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 (in port, Kodiak Island): 57o 47.0200′ N, 152o 25.5543′ W
Date: June 22, 2023
TAS Laura Guertin shows off her Teacher at Sea beanie aboard NOAA Ship OscarDyson
As we return to Kodiak, Alaska, for Leg 1 to wrap up and Leg 2 to begin of the 2023 Summer Survey, it’s exciting to know that even during our shortened expedition time at sea, we’ve collected data that is going to inform Alaska walleye pollock stock assessment models and catch allocation. Any/all data are good data to have! I have thoroughly enjoyed my time on Oscar Dyson and met some incredibly smart, passionate, kind, creative, and innovative people. The NOAA community is filled with amazing individuals that are not only dedicated to the NOAA science mission but then sharing that new knowledge with others. I’ve played a small part in this NOAA community during the expedition (while wearing my NOAA hat!), but I hope my future teaching and outreach efforts will shine an even brighter spotlight on the essential work carried out by NOAA Fisheries and the agency as a whole.
Prior to joining the ship, this past academic year was filled with some highs and lows in teaching and student learning. There’s one topic that I’m not quite sure how to classify – and that’s the emergence of Chat GPT, and how AI is being used in higher education. I was joking with the Instructional Designer at my campus (Penn State Brandywine) that I was going to write a sea shanty about this expedition. Turns out, he was able to get AI (Bing, specifically) to write one for me! So as I wrap up my time as a Teacher At Sea Alumna, I leave you with these versus to sing to your favorite shanty rhythm.
A Song of Pollock and Trawls
Oh we are the surveyors of the Gulf so vast and wide We sail the seas with acoustic gear to find the pollock hide We use sound waves to scan the depths and mark what we have found We measure their abundance and their biomass by the pound
(Chorus)
Yo ho ho as we sing this song On Leg 2 we’ll bring the DriX along Yo ho ho as we sing this song We love our job and we love our fish We love our job and we love our fish
We work in shifts around the clock to cover all the grounds We set the course and speed and time to trawl a certain length We haul the net and sort the catch and check their age and health We record all the data and we share it with the world
(Chorus)
We do this work for science and for management as well We help to keep the fishery sustainable and well We study the pollock’s life history, ecology, and stock We are proud to be part of this crew and this important work
(Chorus)
Oh we are the surveyors of the Gulf so vast and wide We sail the seas with acoustic gear to find the pollock hide We love our job and we love our fish We love our job and we love our fish
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
The Simrad FS70 on the back deck of Oscar Dyson (June 2023)
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.
Screenshot of the display returned by the FS70 during a trawl. The pink/yellow/blue line in the left column is where you see the bottom of the net. This is also represented in the middle column by the multi-colored horizontal line you see in the third circle from the center. (Screenshot from Leg 1 provided by Rick Towler).
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:
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.
Some CamTrawl footage from Leg 1 of 2023 Summer Survey.
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.
CamTrawl being detached from a trawl net after a mid-water trawl (June 16, 2023, on Oscar Dyson)
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).
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
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 18): 55o 15.3391′ N, 160o 17.8682′ W
Data from 2PM (Alaska Time), June 18, 2023 Air Temperature: 8.9 oC Water Temperature (mid-hull): 7.7oC Wind Speed: 4 knots Wind Direction: 182 degrees Course Over Ground (COG): 356 degrees Speed Over Ground (SOG): 12 knots
Date: June 19, 2023
Acoustic fisheries surveys seek to estimate the abundance and distribution of fish in a particular area of the ocean. In my case, this Summer Survey is looking at walleye pollock in the Gulf of Alaska. How is this accomplished? Well, it’s not through this method:
The Alaska walleye pollock is widely distributed in the North Pacific Ocean with the largest concentrations in the eastern Bering Sea. For this expedition, Oscar Dyson is traveling to specific regions in the Gulf of Alaska and running transects perpendicular to the bathymetry/contours (which are not always perpendicular to the shore) to take measurements using acoustics and targeted trawling to determine the abundance and distribution of walleye pollock which informs stock assessment and management models. For this blog post, let’s focus on how and why we can use acoustics to locate fish.
