Summer surveys of the Chukchi Sea indicate that high densities of age-0 gadid fishes, historically Arctic cod (Boreogadus saida) but recently also walleye pollock (Gadus chalcogrammus), dominate the pelagic fish community. Adults are comparatively scarce, suggesting that either overwinter survivorship of age-0 gadids is low, or that they emigrate to other areas of the Pacific Arctic. To examine population movement, we conducted repeat acoustic surveys with saildrone autonomous surface vehicles equipped with echosounders throughout summer 2018. Results of these surveys were published in Levine et al. (2021). The survey was completed by two 7-meter saildrone USVs. The primary water column acoustic instrument for the survey was a Simrad EK80 mini scientific echosounder system equipped with a dual frequency ES38-18/200-18CR transducer (38 kHz split-beam, 200 kHz single beam). The vessels departed Dutch Harbor, AK on 30 June 2018, conducted acoustic surveys of the eastern Chukchi Sea from 20 July to 11 September, and returned to Dutch Harbor on 06 October. The echosounder system was calibrated via the standard sphere method before and after the cruise. Levine, R.M., De Robertis, A., Grünbaum, D., Woodgate, R., Mordy, C.W., Mueter, F., Cokelet, E., Lawrence-Slavas, N. and Tabisola, H. (2021), Autonomous vehicle surveys indicate that flow reversals retain juvenile fishes in a highly advective high-latitude ecosystem. Limnol Oceanogr, 66: 1139-1154. https://doi.org/10.1002/lno.11671

To investigate the distribution, life history, and interactions of biological communities in the U.S. Continental Region of the NE Chukchi Sea, a survey was conducted from August - September 2019. Acoustic data was collected as part of an acoustic-trawl effort to classify the midwater fish community of the region. The survey was conducted along 0.75 degree spaced transect lines from 66.5N to 73N between 168.5W and 156.8W. The primary water column acoustic instrument for the survey was a Simrad EK60 scientific echosounder equipped with a Simrad ES38B 38 kHz transducer and ES120-7C 120 kHz transducer. The ship departed Dutch Harbor, AK on 01 August 2019 and began the survey in the Chukchi Sea on 27 August 2019. The survey ended in Nome, AK on 01 October 2019. The echosounder was calibrated with a 38.1 mm tungsten-carbide sphere via the standard sphere method before and after the survey.

The BCO-DMO site for the project and cruise can be found here. https://www.bco-dmo.org/project/648472 https://www.bco-dmo.org/deployment/806648

The BCO-DMO site for the project and cruise can be found here. https://www.bco-dmo.org/project/648472 https://www.bco-dmo.org/deployment/806648

The BCO-DMO site for the project and cruise can be found here. https://www.bco-dmo.org/project/648472 https://www.bco-dmo.org/deployment/806648

The BCO-DMO site for the project and cruise can be found here. https://www.bco-dmo.org/project/648472, https://www.bco-dmo.org/deployment/777903

The BCO-DMO site for the project and cruise can be found here. https://www.bco-dmo.org/project/648472 https://www.bco-dmo.org/deployment/806648

The BCO-DMO site for the project and cruise can be found here. https://www.bco-dmo.org/project/648472 https://www.bco-dmo.org/deployment/777903

To investigate the distribution, life history, and interactions of biological communities in the U.S. Continental Region of the NE Chukchi Sea, a survey was conducted from August - September 2017. Acoustic data was collected as part of an acoustic-trawl effort to classify the midwater fish community of the region. The survey was conducted along 0.5 degree spaced transect lines from 67N to 72N between 168.5W and 153.25W. The primary water column acoustic instrument for the survey was a Simrad EK60 scientific echosounder equipped with a Simrad ES38-B 38 kHz transducer and ES120-7C 120 kHz transducer. The ship departed Dutch Harbor, AK on 01 August 2017 and began the survey in the Chukchi Sea on 09 August 2017. The survey ended in Nome, AK on 28 September 2017. The echosounder was calibrated with a 38.1 mm tungsten-carbide sphere via the standard sphere method during installation on 24 July 2017 and again at the start of the survey on 01 August 2017.

The primary goals of the survey are to characterize the winter distribution of hake, the hake aggregations, and the fish within those aggregations in order to support an evaluation of the feasibility of a future winter hake biomass survey. The project will use data from an integrated acoustic and trawl survey off the west coast of the U.S. from approximately south of San Diego, CA (latitude 31.6°N along the U.S. EEZ) to approximately Newport, OR (latitude 44.6°N). Our objectives are to: - Conduct 24-hour acoustic, trawl, oceanographic, and zooplankton operations. - Continuously sample multi-frequency acoustic backscatter data using the ship’s Simrad EK60 scientific echosounders (18, 38, and 120 kHz) system. Simrad EK80 broadband echosounders will operate at 70 and 200 kHz. Collectively, the acoustic data will be used to characterize the distribution of hake and describe hake aggregations. -- Collect acoustic data along pre-planned diagonal transects along the coast (hereafter “transects”). -- Collect acoustic data over hake aggregations, where the design will be determined based on the observed aggregation (hereafter “adaptive transects”). - Collect stationary acoustic data 1 hour before sunrise/sunset to 1 hour after sunrise/sunset to evaluate migration (vertical and/or horizontal) of hake aggregations. - Conduct daytime and nighttime trawling (Appendices 3 and 4) to verify hake aggregations and obtain specimens for biological data (length, sex, maturity, age, ovaries, diet, genetics, etc.). -- Multiple trawl samples may be taken on a single hake aggregation to evaluate heterogeneity in sex, maturity, etc. -- Record data from shipboard net mensuration gear to evaluate trawl performance - 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 20-30 meters forward of the codend. - Conduct vertical casts with the ship’s CTD rosette, outfitted with a dissolved oxygen sensor and Niskin bottles, at pre-planned stations along transects and/or at trawl locations (Appendix 2, Table 2, Table 4, and Table 5). These data will be used to describe the vertical and horizontal distributions of hake relative to oceanographic conditions. Niskin water collections will be filtered for evaluation of environmental DNA (eDNA). - Conduct underway CTD (uCTD) casts at pre-planned stations along transects (Appendix 2, Table 6). These data will be used to supplement oceanographic information obtained from the CTD rosettes and will be used to describe the distribution of hake relative to ocean conditions - Continuously collect Acoustic Doppler Current Profiler (ADCP) data along transects. These data will be used to describe the distribution of spawning hake relative to currents. - Conduct vertical ring net zooplankton tows at pre-planned stations along transects (Appendix 1, Figure 1; stations are listed in Appendix 2, Table 2) and bongo net tows (Appendix 1, Figure 1; stations are listed in Appendix 2, Table 3). These data will be used to describe the winter distribution of zooplankton species. - Continuously sample sea-surface temperature, salinity, and chlorophyll-a using the ship’s thermosalinograph and fluorometer. These data will be used to estimate the physical oceanographic habitats for spawning 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. The use of the EK80s will require temporary modification to the ship’s EK60 set-up.