NOAA Teacher at Sea
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, Western Gulf of Alaska
Location (2PM (Alaska Time), June 15): 53o 38.9534′ N, 166o 10.9927′ W
Data from 2PM (Alaska Time), June 15, 2023
Air Temperature: 8.74 oC
Water Temperature (mid-hull): 6.2oC
Wind Speed: 3.55 knots
Wind Direction: 310.61 degrees
Course Over Ground (COG): 64.09 degrees
Speed Over Ground (SOG): 11.61 knots
Date: June 16, 2023
One of the nine key focus areas for NOAA is research (https://research.noaa.gov/). Additional summaries about NOAA’s research activities can be found at NOAA Ocean Today. There are also numerous articles that describe the impact of NOAA’s research activities, such as Five ways NOAA’s research improves hurricane forecasts and other articles listed under Latest News and Features.
And now, it’s time for some science and surveying! Before I dive into the specifics of the methods we are carrying out on Oscar Dyson, I’m sharing this incredibly helpful NOAA Fisheries page that summarizes their Research Surveys, where “Our scientists and partners collect data on the water, from aircrafts, and from shore to understand the abundance, distribution, and health of marine life and habitats. That data forms the scientific foundation for our management and conservation work.”
There is also an informative podcast episode, Learn About NOAA Fisheries Surveys (transcript available at link). This podcast covers the need for sustainable fisheries, the 2013-2016 North Pacific Blob, how surveys were done historically, how surveys are using new technology, the impact of the pandemic, and the concept of being in a “stationary” versus “non-stationary” world. Such a fascinating listen!
There is another podcast episode from the same series that is an excellent follow-on from the episode available above. Surveying Alaska’s Waters (transcript available at link) shares how surveys are a tools that allow NOAA to reach its mission, whether those measurement techniques come from satellites, autonomous vehicles, buoys, ships, drones, etc. Although these tools assist NOAA scientists in collecting data, climate change is playing an even bigger role in making ecosystem management a moving target. Again – worth a listen!
Surveys in the Gulf of Alaska
Trawl surveys have been conducted by Alaska Fisheries Science Center (AFSC) beginning in 1984 to assess the abundance of groundfish in the Gulf of Alaska (2021 Stock Assessment Report, p. 9). Starting in 2001, the survey frequency was increased from once every three years to once every two years on odd-numbered years. This is a flyer that describes the biennial bottom trawl survey in the Gulf of Alaska 2023.
The website Alaska Fish Research Surveys includes field season research briefs going back to 2021. The 2023 field season includes a link to my current expedition, Summer Acoustic-Trawl Survey of Walleye Pollock in the Gulf of Alaska.
The strategy of combining trawl and acoustic surveys was developed by AFSC and the University of Washington. They published a paper in the Canadian Journal of Fisheries and Aquatic Sciences (Kotwicki et al., 2018) that discusses the need to perform acoustic-trawl (AT) and bottom-trawl (BT) surveys to accurately estimate the abundance of fish populations along with their spatial distribution. I’ve provided below part of a news release from the University of Washington describing the content of the publication:
Many species of fish spend some of the time on the ocean bottom, and some of their time far off the bottom, which makes them hard to survey. Acoustic surveys (that bounce sound off fish schools), can estimate the midwater component of so-called “semipelagic” fish, while trawl surveys can measure the portion on the bottom. Now a new method has been developed that combines data from both types of surveys into a single estimate using information about the environment (bottom light, temperature, sand type, and fish size). The new method has been used to assess the status of walleye pollock, which sustains the largest fishery in the United States.
This image from Kotwicki et al., 2018, does an excellent job of showing the two types of survey methods, acoustic and bottom trawling.
What is different for my current expedition is that we are not doing any bottom trawling. We are doing the acoustic piece of the survey and trawling off the bottom. Separate surveys and ships are collecting the bottom data, and then will be combined with our data to provide a more accurate snapshot for the water column for the annual Stock Assessment Report for Walleye Pollock. AT and BT surveys get NOAA to their research objective: informing fish stock assessment models and catch allocation. NOAA publishes an annual 100+page Assessment of the Walleye Pollock Stock in the Gulf of Alaska from the surveys conducted each year (see reports from 2019, 2020, 2021).
Check out this website if you are curious to see images from Bottom Trawl Surveys in Alaska. NOAA’s Groundfish Assessment Program regularly conducts bottom trawl surveys to assess the condition of groundfish and shellfish stocks in Alaskan marine waters).
1883 International Fisheries Exhibition
To prepare to sail on Leg 1 of the Summer Acoustic-Trawl Survey of Walleye Pollock in the Gulf of Alaska, I did a lot of reading and preparation so I could better understand what I would be learning, and how I could then connect the material with my students and additional audiences I see post-expedition. These two books in the image below helped give me a much better picture of not only walleye pollock but the fisheries industry, policy, and practices over time and space.
Each of these books provides some fascinating insight into the history, thought, and even debates, about the nature of ocean resources.
The title of Chapter 4 in Kurlansky’s book gives a hint for how to respond to my questions: “Being The Myth of Nature’s Bounty And How Scientists Got It Wrong For Many Years.” Early in the chapter, Kurlansky states:
“In the 1800s, when the study of fish and oceans was a relatively new science, it was the fishermen who were afraid that fish populations could be destroyed by catching too many fish, especially small fish. Scientists at the time believed that it was impossible to catch too many fish because fish produced so many eggs.” — World Without Fish, p. 53
One of the causes of concern for fishermen was the new technology developing – specifically, engine power, that allowed for even more fish to be caught.
There was a great historical debate on fisheries, too! London was the site of the Great International Fisheries Exhibition of 1883, where a debate about the ocean took place between British scientists Thomas Huxley and Edwin “Ray” Lankester. Huxley gave the inaugural address of the exposition – you can read it in its entirety online. Here are excerpts:
“I believe that it may be affirmed with confidence that, in relation to our present modes of fishing, a number of the most important sea fisheries… are inexhaustible… and probably all the great sea-fisheries, are inexhaustible; that is to say that nothing we do seriously affects the number of fish. And any attempt to regulate these fisheries seems consequently… to be useless.” (*feel free to dive into Huxley’s speech to see his reasoning – the multitudes of fish available, and the destruction is minimal)
Then Lankester gave the final summary speech of the Exhibition – a rebuttal to Huxley. Lankester made the point that the fish in the sea are not unlimited, and captured fish are not readily replaced by others that exist further offshore from the fishing location. He raised the concern that the removal of the parents by fishing was going to impact the production of the young.
Although at the time many gave Huxley the victory in this debate, Huxley did not take into account the new development that I mentioned above – the modern trawl and the steam trawler to pull it, resulting in larger nets and catches. It’s interesting to note that eventually, Huxley studied the impact from engine-driven net draggers and changed his story. Huxley eventually agreed that overfishing was not only possible, but that it was happening.
Now to circle back to why we survey fisheries… it ultimately comes down to ecosystem management. As described in the two audio files at the top of this blog post and in my other posts, as well as the title to Chapter 8 in Kurlansky’s book, “The Best Solution To Overfishing: Sustainable Fishing.” And to engage in sustainable fishing, you need the data to make that happen – hence, fisheries surveys!