Author: Nick Lee

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Nick Lee: Finding Fish, July 6, 2024

NOAA Teacher at Sea
Nick Lee
Aboard NOAA Ship Oscar Dyson
June 29 – July 20, 2024

Mission: Pollock Acoustic-Trawl Survey

Geographic Area of Cruise: Eastern Bering Sea

Date: July 6, 2024

Weather Data from the Bridge:

Latitude: 61° 15.0 N

Longitude: 174° 56.8 W

Wind Speed: 13 knots

Air Temperature: 5.3° Celsius (41.5° F)

Science and Technology Log:

On NOAA Ship Oscar Dyson, the science party’s mission is to understand the population of walleye pollock in the Eastern Bering Sea. To collect data, scientists rely on two main tools: acoustics and targeted trawling. Before any trawling can happen, scientists must first locate fish using acoustics, so I’ll be focusing on acoustics in this blog post – stay tuned for a post on trawling next time!

Scientists use two kinds of acoustics: active and passive. Many of my students are familiar with how bats use echolocation to navigate in the dark – active acoustics relies on the same principle. First, the echosounder on the ship emits a pulse of sound, or ping. This sound travels through the water and bounces off of objects that have different densities than water (such as fish, krill, or the ocean floor). The echosounder then “listens” for and records these echoes, also known as backscatter. Passive acoustics work similarly, except the echo sounder only listens for sound and doesn’t emit any itself.

illustration of a pulse of sound, depicted as a triangle, emanating from the bottom of a ship at the surface of the ocean. the triangle encompasses some of the sea creatures swimming by (depicted as simple white silhouettes) and ends at the ocean bottom.
The echosounder emits a pulse of sound, which gets reflected by objects of different densities, like pollock. Image Credit: Wieczorek, Schadeberg, Reid (2021) “How do Scientists Use Sound to Count Fish in The Deep Sea?” Frontiers for Young Minds. https://kids.frontiersin.org/articles/10.3389/frym.2021.598169

The greater the distance between the echo sounder and the object reflecting the pulse, the greater the amount of time between when the signal was emitted and backscatter. Based on this time, echosounder can determine the depth of the object producing the backscatter. This information is represented visually in an echogram:

Screenshot of an echogram. Backscatter is depicted as colored dots on a grid. in this case, the dots are densest and darkest at the shallowest depths (the ship bottom) and the deepest depths (the hard ocean botttom)
Screenshot of an echogram. The space between vertical grid lines represents 100 pings, and the space between horizontal grid lines represents 10 meters of depth.

The echogram shows depth on the y-axis and time on the x-axis. The intensity of backscatter is color-coded, where more intense backscatter is represented with red and brown, and less intense backscatter is represented with blue and green. The vertical grid lines represent all the backscatter from one ping, and the space between lines represent 100 pings.

On the cruise, pings are typically emitted at a rate of 1 Hz, or once every second. With every new ping, the echo sounder adds data to the right end of the echogram. This means that the horizontal grid lines represent the backscatter at one depth over time (or distance, if the ship is traveling at a constant speed).

At least one scientist monitors the backscatter throughout the duration of the transect. During the first day, the echogram was blank except for some lower-intensity backscatter near the surface and high-intensity reflection from the ocean floor. Because the mission of this cruise is to survey pollock, which tend to live at greater depths, we don’t pay much attention to the backscatter near the surface which is comprised of smaller organisms like krill. However, when scientists notice backscatter consistent with scattering from pollock, they may trawl to collect a sample for more detailed biological information.

Screenshot of two echograms showing low-intensity backscatter and high-intensity backscatter.
Echograms from two different locations showing low-intensity backscatter (left) and high-intensity backscatter (right). When the backscatter looks as it does on the right, the science team may decide to fish in that area.

As we traveled along the first transect line, there was very little backscatter that the science team thought represented pollock. Our CTD (conductivity, temperature, depth) measurements also showed that the water temperature was cold, right around freezing. This may suggest that we were traveling through the Bering Sea cold pool, a mass of cold water that forms from melting ice. This water tends to be too cold for pollock and other fishes, however, other animals, such as snow crabs, can still survive the lower temperatures. Fish like cod prey on snow crab, so the cold pool offers these crab an important refuge from predators. Read more about the importance of the cold pool for crab here!

GIF showing historical bottom temperatures in the Bering Sea from 1983 to 2018. The years 2015, 2016, and 2018 are notably warm.
Historical bottom temperature showing cold pool in blue / purple (Image Credit: NOAA Fisheries)

Personal Log:

The start of the cruise has been busy learning new faces, maritime practices, and scientific terms. However, in the past few days, with the help of meclizine (seasickness medication), I’ve begun to feel more settled and like I have some sense of routine.

