Joan Shea-Rogers: Do You See What We See, July 10, 2018

NOAA Teacher at Sea

Joan Shea-Rogers

Aboard NOAA Ship Oscar Dyson

July 1-22, 2018


Mission: Walleye Pollock Acoustic Trawl Survey

Geographic Area of Cruise: Eastern Bering Sea

Date: July 10, 2018


Weather Data from the Bridge

Latitude: 53ºN

Longitude: 166ºW

Sea Wave Height: 1.5 feet

Wind Speed: 25 knots

Wind Direction: SW

Visibility: 15 Miles

Air Temperature: 52º F

Barometric Pressure: 1010.61mb

Sky: Overcast

Biological Trawl Data:

Letting the Net Out to Sea
Letting the Net Out to Sea

Trawl hauls are how fishing is conducted. A large net is dropped into the water for a specific amount of time. By catching exactly what is in the ocean, the acoustic backscatter can be identified (what the various colored pixels on the echograms represent). Below is an echogram on the screen, the black line is the path of the trawl through the backscatter, the little red circle indicated where the camera was, and the picture at left is pollock passing by the camera and into the back of the net at that point.

Screenshot of an echogram. The black line is the path of the trawl through the backscatter, the little red circle indicates where the camera was, and the picture at left is pollock passing by the camera and into the back of the net at that point.

Samples of pollock and other organisms can be studied and other biological data collected. By counting, measuring, and weighing the pollock and other animals caught in each haul, calculations can estimate the amount of fish in a given area. Acoustic data can be used to determine the number of fish by dividing the measured backscatter by the backscattered energy from one fish (target strength, discussed in the last blog). That gives the number of fish:

To get the backscatter from one fish for the above calculation, we need to know the size and species of the fishes. The trawl provides that information. In the fish lab, species including pollock are identified, lengths are taken, and the number of fish at each length is entered in the computer. Also, the animals including pollock are weighed and a mean weight is determined. The number of fish computed from the acoustic and trawl data multiplied by the mean weight of a fish equals the biomass of the fish (total weight of the population in a given area).

The fisheries biologists developed the software used for all these calculations. This information coupled with the echograms can answer those earlier questions…Where are the pollock in the Bering Sea? How many are there? How big are they? How many adult pollock are there (fish that can be caught) and how many young pollock are present (providing information about future availability and how healthy the population is)?

When I first boarded the ship, I asked the fisheries biologists how they would describe what they do. They responded that they count fish, it’s not rocket science. But you know what? It kind of is!


At Work in the Fish Lab
TAS Joan Shea-Rogers at work in the Fish Lab


What is this information used for?

This information is used to manage the Pollock fishery. Numerical data is given to the entities that set the fishing quotas for the Bering Sea area. Quotas are then divided up between the commercial and individual fishing companies/boats. Once fishermen reach these quotas they must stop fishing. This protects the fishery to ensure that this food source will be healthy and strong for years to come. A similar example from my home state is that of the Illinois is the Department of Conservation. One of their responsibilities is to manage the deer population. Then they can determine how many deer can be harvested each season that still allows for the deer population to thrive.


Personal Blog:

In my last blog post, I talked about preparing for and “weathering the storm”. As with most things at sea and on land, things don’t always turn out as we plan. The stormy weather began with wave heights between 8-10 feet. The ship continually rocked back and forth making walking and everything else difficult. You can tell the experienced sailors because they were much more graceful than I was. I held on to every railing and bolted down piece of furniture that I could. And even then, I would forget and place a pen on the table, which immediately rolled off. While eating I held onto my glass and silverware because as I ate and placed my knife on my plate it rolled off. Dressing was a balancing act, which I was not good at. I finally figured out it was better if I sat in a chair. Luckily for me, my patch for seasickness worked.

While I was sitting in the mess hall (dining room) an alarm rang. The engineers got up read the screen and left. The decision was made by the acting CO (Commanding Officer) that we would have to go back to Dutch Harbor. And now, as I write this, we are docked in Dutch Harbor waiting for word about the status of our voyage. Out here in Dutch Harbor, everything must be shipped in. We wait until parts and people are flown in. The fisheries biologists also have to determine the validity of the data collected on such a short voyage. They also must decide in a timely matter, can this data collection continue after returning to port?

For me, I am holding out hope that all these factors are resolved so that we can go back out to sea. Since November when I turned in my application, this voyage has been such a focal point of my life. If it doesn’t work out (I’ll try not to cry), I will still have had the adventure and learning experience of a lifetime. So here’s hoping……

NOAA Ship Oscar Dyson at Port in Dutch Harbor, AK
NOAA Ship Oscar Dyson at Port in Dutch Harbor, AK


Chelsea O’Connell-Barlow: To Fish Or Not to Fish?…A Question of Sound, September 4, 2017

NOAA Teacher at Sea

Chelsea O’Connell-Barlow

Aboard NOAA Ship Bell M. Shimada

August 28 – September 13, 2017


Mission: Pacific Hake Survey

Geographic Area of Cruise: Northern Pacific Ocean

Date: 9/04/2017


Weather Data from the Bridge:

Latitude: 53.59.372N

Longitude: 133 32.484W

Temperature 59 F

Wind 12.5 knots

Waves 1-2 feet


Science and Technology Log

After spending a few days observing what happens in the Acoustics lab and listening to our Chief Scientist Rebecca (RT) Thomas and acoustician Julia Clemons brainstorm aloud, I had one overriding question…”How do you decide when to fish?”