Walleye pollock (Gadus chalcogrammus) are distributed broadly in the North Pacific Ocean and eastern and western Bering Sea. In the Gulf of Alaska, pollock are considered as a single stock separate from those in the Bering Sea and Aleutian Islands. Image from Alaska Department of Fish and Game.An snapshot of a nautical chart with transects plotted. The first transect was run during Leg 1 on June 14 at the furthest location to the west, then the ship worked its way back east with approximately 40 nautical miles between transects. Once Oscar Dyson reached the Shumagin Islands, survey work shifted into this area..
Our story starts with the fish itself. Alaska walleye pollock have a swim bladder. The swim bladder is an internal organ filled with gas that allows a fish to maintain its buoyancy and stability at depth.
One interesting effect of the swim bladder is that it also functions as a resonating chamber that can produce and receive sound through sonar technology. This connection was first discovered in the 1970s, when low-frequency sound waves in the ocean come in contact with swim bladders and they resonated much like a tuning fork and return a strong echo (see WHOI’s Listening for Telltale Echoes from Fish).
Internal anatomy of a boney fish. From Wikipedia (CC BY-SA 3.0).
The sound pulses travel down into the water column, illustrated by the white cones here, and bounce back when encountering resistance.(from NOAA Fisheries)
NOAA Fisheries uses echo sounding, which works by emitting vertical pulses of sound (often referred to as pings), and measuring the return strength and recording the time for the signal to leave and then return. Anything having a different density from the surrounding water (in our case – fish, plankton, air bubbles, the seafloor) can return a signal, or “echo”.
The strength or loudness of the echo is affected by how strongly different ocean elements reflect sound and how far away the source of the element is. The seafloor usually makes the strongest echo because it is composed of rock which has a density different than the density of water. In fish, the swim bladder provides a contrast from the water. In addition, each fish species has a unique target strength or amount of sound reflected to the receiver. The size and shape of the swim bladder influence the target strength. There is a different target strength to length relationship for each species of fish – the larger the fish, the greater the strength of the returning echo.
It’s important to note that echo sounders cannot identify fish species, directly or indirectly. The only way we know which fish species is causing a signal is based on trawl catch composition. There is nothing within the acoustic data that lets us identify fish species, even with the catch data. This is a subtle, but important, distinction. Acoustic data, particularly calibrated acoustic data, in tandem with the information from the trawl, definitely allows us to count fish.
Where is the echo sounder on Oscar Dyson? Look at the figure in the next section of this post – it’s a sketch of NOAA Ship Rainier, but the placement of the echo sounder is the same for Dyson. You can see a rectangular “board” that is extended down from the center of the ship. This is called – what else – the center board! Attached to the bottom of the center board are the echo sounders. When lowered, the echo sounders sit at 9 meters below the level of the sea (~4 meters below the bottom hull of the ship).
Did you know… Southern Resident killer whales use their own echolocation clicks to recognize the size and orientation of a Chinook’s swim bladder? Researchers report that the echo structure of the swim bladders from similar length but different species of salmon were different and probably recognizable by foraging killer whales. (reported in Au et al., 2010)
It starts with a calibration
Typical setup of the standard target and weight beneath the echo sounder.(from NOAA Fisheries)
Before we can begin collecting data, we need to calibrate the echo sounder. The calibration involves a standard target (a tungsten carbide sphere) with a known target strength. The calibration needs to be completed in waters that are calm and without significant marine life for the best results.
The sphere is suspended below the ship’s hull using monofilament lines fed through downriggers attached to ship railings. One downrigger is in line with the echo sounder on the starboard side, and the other two on the port side. This creates a triangle that suspends the sphere in the center of the echo sounder’s sound beam. By tightening and loosening the lines, the sphere can be positioned under the center of the sound beam and can also be moved throughout the beam. By doing an equipment calibration at the beginning and end of a survey, we can ensure the accuracy of our data.
