echogram – Page 3 – NOAA Teacher at Sea Blog

August 7, 2012August 11, 2021

Allan Phipps: Re-verify Our Range to Target… One Ping Only, August 6, 2012

NOAA Teacher at Sea
Allan Phipps
Aboard NOAA Ship Oscar Dyson
July 23 – August 11, 2012


Mission: Alaskan Pollock Mid-water Acoustic Survey
Geographical Area: Bering Sea
Date: August 6, 2012

Location Data
Latitude: 60°55’68” N
Longitude: 179°34’49” E
Ship speed: 11 knots (12.7 mph)

Weather Data from the Bridge
Wind Speed: 10 knots (11.5 mph)
Wind Direction: 300°
Wave Height: 2-4 ft with a 4-6 ft swell
Surface Water Temperature: 8.7°C (47.6°F)
Air Temperature: 8°C (46.4°F)
Barometric Pressure: 1013 millibars (1 atm)

Science and Technology Log

Previously, we learned how the biological trawl data onboard the NOAA Research Vessel Oscar Dyson are collected and analyzed to help calculate biomass of the entire Bering Sea Walleye pollock population. Last blog, I mentioned that the scientific method for estimating the total pollock biomass is not complete without acoustics data, more specifically hydroacoustics! In fact, hydroacoustic data are the real key to estimating how many pollock are in the Bering Sea! That is why our mission is called the Alaskan Pollock Midwater ACOUSTIC-trawl Survey.

Screenshot showing our transects on leg 3 of the pollock midwater acoustic survey. Fish icons indicate where we validated acoustic data with biological sampling. Hydroacoustic data were collected continuously along north/south transects.

The Oscar Dyson is using hydroacoustics to collect data on the schools of fish in the water below us, but we do not know the composition of those schools. Hydroacoustics give us a proxy for the quantity of fish, but we need a closer look. The trawl data provide a sample from each aggregation of schools and allow the NOAA scientists that closer look. The trawl data explain the composition of each school by age, gender and species distribution. Basically, the trawl data verifies and validates the hydroacoustic data. The hydroacoustics data collected over the entire Bering Sea in systematic transects combined with the validating biological data from the numerous individual trawls give scientists a very good estimate for the entire Walleye pollock population in the Bering Sea.

So what is hydroacoustics and how does it work???

Hydroacoustics (“hydro” = water, “acoustics” = sound) is the field of study that deals with underwater sound. Remember, sound is a form of energy that travels in pressure waves. Sound travels roughly 4.3 times faster in water than in air (depending on temperature and salinity of the water). Here is a link with an interactive animation comparing the speed of sound in water, air, and steel! This change in speed will become very important later… keep reading!

Lower sound frequencies travel farther. This is how humpback whales can communicate over great distances with their whale songs! Click on whale songs to hear one!

Whales are not the only aquatic organisms to use sound! Much like dolphins use sound to echo-locate, people use technology to “see” under water using sound energy. We call this technology SONAR (Sound Navigation And Ranging).

dlphfish1 — An animation of dolphin echo-location (courtesy of Discovery of Sound in the Sea).

On a typical recreational watercraft, this technology can be found in the form of a “fish-finder.”

sonar2 — Recreational “fish-finders” can be found on many personal watercraft (courtesy of Discovery of Sound in the Sea).

In commercial fishing, this technology is used in much the same way, just on a larger scale. Here is an animation showing a commercial trawler using SONAR to locate fish.

colrmako — Commercial fishing boat using hydroacoustics to locate fish. This animation illustrates how a fish shows up as an arch on the onboard display (courtesy of Discovery of Sound in the Sea).

The Oscar Dyson has a much more powerful, extremely sensitive, carefully calibrated, scientific version of what many people have on their bass boats. These are mounted on the pod, which is on the bottom of the centerboard, the lowest part of the ship. The Oscar Dyson has an entire suite of SONAR instrumentation including the five SIMRAD EK60 transducers located on the bottom of the centerboard that operate at different Khertz, the SIMRAD ME70 multibeam transducer located on the hull, and a pair of SIMRAD ITI transducers on the trailing edge of the centerboard (one pointed toward the starboard side, the other toward port).

od-acoustics1 — Illustration of the Oscar Dyson showing the hydroacoustic transducers located on the centerboard and the hull of the ship.

