Frequency- and depth-dependent target strength measurements of individual mesopelagic scatterers Article Swipe

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Mesopelagic zone Biomass (ecology) Target strength Fish <Actinopterygii> Environmental science Broadband Geology Oceanography Biology Fishery Physics Optics Pelagic zone

Christopher Bassett , Andone C. Lavery , Timothy K. Stanton , Emma Cotter ·

YOU? · · 2020 · Open Access · · DOI: https://doi.org/10.1121/10.0001745 · OA: W3071457068

Recent estimates based on shipboard echosounders suggest that 50% or more of global fish biomass may reside in the mesopelagic zone (depths of ∼200–1000 m). Nonetheless, little is known about the acoustic target strengths (TS) of mesopelagic animals because ship-based measurements cannot resolve individual targets. As a result, biomass estimates of mesopelagic organisms are poorly constrained. Using an instrumented tow-body, broadband (18–90 kHz) TS measurements were obtained at depths from 70 to 850 m. A comparison between TS measurements at-depth and values used in a recent global estimate of mesopelagic biomass suggests lower target densities at most depths.