A bottom moored echosounder was deployed at 116.3 m depth in the NW Bering Sea (61.36881 N, 177.17 W) from 26 July 2019 to 31 August 2020. The mooring was instrumented with a battery powered EK80 wideband autonomous transceiver (WBAT, Simrad AS). The echosounder operated an upwards facing depth-rated 70 kHz 18° split-beam transducer (ES70-18CD), positioned upward with a two-axis gimbal equipped with a 0.7 kg counterweight. During the deployment, the WBAT was programmed to transmit an ensemble of 320 narrowband and 35 wideband every two hours. Data were recorded to a range of 155 m. Calibrations had occured in Seattle, Washington either prior to deployment or after recovery using a 38.1-mm tungsten carbide sphere following the standard sphere method (Demer et al., 2015).

A bottom moored echosounder was deployed at 95.6 m depth in the NW Bering Sea (61.85022 N, 176.25066 W) from 26 July 2019 to 31 August 2020. The mooring was instrumented with a battery powered EK80 wideband autonomous transceiver (WBAT, Simrad AS). The echosounder operated an upwards facing depth-rated 70 kHz 18° split-beam transducer (ES70-18CD), positioned upward with a two-axis gimbal equipped with a 0.7 kg counterweight. During the deployment, the WBAT was programmed to transmit an ensemble of 320 narrowband and 35 wideband every two hours. Data were recorded to a range of 155 m. Calibrations had occured in Seattle, Washington either prior to deployment or after recovery using a 38.1-mm tungsten carbide sphere following the standard sphere method (Demer et al., 2015).

A bottom moored echosounder was deployed at 137.6 m depth in the NW Bering Sea (61.06918 N, 177.73993 W) from 26 July 2019 to 31 August 2020. The mooring was instrumented with a battery powered EK80 wideband autonomous transceiver (WBAT, Simrad AS). The echosounder operated an upwards facing depth-rated 70 kHz 18° split-beam transducer (ES70-18CD), positioned upward with a two-axis gimbal equipped with a 0.7 kg counterweight. During the deployment, the WBAT was programmed to transmit an ensemble of 320 narrowband and 35 wideband every two hours. Data were recorded to a range of 155 m. Calibrations had occured in Seattle, Washington either prior to deployment or after recovery using a 38.1-mm tungsten carbide sphere following the standard sphere method (Demer et al., 2015).

The Midwater Assessment and Conservation Engineering (MACE) program of NOAA Fisheries, Alaska Fisheries Science Center (AFSC) conducted acoustic stock assessment surveys in the eastern Bering Sea (EBS) in summer of 2020 to estimate distribution and abundance of walleye pollock (Gadus chalcogrammus). This survey was initially intended as a ship-based survey, but this was cancelled due to the emerging COVID-19 pandemic. The survey was completed by three chartered 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 Alameda, CA on 13-14 May, conducted an acoustic survey of the Bering Sea from 4-20 August, and returned to Alameda on 4 October. The echosounder system was calibrated via the standard sphere method before and after the cruise.

The Midwater Assessment and Conservation Engineering (MACE) program of NOAA Fisheries, Alaska Fisheries Science Center (AFSC) conducted acoustic stock assessment surveys in the eastern Bering Sea (EBS) in summer of 2020 to estimate distribution and abundance of walleye pollock (Gadus chalcogrammus). This survey was initially intended as a ship-based survey, but this was cancelled due to the emerging COVID-19 pandemic. The survey was completed by three chartered 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 Alameda, CA on 13-14 May, conducted an acoustic survey of the Bering Sea from 4-20 August, and returned to Alameda on 4 October. The echosounder system was calibrated via the standard sphere method before and after the cruise.

The Midwater Assessment and Conservation Engineering (MACE) program of NOAA Fisheries, Alaska Fisheries Science Center (AFSC) conducted acoustic stock assessment surveys in the eastern Bering Sea (EBS) in summer of 2020 to estimate distribution and abundance of walleye pollock (Gadus chalcogrammus). This survey was initially intended as a ship-based survey, but this was cancelled due to the emerging COVID-19 pandemic. The survey was completed by three chartered 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 Alameda, CA on 13-14 May, conducted an acoustic survey of the Bering Sea from 4-20 August, and returned to Alameda on 4 October. The echosounder system was calibrated via the standard sphere method before and after the cruise.

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

Sikuliaq Cruise SKQ201711T (EM302)

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