EK60 Water Column Sonar Data Collected During OES0505

Oceanographic Survey of Cross Seamount and Control Sites (OES0505, EK60). The goal of the cruise was to collect physical and biological oceanographic data at three distinct environment in the lee of the Island of Hawaii: a relatively near-shore pelagic environment off Keahole Point, Hawaii, at Finch Seamount (17° 38.070’N, longitude 157° 41.723’W) with a 1052 m deep peak, and at Cross Seamount (18°43.285’ N, longitude 158° 15.710’ W), with an approximately 400 m deep plateau. Data collected consisted of CTD casts, trawl samples, and continuous monitoring of currents and biological acoustic backscatter. CTD cats were conducted at predetermined stations. CTDs were equipped with oxygen sensors and fluorometers and water was sampled at discrete depths during each cast for chloropigments and nutrients measurements. Trawl operations were conducted at predetermined stations using a Cobb trawl at depths of the shallow (nighttime) and deep (day and nighttime) sound scattering layers. Currents were continuously monitored using a RD Instruments Acoustic Doppler Current Profiler (ADCP) operating at 75 kHz frequency. Biological backscatter were recorded using the EK60 echosounder system (38 and 120 kHz) along predetermined transects. During the survey, a High-frequency Acoustic Recording Package (HARP) was deployed for marine mammal observation.