I asked RT this question and it is a multi-factored decision for sure, but seems like the decision could be broken down into 3 parts: what we see, what we know and what is currently happening.

What they see when deciding to fish or not is an echogram created by three acoustic sounders on the ship that send out 3 different frequency wavelengths. The image shows a relatively low frequency 18 kHz, 38 kHz, and a longer wavelength of 120 kHz. Keep in mind that sound travels faster in water than on land so this is a great way to gather information while being minimally invasive to the marine environment.

annotated bridge screens for 9.4 post
Bridge of Bell M. Shimada. The 3 screens we watch during a AWT trawl for Hake.

The backscatter, sound that scatters off of an object or its echo, on the echogram is what they look at to determine what marine life is on the transect we are scouting. As the sound wave bounces off of material in the ocean be it rock, flora or fauna it will create a spot or colored pixel on the echogram. Hake has a particular “look” of backscatter. When the echogram shows this particular hake sign we move in the direction of fishing.

Of course they only know what “hake sign” is because of gathering evidence throughout the course of this multi-year survey. During this survey they have created a huge reference database of hake sign and sign of other integral species to the hake’s environment, for example Euphausiid sp., one of the hake’s favorite food. RT and Julia have both interpreted many echograms and fished to confirm the identity the organisms that created the sign.  They are able to rule out images on the echogram until they find the backscatter that most resembles what they have historically experienced as hake.

The third part of this decision making process is the most variable…what is currently happening. As the boat travels and the sounders are sending out the trio of wavelengths an image of the ocean shelf is created. The scientists are able to see topography and measure the depths of the shelf’s different contours. The Shimada is a 209 foot long boat weighing over 2,400 tons. When deciding to trawl for hake that we suspect are present because of backscatter sign in the echogram the scientists and Commanding Officer always consider the depth to bottom, contours, wind and the maneuverability of the ship. Deploying the Aleutian Wing Trawl (AWT) net to catch hake is a task that involves cooperation and communication between the deck crew, Boatswain, bridge officers and the Chief Scientist. When RT sees a sign on the echogram that she wants to fish, she and Commanding Officer Kunicki quickly discuss the approach, wind direction and depth to get an idea on how the net will be affected and how close the ship can get to the exact sign that she wants to sample.

This is my bare bones description of the process that goes into deciding when to fish on Leg 5 of the Pacific Hake Survey. Stay tuned to see what we learn from comparing the echogram of sign to the actual yield from the AWT fishing net.

For more specifics from NOAA on the Bell M. Shimada’s acoustic and trawling capabilities

Personal Log

This ship is filled with kind, creative and industrious people. I am reminded of this constantly and appreciate this often. To me it is astounding to consider all the work and thought that is involved in a fifteen-day research survey at sea. This is a science survey so there are specific tools, computer programs and labs that must run well. To me, coming in with a science focus, this is most obvious. What I am blown away by are all of the additional layers that work together to make science even possible on this successful voyage. There are several teams at play: engineering, technology, deck, science and the bridge officers. Engineers are constantly maintaining engines, generators (this ship has 4), plumbing, ventilation and so much more. I had a tour today with Engineering Chief Sabrina Taraboletti that I am still trying to process through.

Technology is handled by one person on this ship. He maintains and trouble shoots computers in the acoustics lab, the bridge, the chemical lab and even found time to help maximize signal for the Fantasy Football draft. The deck crew is as versatile as anyone on this ship. We have two types of nets that we fish with. The deck crew is responsible for getting the nets out to fish and back in with the catch. Way easier said than done when we are talking about over a ton of weight with net, camera, chain, and doors. On top of all their other responsibilities many of the men in the deck crew have been helping out in the galley (kitchen) on this leg of the hake survey. Larry is the chief steward (chef) on board this leg and he typically has someone working with him but not on this leg of the Survey. So in addition to working their 12 hour shift, many of the deck crew have been working with Larry to prep food, clean up the mess (dining area), do dishes or even create their own personal specialties for dinner. We have been spoiled by Matt’s rockfish, Joao’s fresh salsa and soups and our Operations Officer Doug’s amazing BBQ. Liz and I even got to help out and make some donuts with Larry. Eating is great on the Shimada!

Liz & OCB makin the donuts
Liz and OCB making the donuts – thanks for the lesson Larry.

The Shimada team is rounded out with the bridge crew made up of 4 officers. The officers on a NOAA ship have a foundation of science knowledge and extensive nautical training. Before we go fishing I get to participate in the marine mammal watch up in the bridge. As I look for whales, dolphins and other marine mammals near the boat I can listen to the Captain and officers working their magic. We have had an incredibly smooth trip thus far which I credit to our Officers and of course Mother Nature.









Did You Know?

our Viperfish for blog
Who is this?

