Processed echosounder data and pelagic fish biomass estimates from the 2012, 2015 and 2016 vessel-based surveys of the Chagos Archipelago MPA (dataset)

Calibrated echosounder data (38 and 120 kHz) were collected from the M/V Pacific Marlin patrol boat using a pole-mount and towed-body during 3 surveys conducted in 2012 (22/11-08/12), 2015 (09/01-27/01), and 2016 (05/02-24/02). Data were processed using Echoview software (version 8.1) to remove noise (surface/transient and background) and values of backscattering intensity were integrated over the top 200 m of the water column to obtain estimates of along-track pelagic fish echo intensity. These values were then converted into fish biomass by applying site-specific fish target strength values that were derived from observations of pelagic fish distributions made using baited remote underwater video systems (BRUVs). For more information on methods used, please see linked publication (Letessier et al., 2021).