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2017 Joint US & Canada Pacific Hake Acoustic and Trawl Survey (SH1707, EK80)
Our objectives are to: ? Conduct acoustic and trawl operations in daytime hours (i.e., between sunrise and sunset) to estimate the distribution and abundance of Pacific hake. ? Collect multi-frequency acoustic backscatter data using the ship?s Simrad EK60 scientific echosounders (18, 38, and 120 kHz) system in daytime hours. Collect broadband acoustic data with Simrad EK80 broadband echosounders operating at central frequencies of 70 and 200 kHz. Collectively, the acoustic data will be used to characterize the distributions and abundances of hake, myctophids, gelatinous zooplankton, and krill. The use of the EK80s will require temporary modification to the ship?s EK60 set-up (see section II.C.a.v). i.Collect acoustic data along pre-planned transects along the coast (hereafter ?transects?). ? Conduct daytime trawling to classify observed backscatter layers to verify hake aggregations and obtain specimens for biological data (length, sex, maturity, age, ovaries, diet, genetics, etc.). We request to have at least two experienced fishing officers on board at all times for all five legs. i. Trawling operations will be the primary method for interpreting the acoustic data. We will sample midwater and near-bottom echosign using an Aleutian Wing Trawl 24/20 (AWT). Trawl gear performance will be monitored during sampling for depth, net opening, and other parameters on the AWT with a Simrad ITI Trawl Eye and a Simrad FS-70 third wire Netsounder. We will also deploy temperature-depth recorders on the trawls, which we will supply. ii. Record data from shipboard net mensuration gear to evaluate trawl performance. ? Conduct IVC Transects: Conduct an Inter-Vessel Calibration (IVC) between the NOAA Ship Bell M. Shimada and the Canadian?s charter vessel Nordic Pearl to compare acoustic and fishing results of Pacific hake. The IVC is critical to ensure consistent data quality of the ongoing Joint US-Canada Pacific Hake Integrated Acoustic Trawl Survey, as the Canadian vessel W.E. Ricker was decommissioned and the Nordic Pearl will be filling its place this Summer. ? Use a portable x-ray system (Appendices 5 and 6) to take radiographic images of fish swimbladders ? Optically verify the presence of non-hake scatterers during trawling using a video camera and light(s) attached to the upper panel of the midwater trawl approximately 10-20 meters forward of the codend. ? Conduct vertical ring net zooplankton tows at pre-planned stations along transects (Appendix 2, Table 2) during daytime operations on a subset of six transects total for the survey area. These data will be used to describe the summer distribution of zooplankton species. ? Conduct vertical casts with the ship?s CTD rosette, outfitted with (2) temperature sensors, (2) conductivity sensors, (2) dissolved oxygen sensors, (1) fluorometer, and (1) altimeter. These casts will be conducted at pre-planned stations along transects (Appendix 2, Table 3) primarily at night. These data will be used in combination with acoustic backscatter data, to describe the vertical and horizontal distributions of hake relative to oceanographic conditions. ? Optically sample the watercolumn zooplankton assemblage using a Video Plankton Recorder (VPR). The VPR will be mounted on the CTD rosette in the place of three Niskin bottles, and will be deployed on each CTD cast. The VPR?s data will be used to evaluate the instrument?s sampling effectiveness relative to vertical ring net zooplankton tows, and will also serve as a zooplankton sampler for those CTD casts not matched with vertical zooplankton tows. ? Conduct underway CTD (uCTD) casts at pre-planned stations along transects (Appendix 2, Table 4). These data will be used to supplement oceanographic information obtained from the CTD rosettes and will contribute to the description of hake distribution relative to ocean conditions ? Continuously collect Acoustic Doppler Current Profiler (ADCP) data along transects. These data will be used to describe the distribution of hake relative to currents. ? Conduct daytime Methot net tows to verify the identity of acoustic targets suspected to be euphausiids and obtain specimens for species identification and length. ? Continuously sample sea-surface temperature, salinity, and chlorophyll-a using the ship?s thermosalinograph and flow-through fluorometer. These data will be used to estimate the physical oceanographic habitats for hake. ? Continuously sample air temperature, barometric pressure, and wind speed and direction using the ship?s integrated weather station. ? Collect broadband acoustic data with EK80 echosounders operating at central frequencies of 70 and 200 kHz. ? All transect waypoints, CTD rosette, underway CTD and Zooplankton station locations will be provided to the navigational officer in Nobeltec format prior to the start of the survey.