Latitude: N 26° 03.476′
Longitude: W 080° 20.920′
Weather Data from home
Wind Speed: 7.8 knots (9 mph)
Wind Direction: East
Wave Height: 2 ft
Surface Water Temperature: 28.9°C (84°F)
Air Temperature: 30°C (86 °F)
Barometric Pressure: 1016 millibars ( 1 atm)
Science and Technology Log:
Below are the numbers that Johanna (my fellow Teacher at Sea) put together at the end of our mission.
We completed 44 hauls in our leg of the survey and caught approximately 118,474 pollock. All of those pollock weighed a collective 24,979.92 kg (= 25 tons)! Last year’s official total allowable catch (called a quota) for all commercial fishermen in Alaska was 1.17 million tons!
So, we only caught 25 tons/ 1,170,000 tons = 0.00002 = 0.002% of the yearly catch in our study.
The estimated population of pollock in the Bering Sea is 10 million tons (10,000,000 T). This means we caught only 0.00025% of the entire pollock population!
So, as you can see, in the big picture, our sampling for scientific analysis is quite TINY!
Continuing with more cool pollock data…
We identified 7,276 males and 7,145 females (and 2,219 were left unsexed)
We measured 16,640 pollock lengths on the Ichthystick!
Pollock lengths ranged from 9cm to 74cm
We measured 260 lengths of non-pollock species (mostly jellyfish, pacific herring, and pacific cod)
We collected 1,029 otoliths for analysis
After two full days of travel including a long red-eye flight across country, I am back in Ft Lauderdale, Florida. I had the most incredible experience as a NOAA Teacher at Sea on the Oscar Dyson! The trip was absolutely amazing! Here are some parting shots taken on my last day in Dutch Harbor, Alaska.
In closing, I would like to thank a few people. The NOAA Corps officers and deck crew are wonderful and do a great job running a tight ship. I would like to thank them all for keeping me safe, warm, dry, and well fed while out at sea. They all made me feel right at home.
The NOAA scientists Taina, Kresimir, Rick and Darin did a fabulous job patiently explaining the science occurring onboard and I appreciate them letting me become a part of the team! I loved immersing myself back in the practice of real scientific inquiry and research!
I would like to thank the NOAA Teacher at Sea program for allowing me to take part in this incredible research experience for teachers! Teachers and students in my district are very excited to hear about my experiences and I look forward to continuing to share with them about NOAA Teacher at Sea! Sign me up, and I’d be happy to “set sail” with NOAA again.
Finally, I would like to thank my readers. I truly enjoyed sharing my experiences with you and hope that, through my blog, you were able to experience a bit of the Bering Sea with me.
Latitude: 53°54’41” N
Longitude: 166°30’61” E
Ship speed: 0 knots (0 mph) In Captains Bay at Dutch Harbor during calibration.
Weather Data from the Bridge
Wind Speed: 17 knots (19.5 mph)
Wind Direction: 184°
Wave Height: 1-2 ft
Surface Water Temperature: 10.2°C (50.4°F)
Air Temperature: 12.5°C (54.5°F)
Barometric Pressure: 1005.9 millibars (0.99 atm)
Science and Technology Log:
Imagine a time when fish surveys could be done through remote sensing, thus eliminating the need to catch fish via trawling to verify fish school composition, length, weight, and age data. During our “Leg 3” of the Alaska Pollock Acoustic Midwater Trawl Survey, we caught, sorted, sexed, and measured 25 tons of pollock! While this amounts to only 0.002% of the entire pollock quota and 0.00025% of the pollock population, wouldn’t it be nice if we could determine the pollock population without killing as many fish?
Introducing the “Cam-Trawl,” a camera-in-net technology that NOAA scientists Kresimir and Rick are developing to eventually reduce, if not eliminate, the need to collect biological specimens to verify acoustic data. Cam-Trawl consists of a pair of calibrated cameras slightly offset so the result is a stereo-camera.
The importance of setting up a stereo-camera is so you can use the slightly different pictures taken at the same time from each camera to calculate length of the fish in the pictures. Eventually, a computer system might use complex algorithms to count and measure length of the fish that pass by the camera. If the kinks are worked out, the trawl net would be deployed with the codend open, allowing fish to enter the net and flow past the camera to have their picture taken before swimming out of the open end of the net. Some trawls would still require keeping the codend closed to determine gender ratios and weights for extrapolation calculations; however, the use of Cam-Trawl would significantly reduce the amount of pollock that see the fish lab of the Oscar Dyson. On this leg of the survey, the NOAA scientists installed the Cam-Trawl in a couple of different locations along the trawl net to determine where it might work best.