Crazy cool catch of the day…can you figure out what type of fish this is?

Here is a clue…they have specially adapted cells called photocytes that create light producing organs called photophores.  The photophores run along the sides of the fish and help them to lure prey and attract mates.

Viperfish from strangeanimals site
photo credit:



This is a Viperfish.

Viperfish live in the deep ocean and migrate vertically as the day goes on in order to catch prey. They typically live around 1,500m (4,921 ft) and in the night will end up around 600m (1,969 ft) at night. This particular fish appears to have photophores along its mouth but it is difficult to be 100% sure from this specimen.



Nichia Huxtable: These ARE the Fish You’re Looking For, May 4, 2016

NOAA Teacher at Sea

Nichia Huxtable

Aboard NOAA Ship Bell M. Shimada

April 28 – May 9, 2016

Mission: Mapping CINMS

Geographical area of cruise: Channel Islands, California

Date: May 4, 2016

Weather Data form the Bridge: 0-2ft swells, partly cloudy, slightly hazy

Science and Technology Log:

We’ve been waiting for you, rockfish. We meet again, at last. You might wonder why scientists need to know the location and population densities of rockfish in the Channel Islands National Marine Sanctuary. Well, rockfish are tasty and commercially important, plus they are an important component of healthy marine ecosystems.  To estimate how many there are and where they’re at, you’ll need lots of equipment and fisheries biologist, Fabio Campanella.

Fabio Campanella and Julia Gorton getting some fresh air. Breaks are important to help them stay on target.

Monitor showing the EK60 in action. Your eyes can deceive you…watch out for the acoustic dead zone!
First, let’s start with the equipment. Shimada has an EK60, which is essentially a fish finder: the computer’s transducer sends out sonic “pings” that become a single acoustic “beam” in the water. It covers about 7° at one time, so think of it as taking a cross section of the water column. The beam bounces off any solid object in the water and returns to the transducer. The size and composition of the object it hits will affect the quality of the returning pings, which allows Fabio to discern between seafloor, small plankton, and larger fish, as well as their location in the water column. One drawback of this system is the existence of an acoustic dead zone, which is an area extending above the seafloor where fish cannot be detected (think of them as sonar blind spots).


Do. Or do not. There is no try. Fabio Campanella hard at work in Shimada‘s Acoustic Lab.


Starry rockfish (Sebastes constellatus)
It’s a trap! Nope, it’s a starry rockfish (Sebastes constellatus) found in the CINMS.

Ideally, acoustic data collection is done simultaneously with ground truthing data. Ground truthing is a way to verify what you’re seeing. If you think the EK60 is showing you a school of herring, you can run nets or trawls to verify. If it’s in an area that is untrawlable, you can use ROVs or stationary cameras to identify fish species and habitat type. Species distribution maps are also useful to have when determining possible fish species.


EK60 data shown on the bottom; ME70 data on top right; 3-D visualization of the school on the top left.
EK60 data shown on the bottom; ME70 data on top right; 3-D visualization of the school on the top left. Witness the power of this fully operational Echoview software.

If Fabio finds something especially interesting on the EK60, such as a large school of fish, he can refer to the data simultaneously collected by the ME70 multibeam sonar to get a more detailed 3-D image. Since the ME70 uses multiple beams and collects 60 degrees of data, he can use it to (usually) get a clear picture of the size and shape of the school, helping him identify fish species and density. So why does he use the EK60 first if there is so much more data provided by the multibeam? Well, the amount of data provided by the ME70 is incredibly overwhelming; it would take weeks of data analysis to cover just a tiny section of the marine sanctuary. By using the EK60 to cover large areas and the ME70 to review small areas of specific interest, he is able to create fish distribution and density maps for the largest areas possible.

After collecting data from the two sonars, it needs to be processed. The method you use to process the data depends on your goal: biomass, population densities, and fish locations are all processed differently. Since rockfish are found close to hard, rocky seafloor, data analysis becomes quite complicated, as it becomes difficult to discriminate the fish from the seafloor. Hard bottoms also introduce a lot of bias to the data; for these, and other, reasons there are very few hard bottom studies for Fabio to refer to.

Cleaned data. I’ve got a good feeling about this.
But back to the data analysis. Once data is collected, it is loaded into Echoview software. Fabio then removes the background noise coming from other equipment, averages the data to reduce variability, and manually modifies the seafloor line (rocky bottoms with lots of pinnacles give incorrect bottom data). This last step is crucial in this mission because the focus is on rockfish who live close to the bottom.



School of fish shown on the right of the screen and the frequency response shown on the left. Fish are not lost today. They are found.
The clean echogram is then filtered for frequencies falling in the suitable range for fish with swimbladders (a gas-filled organ used to control their buoyancy). Object with a flat response at all frequencies (or slightly higher at low frequencies) will most likely be fish with swimbladders, whereas a high response to high frequencies will most likely not be fish (but it could be krill, for example). Once Fabio has made the final fish-only echogram, he exports the backscatter and uses it to create biomass or density estimates. All of these steps are necessary to complete the final product: a map showing where rockfish fish are in relation to the habitat.

