Kathleen Harrison: First Trawl, July 7, 2011

NOAA Teacher at Sea
Kathleen Harrison
Aboard NOAA Ship  Oscar Dyson
  July 6– 17, 2011

Location:  Gulf of Alaska
Mission:  Walleye Pollock Survey
Date: July 7, 2011

Weather Data from the Bridge
True Wind Speed:  18.7 knots
True Wind direction:  145.55°
Sea Temperature:  8.12° C
Air Temperature:  9.65° C
Air Pressure:  1013.2 mb
Ship’s Heading:  299°, Ship’s Speed:  11.8 knots
Latitude:  54.59°N, Longitude:  145.55°W

Science and Technology Log
The primary mission of the Oscar Dyson Walleye Pollock Survey is to estimate the biomass (mass of the living fish) of the Pollock in the Gulf of Alaska.  Read about why Pollock are important here:  Pollock    Now, you can’t exactly go swimming through the Gulf of Alaska (brrrr) and weigh all of the fish, so the NOAA scientists on board use indirect methods of measuring the fish to come up with an estimate (a very accurate estimate).  Two of these methods include using nautical charts, and trawling.

Nautical charts are used for navigation, and location.  The Oscar Dyson has several systems of charts, including electronic and paper.  Each chart contains latitude, longitude, and ocean depth, as well as lands masses and islands.  A chart that shows ocean depth is called a bathymetric chart.

bathymetric map

Here is a bathymetric map for part of the Gulf of Alaska. The change in color from green to blue shows the edge of the continental shelf.

These need updating continually, because the sea floor may change due to volcanic eruption or earthquakes.  The Officer of the Deck (OOD, responsible for conning and navigating the ship) needs to know how deep the ship sits in the water, and study the bathymetric charts, so that the ship does not go into shallow water and run aground.  The lines on the bathymetric chart are called contour lines, depth is shown by the numbers on the lines.  Sometimes every line will have a number, sometimes every 5th line will have a number.   A steep slope is indicated by lines that are close together, a flat area would have lines that are very far apart.  The OOD also need to know where seamounts (underwater volcanoes) and trenches (very deep cracks in the ocean floor) are because these may affect local currents.  GPS receivers are great technology for location, but just in case the units fail, and the ship’s technology specialist is sick, the OOD needs to know how to use a paper chart.  He or she would calculate the ship’s position based on ship’s speed, wind speed, known surface currents, visible land masses, and maybe even use star positions.  Here in Alaska, star position is helpful in the winter, but not in summer.  (Do any of my readers know why?)

The Oscar Dyson’s charted course follows a series of parallel straight lines around the coast of Kodiak Island, and other Aleutian Islands.  These are called transects, and allows the scientists to collect data over a representative piece of the area, because no one has the money to pay for mapping and fishing every square inch.

The Chief Scientist on the Oscar Dyson is always checking our location on the electronic chart at his desk.  It looks something like this:

map of transects, Gulf of Alaska

This chart shows some of the transects for the Oscar Dyson in the Gulf of Alaska.

Several things are indicated on this chart with different symbols:  the transect lines that the ship is traveling (the straight, parallel lines), where the ship has fished (green fish), where an instrument was dropped into the water to measure temperature and salinity (yellow stars), and various other ship activities.  It also shows the ocean depth.  This electronic version is great because the scientists can use the computer to examine a small area in more detail, or look at the whole journey on one screen.

They can also put predicted activities on the map, and then record actual activities.  The scientists also use several systems for the same thing;  recording the ship’s path and activities in the computer, as well as making notes by hand in a notebook.

When the scientists want to catch fish, they ask the crew to put a trawling net into the water.  The basic design of the trawl is a huge net attached to 2 massive doors.

otter trawl

This is the basic design for a trawl net, showing the doors that hold the net open, and the pointed end, where the fish are guided, called the cod end.

The doors hold the net open, as it is dragged behind the boat.  There are 2 different trawling nets aboard the Oscar Dyson:  one that trawls on the bottom called the PNE (Poly Nor’Easter), and one that trawls midway in the water column called the AWT (Aleutian Wing Trawl).  Another net called the METHOT can be used to collect plankton and small fish that are less than 1 year old.  The scientists determine the preferred depth of the net based on the location of fish in the water column; the OOD gets the net to this requested depth and keeps it there by adjusting the ship’s speed and the amount of trawl warp (wire attached to the net).
A trawl typically lasts 15 – 20 minutes, depending on how many fish the scientists estimate are in the water at that point (more about this later).  Today, a bottom trawl was performed, and 2 tons of fish were caught!  The net itself weighs 600 pounds, and is handled by a large crane on the deck at the stern (back) of the ship.  Operating the trawl requires about 6 people, 3 on the deck, and 3 on the bridge at the controls.  When the scientists judge that there are the right amount of fish in the net, it is hauled back onto the deck, weighed, and is emptied into a large table.

poly nor'easter

Here is the PNE being weighed with the cod end full of fish.

