统计单元，计算得到航海面积散射系数（NASC）。有关声学数据分析方法的更多细节，请参考Davison等人（2015a）的相关研究。