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Deep-Pelagic Nekton Dynamics of the Gulf of Mexico (DEEPEND)- DP01 (EK80)
Patterns in acoustically derived biological scatter through the water column will be collected with multi-frequency scientific echosounders (Simrad EK60) operating at 18kHz, 38kHz, 70kHz and 120kHz following protocols developed during the NOAA NRDA DAP data collection operations. Specifically, during each cruise, transducers will be installed on a rigid pole mounted to the side of the ship, and calibrated at sea for operating conditions following protocols developed by Dr. Boswell during the ONSAP/DAP cruises. The dynamics of the mesopelagic scattering community will be examined through the depth dependent scattering responses at both frequencies (18 and 38kHz) as well as through the difference between the mean volume backscattering strength (MVBS; in dB) at 18 kHz and 38 kHz (dMVBS(18-38)). In addition, scatterers in the upper water column (~150m) will be examined by analyzing the all four available frequencies. By integrating both methods, the magnitude of biological scattering at discrete-depth intervals will be classified into major taxonomic components (e.g., fluid-like crustaceans, swimbladdered fishes) based on resonant properties and behavior. The biological data and ship data collected during this cruise are available in GRIIDC datasets R4.x257.226:0001 and R4.x257.226:0003, respectively.