Then the scientists (and me) go to work:  sorting the fish by species into baskets, counting the fish, and measuring the length of some of them.  NOAA technology specialists have designed a unique data collection system, complete with touch screens.  A fish is placed on a measuring board, and the length is marked by a  magnetic stylus that is worn on the finger.  The length is automatically recorded by the computer, and displayed on a screen beside the board.  I measured the length of about 50 Atka Mackerel after the first trawl.

using the measuring board

In the fish lab, this mackerel is having his length measured. The data goes directly into the computer, and shows up on the screen in front of me.

By sampling the fish that come up in the trawl net, the scientists can estimate the size of the population.  Using the length, and gender distribution, they can calculate the biomass.

Personal Log
Some great things about living on the Oscar Dyson:  the friendly and helpful people, the awesome food, the view from the bridge.

Some challenging things about living on the Oscar Dyson:  taking a shower, putting on mascara, staying in bed while the ship rolls.

I started my 12-hour shifts, working from 4 am to 4 pm.  Well, maybe working is not the right word, I actually worked about 3 hours, and asked a lot of questions during my first shift.  The scientists are very patient, and explain everything very well.  We did one trawl today, and it was a good one.  I enjoyed sorting and counting the fish, and then measuring the length of them.  I will probably take a shower, eat dinner, and read for a short time before climbing into bed.  I have the top bunk, and it is plenty of room, except I can’t sit up straight.  Here is a picture of the stateroom.  After my shift, I will probably take a shower, eat dinner, watch a movie and fall asleep around 8:30.

view of my room

Standing at the door, this is the view into my stateroom. The bunks are on the right, the desk and closets are on the left. There is a tiny bathroom, as well as a small refrigerator.

The weather today has been windy, so there are 6 – 8 foot swells, and the ship is rolling a bit.  I have not been seasick yet – yippee!  The wind is supposed to calm down tomorrow, so hopefully we will have a smoother ride tomorrow night.

I learned the difference between pitch, roll, and heave:  pitch is the rocking motion of the ship from bow to stern (front to back), roll is the motion from side to side, and heave is the motion up and down.  The Oscar Dyson is never still, demonstrating all 3 motions, in no particular pattern.  Imagine standing in a giant rocking chair, and someone else (that you can’t see) is pushing it.

Here is a view from the bridge:

from the aft deck

View from the deck in front of the bridge, showing a gyrorepeater (the white column on the right), and a windbird (anemometer and wind vane) on top of the forward mast. You can also see a horizontal black bar in the center of the picture - that is the provisions crane.

Species seen today:
Northern Rockfish
Dusky Rockfish
Walleye Pollock
Pacific Ocean Perch
Kelp Greenling
Atka Mackerel
Pacific Cod
Fanellia compresson (octocoral)
Sea Urchin
Kelp

Kathryn Lanouette, August 1, 2009

NOAA Teacher at Sea
Kathryn Lanouette
Onboard NOAA Ship Oscar Dyson
July 21-August 7, 2009 

Mission: Summer Pollock Survey
Geographical area of cruise: Bering Sea, Alaska
Date: August 1, 2009

This sonar-generated image shows walleye pollock close to the sea floor. The red line at the bottom of the image is the sea floor. The blue specks at the top of the image are jellyfish floating close to the water’s surface.

This sonar-generated image shows walleye pollock close to the sea floor. The red line at the bottom of the image is the sea floor. The blue specks at the top of the image are jellyfish floating close to the water’s surface.