When I’m on shift, I bounce around between a few different places. The science team tends to be in the acoustics lab, where we monitor backscatter and make decisions on when to fish.

Photo of the acoustics lab. Computers and many computer screens mounted on the wall above a long desk.
Acoustics lab, also called “the cave” for its lack of windows.

Once the scientists decide to fish, we first go up to the bridge, where NOAA officers control the direction and speed of the ship. The bridge has windows on all sides, so we’re able to make sure there are no marine mammals before putting the net in the water.

From the bridge, you can also see the trawl deck, where the deck crew works in collaboration with NOAA officers to put the net in the water. Once the fish are caught and hauled back to the ship, the science team processes the catch in the fish lab.

Photo of the bridge. Navigation computers surrounded by windows.
Photo of the trawl deck. Unspooled trawl net visible in A-frame.
The bridge and its view of the trawl deck.

When we’re not working, we’ll grab food from the galley / mess deck. The stewards on the ship serve three meals a day, but since I’m on the night shift, I often heat up leftovers or take advantage of the wide selection of snacks they leave out. There’s also a lounge, two gyms, and places to do laundry while at sea!

Photo of the galley, the ship's cafeteria. Tables and chairs, a refrigerator. Chair legs are capped with tennis balls to reduce sliding.
The galley, where food is available 24 hours a day!

Did you know?

NOAA Ship Oscar Dyson  has six onboard laboratories including a wet lab, dry lab, electronics lab, bio lab, acoustics lab, and hydrographics lab. Read more about the ship here!

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Nick Lee: First Days at Sea, July 2, 2024

NOAA Teacher at Sea

Nick Lee

Aboard NOAA Ship Oscar Dyson

June 29 – July 20, 2024

Mission: Pollock Acoustic-Trawl Survey

Geographic Area of Cruise: Eastern Bering Sea

Date: July 2, 2024

Weather Data from the Bridge:

Latitude: 59° 54.8 N
Longitude: 171° 54.9 W
Wind Speed: 14 knots
Air Temperature: 5.0° Celsius (41° F)

Science and Technology Log:

We’ve been sailing for just under two days, and I’ve already had an opportunity to witness lots of science aboard NOAA Ship Oscar Dyson! 

We spent the first day transiting to the start of the survey – I am part of Leg 2 for this cruise, and so we are picking up where Leg 1 left off. Since we won’t be able to find every pollock in the Bering Sea, we will need to rely on a representative sample, and then our data will be used to estimate the total stock.

The map below shows the intended path of our cruise, and the vertical lines represent transects, or lines along which we will collect data, spaced 40 nautical miles (or 74 km) apart so that we can cover the entire region with the time we have. Since we just recently arrived at the start of our survey, I’m still learning about the different data the science team will be collecting – more on that in a future blog post!

nautical chart of the Bering Sea, showing the land of Alaska to the east and a portion of Russia in the northwest. The cruise trajectory is overlaid in bold blue or red lines, with north-south transects connected by shorter westward connections. The blue transects start in Dutch Harbor and head west; the red transects are farther west
Map of the survey with the portion that I’ll be participating in shown in red, and the portion that has already been completed in blue.

On our way to our survey site, I was able to launch a drifter buoy through NOAA’s Adopt-a-Drifter Program. Unlike some other buoys, a drifter buoy is not fixed to the ocean floor. Instead, they float and “drift” with the ocean currents. Importantly, drifters are equipped with some sort of drogue – an underwater anchor. This way, the surface float (and the drogue) will move with ocean currents, but won’t be influenced as much by wind.

illustrated diagram of a drifter buoy. a white ball floats at the water line; this is labeled "Surface float - designed for moving on the surface with currents." The float has an Antenna, labeled: "the drifters transmit the data they collect as well as their position via satellite." Data is depicted as a gray triangle extending up from the antenna to a satellite in the sky, which is communicating with a satellite dish on land. Beneath the float, down into the water, extends a black cable, thicker toward the float. It's labeled: "Sensors: Sea Surface Temperature sensor and various measuring systems." The cable connects to what appears to be gray cylindrical tube, waving in the water labeled "Drogue: The buoys have some form of subsurface drogue or sea anchor."
Drifter Buoy diagram (Image Credit: NOAA Adopt a Drifter Program)

Deploying a drifter is as simple as dropping it into the ocean! I was able to deploy our first drifter last night off the stern (back of the ship). Our drifter was wrapped in biodegradable packaging for a safe deployment, but once in the water it should have opened up and extended to its full length.

a repeating video clip of Nick starting to toss the drifter buoy over the rail of NOAA Ship Oscar Dyson. he is wearing a helmet and a life vest, and looking away from the camera.
Deploying an ocean drifter.