Below are some photos taken by Cam-Trawl of fish inside the AWT trawl net. Remember, there are two cameras installed as a stereo-camera that create two images that are taken at slightly different angles. In the photos below, I only picked one of the two images to show. In the video that follows, you can see how scientists use BOTH photos to calculate the lengths of the fish captured on camera.
Another NOAA innovation using stereo cameras is called “Trigger-Cam.” Trigger-Cam is installed into a crab pot to allow it to sit on the ocean floor. For this type of camera deployment, the NOAA scientists removed the crab pot net so they would not catch anything except pictures.
The real innovation in the Trigger-Cam is the ability to only take pictures when fish are present. Deep-water fish, in general, do not see red light. The Trigger-Cam leverages this by using a red LED to check for the presence of fish. If the fish come close enough, white LEDs are used as the flash to capture the image by the cameras.
The beauty of this system is that it uses existing fishing gear that crab fishermen are familiar with, so it will be easily deployable. Another stroke of brilliance is that the entire device will cost less than $3,000. This includes the two cameras, lights, onboard computer, nickel-metal hydride batteries, and a pressure housing capable of withstanding pressures of up to 50 atmospheres (500 meters) as tested on the Oscar Dyson! Here is a short animated PowerPoint that explains how Trigger-Cam works. Enjoy!
Here are a couple of picture captured by the Trigger-Cam during trials!
While these pictures were captured during tests in Dutch Harbor, they do provide proof-of-concept in this design. With a cheap, easily deployable and retrievable stereo-camera system that utilized fishing gear familiar to most deck hands, Trigger-Cams might contribute to NOAA’s future technology to passively survey fish populations.
A little fun at sea! We needed to do one last CTD (Conductivity, Temperature, Depth), and decided to lower the CTD over deep water down to 500 meters (1,640.42 ft)! Pressures increases 1 atmosphere for every 10 meters in depth. At 500 meters, the pressure is at 50 atmospheres!!! We wondered what would happen if… we took styrofoam cups down to that depth. We all decorated our cups and put them in a net mesh bag before they took the plunge. Here is a picture showing what 50 atmospheres of pressure will do to a styrofoam cup!
We missed the Summer Olympics while out on the Bering Sea. T-T We did get in the Olympic spirit and had a race or two. Here is a little video in the spirit of the Olympics…
All for now… We are back in Captains Bay, Dutch Harbor, but are calibrating the hydroacoustic equipment at anchor. Calibration involves suspending a solid copper sphere below the ship while the NOAA scientists check and fine-tune the different transducers. This process will take about 7 hours! We have been out at sea for 3 weeks, are currently surrounded by land, but must wait patiently to finish this last and very important scientific task. If the calibration is off, it could skew the data and result in an inaccurate population estimation and quotas that may not be sustainable! This Landlubber can’t wait to have his feet back on terra firma. The thought of swimming crossed my mind, but I think I’ll wait. Then we will see if I get Land Sickness from being out at sea for so long…
Latitude: 60°25’90” N
Longitude: 177°28’76” W
Ship speed: 3 knots (3.45 mph)
Weather Data from the Bridge
Wind Speed: 5 knots (5.75 mph)
Wind Direction: 45°
Wave Height: 2-4 ft with a 2 ft swell
Surface Water Temperature: 8.6°C (47.5 °F)
Air Temperature: 8°C (46.4 °F)
Barometric Pressure: 1019 millibars (1 atm)
Science and Technology Log:
In my last blog, we learned about how the scientists onboard the Oscar Dyson use some very sophisticated echo-location SONAR equipment to survey the Walleye pollock population.
Can the Walleye pollock hear the “pings” from the SONAR?
No. Unlike in the movies like “The Hunt for Red October” where submarines are using sound within the human audible range to “ping” their targets, the SONAR onboard the Oscar Dyson operates at frequencies higher than both the human and fish range of hearing. The frequency used for most data collection is 38 kHz. Human hearing ranges from 20 Hz to 20 kHz. Walleye pollock can hear up to 900 Hz. So, the pollock cannot hear the SONAR used to locate them…
Can the Walleye pollock hear the ship coming?
Normally, YES! Fish easily hear the low frequency noises emitted from ships.