Weather Data from the Ship’s Bridge 
Visibility: 10+ nautical miles
Wind direction: variable
Wind speed:  less than 5 knots, light
Sea wave height: 0 feet
Air temperature: 7.9˚C
Seawater temperature: 8.6˚C
Sea level pressure: 30.1 inches Hg
Cloud cover: 7/8, stratus

Science and Technology Log 

In addition to the Aleutian wing trawl (which I explained in Day 5 NOAA ship log) and Methot (which I explained in Day 8 NOAA ship log), scientists also use a net called an 83-112 for bottom trawls. The 83-112 net is strong enough to drag along the sea floor, enabling it to catch a lot of the animals that live in, on, or near the sea floor. This afternoon, we conducted the first bottom trawl of our cruise. Bottom trawls are usually conducted in two situations: if the walleye pollock are too close to the sea floor to use an Aleutian wing trawl or if the scientists want to sample a small amount of fish (because the 83-112’s net opening is smaller than the Aleutian wing trawl’s net). From the looks of the sonar-generated images, it appeared that most of the walleye pollock were swimming very close to the bottom so the scientists decided it would be best to use the 83-112 net.

Here I am holding one of the skates that was caught in the bottom trawl

Here I am holding one of the skates that was caught in the bottom trawl

Once the fish were spotted, we changed our course to get ready to trawl. Usually the trawl is made into the wind for stability and net control. Once the ship reached trawling speed, the lead fisherman was given the “OK” to shoot the doors. Slowly, the net was lowered to 186 meters below the surface, the sea depth where we happened to be. The water temperature down there was about 1˚C (compared to 7˚C on the sea’s surface).  I had heard from a previous Teacher At Sea that bottom trawls brought up a wide variety of animal species (compared to the relatively homogenous catches in mid-water trawls). And sure enough, when the net was brought up, I couldn’t believe my eyes!

All told, we sorted through over 7,000 animals, a total of 36 different species represented in the total catch. It took 4 of us over 4 hours to sort, measure, and weigh all these animals. There were over 350 walleye pollock in this catch as well as skates, octopi, crabs, snails, arrowtooth flounder, sea anemones, star fish, and dozens of other animals. Some of them were even walking themselves down the table.

During this catch, I also learned how to take the ear bones, or otoliths, out of a walleye pollock. Why ear bones you might ask? Using the ear bones from a walleye pollock, scientists are able to determine the exact age of the fish. Misha Stepanenko, one of the two Russian scientists on board the Oscar Dyson, showed me how to cut partially through the fish’s skull and take out two large ear bones. Once they were taken out, I put them in a solution to preserve them. Back in NOAA’s Seattle lab, the ear bones are stained, enabling scientists to count the different layers in each ear bone. For every year that the fish lives, a new layer of bone grows, similar to how trees add a layer for each year that they live. By learning the exact age of a fish, scientists are able to track age groups (called “cohorts”), allowing more precise modeling of the walleye pollock population life cycle.

A diagram of an otolith, or ear bone, of a fish.  You can see that it’s a lot like looking at tree rings!

A diagram of an otolith, or ear bone, of a fish. You can see that it’s a lot like looking at tree rings!

Personal Log 

So far this trip, we have sailed within 15 miles of Cape Navarin (Russia) on at least two different occasions but fog and clouds prevented any glimpse of land both times. It was a frustrating feeling knowing that land was so close, yet impossible to see. After 12 days of looking at nothing but water and sky, seeing land would have been a welcome treat.

Despite not seeing land, I still felt like I was in Russia just from listening to different fishing vessels communicate with one another. On our first night in Russian waters, we sailed through a heavy fog, with 7 or 8 different boats fishing nearby. I was impressed with how Ensign Faith Opatrny, the Officer on Deck at the time, communicated with various vessels, using collision regulations (“the rules of the road”) to navigate safely. On a culinary note, I got my first chance to eat some of a catch. After most trawls, we discard remaining inedible specimens overboard. After our bottom trawl however, one of the scientists filleted some of the cod. The next day, the stewards cooked it up for lunch. It tasted great and it felt good to be eating some of the fish that we sampled.

A graph showing the adult walleye pollock biomass estimates from 1965 to 2008.

A graph showing the adult walleye pollock biomass estimates from 1965 to 2008.

As the cruise starts to wind down, I also want to express my gratitude to all the NOAA scientists and Oscar Dyson crew. Everyone in the science group took time to explain their research, teach me scientific techniques, and answer my many questions. On numerous occasions, the deck crew explained the mechanics of fishing nets as well as the fishing process. The engineering crew gave me a tour of the engine rooms, describing how four diesel engines power the entire boat. The survey techs explained how different equipment is operated as well as the information it relays back to the scientists. The NOAA Corps officers showed me how to read weather maps, take coordinates, and explained ship navigation. The ship’s stewards described the art and science behind feeding 33 people at sea. And the USFWS bird observers patiently showed me how to identify numerous bird species. From each of them, I learned a tremendous amount about fisheries science, fishing, boats, sailing, birding, and life in the Bering Sea. Thank you!