Once deployed, the drifter transmits its location via satellite, and scientists are able to use this data to better understand ocean currents. You can track my drifter’s trajectory here!

In addition to a GPS that tracks location, drifters are often equipped with sensors for temperature, pressure, salinity, and more. Below is the path my drifter took in its first day after deployment, and the sea temperatures it encountered.

a map of a small section of the ocean between 191.2 to 192.0 degrees W and 55.4 to 56.2 degrees N. A series of colored squares form a small spiral in the middle; the squares range in color from orange to purple. Beneath the map there's a key explaining that the colors indicate temperature, ranging from purple (6 degrees Celsius) to red (7 degrees Celsius.)
Drifter trajectory and sea surface temperature.

I also was able to observe the deployment of a CTD (conductivity, temperature, and depth) sensor. CTD measure some of the same properties as drifters, but CTDs are lowered down into the water and then raised back into the boat. This means that CTDs only collect data at one geographic location at a time, however, they collect data throughout the entire water column, from the surface down to the ocean floor (~80 meters at our last deployment). CTDs can also collect water samples at different depths, allowing scientists to study them further. NOAA has a great resource on CTDs here!

view of the conductivity, temperature, and depth probe (in the center of a cylindrical metal apparatus) suspended from a cable just beyond the railing of the ship; it is about 10 feet above the ocean's surface at this point. in the distance, the sky is gray and cloudy, and the ocean is gray and calm.
CTD being lowered to collect data.

Personal Log:

When I applied to NOAA’s Teacher at Sea Program, I was told that one thing that was required of all its participants was flexibility. This is especially true for cruises leaving from Dutch Harbor, where bad weather and flight cancellations are common. On this leg, a series of travel delays meant that we left port a day later than expected. However, this meant that I was able to spend some time exploring Dutch Harbor!

Dutch Harbor is one of the most remote and beautiful places I’ve ever visited. During my wanderings around the town, I spotted whales, a fox, and plenty of bald eagles. Alaska’s military history is also apparent in the hills surrounding Dutch Harbor, which are full of World War II bunkers.

view of calm blue ocean waters from a green hillside; in the distance, two ships are visible
view under the archway of a bunker - there's sand underneath and open vegetation beyond
a bald eagle perches on driftwood on the beach
Views from Dutch Harbor (left), inside a World War II bunker (center), and one of many bald eagles (right).

Since we left port, there’s been a lot to adjust to about living on a ship. The ship is a bit of a maze – lots of narrow hallways and hidden staircases. After making a lot of wrong turns, I’m starting to get a sense of the layout.

Work happens on the ship at all hours of the day – I’ve been assigned the night shift (4 pm – 4 am), so as a natural morning person, I’ve completely changed my sleep schedule! Because someone is always working, that also means that someone is always trying to sleep, so I’ve learned to be careful about not letting doors slam behind me.

view of a stateroom: two berths (bunk beds), a chair, a window with curtains, a hiking backpack and a bag.
My stateroom for the next three weeks.

This morning, we practiced our first set of safety drills. To simulate what would happen if we needed to abandon ship, everyone was required to don a survival suit (also called a “Gumby suit”). It was quite a process to put on the suit – luckily one of the other scientists, Mike, gave me some pointers ahead of time!

Nick poses, thumbs up, for a photo in the survival suit; it covers his mouth and nose
Gumby suit

I’m looking forward to learning more about life at sea over the next few weeks!

Did You Know?

NOAA Ship Oscar Dyson was named after an Alaskan fisherman and activist who worked to improve the industry for other Alaskans (https://www.omao.noaa.gov/marine-operations/ships/oscar-dyson )

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Nick Lee: Teacher at Sea Introduction, June 21, 2024

NOAA Teacher at Sea
Nick Lee
Aboard NOAA Ship Oscar Dyson
June 29 – July 20, 2024

Mission: Pollock Acoustic-Trawl Survey

Geographic Area of Cruise: Eastern Bering Sea

Date: June 21, 2024

Introduction:

Hello! My name is Nick Lee, and I am excited to be one of this year’s Teachers at Sea! I teach 11th/12th Grade Environmental Science and Computer Science at Codman Academy Charter Public School, located in Dorchester, MA (a neighborhood of Boston).

Nick stands on a small boat, wearing a life vest and holding a scientific instrument, probably one that measures water chemistry. We can see calm water surrounding the boat and a semi-developed shoreline not far in the distance.
Photo Credit: Ed Yoo

I love teaching Environmental Science, because I’m able to take students outside of the classroom on fieldwork (at Codman, we call academic field trips ‘fieldwork’). We have studied the trees in our schools microforest, visited local farms, and explored different parts of the Greater Boston coastline. This past year, we were fortunate to work with the Cohasset Center for Student Coastal Research, a partnership that allowed us to take students out on the water and collect samples in the intertidal zone.