If you are operating a research vessel trying to get an accurate estimate on how many fish are in a population, and those fish are avoiding you because they hear you coming, you will end up with artificially low populations estimates! The International Council for the Exploration of the Seas (ICES) established noise limits for research vessels that must be met in order to monitor fish populations without affecting their behavior. Fish normally react to a threat by diving, and that reduces their reflectivity or target strength, which reduces the total amount of backscatter and results in lower population estimates (see my last blog).
That is why NOAA has invested in noise-reducing technology for their fish survey fleet. The Oscar Dyson was the first of five ships build with noise-reducing technology. These high-tech ships have numerous strategies for reducing noise in the range that fish might hear.
There are two main sources of engine noise onboard a ship: machinery noise and propeller noise.
The best acoustic ship designs are going to address the following:
1) Address hydrodynamics with unique hull and propeller design.
2) Use inherently quiet equipment and choose rotating rather than reciprocating equipment.
3) Use dynamically stiff foundations for all equipment (vibration isolation).
4) Place noisier equipment toward the centerline of the ship.
5) Use double-hulls or place tanks (ballast and fuel tanks) outboard of the engine room to help isolate engine noise.
6) Use diesel electric motors (diesel motors operate as generators while electric motors run the driveshaft.
The U.S. Navy designed the Oscar Dyson’s hull and propeller for noise quieting. This propeller is designed to eliminate cavitation at or above the 11 knot survey speed. Not only does cavitation create noise, it can damage the propeller blades.
The Oscar Dyson’s hull has three distinguishing characteristics which increase its hydrodynamics and reduce noise by eliminating bubble sweep-down along the hull. The Oscar Dyson has no bulbous bow, has a raked keel line that descends bow to stern, and has streamlined hydrodynamic flow to the propeller.
To reduce a ship’s noise in the water, it is absolutely crucial to control vibration. The Oscar Dyson has four Caterpillar diesel gensets installed on double-stage vibration isolation systems. In fact, any reciprocating equipment onboard the Oscar Dyson is installed on a double-stage vibration isolation system using elastomeric marine-grade mounts.
Since the diesel engines are mounted on vibration isolation stages, it is necessary to also incorporate flexible couplings for all pipes and hoses connecting to these engines.
Any equipment with rotating parts is isolated with a single-stage vibration system. This includes equipment like the HVAC, the electric generators for the hydraulic pumps, and the fuel centrifuges that remove any water and/or particles from the fuel before the fuel is pumped to the diesel generators.
Low Noise Equipment:
The only equipment that does not use vibration isolation stages are the two Italian-made ASIRobicon electric motors that are mounted in line with the prop shaft. Both are hard-mounted directly to the ship because they are inherently low-noise motors. This is one of the benefits of using a diesel-electric hybrid system. The diesel motors can be isolated in the center of the ship, near the centerline and away from the stern. The electric motors can be located wherever they are needed since they are low noise.
Even the propeller shaft bearings are special water-lubricated bearings chosen because they have a low coefficient of friction and superior hydrodynamic performance at lower shaft speeds resulting in very quiet operation. They use water as a lubricant instead of oil so there is a zero risk of any oil pollution from the stern tube.
Acoustic Insulation and Damping Tiles:
The Oscar Dyson uses an acoustic insulation on the perimeter of the engine room and other noisy spaces. This insulation has a base material of either fiberglass or mineral wool. The middle layer is made of a high transmission loss material of limp mass such as leaded vinyl.
The Oscar Dyson also has 16 tons of damping tiles applied to the hull and bulkheads to reduce noise.
All of these noise-reducing efforts results in a fully ICES compliant research vessel able to survey fish and marine mammal populations with minimal disturbance. This will help set new baselines for population estimates nationally and internationally.
As you can see from the graph above, The Oscar Dyson is much quieter than the Miller Freeman, the ship that it is replacing. You can see the differences in the hull design from the picture below.
Next blog, I will write about new, cutting edge technology that might reduce the need for biological trawling to verify species.
Special thanks to Chief Marine Engineer Brent Jones for the tour of the engineering deck and engine room, and for the conversations explaining some of the technology that keeps the Oscar Dyson going.
I found out drills aboard ships are serious business! Unlike a fire drill at school where students meander across the street and wait for an “all clear” bell to send them meandering back to class, fire drills on a ship are carefully executed scenarios where all crew members perform very specific tasks. When out at sea, you cannot call the fire department to rescue you and put out a fire. The crew must be self-reliant and trained to address any emergency that arises. When we had a fire drill, I received permission from Commanding Officer Boland to leave my post (after I checked in) and watch as the crew moved through the ship to locate and isolate the fire. They even used a canister of simulated smoke to reduce visibility in the halls similar to what would be experienced in a real fire!