Answer to July 28 (Tuesday) Log: How has the walleye pollock biomass changed over time? 
In the past few years, the walleye pollock biomass has decreased (according to the acoustic-trawl survey, the survey that I joined.) It should be noted that there is a second complementary walleye pollock survey, the eastern Bering Sea bottom trawl survey. This survey studies walleye pollock living close to the sea floor. As walleye pollock age, they tend to live closer to the sea floor, thus the bottom trawl survey sometimes shows different biomass trends than the acoustic-trawl survey. Both surveys are used together to manage the walleye pollock stock.

An up-close look at one of the squid’s tentacles

An up-close look at one of the squid’s tentacles

Animals Seen 
Auklet, Arrowtooth flounder, Basket star, Bering skate, Cod, Hermit crab, Fin whale, Fur seal, Octopus, Sculpin, Sea mouse, Sea slug, Shortfin eelpout, Snow crab, Squid, and Tanner crab.

New Vocabulary: Bottom trawl – fishing conducted on and near the bottom of the sea floor. Catch – fish brought up in a net. Shoot the doors – a fishing expression that means to lower the 2 metal panels that hold open the fishing nets in the water. Stewards – the name for cooks on a ship. Table – nickname for the conveyor belt where the fish are sorted for sampling. Vessels – another word for ships. 

John Schneider, July 27-29, 2009

NOAA Teacher at Sea
John Schneider
Onboard NOAA Ship Fairweather 
July 7 – August 8, 2009 

Mission: FISHPAC
Geographical Area: Bering Sea
Date: July 27-29, 2009

Position
In transit to Bristol Bay, AK

Weather Data from the Bridge 
Weather System: highly variable in the Bering Sea
Barometer: falling on the second day
Wind: Ranging from light and variable to 35 kts
Low Temperature: 7.0º C
Sea State: initially <1-2 feet up to 8 feet on the evening of the 29th

The sheet above shows legs 5-10 of FISHPAC in the Bering Sea, AK

The sheet above shows legs 5-10 of FISHPAC in the Bering Sea, AK

What Is FISHPAC? 

The Magnusen-Stevens Fisheries Conservation Management Act includes the broad designation of “Essential Fish Habitat” (EFH) as including myriad parameters which are to be considered for all life stages of the managed species. Included in them are bottom type, epifauna and infauna, grain size, and organic debris. Additionally, studies are to span the life cycles of those species.  There is an enormous amount of historical data relating to commercial fisheries catches, but the data have not been assembled as a whole and screened for accuracy.  Additionally, there has been virtually no search for correlations within the data. Dr. Bob McConnaughey is engaged in seeking correlations between bottom characteristics, managed species and sorting through extant records in the search for utilizing sonar data to anticipate species presence in the Bering Sea.  The phrase I’ve heard is “using bottom characteristics as proxy for prey identification.” Earlier cruise results can be viewed here.  It would take a long time to describe all that they do at the Alaska Fisheries Service Center, so what I highly recommend is that you spend a while at their site.

Science and Technology Log 

SeaBoss on deck

SeaBoss on deck

In addition to searching for correlations between trawl catch data and bottom characteristics, Dr. McConnaughey and his team are trying to determine if sound data (Multi-beam Echo Sounders and Side Scan Sonar) can be used in anticipating what species will likely be present in a given area. There are 69 managed commercial species in Alaska alone, which represent an enormous proportion of the commercial US catch, and if technology and research can be gained here, it can conceivably be applied elsewhere.  The Alaskan fisheries have also not been subjected to as much commercial fishing as, say, the coast of New England due to the remote, harsh and generally newly populated area which is Alaska. Commercial fishing here is, for the most part, less than 50 years old compared to the hundreds of years off the East Coast.

SeaBoss being deployed. It is suspended from the J-Frame and swung outboard. Tending the SeaBoss can be hazardous so crew members are tethered to the deck.

SeaBoss being deployed. It is suspended from the J-Frame and swung outboard. Tending the SeaBoss can be hazardous so crew members are tethered to the deck.