Krill shown on the right and frequency response shown on the left. Judge them by their size, we do.








The final product. When making accurate maps of rockfish, there is no such thing as luck.
Personal Log:

It seems I overpacked sunscreen…12 hours of my day are spent in the acoustics lab staring at monitors, with brief breaks every so often to look for whales and other wildlife. This mission is so technical. I am grateful for the hours spent asking the scientists questions and having them explain the details of their work. Lately, the big screen TV in the lab has been turned on with some great movies playing. So far we’ve watched, Zootopia, Deadpool, LoTR, and, of course, The Force Awakens. May the 4th be with you…always.

Word of the Day: Holiday.

A holiday is an area in your bathymetry map that does not include any data (think of it as “holes in your data”). It’s like you’ve painted a picture, but left a blank splotch on your canvas.


Andrea Schmuttermair, Pollock Processing Gone Wild, July 12, 2015

NOAA Teacher at Sea
Andrea Schmuttermair
Aboard NOAA Ship Oscar Dyson
July 6 – 25, 2015

Mission: Walleye Pollock Survey
Geographical area of cruise: Gulf of Alaska
Date: July 12, 2015

Weather Data from the Bridge:
Latitude: 55 25.5N
Longitude: 155 44.2W
Sea wave height: 2ft
Wind Speed: 17 knots
Wind Direction: 244 degrees
Visibility: 10nm
Air Temperature: 11.4 C
Barometric Pressure: 1002.4 mbar
Sky:  Overcast

Science and Technology Log

I’m sure you’re all wondering what the day-to-day life of a scientist is on this ship. As I said before, there are several projects going on, with the focus being on assessing the walleye pollock population. In my last post I talked about the transducers we have on the ship that help us detect fish and other ocean life beneath the surface of the ocean. So what happens with all these fish we are detecting?

The echogram that shows data from the transducers.
The echogram that shows data from the transducers.

The transducers are running constantly as the ship runs, and the information is received through the software on the computers we see in the acoustics lab. The officers running the ship, who are positioned on the bridge, also have access to this information. The scientists and officers are in constant  communication, as the officers are responsible for driving the ship to specific locations along a pre-determined track. The echograms (type of graph) that are displayed on the computers show scientists where the bottom of the ocean floor is, and also show them where there are various concentrations of fish.

This is a picture of pollock entering the net taken  from the CamTrawl.
This is a picture of pollock entering the net taken from the CamTrawl.

When there is a significant concentration of pollock, or when the data show something unique, scientists might decide to “go fishing”. Here they collect a sample in order to see if what they are seeing on the echogram matches what comes up in the catch. Typically we use the Aleutian wing trawl (AWT) to conduct a mid-water trawl. The AWT is 140 m long and can descend anywhere from 30-1,000 meters into the ocean. A net sounder is mounted at the top of the net opening. It transmits acoustic images of fish inside and outside of the net in real time and is displayed on a bridge computer to aide the fishing operation. At the entrance to the codend (at the end of the net) a CamTrawl takes images of what is entering the net.

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Once the AWT is deployed to the pre-determined depth, the scientists carefully monitor acoustic images to catch an appropriate sample. Deploying the net is quite a process, and requires careful communication between the bridge officers and the deck crew. It takes about an hour for the net to go from its home on deck to its desired depth, and sometimes longer if it is heading into deeper waters. They aim to collect roughly 500 fish in order to take a subsample of about 300 fish. Sometimes the trawl net will be down for less than 5 minutes, and other times it will be down longer. Scientists are very meticulous about monitoring the amount of fish that goes into the net because they do not want to take a larger sample than needed. Once they have determined they have the appropriate amount, the net is hauled back onto the back deck and lowered to a table that leads into the wet lab for processing.

Here the scientists, LT Rhodes, and ENS Kaiser assess the catch.
Here the scientists, LT Rhodes, and ENS Kaiser assess the catch.

We begin by sorting through the catch and pulling out anything that is not pollock. We don’t typically have too much variety in our catches, as pollock is the main fish that we are after. We have, however, pulled in a few squid, isopods, cod, and several jellies. All of the pollock in the catch gets weighed, and then a sub-sample of the catch is processed further. A subsample of 30 pollock is taken to measure, weigh, collect otoliths from, and occasionally we will also take ovaries from the females. There are some scientists back in the lab in Seattle that are working on special projects related to pollock, and we also help these scientists in the lab collect their data.

The rest of the sub-sample (roughly 300 pollock) is sexed and divided into a male (blokes) and female (sheilas) section of the table. From there, the males and females are measured for their length. The icthystick, the tool we use to measure the length of each fish, is pretty neat because it uses a magnet to send the length of the fish directly to the computer system we use to collect the data, CLAMS. CLAMS stands for Catch Logger for Acoustic Midwater Survey. In the CLAMS system, a histogram is made, and we post the graphs in the acoustics lab for review. The majority of our pollock so far have been year 3. Scientists know this based on the length of pollock in our catch. Once all of the fish have been processed, we have to make sure to clean up the lab too. This is a time I am definitely thankful we have foul weather gear, which consists of rubber boots, pants, jackets and gloves. Fish scales and guts can get everywhere!