Late last night, we finished running our transects! Our last trawl on transect was a bottom trawl which brought up some crazy creatures! Here are a couple of photos of some of the critters we found.
Next blog will probably be my last from Alaska. T-T
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.
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).
On a typical recreational watercraft, this technology can be found in the form of a “fish-finder.”
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.
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).
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).
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.
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.
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.
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!
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.
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!
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.
Latitude: 61°12’61” N
Longitude: 178°27’175″ W
Ship speed: 11.6 knots (13.3 mph)
Weather Data from the Bridge
Wind Speed: 11 knots (12.7 mph)
Wind Direction: 193°
Wave Height: 2-4 ft (0.6 – 1.2 m)
Surface Water Temperature: 8.3°C ( 47°F)
Air Temperature: 8.5°C (47.3°F)
Barometric Pressure: 999.98 millibars (0.99 atm)
Science and Technology Log
At the end of last blog, I asked the question, “What do you do with all these fish data?”
The easy answer is… try and determine how many fish are in the sea. That way, you can establish sustainable fishing limits. But there is a little more to the story…
Historically, all fisheries data were based on length. It is a lot easier to measure the length of a fish than to accurately determine its weight on a ship at sea. To accurately measure weight on a ship, you have to have special scales that account for the changes in weight due to the up and down motion of the ship. Similar to riding a roller coaster, at the crest of a wave (or top of a hill on a roller coaster), the fish would appear to weigh less as it experiences less gravitational force. At the trough of a wave (or bottom of a hill on a roller coaster), the fish would experience more gravitational force and appear to weigh more. Motion compensating scales are a more recent invention, so, historically, it was easier to just measure lengths.
For fisheries management purposes, however, you want to be able to determine the mass of each fish in your sample and inevitably the biomass of the entire fishery in order to decide on quotas to determine a sustainable fishing rate. So, you need to be able to use length data to estimate mass. Here is where science and math come to the rescue! By taking a random sample that is large enough to be statistically significant, and by using the actual length and weight data from that sample, you can create a model to represent the entire population. In doing so, you can use the model for estimating weights even if all you know is the lengths of the fish that you sample. Then you can extrapolate that data (using the analysis of your acoustic data – more on this later) to determine the entire size of the pollock biomass in the Bering Sea.
How do they do that? First, you analyze and plot the actual lengths vs. weights of your random sample and your result is a scatter-plot diagram that appears to be an exponential curve.
Then you create a linear model by log-transforming the data. This gives you a straight line.
Next, you back-transform the data into linear space (instead of log space) and you will have created a model for estimating weight of pollock if all you know are the lengths of the fish. This is close to a cubic expansion which makes sense because you are going from a one-dimensional measurement (length) to a 3-dimensional measurement (volume).
Scientists can now use this line to predict weights from all of their fish samples and then extrapolate to determine the entire biomass of Walleye pollock population in the Bering Sea (when combined with acoustic data… coming up in the next blog!) when the majority of the data collected is only fish lengths.
Another interesting question… How does length change with age? Fish get bigger as they get older, all the way until they die, which is different from mammals and birds. However, some individual fish grow faster than others, so the relationship between age and length gets a little complicated. How do you determine the age distribution of an entire population when all you are collecting are lengths?
Just like weight, you can determine the age from a subset of fish and apply your results to the rest. This works great with young fish that are one year old. The problem is… once you get beyond a one-year-old fish, using lengths alone to determine age becomes a little sketchy. Different fish may have had a better life than others (environmental/ecological effects) and had plenty to eat, great growing conditions, etc and be big for their age relative to the rest of the population. Some may have had less to eat and/or unfavorable conditions such as high parasite loads leading them to be smaller… There are also other things to consider such as genetics that affect length and growth rate of individuals. Here is where the collection of otoliths becomes important. By collecting the otoliths with the lengths, weights, and gender data, the scientists can look at the age distributions within the population. The graph below shows that if a pollock is 15 cm long, it is clearly a 1 year old fish. If a pollock is 30 cm long, it might be a 2 year old, a 3 year old, or a 4 year old fish, but about 90% of fish at this length will be 3 years old. If a fish is 55 cm long, it could be anywhere from 6 to 10+ years old!