Alaska has over 45,000 miles of coastline, contains 70% of the United States continental shelf, and 28% of the Exclusive Economic Zone (a 200 mile legal designation) yet much of that area has never been properly surveyed. With the prospect of a warming climate and potential northerly relocation of commercially viable species, it is essential to document as much of this area as possible before long-term damage may be inflicted on it. In order to evaluate the EFH parameters, one of the tools the FISHPAC team uses to gather bottom samples is an apparatus called the SeaBoss (Sea Bed Observation System.)

SeaBoss on the way up--it can be seen as deep as about 5 to 10 meters

SeaBoss on the way up–it can be seen as deep as about 5 to 10 meters

SeaBoss allows the team to gather a 0.1m2 bottom sample, descending and forward looking video and still pictures taken just before it hits the bottom. SeaBoss gets deployed twice at each site.  The first sample is brought up and dumped into a sieve with a 1mm grid size.  It is then gently hosed off with seawater to clear away the inorganic materials and large particles.  The remaining biomass is put into containers with formalin solution for 2 days and then put into an alcohol solution to prevent decay.  Those samples will be quantified back in the lab in the Seattle area. With the second sample from roughly the same bottom area, samples are taken of the bottom material itself from the surface and from a couple of centimeters below the surface.  These, too, will be quantitatively evaluated back in the lab for grain sizes present and the proportions of those grain sizes in the sample. For background information on the SeaBoss, go here.

Jim Bush in the bosun’s chair.  Rick Ferguson (l) and Chief Bosun Ron Walker assisting.

Jim Bush in the bosun’s chair. Rick Ferguson (l) and Chief Bosun Ron Walker assisting.

Personal Log 

Before we left Dutch Harbor, we took on fuel (about ¼ of a load – only 22,000 gallons!) We took on ship’s stores (food.) 100+ gallons milk, 25 cases produce, a couple hundred pounds of meat (beef, chicken, pork, lamb,) scores of loaves of bread, and numerous cases of ice cream as well as other things.  It took several hours to stow it all away.  We also took on about 10 pallets of scientific gear for the FISHPAC team.  One of the more interesting scenes was watching AB Jim Bush rigging the A-Frame for deploying some of the equipment off of the fantail.

Questions for You to Investigate 

Check out the web sites I listed, there’s some really cool stuff on them.

New Terms/Phrases 

Biomass – organic matter created by living things epifauna – living animals on the surface of the bottom infauna – living animals in the bottom quantitatively – using numerical values

 

Kathryn Lanouette, July 28, 2009

NOAA Teacher at Sea
Kathryn Lanouette
Onboard NOAA Ship Oscar Dyson
July 21-August 7, 2009 

Here I am sorting different zooplankton species

Here I am sorting different zooplankton species

Mission: Summer Pollock Survey
Geographical area of cruise: Bering Sea, Alaska
Date: July 28, 2009

Weather Data from the Ship’s Bridge 
Visibility: 8 nautical miles
Wind direction:  015 degrees (N, NE)
Wind speed:  7 knots
Sea wave height: 1 foot
Air temperature: 7.6˚C
Seawater temperature: 7.3˚C
Sea level pressure: 29.8 inches Hg and falling
Cloud cover: 8/8, stratus

Science and Technology Log 

In addition to studying walleye pollock, NOAA scientists are also interested in learning about the really tiny plants (phytoplankton) and animals (zooplankton) that live in the Bering Sea.  Plankton is of interest for a two reasons. First, phytoplankton are the backbone of the entire marine food chain. Almost all life in the ocean is directly or indirectly dependent on it. By converting the sun’s energy into food, phytoplankton are the building blocks of the entire marine food web, becoming the food for zooplankton which in turn feed bigger animals like small fish, crustaceans, and marine mammals. Second, zooplankton and small fish are the primary food source for walleye pollock. By collecting, measuring, and weighing these tiny animals, scientists are able to learn more about the food available to walleye pollock. In addition, every time the scientists trawl for walleye pollock, the stomachs of 20 fish are cut out and preserved. Back at a NOAA lab in Seattle, the contents of these fish stomachs will be analyzed, giving scientists a direct connection between walleye pollocks’ diet and specific zooplankton populations found throughout the Bering Sea.

A simplified marine food chain  (Note: A complete marine food web involves hundreds of different species.)

A simplified marine food chain (Note: A complete marine food web involves hundreds of different species.)