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Personal Log

Here is one of many jellies that we caught. .
Here is one of many jellies that we caught. .

I am finally adjusting to my nighttime shift schedule, which took a few days to get used to. Luckily, we do have a few hours of darkness (from about midnight until 6am), which makes it easier to fall asleep. My shift runs from 4pm-4am, and I usually head to bed not long after my shift is over, and get up around noontime to begin my day. It’s a little strange to be waking up so late in the day, and while it is clearly afternoon time when I emerge from my room, I still greet everyone with a good morning. The eating schedule has taken some getting used to- I find that I still want to have breakfast when I get up. Dinner is served at 5pm, but since I eat breakfast around 1 or 2pm, I typically make myself a plate and set it aside for later in the evening when I’m hungry again. I’ll admit it’s a little strange to be eating dinner at midnight. There is no shortage of food on board, and our stewards make sure there are plenty of snacks available around the clock. Salad and fruit are always options, as well as some less healthy but equally tasty snacks. It’s hard to resist some of the goodies we have!

Luckily, we are equipped with some exercise equipment on board to battle those snacks, which is helpful as you can only walk so far around the ship. I’m a fan of the rowing machine, and you feel like you’re on the water when the boat is rocking heavily. We have some free weights, an exercise bike and even a punching bag. I typically work out during some of my free time, which keeps me from going too crazy when we’re sitting for long periods of time in the lab.

Up on the bridge making the turn for our next transect.
Up on the bridge making the turn for our next transect.

During the rest of my free time, you might find me hanging out in the lounge watching a movie (occasionally), but most of the time you’ll find me up on the bridge watching for whales or other sea life. The bridge is probably one of my favorite places on the ship, as it is equipped with windows all around, and binoculars for checking out the wildlife. When the weather is nice, it is a great place to sit outside and soak in a little vitamin D. I love the fact that even the crew members that have been on this ship for several years love seeing the wildlife, and never tire of looking out for whales. So far, we’ve seen orcas, humpbacks, fin whales, and Dall’s porpoises.




Did you know? Otoliths, which are made of calcium carbonate, are unique to each species of fish.

Where on the ship is Wilson?

Wilson the ring tail camo shark is at it again! He has been exploring the ship even more and made his way here. Can you guess where he is now?

Where's Wilson?
Where’s Wilson?
Where's Wilson?
Where’s Wilson?

Kathleen Harrison: Finding Fish, July 12, 2011

NOAA Teacher at Sea
Kathleen Harrison
Aboard NOAA Ship  Oscar Dyson
July 4 — 22, 2011

Location:  Gulf of Alaska
Mission:  Walleye Pollock Survey
Date: July 12, 2011

Weather Data from the Bridge
Air Temperature:  10.15° C, Sea Water Temperature:  7.6° C
True Wind Speed:  12.26 knots, True Wind Direction:  191.38°
Very foggy, visibility < 1/4 mile
Door open on bridge to hear other fog horns
Latitude:  56.07° N, Longitude:  158.08° W
Ship Heading:  24°, Ship Speed:  11.7 knots

Science and Technology Log:  Finding Fish

In a previous log, I talked about using nautical charts and trawling as 2 methods used in calculating the biomass of Walleye Pollock in the Gulf of Alaska.  Finding the fish to catch is tricky business in the ocean, they don’t usually come up to the surface and say hi.  The NOAA scientists working on the Walleye Pollock Survey spend a lot of time looking for fish, so that their trawling efforts won’t be wasted (that is the general idea, anyway).  How do you look for fish in the ocean?  With acoustics, of course, another method used in calculating biomass.

Acoustics is the use of sound, which will travel through the water, and bounce off of objects that it hits.  There is Simrad ER60 echosounder  that operates 5 transducers mounted on the center board under the ship, and it continuously sends out sound waves.

multibeam sonar mapping the ocean floor
The Simrad ER60 echosounder sends sound directly under the ship, finding fish anywhere in the water column.

In the Acoustics Lab of the Oscar Dyson, the data from the multi-beam echosounder is being studied all of the time.  The sound waves leave the device, travel down, hit the swim bladder in a fish (the fish doesn’t even know), and reflect back to the ship.  The time it takes for the sound to return is used to calculate the distance down, and a computer generated picture called an echogram is produced.

echogram shows surface, fish, and bottom
The echogram shows plankton at the surface in blue/green, fish near the bottom as red/brown spots, and the ocean floor as a red/brown line.

The echogram tells the scientists several things.  The surface of the water is shown, with surface dwelling organisms such as krill, phytoplankton, zooplankton, and juvenile fish.  The fish that are mid-water are shown as well, showing up as red or blue dashes or blobs.  This is where the Pollock usually are.  Some fish are bottom feeders, and the red and blue dashes on the bottom represent those.  The ocean floor is also shown, which is very important when choosing which type of trawl to use.   If the bottom is flat, the Poly Nor’Easter could be used to capture to fish on the bottom.  The Aleutian Wing Trawl might be used in mid water if the bottom is rocky and irregular.