Collection of otoliths is the only way to accurately determine the age of the fish in the random sample and be able to extrapolate that data to determine the estimated age of all the pollock in the fishery. Here is a photo comparing otolith size of Walleye pollock with their lengths.
If we wanted to find out exactly how old each of these fish were, we would need to break the otoliths in half to look at a cross section. Below is what a prepared otolith looks like (courtesy of Alaska Fisheries Science Center). You can try counting rings yourself at their interactive otolith activity found here.
All of these data go into a much more complicated model (including the acoustic-trawl survey walleye pollock population estimates) to accurately estimate the total size of the fishery and set the quotas for the pollock fishing industry so that the fishery is maintained in a sustainable manner.
Next blog, we will learn about how the various ways acoustic data fit into this equation to create the pollock fishery model!
Ok, so here is a long overdue look at the NOAA Ship Oscar Dyson that I am calling home for three weeks. I was pleasantly surprised when I saw my state room. It is bigger than I thought it would be and came with its own bathroom. I was also pleasantly surprised to learn I would be sharing my state room with Kresimir Williams, one of the NOAA scientists and an old college friend of mine! Here is a picture of our room.
The room has a set of bunk beds. Thankfully, my bed is on the bottom. I do not know how I would have gotten in and out of bed in the rough seas we had over the last couple of days. If I do fall out of bed, at least I will not have far to fall. Last year, the ship rocked so hard in rough seas that one of the scientists fell head first out of the top bunk! The room also had two lockers that serve as closets, a desk and chair, and our immersion suits (the red gumby suits). The bathroom is small and the shower is tiny! Notice the handles on the wall. These are really handy when trying to shower in rough seas!
Next, we have the Galley or Mess Hall. This is where we have all of our meals prepared by Tim and Adam. Notice that all of the chairs have tennis balls on the legs and that each chair has a bungee cord securing it to the floor! There are also bungee cords over the plates and bowls. Everything has to be secured for rough seas.
The Mess Hall also has a salad bar, cereal bar, sandwich fixings, soup, snacks like cookies, and ice cream available 24 hours a day. No one on board is going hungry. The food has been excellent! We have had steaks, ribs, hamburgers and fish that Tim has grilled right out on deck. Here is a picture of my “surf and turf” with a double-baked potato.
Most of my work here on board (other than processing fish) has been in the acoustics lab, also known as “The Cave” since it has no windows. This is where the NOAA scientists are collecting acoustic data on the schools of fish and comparing the acoustic data with the biological samples we process in the fish lab.
I also spend some time up on the Bridge. From the Bridge, you can see 10 to 12+ nautical miles on a clear day. This morning, we saw a couple of humpback whales blowing (surfacing to breathe) about 1/4 mile off our starboard side! A couple of days ago (before the weather turned foul), we spotted an American trawler.
Today, we got close enough to see the Russian coastline! Here is a picture of a small tanker ship with the Russian coastline in the background!
Here are some pictures of the helm and some of the technology we have onboard to help navigate the ship.
I have also spent some time in the lounge. This is where you can go to watch movies, play darts (yea, right! on a ship in rough weather???), or just relax. The couch and chairs are so very comfy!
When you have 30 people on board and in close quarters, you better have a place to do laundry! Here is a picture of our very own laundromat.
All for now. Next time, I will share more about life at sea!
Latitude: N 61°39’29”
Longitude: W 117°55’90”
Ship speed: 11.7 knots (13.5mph)
Weather Data from the Bridge
Wind Speed: 26 knots (30mph)
Wind Direction: 044°
Wave Height: 4 meters (12 ft)
Surface Water Temperature: 8.2°C ( 46.8°F)
Air Temperature: 7.4°C (45°F)
Barometric Pressure: 994 millibar (0.98 atm)
Science and Technology Log:
Last blog, we learned about the different trawl nets and how the NOAA scientists are comparing those nets while conducting the mid-water acoustic pollock survey. We left off with the fish being released from the codend onto the lift table and entering the fish lab. Here is where the biological data is collected.
The fish lab is where the catch is sorted, weighed, counted, measured, sexed, and biological samples such as the otoliths, or earbones, are taken (more about otoliths later in this post). First, the fish come down a conveyor belt where they are sorted by species (see video above). Typically, the most numerous species (in our case pollock) stay on the conveyor and any other species (jellyfish and/or herring, but sometimes a salmon or two, or maybe even something unique like a lumpsucker!), are put into separate baskets to weigh and include in the inventory count. In the commercial fishing industry, these species would be considered bycatch, but since we are doing an inventory survey, we document all species caught. Here are some pictures of others species caught and included in the midwater survey.