Two important zooplankton groups in the Bering Sea are copepods and euphausiids (commonly referred to as krill). Euphausiids are larger and form thick layers in the water column. In order to catch euphausiids and other zooplankton of a similar size, a special net called a Methot is lowered into the water. This fine meshed net is capable of catching animals as small as 1 millimeter. The same sonar generated images that show walleye pollock swimming below the water’s surface are also capable of showing layers of zooplankton. Using these images, the scientists and fishermen work together, lowering the net into the zooplankton layers.

The Methot net is the square shaped net in the background. It was just brought up and is filled with hundreds of zooplankton.

The Methot net is the square shaped net in the background. It was just brought up and is filled with hundreds of zooplankton.

Once the Methot net is back onboard the boat, its contents are poured through fine sieves and rinsed. All species are identified. A smaller sub sample is weighed and counted. This information is applied to the entire catch so if there were 80 krill, 15 jellyfish, and 5 larval fish in a sub sample, then scientists would approximate that 80% of the entire catch was krill, 15% was jellyfish, and 5% was larval fish. Having only seen photos of some of these zooplanktons, it was interesting to hold them in my hands and look at them up close. They seemed better suited for space travel or a science fiction movie than the Bering Sea!

Personal Log 

The day before, I caught my first glimpse of Dall’s porpoises. This pod of porpoises came swimming alongside the boat. It was awesome to see their bodies rise and fall in the water. I was surprised at how quickly they were swimming, darting in and out of the Oscar Dyson’s wake. Today, I also got my first glimpse of a whale! It was a fin whale, a type of baleen whale, about 20 meters from the boat. It was exciting to watch such a large mammal swimming in such a vast expanse of water. I’m hoping to see a few more marine mammal species before we return to port. The seas have been very calm for the last five days, at times as smooth as a mirror. I’m surprised that I’ve gotten used to falling asleep in the early morning hours and waking around midday. Now that I’ve adjusted to the 4pm to 4am shift, I’m wondering how strange it will be to return to my regular schedule back on the east coast.

Answer to July 25th Question of the Day: Why are only some jellyfish species capable of stinging? 
As I picked up my first jellyfish in the wet lab (asking at least twice “Are you sure this won’t sting?”), I wondered why some jellyfish don’t sting.  So I did some reading and asked some of the scientists a few questions. Here is what I found out: All jellyfish (called “gelatinous animals” in the scientific world) have stinging cells (nematocysts) in their bodies. When a nematocyst is touched, a tiny barb inside fires out, injecting toxin into its prey.  It seems that in some jellyfish, the barbs are either too small to pierce human skin or that nematocysts don’t fire when in contact with human skin.

One euphausiid and two different species of hyperiid amphipod (They are between 1-3 cm long)

One euphausiid and two different species of hyperiid amphipod

Animals Seen 
Capelin, Dall’s porpoise, Euphausiid, Fin whale, Hyperiid amphipod, and Slaty-backed gull.

New Vocabulary: Baleen whale – a whale that has plates of baleen in the mouth for straining plankton from the water (includes rorqual, humpback, right, and gray whales). Methot net – a square framed, small meshed net used to sample larval fish and zooplankton. Phytoplankton – plankton consisting of microscopic plants. Plankton – small and microscopic plants and animals drifting or floating in the sea or fresh water. Trawl – to fish by dragging a net behind a boat. Zooplankton – plankton consisting of small animals and the immature stages of larger animals

Question of the Day: How has the walleye pollock biomass changed over time?

 

Kathryn Lanouette, July 25, 2009

NOAA Teacher at Sea
Kathryn Lanouette
Onboard NOAA Ship Oscar Dyson
July 21-August 7, 2009 

Mission: Summer Pollock Survey
Geographical area of cruise: Bering Sea, Alaska
Date: July 25, 2009

Walleye pollock (Theragra chalcogramma)

Walleye pollock (Theragra chalcogramma)

Weather Data from the Ship’s Bridge 
Visibility: 10+ miles (to the horizon)
Wind direction: 030 degrees (NE)
Wind speed: 15 knots
Sea wave height: 4-6 feet
Air temperature: 6˚C
Seawater temperature: 6.4˚C
Sea level pressure: 29.85 inches Hg and rising
Cloud cover: 8/ 8, stratus

Science Log 

Why study walleye pollock? Before even setting sail, I wondered why NOAA scientists were interested in studying walleye pollock. It turns out that walleye pollock is the largest fishery, by volume, in the USA. In one year, about 1 million metric tons of walleye pollock are fished, mostly from the waters of the Bering Sea. Given that walleye pollock accounts for such a large percentage of the total fish caught in the United States, I was curious why I had never seen it on restaurant menus or rarely seen it at supermarket fish counters. It is because walleye pollock is usually processed into other things – like fish sticks, imitation crabmeat, and McDonald’s fish fillet sandwiches. So it seems that walleye pollock is that mild white fish you often eat when you don’t know for sure what kind of fish you are eating.