Now, looking at the fish from the surface is nice, but wouldn’t it be better to see them close up?  Of course!  The scientists have another tool at their disposal, and no, it isn’t me diving down to the fish (brrr).  This tool is called a Drop Target Strength, or DTS.

echosounder can be dropped into water
The Drop Target Strength (DTS) can be lowered into the water, and get closer to the fish. The information is fed into the computer by a water proof cable.

About once a day, or every other day, the DTS is lowered over the side, and it starts sending out sound waves (3 pings/second), just like the echosounder mounted on the ship.  The advantage with the DTS, though, is that it is closer to the fish, giving a more detailed and accurate picture.  Individual fish can be sighted.  Taking a picture of a fish is kind of like taking a picture of a toddler, they don’t hold still very well.  So, a count of the fish on the echogram might not be exact.  Also, they might change the angle of their body, making the sound wave reflect off their swim bladder at a different angle.  The colors on the echogram are significant:  brown and red mean a strong signal, yellow is medium, and green and blue indicate a weak signal.

echogram shows individual fish
Studying the echogram from the DTS gives scientists a better picture of where the fish are. Each individual wavy line is probably a separate fish.

The scientists will study the echograms to determine where the fish are, and make a decision to fish or not.  Once fishing begins, they will move from the acoustics lab to the bridge, and study the echograms there.  An estimate of how many fish are in the net is made, and then the scientists will ask the crew to “haul back” the net.   (I am learning a whole new language!)  Then, things get very busy as we head to the fish lab to process the fish.

scientists at their desks in the acoustics lab
Here are the NOAA scientists that I am privileged to work with on the Oscar Dyson: (left to right) Darin Jones, Fish Biologist, Denise McKelvey, Fish Biologist, Neal Williamson, Chief Scientist.

New species seen:

Giant Pacific Octopus (juvenile, 1 cm)

Opalescent Squid

Chinook (King) Salmon

Egg yolk jelly fish

Sculpin (juvenile)

North Pacific sea nettle

Spud sponge

tiny squid, only 2 cm long
These are juvenile squid, about 2 cm long. They are nearly transparent.
giant pacific octopus, juvenile, only 1 cm
This is a juvenile Giant Pacific Octopus, only 1 cm wide, complete with 2 huge eyes, and 8 perfect legs.

Personal Log

My days have developed a routine now:  wake at 3:30 am (ugh), start my shift in the acoustics lab about 4:00, breakfast at 7:30, lunch at 11:30, end my shift at 4:00 pm, dinner at 5:30, shower, in bed by 8:00.

my window and life boats
See the orange life saving ring? My window is just to the right of the ring. The 3 white canisters on the back wall hold life rafts that inflate upon release of the canister.

In between these times, I work on my Teacher at Sea log, post pictures on Facebook, read and answer e-mail, visit the bridge and ask lots of questions, and of course, process fish whenever there is a trawl (very fun).  Today marks the halfway point of our cruise!  The ship is quieter than I thought, even though there are 35 people on board, the most that I ever see might be 10 during mealtimes.  There is constant background noise of the ship’s engines, waves hitting the bow of the ship, creaks and groans of the furniture as the ship rolls, but I am used to it now, and hardly notice it.  I am thankful for the calm weather that we have had so far.

Sue Zupko: 10 Steamin’ an’ a Beamin’

NOAA Teacher at Sea: Sue Zupko
NOAA Ship: Pisces
MissionExtreme Corals 2011; explore the ocean bottom to map and study health of corals and their habitat
Geographical Area of Cruise: SE United States deep water from off Mayport, FL to St. Lucie, FL
Date: June 4, 2011

Weather Data from the Bridge
Position: 29.1° N  80.1°W
Time: 11:00 EDT
Wind Speed: calm
Visibility: 10 n.m.
Surface Water Temperature: 27.6°C
Air Temperature:27.6°C
Relative Humidity: 72%
Barometric Pressure:1018.4 mb
Water Depth: 85.81 m
Salinity: 36.55 PSU

When the strong current from the Gulf Stream stretched the tether of  the ROV  and broke one of the three fiber optic cables inside, it was time to come up with a new plan.  What do you do in the middle of the ocean if the main gear is not functioning?  Plan B.  Well, Plan B was using the spare fiber optic in the tether.  The spare one then broke as a result of being rubbed, most likely, by the sharp end of the original broken fiber during the next dive.  Now we had to go to Plan C .  Fortunately the ROV crew is experienced, and, like Boy Scouts, were prepared.  They brought a spare ROV and tethers from their lab in La Jolla (pronounced La Hoya), CA just in case.    The ship is running the sonar gear back and forth over the area we plan to dive tomorrow, mapping out the bottom, looking for coral mounds.  This process is called “mowing the lawn” since you run the beams back and forth to get complete coverage of the bottom, and it looks like the lines on the lawn left by the mower.  Think of the beam as having the shape of a flashlight’s beam shining on the floor.  Another interesting feature is that the acoustic beam can also read what fish are present.  It needs to have a swim bladder for the signal to bounce back.  When it does, based on the sound, an experienced acoustician can read what fish the signal represents.  Sharks don’t have a swim bladder like most fish do so their signals are a bit more difficult to read.