This “fish-finder” technology works by emitting a sound wave at a particular frequency and waiting for the sound wave to bounce back (the echo) at the same frequency. The time between sending and receiving the sound wave determines how far away an object is, whether it be the bottom or fish. When the sound waves return from a school of fish, the strength of the returning echo helps determine the fish density (how many fish are there).

An echogram taken from the Oscar Dyson. Shades of yellow and red show extremely large, dense schools of fish. The solid red at the bottom of the picture is the bottom of the sea which is at 94.12 meters at this location.

Another piece of the puzzle… how reflective an individual fish is to sound waves. This is called target strength. Each fish reflects sound energy sent from the transducers, but why? For fish, we rely on the swim bladder, the organ that fish use to stay buoyant in the water column. Since it is filled with air, it reflects sound very well. When the sound energy goes from one medium to another, there is a stronger reflection of that sound energy. The bigger the fish, the bigger the swim bladder; the bigger the swim bladder, the more sound is reflected and received by the transducer. We call this backscatter, or target strength, and use it to estimate the size of the fish we are detecting. This is why fish that have air-filled swim bladders show up nicely on hydroacoustic data while fish that lack swim bladders (like sharks), or that have oil or wax filled swim bladders (like Orange Roughy) have weak signals.

pumkinseed-sunfish-670 — X-ray of fish showing the presence of a swim bladder (courtesy of DeAnza College).

Target strength is how we determine how dense the fish are in a particular school. Scientists take the backscatter that we measure from the transducers and divide that by the target strength for an individual and that gives you the number of individuals that must be there to produce that amount of backscatter. 100 fish produce 100x more echo than a single fish. We extrapolate this information to all the area of the Bering Sea to estimate the pollock population.

Transect_27_awt133 — A close look at part of Transect 27. In this echogram, the area backscatter numerical values are included. At the top of the water column, you can see what are probably jellyfish which have little backscatter since they have no swim bladders. Along the bottom are groundfish. In the center of the water column are several large schools of Walleye pollock with strong backscatter. The square that has a value of 2403.54 shows several large schools!

So the goal is to measure the hydroacoustic density along each transect and extrapolate that data to represent the entire survey area between transects (the area not sampled because the Oscar Dyson can’t cover every square meter of the Bering Sea). When you combine the hydroacoustic data for all of the 30 transects (a total of ~5,000 nautical miles in an area of 100,000 square nautical miles) and the lengths collected in the biological trawl data, you can convert the length data into target strength data to create a distribution of target strengths and find the average target strength for the population. In doing so, you get a complete picture of the Walleye pollock population in the Bering Sea.

Screen shot 2012-08-06 at 4.57.45 PM — The BIG picture. This is the combination of hydroacoustic data and biological trawl data analyzed to show what the entire walleye pollock population looked like for 2009 (courtesy of the Alaska Fisheries Science Center www.afsc.noaa.gov/Publications/ProcRpt/PR2010-03.pdf). Analysis is still being done on the current survey. This year’s results will be out in a report this fall. Expect some changes!

But there’s more!!! Scientists ALSO use hydroacoustic data when trawling to determine if they have caught a large enough sample size to collect fish length data to validate their target strength data. If you recall reading my first blog from sea that taught about the parts of the net, I wrote about and had a drawing of the “kite” on which the “turtle” was attached. The “turtle” is a SIMRAD FS70 trawl SONAR. It has a downward facing transponder that shows a digital “picture” of the size of the net opening. You can also see individual fish and/or schools of fish enter the net by watching this display. Since the scientists only need about 300 fish for a statistically significant sample, they watch this screen carefully so that they do not take more fish than they need. When the lead scientist thinks there are enough fish in the net, she gives the request to the Officer on Deck to “haul back.” Unlike commercial trawlers, a typical trawl on the Oscar Dyson only lasts 25 minutes. Sometimes, we are only officially fishing for 5 minutes if we pull through a large school.