Above is a map showing the 31 transect lines of the walleye pollock survey area. I have joined the cruise that is sailing along the 8 transect lines closest to Russia.

Above is a map showing the 31 transect lines of the walleye pollock survey area. I have joined the cruise that is sailing along the 8 transect lines closest to Russia.

In addition to supporting a major multi-billion-dollar fishing industry, walleye pollock is a fundamental species in the Bering Sea food web. It is an important food source for Steller sea lions as well a variety of other marine mammals, birds, and fish. The population size, age composition, and geographic distribution of walleye pollock significantly affect the entire Bering Sea ecosystem. What do scientists hope to learn about walleye pollock? NOAA scientists are primarily interested in calculating the total biomass of walleye pollock. To estimate how many walleye pollock are in the Bering Sea, scientists sample the fish, recording their age, length, weight, male/female ratio, and geographic location. This information is used by North Pacific Fishery Management Council (NPFMC) to set sustainable fishing quotas for the following year. The NPFMC, whose membership comprises university, commercial, and government representatives, uses NOAA’s survey data, fishery observer program data, as well as catch statistics from the commercial fishing industry, to determine how much walleye pollock can be fished in the coming year.

An illustration of the Oscar Dyson sending down sound waves (in order to “see” the animals swimming below the water’s surface.)

An illustration of the Oscar Dyson sending down sound waves (in order to “see” the animals swimming below the water’s surface.)

Where do scientists study walleye pollock? Every year or two, a NOAA research ship (usually the Oscar Dyson) travels throughout the Bering Sea, following approximately 31 transect lines. These transect lines can be anywhere from 60 to 270 miles long. These lines were selected because they include areas where either walleye pollock spawn in the winter or feed in the summer. As the ship travels along these lines, its sonar system uses sound waves to locate fish and other animals living below the water’s surface. As the sound waves return to the ship, they create different images, depending on which animals are swimming in the water below. Using these images, the scientists decide whether or not they should lower the nets and sample the walleye pollock. They also continuously store digital data from the images, later using this information to estimate the total biomass of the fish species. On this 18 day research cruise, the scientists are hoping to travel the last 8 transect lines (over 1,500 nautical miles).  Each transect line takes us into Russian waters. On Thursday, we reached our first transect line. Within hours of traveling along this first line, many schools of walleye pollock were spotted. After the fish net was brought up, I was amazed at the number of fish that came sliding down the conveyor belt into the science lab. I helped weigh and measure hundreds of fish, a quick introduction to the whole process!

Personal Log 

The mouth of a Pacific lamprey

The mouth of a Pacific lamprey

We traveled into Russian waters today, crossing the International Date Line as we went. So technically, Saturday became Sunday this afternoon! But later in the evening, we completed the transect line, turned, and headed back into Saturday just as night fell. Luckily, the time never changes here on the boat. The scientists and crew live on Alaska Daylight Time (ADT), regardless of how far we travel to the north and west. I’ve see a few whales spouting but so far, I haven’t been able to identify any. In the coming days, I am hoping to get a glimpse of their backs or flukes (tails). It has been exciting seeing so many animals – some of which I never even knew existed. A few of these animals look a bit scary, like this Pacific lamprey. Its mouth forms a suction and then all those small yellow teeth go to town, letting it feed on the blood and tissue of its prey. Even the small tongue in the back of its mouth is toothed! 

The rare short-tailed albatross

The rare short-tailed albatross

Animals Seen 
Hyperiid amphipod  Aequorea species, Chrysaora melanaster jellyfish,  Euphausiids (aka krill), Pacific lamprey, and Short-tailed albatross.

New Vocabulary:  Biomass – the total amount of a species, by weight Cruise – nautical trip, for science research or fun. Quotas – a limited or fixed number or amount of things. Sample – to study a small number of species from a bigger group. Transect Line – a straight line or narrow section of land or water, along which observations and measurements are made

Question of the Day 
Why are only some jellyfish species capable of stinging?