The goal of each trawl is to randomly select a sample of 300 pollock to measure as a good representation of the population (remember your statistics! Larger sample sizes will give you a better approximation of the real population). If more than 300 pollock are caught, the remainder are weighed in baskets and quickly sent back to sea. All of the catch is weighed so the scientists can use the length and gender data taken from the sample to extrapolate for the entire catch. This data is combined with the acoustics data to estimate the size of the entire fishery (more on acoustic data in a future post). Weights are entered via touch screen into a program (Catch Logger for Acoustic Midwater Surveys – CLAMS) developed by the NOAA scientists onboard.
The 300 pollock are sexed to determine the male/female ratio of this randomly selected portion of the population. Gender is determined by making an incision along the ventral side from posterior to anterior beginning near the vent. This exposes the internal organs so that either ovaries or testes can be seen. Sometimes determining gender is tricky since the gonads look very different as fish pass through pre-spawning, spawning, or post-spawning stages. When we determine gender, the fish are put into two separate hoppers, the one for females is labeled “Sheilas” and the hopper for males is labeled “Blokes.”
We use an Ichthystick to then measure the males and females separately to collect length data for this randomly selected sample. Designed by NOAA Scientists Rick and Kresimir, the Ichthystick very quickly measures lengths by using a magnet placed at the fork of the fish’s tail (when measuring fork-length). This sends a signal to the computer to record the individual fish’s length data immediately into a spreadsheet and the software creates a population length distribution histogram in real-time as you enter data.
A randomly selected subset of 40 pollock get individually weighed, length measured, sexed, evaluated for gonadal maturity and have the otoliths removed. Otoliths (oto = ear, lithos = bone) are calciferous bony structures in the fish’s inner ear. These are used to determine age when examined via cross-section under a dissecting scope. The number of rings corresponds to the age of the pollock, similar to rings seen in trees. The otoliths are taken by holding the fish at the operculum and making an incision across the top of the head to expose the brain and utricle of the inner ear. The otolith is found inside the utricle. Forceps are used to extract the otoliths, which are then washed and put in individual bar-coded vials with glycerol-thymol solution to preserve them for analysis back at the Alaska Fisheries Science Center.
Watch this short video to see what the entire process of data collection looks like.
So… why collect all of this data? How is this data analyzed and used? Stay tuned to my next blog!
Well, I can officially say… the honeymoon is over. The Bering Sea had been so extremely kind to us with several days of great weather while we had a high pressure system over us. We enjoyed spectacular sunrises and sunsets, cloudless days and calm seas.
Now… we have a low pressure system on top of us. Last night, we experienced 35 knot winds and 12 foot seas. I have spent a lot of time in my room in the past 24 hours… Late this morning, the sun came out and the winds calmed down, but the barometric pressure was still very low (around 990 mbars) which basically meant we were in the center of the low pressure system (similar to the eye of a hurricane, but not as strong… thank goodness!). We had a few hours relief, but we are back to pounding through the waves as the wind picks back up. It will be another long and sleepless night for this landlubber…
On a positive note, we did see two Laysan Albatrosses (Phoebastria immutabilis) from the Bridge as the winds began to kick up. They seemed to really enjoy the high winds as they soared effortlessly around the ship. The Officer on Deck (OOD) also said he saw a humpback breaching, but by the time I got up to the Bridge, it had moved on…
Next blog, I will share pictures of my room, the galley, “the cave,” the Bridge, etc. Right now, I am just trying to hold on to my mattress and my stomach…
Ship speed: 3.8 knots (4.4 mph) currently fishing
Weather Data from the Bridge
Wind Speed: 6.9 knots (7.9 mph)
Wind Direction: 30°T
Wave Height: 2ft with 2-4ft swells
Surface Water Temperature: 8.7°C ( 47.7°F)
Air Temperature: 7.9°C ( 46.2°F)
Barometric pressure: 1005.8 millibar (0.99 atm)
Science and Technology Log:
Since the main goal of this voyage is the acoustic-trawl survey of the mid-water portion of the Alaskan pollock population, I thought I would start by telling you how we go fishing to catch pollock! This isn’t the type of fishing I’m used to… Alaskan pollock is a semi-demersal species, which means it inhabits from the middle of the water column (mid-water) downward to the seafloor. This mid-water survey is typically carried out once every two years. Another NOAA Fisheries survey, the bottom trawl survey, surveys the bottom-dwelling or demersal portion of the pollock population every year. I will begin by describing how we are fishing for pollock on this acoustic-trawl survey.