What are the data telling us?

The Walleye pollock data suggest that the population is currently stable; however, there is some evidence of pollock in waters that have traditionally been north of their uppermost documented population range. Are warmer waters due to climate change to blame for this possible shift? Here is an interesting article that addresses this issue and raises several other trends regarding pollock population response to changes in food source and predation due to climate change. Click on the picture to open the article!

fishsticks_title1 — How might climate change affect fish sticks? Click on the picture to read more!

The economic and ecological implications of a shifting pollock population range are a bit unsettling. Fish do not know political boundaries. As the pollock population range possibly shifts north, more of that range will lie within Russian waters than in previous years. This may hurt the U.S. commercial fishing industry as they settle for less of a resource that was once abundant. Since quotas are set based on last year’s numbers, there is a time lag which may result in overfishing in U.S. waters that might lead to a collapse in the Alaskan Walleye pollock fishing industry. The U.S. has invested a tremendous amount of research into maintaining a sustainable pollock fishery. Other countries may be responding to a variety of factors in which sustainability is just one when they are managing pollock stocks and setting catch quotas. Since pollock is a trans-boundary stock, this could lead to greater uncertainty in management of the entire population if pollock increasingly colonize more northern Bering Sea waters as influenced by climate change.

Food for thought…

Next blog, we will learn about cutting edge technology that may eventually make hauling back fish and collecting biological fish data on board the acoustic survey missions obsolete.

Personal Log

It’s tomorrow, TODAY! This morning at 6am Alaska Time, we crossed the International Date Line (IDL). The IDL is at 180° longitude. General Vessel Assistant Brian Kibler and I went out to the bow of the ship so we would be the first onboard to cross the line!

BeringSea — Map of the Bering Sea showing both the International Date Line and the 180th longitude. Our closest point to Russia was 12 nautical miles from Cape Navarin which is very close to 180 longitude.

Over the next two days, our transects take us back and forth over the IDL 3 more times. Fortunately, onboard our Oscar Dyson time warp machine we simply observe the Alaska Time Zone (the time zone from our port of call). With everyone onboard operating different shifts, and with 24/7 operations, it would be quite confusing if we kept changing our clocks to observe the local time zone.

Mariners who cross the IDL when at sea are inducted into the “Order of the Golden Dragon” and receive a certificate with the details of this momentous crossing. There are several other notorious crossing that receive special recognition. They are:

▪     The Order of the Blue Nose for sailors who have crossed the Arctic Circle.
▪     The Order of the Red Nose for sailors who have crossed the Antarctic Circle.
▪     The Order of the Ditch for sailors who have passed through the Panama Canal.
▪     The Order of the Rock for sailors who have transited the Strait of Gibraltar.
▪     The Safari to Suez for sailors who have passed through the Suez Canal.
▪     The Order of the Shellback for sailors who have crossed the Equator.
▪     The Golden Shellback for sailors who have crossed the point where the Equator crosses the International Date Line.
▪     The Emerald Shellback or Royal Diamond Shellback for sailors who cross at 0 degrees off the coast of West Africa (where the Equator crosses the Prime Meridian)
▪     The Realm of the Czars for sailors who crossed into the Black Sea.
▪     The Order of Magellan for sailors who circumnavigated the earth.
▪     The Order of the Lakes for sailors who have sailed on all five Great Lakes.

July 15, 2011April 28, 2021

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.

June 8, 2011April 28, 2021

Sue Zupko: 10 Steamin’ an’ a Beamin’

NOAA Teacher at Sea: Sue Zupko
NOAA Ship: Pisces
Mission: Extreme 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.

July 28, 2007April 1, 2021

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.

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.

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

Conductivity (salinity) Profile from CTD readings

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 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.

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.

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)