Here I am holding up a Chrysaora melanaster jelly fish (Luckily this species doesn’t sting!)

Holding up a Chrysaora melanaster jelly fish (Luckily this species doesn’t sting!)

Mary Anne Pella-Donnelly, September 11, 2008

NOAA Teacher at Sea
Mary Anne Pella-Donnelly
Onboard NOAA Ship David Jordan Starr
September 8-22, 2008

Mission: Leatherback Use of Temperate Habitats (LUTH) Survey
Geographical Area: Pacific Ocean –San Francisco to San Diego
Date: September 11, 2008

Weather Data from the Bridge 
Latitude: 3647.6130W Longitude: 12353.1622 N
Wind Direction: 56 (compass reading) NE
Wind Speed: 25.7 knots
Surface Temperature: 15.295

Bongo net being deployed to collect specimens

Bongo net being deployed to collect specimens

Science and Technology Log 

One oceanographic phenomena of interest is the deep scattering layer (DSL). This is a zooplankton and micronekton rich layer that is found below the depth that light penetrates to in the daytime. After sunset, this DSL layer migrates up closer to the surface.  In some locations the daytime DSL may be at a depth of 225-250 m depth in this area of the California current ecosystem, and 0-100 m during the night. It is hypothesized that the organisms stay deeper down during the daytime to avoid predation, and move up toward the surface at night when it is safer from predators.  Oceanographers take advantage of this information. Every evening, two hours after sunset, bongo nets are deployed to a depth of 200m and then slowly brought to the surface to get a sample of the entire water column.  The purpose is to collect samples of those organisms that are found in the DSL. During the day these organisms would be much deeper down below the surface, but at night they are much closer.

Chart that converts wire length and angle to depth

Chart that converts wire length and angle to depth

The process begins with opening up the large plankton nets and attaching a weight in between the loops of the frame.  The frame is hooked to a cable that is maneuvered by a winch operator.  After the bongo net is swung out from the ship, a large protractor, an inclinometer, is attached. This is used to give the Officer of the Deck (OOD) driving on the bridge an indication of speed needed to deploy the net at. The OOD adjusts the speed of the ship to maintain the required angle, which allows the net to remain open for collection and reach the desired depth. Looking at the chart above, you can see that the angle the wire is deployed at, along with the amount of wire paid out, can be converted to a given depth. Trigonometry at work. There is also a flow meter attached inside each of the bongo loops. The readings from this give an indication of the volume of water that passed through the nets. When the bongo is retrieved, before the end is detached, each net is rinsed with salt water from a hose in order to retrieve as much of the sample as possible in the cod end. This end is detached and brought into the lab.  One of the samples is examined in the lab, for relative types, while the other sample is preserved in formaldehyde and sodium borate for later examination and identification.

Stateroom on the Jordan

Stateroom on the Jordan

Personal Log 

It is very interesting being rocked to sleep each night.  Being on the top bunk, I am about 2 feet from the ceiling, with several pipes suspended from the ceiling.  Once settled in bed, there is little opportunity to move around much.  But being slowly rocked from side to side is a very interesting sensation, and is relaxing.  It is becoming easier to tell how calm the water is that the ship is moving through, or a little about the weather, since sometimes we rock up and down, instead of from side to side. We were told that when it gets really rough it is a good idea to place a life jacket under the edge of the mattress to keep us from falling out.  Each bed has a dark curtain edging it, since many of the crew and scientists may have opposite shifts. Since there is no porthole in my stateroom, when the lights are out and the curtain is closed, it is very dark. It would be impossible to tell night from day, except by an internal clock or a timepiece.  It has been comfortable sleeping.  Getting up is the only difficult part, maneuvering in the small space of the bunk and being careful not to disturb my bunkmate, Liz.  Her schedule varies from mine, due to her bongo net responsibilities and CTD expertise.  So far the sleeping arrangement has worked out well.

Words of the Day 

 Stateroom dresser aboard the Jordan

Stateroom dresser aboard the Jordan

Distribution: the local species and numbers of organisms in an area; Biomass: the combined mass of a sample of living organisms; Micronekton: free swimming small organisms; Zooplankton: small organisms that move with the current; Predation: the process of organisms eating other organisms to survive; Inclinometer: protractor designed to measure altitude from the horizon.

Questions of the Day 

  1. What organisms do you know of that change their feeding strategy at different times of the day?
  2. In the local creek, river, or lake near you, are there both micronekton and zooplankton?  How could you find out?