Gulf of Alaska | Ecosystem Perspectives
Adding echosounders and an acoustic brain to characterize water column biomass distributions Presenter: Hank Statscewich , hank.stats@alaska.edu, University of Alaska Fairbanks John Horne , jhorne@uw.edu, University of Washington School of Aquatic and Fishery Sciences Seth Danielson , sldanielson@alaska.edu, University of Alaska Fairbanks, College of Fisheries and Ocean Sciences Increased spatial domains, expanded ecosystem surveys, and decreasing budgets limit the ability of research vessels to meet population abundance and ecosystem management survey requirements. Underwater gliders are an alternative but apart from phytoplankton, gliders are rarely used as biological sampling platforms due to space, power, and bandwidth constraints. Active acoustics can sample larger animals but autonomous echosounder installations limit data access until after vehicle recovery. We have integrated a Simrad EK80 WBT mini echosounder and a 200 kHz transducer in a flooded sensor bay onto a Slocum underwater glider. An ARM-based Odroid single board computer interfaces with the glider science computer to provide a suite of biomass distribution metrics (EchoMetrics) and a coarse density map (pseudogram). Acoustic backscatter values over a 60 m range are acquired during each ascent and stored internally at full resolution. Layered backscatter output values are simultaneously processed to calculate EchoMetric and pseudogram values, combined in export variables, and then sent to the science computer for satellite transmission. Exported variables are later deconvolved and processed to produce EchoMetric plots and pseudograms for display on the AOOS web data portal in near-real-time. These data products quantify biomass distribution along the glider trackline and, when combined with physical sensor data, characterize biomass distribution and habitat conditions. Collectively, these data products can be used to adapt survey designs of additional sampling assets and to increase glider sampling effort at features of interest. A single echosounder and acoustic brain equipped G2 gliders has been deployed for two survey missions in February and June 2022 in the Gulf of Alaska to investigate salmon and their prey.
Alaska Marine Science Symposium 2023 164
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