One of the port side downriggers
A weight that goes at the bottom of the filament to ensure the calibration sphere remains below the echo sounder
The tungsten carbide sphere attached to the line, being lowered over the side
Mission: 2023 Summer Acoustic-Trawl Survey of Walleye Pollock in the Gulf of Alaska
Geographic Area of Cruise: Islands of Four Mountains area, Western Gulf of Alaska Location (2PM (Alaska Time), June 14): 52o 30.9860′ N, 169o 08.0942′ W
Data from 2PM (Alaska Time), June 14, 2023 Air Temperature: 8.11 oC Water Temperature (mid-hull): 8.0oC Wind Speed: 8.27 knots Wind Direction: 243.96 degrees Course Over Ground (COG): 239.25 degrees Speed Over Ground (SOG): 13.05 knots
Date: June 15, 2023
I’m trained as a geologist and oceanographer. My teaching and research has focused on the physical sciences, which is why I’m so excited to have the opportunity to work with scientists in the life sciences. But before I start with the acoustic-trawl survey of walleye pollock, I had to do my homework – namely, learn something about this fish!
There is a wealth of resources on NOAA’s website that are providing me the introductory overview or “101” on pollock and the overall mission of maintaining sustainable fisheries. I started by viewing this NOAA video on Alaska’s Pollock Fishery: A Model of Sustainability.
This video shared so much but also generated so many more questions! I decided to take a step back and do a deeper dive into some of these topics, starting with the fish…
Alaska (walleye) pollock
Alaska pollock (Gadus chalcogrammus) on the sorting table, from NOAA Photo Library
NOAA Fisheries is doing an incredible volume of work in the Alaska region – including a focus on the Alaska pollock.
A member of the cod family, Alaska pollock (Gadus chalcogrammus) is also referred to as pollock, walleye pollock, and Pacific pollock. The NOAA Fisheries Species Directory for Alaska pollock states that Alaska pollock typically grow between 12 and 20 inches and weigh between 1 to 3 pounds. Their speckled coloring allows them to blend in with the seafloor to avoid predators such as Stellar sea lions, fish, seabirds – even older pollock will feed on juvenile pollock! Humans feed on pollock in products from fillets to fish sticks to surimi.
Alaska pollock are found throughout the North Pacific Ocean but are most common in the Bering Sea. Pollock migrate inshore to shallow water to breed and feed in the spring, then move back to warmer, deeper waters in the winter.
The word “fishery” is used in many ways. It can refer to the occupation, industry, or season for catching fish. It can also refer to the area of ocean where fish are caught, or the business of catching the fish. U.S. fisheries include commercial (catching/marketing fish and shellfish for profit), recreational (fishing for sport/pleasure), and subsistence (fishing for personal/family/community consumption or sharing.
Next, what is meant by sustainable fisheries? NOAA defines this in the following video and in the quote below:
“U.S. fisheries are big business, providing jobs and recreation and keeping our coastal communities vibrant. In fact, the United States is a global leader in responsibly managed fisheries and sustainable seafood. Working closely with commercial, recreational, and small-scale tribal fishermen, we have rebuilt numerous fish stocks and managed to create some of the most sustainably managed fisheries in the world. U.S. fisheries are scientifically monitored, regionally managed, and legally enforced under 10 national standards of sustainability. Managing sustainable fisheries is a dynamic process that requires constant and routine attention to new scientific information that can guide management actions.” — from NOAA Fisheries – Sustainable Fisheries
NOAA’s FishWatch website is a great place to find the most up-to-date information on popular seafood harvested or farmed in the United States. This helps each of us as consumers to make smart choices! Check out the page for the Alaska pollock to see the details available for this fish, currently classified as a smart seafood choice because it is “sustainably managed and responsibly harvested under U.S. regulations.” This is so important to note, as according to FishWatch, the Alaska pollock fishery is one of the most valuable in the world, with commercial landings of Alaska pollock from the Bering Sea and Gulf of Alaska in 2020 totaling more than 3.23 billion pounds and were valued at approximately $420 million.