The Oscar Dyson carries two different types of trawling nets for capturing fish as part of the mid-water survey, the AWT (Aleutian Wing Trawl which is a mid-water trawl net) and the 83-112 (a bottom-trawl net that is named for the length of its 83 foot long head rope that is at the top of the mouth of the net and the 112 foot long weighted foot rope at the bottom of the mouth of the net). One of the research projects on board the Oscar Dyson is a feasibility study that involves a comparison of the AWT and using the 83-112 bottom-trawl net as if it were a mid-water net. The 83-112 is much smaller than the AWT, so there is concern with the fish avoiding this net and thus causing a reduction in catch. While the bottom trawl survey acquires good information on the bottom-dwelling pollock using the 83-112 bottom trawl, if they also used this net to sample in mid-water they could help “fill in” estimates of mid-water dwelling pollock in years when the acoustic mid-water trawl survey does not occur.
When the net is deployed from the ship, the first part of the net in the water is called the cod end. This is where the caught fish end up. The mesh size of the net gets smaller and smaller until the mesh size at the cod end is only ½ inch (The mesh size at the mouth of the net is over 3 meters!).
The AWT is also outfitted with a Cam-Trawl, which is the next major part that hits the water. This is a pair of cameras that help scientists identify and measure the fish that are caught in the net. Eventually, this technology might be used to allow scientists to gather data on fish biomass without having to actually collect any fish (more on this technology later). This piece of equipment has to be “sewn” into the side of the net each time the crew is instructed to deploy the AWT. The crew uses a special type of knot called a “zipper” knot, which allows them to untie the entire length of knots with one pull on the end much like yarn from a sweater comes unraveled.
Along the head rope, there is a piece of net called the “kite” where a series of sensors are attached to help the scientists gather data about the depth of the net, the shape of the net underwater, how large the net opening is, determine if the net is tangled, how far the net is off the bottom, and see an acoustic signal if fish are actually going into the net (more on these sensors later, although the major acoustic sensor is affectionately called the “turtle”).
Once the kite is deployed, a pair of tom weights (each weighing 250 lbs), are attached to the bridal cables to help separate the head rope from the foot rope and ensure the mouth of the net will open. Then, after a good length of cable is let out, the crew transfers the net from the net reel to the two tuna towers and attach the doors. The doors act as hydrofoils and create drag to ensure the net mouth opens wide. Our AWT net usually has a 25 meter opening from head rope to foot rope and a 35 meter opening from side to side.
The scientists use acoustic data to determine at what depth they should fish, then the OOD (Officer on Deck) uses a scope table to determine how much cable to let out in order to reach our target depth. Adjustments to the depth of the head rope can be made by adjusting speed and/or adjusting the length of cable released.
The scientists use more acoustic data sent from the “turtle” to determine when enough fish are caught to have a scientifically viable sample size, then the entire net is hauled in. Once on board, the crew uses a crane to lift the cod end over to the lift-table. The lift-table then dumps the catch into the fish lab where the fish get sorted on a conveyor belt. More on acoustics and what happens in the fish lab in my next blog!
WOW! What an adventure!!! So I must get you caught up on some of the happenings thus far. After a mix-up where my reservation was cancelled on the Saturday afternoon flight from Anchorage to Dutch Harbor and the threat of being stranded in Anchorage for another day, I finally made it to Dutch. The weather cooperated (which is not the case more often than not), and we landed on Dutch Harbor after a quick refueling stop in King Salmon. Since we landed after 8pm, we went straight to one of the few restaurants in Dutch Harbor and had a late dinner before heading to the Oscar Dyson for the night.
Sunday morning, we went with several of the scientists out to Alaska Ship Supply to get some gear. I picked up my obligatory “Deadliest Catch” shirt and hat as all tourists do here in Dutch Harbor. We made three trips to the airport throughout the day to see if some of the science gear and luggage came, but came back disappointed. On one of our trips to the airport, we had lunch at the airport restaurant. I had Vietnamese Pho, which is a beef noodle soup, but it wasn’t nearly as good as the Pho my wife makes. 🙂 We also drove up the “Tsunami Evacuation Route” to an overlook where we could see all of Dutch Harbor and the town of Unalaska. Later, we drove around Unalaska and stopped to check out some tidal pools on our way back to the Oscar Dyson. In the afternoon, we checked out the World War II museum that was absolutely fascinating! I did not know Dutch Harbor was bombed by the Japanese and that so many American soldiers were stationed in the bunkers surrounding the harbor. For dinner, I had black cod (sablefish) at the Grand Aleutian Hotel. Yummy!
