Finite amplitude sound propagation effects in volume backscattering measurements for fish abundance estimation

Measurement data from a trawl survey conducted in the North Sea with R/V "G. O. Sars", passing several times over a group of Atlantic mackerel schools. The measurements are of the relative area backscattering coefficient (relative to 38 kHz) measured at (1) 120 kHz with 250 W transmit power setting, (2) 120 kHz with 1000 W power setting, (3) 200 kHz with 120 W power setting, and (4) 200 kHz with 1000 W power setting. A Simrad EK-60 echosounder system was used, alternating between the low (1, 3) and high (2, 4) power settings throughout the measurement series. Simulation data corresponding to the measurements, calculated using the Bergen Code numerical solver of the KZK Equation. The medium parameters input to the simulations are based on CTD data from the survey measurements. The transducer and amplitude data were found by laboratory measurements on echo sounders of the same type as used in the survey. .m files are included for both .mat data files, with details on how to read the data. An article based on the data has been submitted to Acta Acustica.Funding was received from The Research Council of Norway and Norwegian Seafood Research Fund