NOAA Teacher at Sea
Laura Guertin
Aboard NOAA Ship Oscar Dyson
June 10 – June 22, 2023
Mission: 2023 Summer Acoustic-Trawl Survey of Walleye Pollock in the Gulf of Alaska
Geographic Area of Cruise: Islands of Four Mountains area, to Shumagin Islands area
Location (2PM (Alaska Time), June 19): 55o 30.9384′ N, 159o 47.6478′ W
Data from 2PM (Alaska Time), June 19, 2023
Air Temperature: 8.2 oC
Water Temperature (mid-hull): 6.8oC
Wind Speed: 18 knots
Wind Direction: 62 degrees
Course Over Ground (COG): 30 degrees
Speed Over Ground (SOG): 11 knots
Date: June 20, 2023
To conduct a fisheries survey or any oceanographic research expedition, there’s an enormous checklist of items you need on a ship. Jokingly, those on board will tell you that food and internet access are at the top of the list. But there’s no doubt that technology and its function, application, durability, etc., are critical during the time at sea. For example, see NOAA’s explainers for Ocean Exploration Technology: How Robots Are Uncovering the Mysteries of the Deep and Collecting and Visualizing Deep-Sea Data. For a broader look at the technologies NOAA uses to explore the ocean (vessels and submersibles, observing systems and sensors, communication technologies, and diving technologies), see Exploration Tools.
Leg 2 of this Summer Survey will be bringing on board the DriX, an uncrewed surface vehicle (USV), to see if this technology can improve the efficiency of collecting acoustic and biological data to estimate pollock abundance when working alongside Oscar Dyson. To read more/see a video, check out NOAA’s article, Uncrewed Surface Vehicles Complement NOAA Vessels for More Efficient Fisheries Surveys.
Trawl Sonar
Trawl sonar units are used to provide a rough estimate of how many fish are going into the trawl net. The device (which we’ve been using on our expedition, a Simrad FS70 nicknamed “the turtle”) is a third wire system that in real time establishes communication between the submerged sonar head and the bridge. On this cruise, the trawl sonar unit is placed on the headrope of the trawl net (i.e., on the top of the mouth of the net). It communicates its depth back to the ship. It also scans the mouth of the net and relays any acoustic images of things going into the net back to the ship. These data allow the scientists and crew to adjust the depth of the net and length of time the trawl net remains in the water to collect samples. Our goal is to collect enough fish (approximately one ton) to have a representative sample of the various species and lengths of fishes in the water column.
The Simrad FS70 makes an appearance in the NOAA video Alaska’s Pollock Fishery: A Model of Sustainability. NOAA Ship Bell M. Shimada uses this FS70 trawl sonar unit for Pacific hake acoustic trawl surveys (see article).
CamTrawl
One fascinating piece of technology we’re using on this pollock survey is the CamTrawl. This article I found will give you everything you would want to know about CamTrawl in a non-technical summary:
–> Developing 3D Stereo Camera Technology to Support Sustainable Fisheries (from NOAA)
Introduced in 2012, the CamTrawl is a stereo camera system when attached to a trawl net, can provide data about fish without ever touching a fish. This 3D imagery records fish passing by the camera towards the codend (the closed end of the trawl net), which provides species and size composition data as well as how fish behave in the trawl net to be collected from within a midwater survey trawl. CamTrawl is used to verify the trawl catch and specimen data, and in some cases, can be used to determine where in the water column the species entered the net. These data help inform ecosystem-based fisheries management.
The CamTrawl on Oscar Dyson for 2023 Summer Survey. The orange balls are flotation devices, the two “eyes” in the middle are the stereo camera and computer system, with the battery power across/under the eyes. The four round devices in the corner are lights used during the image recording. 
Top-down view of the CamTrawl. The front of the camera set-up is the wider side of the trapezoidal frame (top of image) which is then attached to the trawl net. 
Figure 1 from Williams et al. (2016). CamTrawl system description. 
CamTrawl attached to trawl net about to be set off the back of Oscar Dyson.
The CamTrawl has uses and applications beyond our walleye pollock survey. It can go to depths of the ocean where it is not possible to lower a trawl net and capture data on other fish species like the bottom-dwelling rockfish. CamTrawl can explore and map deep-sea corals, and there is potential for collaborative research with the fishing industry.
The CamTrawl was developed by NOAA scientists Kresimir Williams and Rick Towler (both of whom I’m sailing with on Oscar Dyson for Leg 1). I feel incredibly fortunate to have sailed with these two scientists and to hear how NOAA encourages their researchers to be creative and experiment with developing technologies to advance NOAA’s overall mission and expedition objectives.
Curious to see more? Check out this Salmon shark caught on CamTrawl underwater camera. Below is a picture of a salmon shark from the Shumagin Islands, Alaska area in February 2017 (photo provided by Sarah Stienessen).
Additional sources for exploration:
Using AI and 3D stereo cameras to support fisheries (National Fisherman, March 12, 2023)
Boldt et al. (2018). Development of stereo camera methodologies to improve pelagic fish biomass estimates and inform ecosystem management in marine waters. Fisheries Research, 198. https://doi.org/10.1016/j.fishres.2017.10.013
Williams et al. (2018). A method for computing volumetric fish density using stereo cameras. Journal of Experimental Marine Biology and Ecology, 508. https://doi.org/10.1016/j.jembe.2018.08.001
Williams et al. (2016). Automated measurements of fish within a trawl using stereo images from a Camera-Trawl device (CamTrawl). Methods in Oceanography, 17. https://doi.org/10.1016/j.mio.2016.09.008