Two students, wearing hoodies with the hoods obscuring their faces, stand in the seaweed wrack on a shoreline holding large white buckets. One is dipping the bucket into the water to take a sample, while the other, wearing a life vest, waits nearby. We see a small white skiff with an outboard motor, anchored in the water, in the far corner of the photo.
Environmental Science exploring the intertidal zone at the Cohasset Center for Student Coastal Research (Photo Credit: Ed Yoo)

My students even had the opportunity to build an ocean drifter, which helps scientists track currents and marine debris. A local fisherman helped us launch the drifter, and we’ve been tracking its movement off the coast of Massachusetts (you can find its current location here: https://studentdrifters.org/tracks/drift_stonehill_2024_1.html). I’ll hopefully be launching another drifter in the Eastern Bering Sea this summer, and next year’s students will be able to compare the paths the two drifters take.

a Google Earth aerial view of the coast of Massachusetts with two trajectories displayed in white and teal lines around the water; the trajectory lines are very squiggly, indicating that the buoys spent a while circling in the bay before clearing the "hook" of Cape Cod.
Path of Codman’s Ocean Drifter (white) as of June 21, 2024

I’m looking forward to learning more about marine science this summer, and I hope to bring back as much knowledge as possible for my students!

Science and Technology Log:

In a little over a week, I will be sailing aboard NOAA Ship Oscar Dyson as part of the science team on a pollock survey. Just getting to NOAA Ship Oscar Dyson will be an adventure – I’ll be flying from Boston to Seattle, Seattle to Anchorage, and then Anchorage to Dutch Harbor! 

starboard view of NOAA Ship Oscar Dyson (R 224) underway
NOAA Ship Oscar Dyson (Photo credit: NOAA)

I’ve already been in touch with two members of the science team: Abigail McCarthy and Robert Levine. Both were kind enough to send me some reading to learn about the ship’s mission – there’s a lot of new terms but I’m starting to get a better picture of what we’ll be doing!

We will be sailing on a Midwater Assessment and Conservation Engineering (MACE) survey, collecting data on primarily walleye (Alaska) pollock. Most of my job will be to help process the fish in the trawl catch, recording data like fish species, length, and age. The data we collect will help scientists learn more about the current pollock population in the Eastern Bering Sea, ultimately informing the quotas (limits) set for commercial fishing operations. 

a scientific illustration of an Alaska pollock, showing the characteristic three dorsal fins
Alaska pollock, also known as walleye pollock. (Photo credit: NOAA)

This process is crucial to prevent overfishing – in 2022 commercial fishermen caught over 2.7 billion pounds of Alaska pollock (valued at $316 million) from the Bering Sea and Gulf of Alaska. (https://www.fisheries.noaa.gov/species/alaska-pollock). While these numbers may seem high, careful management has kept commercial pollock fishing operations sustainable. In fact, NOAA calls US wild-caught Alaska Pollock a “smart seafood choice because it is sustainably managed and responsibly harvested under U.S. regulations” (https://www.fisheries.noaa.gov/species/alaska-pollock/seafood).

I’m grateful for the opportunity to be a part of such important work for the future of our oceans and fisheries!

Personal Log:

I am originally from St. Louis, Missouri, far from the ocean. However, since I’ve been teaching environmental science in Boston, I’ve had the opportunity to learn more about our planet’s oceans and the importance of protecting them.

Last year, through the generous support of the Pat Cooke Foundation, I was able to travel to the Netherlands, where I spent two weeks working with a small-scale fishing company. There, I was able to catch wild oysters and sea bass, and participate in all steps of seafood production, from catching and processing fish to selling direct to consumers in restaurants and markets. I also learned how most fish we buy in supermarkets change hands many times, sometimes traveling across the world for days or even weeks before being purchased by the consumer. This experience has made me passionate about sustainable seafood – recently, I’ve been trying to buy only seafood local to Massachusetts and New England.

Nick stands on the back of a fishing vessel in the ocean; land is only barely visible at the horizon far in the distance. He's wearing a long sleeved shirt, gray fishing overalls, boots, black gloves, and a hat. In his left hand he grasps three fish by their gills. Behind him on the deck we see crates for holding fish. The sky is partially clouded in lovely shades of blue, pink, and purple.
Last summer, I worked with a small-scale fishing company in the Netherlands that caught and sold wild oysters and sea bass.

I’m excited to be back working with fish this summer, and I’m looking forward to learning more about sustainable fishing from the scientists and crew aboard NOAA Ship Oscar Dyson.

Did You Know?

Many fish, birds, and mammals including Steller sea lions depend on Alaska pollock as a food source (https://www.fisheries.noaa.gov/species/alaska-pollock/overview).