I was just up on the bridge and it seems we hit “pay dirt” (like gold miners).  The captain had been explaining to me a symbol shown on the Electronic Chart Display System (ECS).   It looks like a graphic math problem showing the intersection of lines, in this case one line running on a 110° angle with three lines parallel to each other intersecting it.  The line in the middle is a bit longer than the other two.  I asked how he knew what that symbol meant.  Apparently, there is a book for everything on the bridge.  He whipped out his handy-dandy book entitled, Chart No. 1.  It is a key to reading nautical charts (maps).  He searched for the correct page with bottom obstructions of all types and showed me that symbol and what it means.  Whenever I have a question, the bridge crew whips out a book of some type to let me see the answer.  It’s really interesting.  The Pisces is a really modern ship with the latest electronic navigation and scientific features.  The other day I asked about navigating without power.  There is a book for that.  Bowditch American Practical Navigator has everything you need to know about crossing the ocean without electronics.  As it says on my classroom door, “Reading makes life a lot easier.”  Turns out that symbol is a shipwreck.

Laura sitting in front of computer screen
Laura Kracker looks at maps

But I digress.  Back to the pay dirt (we struck gold).  Laura Kracker, our geographer started getting excited.  “Look at this!  Look at this!  Write down these coordinates.”

She went running back to the acoustics lab (where they use sound echos to map the ocean floor and the presence of fish) to mark the location along the transect (lines we’re running) because we apparently were over coral mounds.  Using  information gathered by others in years past as a guide, they were mowing the lawn with the sonar to find interesting habitat to study with the ROV.  As the ship went back and forth along the planned transect to develop a much better map than existed, Laura would radio the bridge about any changes to the courseto pinpoint the best areas for us to study over the next couple of days.

ROV crew working on transferring gear from one ROV to the other on deck
ROV crew swtiches gear from one ROV to the other

Everyone was very excited.  So, although the ROV had to be switched out, which took a lot of work, we made good use of the time on the ship.  After a whole day of mapping, it’s now late at night and the map looks gorgeous.  This is important work and many cruises are devoted entirely to mapping.  Andy David, our lead scientist, says this acoustic mapping is useful to many people and will allow more precise coral surveys for years to come.

Roy Arezzo, July 28, 2007

NOAA Teacher at Sea
Roy Arezzo
Onboard NOAA Ship Oscar Dyson
July 11 – 29, 2007

Mission: Summer Pollock Survey
Geographical Area: North Pacific, Alaska
Date: July 28, 2007

Weather Data from Bridge 
Visibility: 10 nm (nautical miles)
Wind direction:   240° (SW)
Wind speed:   10 knots
Sea wave height: 3 foot
Swell wave height: 0 feet
Seawater temperature: 8.6 °C
Sea level pressure: 1020.5 mb (millibars)
Air Temperature: 0°C
Cloud cover: 8/8, Stratus

Creature at Sea:  Roy holds a sea pen in the top picture and a basket star (bottom) from the bottom trawl study
Creature at Sea: Roy holds a sea pen

Science and Technology Log: Wrap Up 

The Echo Integration-Trawl Survey of Walleye Pollock closed the season with a total of 74 Aleutian wing trawls (AWT mid-water trawls), 19 bottom trawls, 27 Methot trawls (plankton) and 81 ConductivityTemperature-Depth Sensor Package deployments (CTD water quality checks) collecting a wealth of biological and physical oceanographic data. The crew and scientists are excited to be headed back to shore but also there is a good feeling regarding the mission of the trip and the validity of the data collection. Of the 50,840 Kg of fish netted more then half was caught in the 44 AWT mid-water trawls executed this third leg of the survey.  During this time we took the length of 16,761 individual pollock and identified 19 other species of fish.I spent some time looking at graphs of preliminary data to try and make sense of what was accomplished from the work done during the sail. This past winter had a higher incidence of sea ice relative to the previous years. Generally the colder and saltier the water, the greater the density and the deeper it sinks. Although this concept was illustrated in salinity measurements at different depths (deeper being saltier) we found this not to be true when looking at temperature profiles.

Basket star
Basket star

In the sea, deeper does not always mean colder. The Bering shelf is influenced by more than one current system and we found the data taken from the northern parts of the transect along the shelf had colder water than the southern areas as expected but along the slope near the edge of the deep basin the water remained consistently warmer relative to the shelf water despite the latitude change, rarely dipping below 1°C. Generally, we found colder water near the bottom of the shelf between 50 and 100 meters then we did near the bottom of the deeper slope at 200 meters or more. This is mainly due to ice melt in the northern latitudes slowly moving cold water along the bottom of the shelf, where as the deep basin and slope are influenced by slightly warmer currents moving northwest from the Aleutian chain. As a teacher working on the water in the east I came out here assuming the deep areas would be colder but instead I was schooled on currents and their influence on water temperatures.

Leg 3 Transects of Pollock Survey Area: Fish symbols indicate trawl locations. Circles represent CTD readings and diamonds represent the line between Russian and US fishing grounds.
Leg 3 Transects of Pollock Survey Area: Fish symbols indicate trawl locations. Circles represent CTD readings and diamonds represent the line between Russian and US fishing grounds.

