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Abstract:
This dataset is a collection of of output from different sources. All data were collected during an IMR funded cruises, work was put into collating and publishing them as part of the EU funded project "Ecologically and economically sustainable mesopelagic fisheries" (MEESO). The aim is to present data that helps interpretation of catch and jull-mounted acoustic data, which are already published in the ICES trawl-acoustic database.
The dataset contains diverse sources of data, as they were registered onboard. It contains raw CTD output data from the ships Seabird CTD instrument for all stations covered, as well as underway vessel activity, positions, and weather station and thermosalinograph data collected during the cruise.
Underway and vertical profiles of light levels were measured with TriOS hyperspectral sensors, these data have been processed by converting spectrally resolved energies into photon counts, which have been integrated over the bandwidth 400 - 700 nm, and are reported as photosynthetically active radiation (PAR) in units of mol quanta per m2 and second.
During the cruise the tow-body MESSOR was routinely deployed. This unit is equipped with a number of sensors, we here report depth resolved size spectra recorded by two types of optical sensors, as well as depth resolved densities of organisms, estimated through counting of resolved echoes at close ranges to the tow-body.
The size spectra from the Optical Particle Counter (OPC) is based on particle sizes estimated directly by the calibrated instrument, sizes are reported as equivalent circular diameters. These data have been binned in logarithmically spaced size bins and linearly spaced depth bins, and are reported in units of # per cm3.
The size spectra from the Video Plankton Recorder(VPR) is based on particle sizes estimated from the total area of in-focus images, using equivalent circular diameter. These data have been binned in logarithmically spaced size bins and linearly spaced depth bins, and are reported in units of # per dm3.
Densities of organisms were estimated from counts of accepted single echo detections in data from a 120 kHz broadband echosounder (EK80, WBTUBE). Echo detections were performed on pulse compressed data, using the full bandwith available (varies per station). Echoes were detected at a threshold of -90 dB, peaks more than 6 dB above background levels (2 way) were accepted as originating from organisms. Inference based on the weaker echoes should be avoided, we recommend thresholding the data further prior to usage. Per ping counts of echoes within acceptable ranges from the transducer were then converted to densities by divinding with the nominal (3 dB beamwidth) ensonified volume of the the beam, and initial averages were then computed for 30 second ping blocks (average ping rate per second 4 to 1).The table reports average densities per TS class and depth range, in the table N is the number of 30 second ping blocks used in the calculation of the depth range average.