Alaska pollock library of articles
Several articles on NOAA’s website were helpful in not only providing me more background information to prepare for my time on Oscar Dyson, but the content really showed me the context of what NOAA is doing for fisheries research/management and why it matters. My students probably recognize this as a list of articles I would give them to develop their current event literacy, as these are recent dates of publication and from a credible source (NOAA, of course!) – and of course, contribute to advancing their ocean literacy.
If you wish to learn more about the current state of Alaska pollock research with NOAA, I highly recommend these recent articles from NOAA Fisheries News & Announcements:
For podcast fans, this 2013 NOAA Fisheries podcast episode titled Keeping an Eye on Pollock is an excellent overview of how “scientists and fishermen work together to understand how walleye pollock respond to a changing environment” (transcript available online).
NOAA Fisheries podcast, Keeping an Eye on Pollock
In reviewing these articles and the podcast, it is clear that NOAA is focused on advancing the technology to survey Alaska pollock with new tools such as saildrones. There is also an interest in closely monitoring the impact climate change is having on the juvenile and adult populations of pollock (see the NOAA Fisheries site on Climate Change). This video, released January 2022, is a great snapshot of how NOAA Fisheries is preparing and responding to the impacts of climate change (link to web page that supports the video).
OK, I’m feeling good about my background on the “what” and “why” of Alaska pollock, and I hope you are, too! Next, it’s time to share the activities of the science team that is applying science knowledge and technology tools to studying pollock on Oscar Dyson!
Mission: 2023 Summer Acoustic-Trawl Survey of Walleye Pollock in the Gulf of Alaska Geographic Area of Cruise: Islands of Four Mountains area, Western Gulf of Alaska Location (in transit, location recorded on June 12 at 2PM (Alaska Time)): 56o 45.1227′ N, 155o 38.3353′ W
Data from 2PM (Alaska Time), June 12, 2023 Air Temperature: 7.72 oC Water Temperature (mid-hull): 6.8oC Wind Speed: 18.71 knots Wind Direction: 201.27 degrees Course Over Ground (COG): 207.53 degrees Speed Over Ground (SOG): 11.46 knots
Date: June 13, 2023
NOAA Ship Oscar Dyson as it docked in Kodiak, Alaska, on February 6, 2022
The journey of NOAA Ship Oscar Dyson begins as we are underway from Kodiak Island and head out along the Aleutian Islands.
Every NOAA ship has a name – but who is behind the name? I dedicate this blog post to Oscar Dyson (both Oscar Dysons, actually!)
Launched in 2003 and commissioned in 2005, the ship is named after Alaskan fisherman Oscar Dyson, a pioneer in Alaska’s fishing industry for half a century before his death in 1995. A well-known fishing activist and an industry advisor to government, Dyson was dedicated to improving the industry for the many Alaskans who make their living at sea. The ship is homeported in Kodiak, Alaska.
Peggy Dyson, wife of Oscar, christened the ship at its launch on October 17, 2003, in the VT Halter Marine shipyard in Moss Point, Mississippi. The first commanding officer was Commander Frank Wood.
Oscar Dyson (and Peggy!)
Oscar Dyson made an impact in Kodiak and across Alaska. I found a transcript of a Congressional Record read in 1995 less than two weeks after his passing with a detailed biography. There is a scholarship named for Oscar and his wife Peggy managed by the University of Alaska Fairbanks with a description I found online in 2022 that reads:
Oscar Dyson was a dedicated fisherman who turned his hobby into a business and his life’s work for 50 years. A Kodiak resident, Oscar had ample opportunity to partake in Alaska’s expansive fishing opportunities, but he also pioneered the crab fishing industry in Alaska. Oscar co-founded All Alaskan Seafoods (one of the largest seafood processing companies in the state) and built military bases during World War II …. The Oscar Dyson Memorial Scholarship was created in his honor and funded by numerous fishing and seafood companies within Alaska — a fitting homage to a man who did so much to develop Alaska’s marine economy. Oscar thought of himself — first, last and always — as a fisherman.
