Acoustic data during RV SONNE cruise SO287@en

Acoustic data were recorded from December 12, 2021, to January 11, 2022, using a Simrad EK60 hull-mounted echosounder operating at four frequencies ( 18, 38 , 120, and 200 kHz) along the cruise track. The system operated continuously (24/7) with a 20 log R time-varied gain function, a pulse length of 1.024 ms, and a maximum transmission power of 2000 W. Data processing was conducted using the in-house software Matecho (Perrot et al., 2018) for echogram corrections, noise reduction, and extraction of fish schools and scattering layers (SSLs). Sound speed corrections were applied using temperature and salinity data from CTD measurements (Coly et al., 2022). The corrected data were echo-integrated at 0.1 nautical mile (nmi) intervals, and the Nautical Area Scattering Coefficient (NASC, m² nmi⁻²) was used to assess spatial variability as a proxy for marine biomass. SSLs with mean volume backscattering strength (Sv) below -70 dB (relative micronektonic biomass) were extracted, and their descriptors were computed.本数据集的声学数据采集于2021年12月12日至2022年1月11日，采用船壳安装的Simrad EK60回声测深仪沿航行航迹采集，该设备工作于4个频率：18、38、120及200 kHz。该系统采用20lgR时变增益函数，脉冲持续时间为1.024 ms，最大发射功率达2000 W，且全天候（24小时不间断）持续运行。数据处理采用自主开发的专用软件Matecho（Perrot等，2018）完成回声图校正、噪声抑制、鱼群与散射层（SSLs）提取等操作。声速校正基于温盐深（Conductivity Temperature Depth, CTD）测量获取的温度与盐度数据完成（Coly等，2022）。校正后的数据以0.1海里（nmi）为间隔进行回声积分，并采用海面散射系数（NASC，单位为平方米每平方海里，m² nmi⁻²）表征空间变异性，以此作为海洋生物量的替代指标。提取平均体积反向散射强度（Sv）低于-70 dB（对应相对小型自游生物量）的散射层，并计算其各项特征参数。