CalCOFI 1207OS 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.