There is a dock in Kodiak named after Oscar Dyson with a marker to note his contributions and achievements (*photos taken by me as I spent some time exploring Kodiak in 2022)
Entrance sign for Oscar’s Dock
View of the dock
Memorial plaque for Oscar Dyson
View beyond Oscar’s Dock
And I’d like to give a shout-out to his wife Peggy, who made significant contributions of her own to the fishing community. Between 1965 and 2000, Peggy Dyson broadcast the marine weather from her house in Kodiak, twice a day over single sideband radio. She also reported sports scores and election results! The Kodiak Maritime Museum has a wonderful description of Peggy, including an audio clip of her voice, on their webpage, Peggy Dyson, Voice of the North Pacific. And NOAA Ship Oscar Dyson has a launch named Peggy D!
The launch Peggy D on NOAA Ship Oscar Dyson
NOAA Ship Oscar Dyson
The NOAA Oscar Dyson pulled into the Port yesterday. Homeported in Kodiak, Alaska, Oscar Dyson is the first in a class of ultra-quiet fisheries survey vessels built to collect data on fish populations, conduct marine mammal and seabird surveys, and study marine ecosystems. pic.twitter.com/zZ2gGzuYvd
NOAA Ship Oscar Dyson plays a major role in collecting data used in the management of Alaska pollock, one of the world’s largest commercial fisheries. At 208-feet in length with a cruising speed of 12 knots and an endurance of 40 days at sea, Oscar Dyson can support 24 crew and 15 scientists (*see additional Specifications). The six onboard laboratory spaces include: a wet lab, dry lab, electronics/computer lab, bio lab, acoustics lab and hydrographics lab. Oscar Dyson sails primarily in the Gulf of Alaska and Bering Sea.
I look forward to sharing more information about the ship and stories from my time at sea. But I don’t want to repeat the incredible work done by educators that sailed before me. Here are some excellent recent blog posts by other educators that have sailed on Oscar Dyson that describes everything from the facilities to the work involved on a fisheries survey:
View of NOAA Ship Oscar Dyson just as she docked in Kodiak, Alaska, on February 6, 2022
Old Ships, New Ships
The first NOAA ship I sailed on, Thomas Jefferson, started its life as US Naval Ship Littlehales. From January 1992 to January 2003, Littlehales recorded 85,018 hydrographic survey miles along the coast of Africa and in the Red Sea and Mediterranean Sea. Littlehales ended its time with the Navy and then renamed Thomas Jefferson and officially entered the NOAA fleet on July 8, 2003 (*see About Thomas Jefferson which also explains why the ship was named after the former U.S. president).
Oscar Dyson was new construction, the first of four planned 208-foot NOAA fisheries survey vessels.
In my first post, I mentioned how I’m reflecting upon this year being the 150+-year celebration of H.M.S. Challengerexpedition. Launched in 1858, Challenger was a small warship with cannons assigned to coastal patrols and to support larger ships in the British naval fleet, not built for a science expedition. Modifications to Challenger were funded by the British government through the navy to include laboratories and accommodations for six civilian scientists to join the 250 British Royal Navy sailors and officers for the 3+ year journey at sea. I could not find information on why the navy chose “Challenger” as the name of the ship – but this ship’s name was the inspiration for the NASA space shuttle, the lunar module on the Apollo 17 mission, the scientific ocean drilling vessel Glomar Challenger, and even Sir Author Conan Doyle is said to have named his recurring character Professor Challenger after this ship. (*information from Macdougall, 2019)