Through much of the cruise the lead scientists on shift spend enormous amounts of time monitoring the acoustic signal (echograms) from sounds waves beamed below the ship. When they find a significant mass of pollock they often would take a sample – go fishing. Using patterns on computer monitors scientists are able to hypothesize which signals indicate pollock. Both the length data taken from measuring fish and the acoustic estimates are used to come up with biomass numbers. In the echogram in figure 3 there is what appears to be a signal indicating mixed size pollock. We know that pollock schools tend to be homogeneous with respect to age and size. The strong blue layer at the top of the echogram represents plankton near the surface and in this instance the fish are mostly near the bottom with larger fish indicated in blue and more evenly dispersed, while dense schools of small fish show up as odd shaped clumps with lighter colors. When we sampled this water we found this to be true; we observed two groups of pollock, large adults and small two year old juveniles. The data in Figure 4 (histogram lengths) shows the two size groups. Cannibalism may be part of the reason the smaller fish stick together in separate densely packed schools.

Temperature Profile from CTD readings
Temperature Profile from CTD readings
Conductivity (salinity) Profile from CTD readings
Conductivity (salinity) Profile from CTD readings
Echogram of trawl haul
Echogram of trawl haul
Trawl histogram
Trawl histogram

In the echogram, we see more evenly dispersed adult pollock. This is verified by the haul 92 histogram in figure 6 that shows that most of the pollock sampled where between 40 and 55 centimeters long. Looking at the distribution of pollock in our study area (Figure 7) shows a consistent band of greater incidence of fish near the slope particularly to the western parts of the study area. As the fishery scientists fine tune hydro-acoustic technology they hope to get a better understanding in zooplankton (Figure 8) trends that influence survivorship of young Pollock.  A Krill Survey would be ambitious but by looking at the higher frequency acoustic waves, verified with Methot Trawls, one can estimate krill biomass in pollock regions. Environmental monitoring of chlorophyll concentration (phytoplankton measured from CTD water samples analyzed back on shore) and krill biomass (zooplankton) relative amounts from year to year can help create a better understanding of the resources necessary to support fish stocks.

FIGURE 7: Preliminary data of pollock distribution throughout the survey area
FIGURE 7: Preliminary data of pollock distribution throughout the survey area
FIGURE 8: Preliminary data of zooplankton estimates through out the pollock survey area
FIGURE 8: Preliminary zooplankton estimates throughout the pollock survey area

I would like to thank Chief Scientist, Paul Walline and B-Watch Chief ,Patrick Ressler for taking the time to explain to me the science of hydroacoustic survey analysis and sharing with me their preliminary data.

Chief Scientist, Paul Walline, monitoring the echogram from the bridge of OSCAR DYSON.
Chief Scientist, Paul Walline, monitoring the echogram from the bridge of OSCAR DYSON.

Bird of the Day: 

The bird survey folks identified over 35 species on our trip. I became familiar at least 6 species of birds that I felt comfortable identifying on the fly. When there were hundreds of birds circling the boat there was sometimes one type of bird that stood out making identification a snap. The Auks are related to penguins and have rounder body shapes and unique flight patterns. Like penguins of the southern hemisphere, the denser body composition makes them excellent at swimming under water, but they less nimble taking off and flying in the air compared to sleeker less dense seabirds like the gulls. Unlike penguins all 13 species of auks in the northern hemisphere can fly. The two most abundant types observed onboard are the Murres and the Puffins. I was fortunate to see two species of puffin this trip, the Horned and Tufted Puffin, seemingly too exotic for the Bering Sea. Both have specialized large colorful beaks for carrying multiple prey items and attracting mates. As we sail southeast we are fortunate to be seeing more of them.

Personal Log: 

Patrick, always with a smile, takes a break from the computer screens to look at the catch.
Patrick, always with a smile, takes a break from the computer screens to look at the catch.

These last few days, despite the lack of fishing, have not been without excitement. The bottom-study video sled captured Dall’s Porpoises swimming under water as it was deployed off the stern. As we head southeast there seems to be more whales and clearer skies. This evening we saw dozens of fin whales and one pod was feeding so close that I was able to see baleen. The whales’ baleen is used to screen their plankton food.  I learned the Right Whale has asymmetrical coloring on its baleen and the right side has a lighter off-white color, which we were able to see from the port side of the ship. I would like to take this opportunity to express my gratitude to the crew of the OSCAR DYSON for their help in getting acclimated to the Bering and to NOAA’s Teacher at Sea program for providing this amazing experience.

Question of the Day 

Today’s question: What is next for the OSCAR DYSON? She is headed back out to the Bering to find rare Right Whales. Check out ship tracker at NOAA’s website or the OSCAR DYSON Web site for more info.

Previous Question: How much fish did we catch? 26,575 kilograms (summer extra credit – convert this number to pounds and metric tons)

Horned Puffin (Fratercula corniculata)
Horned Puffin (Fratercula corniculata) 
Tufted Puffin (Fratercula cirrhata)
Tufted Puffin (Fratercula cirrhata)