CalCOFI 0911NH 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.

本研究通过安装于船舷的Simrad EK60分体波束回声测深仪（split-beam echo sounder）采集各测站间的声学背散射数据，该设备搭载5个工作频率：18、38、70、120及200kHz。每次科考航次前，均采用标准球体法（Foote等，1987）对EK60设备进行校准。脉冲时长设置为1.024毫秒，脉冲重复频率为0.5次/秒。38kHz换能器的波束角为7°，18kHz换能器的波束角为11°；18kHz与38kHz换能器的发射功率均为2千瓦。由于在船舶航速（10节）下，三个最高工作频率无法可靠穿透日间深层散射层（deep scattering layer, DSL）的分布深度，因此本研究未采用这三个频率的采集数据。声学数据通过Echoview软件完成处理与噪声剔除操作。以100米距离分段、5米深度间隔为统计单元，计算航行面积散射系数（Nautical Area Scattering Coefficient, NASC）。有关声学数据分析方法的更多细节，可参考Davison等（2015a）的相关研究。