Monday we embarked on our adventure shortly after noon. We had to leave the dock because another ship was scheduled to offload there in the afternoon. The scientists’ equipment arrived on a late Monday morning cargo flight, but they didn’t make it to the ship on time!!! We couldn’t go to sea without them, so we deployed the “Peggy D” to go pick them up and bring them aboard!
Once we had our missing scientists, we left the safety of Dutch Harbor and ventured into open water. On our way, we saw dozens of humpback whales! None of the whales breached (jumped out of the water), but several of them fluked (dove and put their tail out of the water).
We started our day and a half journey to get to the starting point of our survey transects (the end point of last month’s survey). On our trip out, we experienced 6 to 10 ft seas and a 25 knot wind. It was a “gentle” welcome to the Bering Sea, but I struggled to get my sea legs underneath me. Meclizine is great motion sickness medication, but it sure knocked me out. I feel better now that I am not taking anything and am used to the rocking deck. While we made our way to our first transect, we had a couple of emergency drills. Here I am with fellow Teacher at Sea, Johanna, in our immersion suits as we completed our abandon ship drill.
On Wednesday morning, we began our first transect and did our first trawl along the transect (more on that later). I learned how to work in the fish lab collecting biological data on the catch we brought on board. I have been struggling to adjust to both my shift, which is 4am to 4pm, and the fact that the sun sets around 1am and rises at about 7am.
Thursday morning I woke on time and observed the survey scientists and crew deploying the CTD (Conductivity, Temperature, Depth) rosette from the hero deck (on the starboard side).
We also had beautiful clear skies and I was able to see Venus and Jupiter. At sunrise, I saw the GREEN FLASH!!! It was a beautiful start to the day.
We processed one mid-water AWT (Aleutian Wing Trawl) trawl that was all pollock, then switched to the 83-112 bottom trawl net (83 foot long head-rope and 112 foot long foot-rope) and pulled up a lot of jellyfish with our pollock.
Last night, I finally got a really good night sleep! This morning (Friday), I watched the CTD deployment again and learned more about the data being collected (more on this later). No spectacular sunrise this morning as it was the typical gray, foggy weather. I went up and spent some time on the bridge and Chelsea, our navigator/medic, taught me a lot about the instrumentation used for navigating the ship. There sure is a lot of technology on board!!!
From the bridge, we saw a pod of Dall’s Porpoise feeding, splashing around, and moving fast! We processed another AWT trawl of pollock that had quite a few herring mixed in. We traveled further into Russian waters than originally anticipated as we tried to identify the northern boundaries of the pollock population to get the best picture of the entire pollock range. We spotted a huge Russian trawler from the bridge!
We then headed south again towards American waters, but needed to do a quick water column profile test. Since we did not want to stop to drop the CTD again, I got to deploy a XBT (Expendable Bathythermograph)! After all the talk about safety briefings, the use of ballistics, and outfitting me with every piece of safety gear we could muster, I got ready to fire the XBT!!! Turns out, when you pull the firing pin, the XBT just slides out of the tube… no fireworks, no big bang… just a small kurplunk as the XBT enters the water. We all had a good laugh at my expense. See, scientists know how to have fun!
WOW! So I have just scratched the surface of our voyage thus far! Next time, I will give you a snapshot of what life was like aboard the ship.
At South Plantation High, I am the sponsor of our Solar Knights Racing Team that has won 1st place in the nation twice in the past six years at the high school level Solar Car Challenge (see video below)! We have been building and racing solar cars at the high school level for six years! Two of the races we have competed in were cross-country, the latest of which went from Fort Worth, Texas to Boulder, Colorado over 7 days in July 2010. Last year’s race was a track race at the Texas Motor Speedway.
I also sponsored our school’s Project ORB (Operation Reef Ball) and deployed thirty 500-1,500 lb concrete reef balls off the coast of
South Florida to encourage coral colonization and propagation to offset some of the damage done to our beautiful South Florida coral reefs. Recently, I had the privilege of presenting a poster session about our Project ORB at the European Geophysical Union conference in Vienna, Austria!
One of my favorite senior projects was a solar-powered kayak, which would improve accessibility to the Florida Everglades as well as other coastal environments for persons with disabilities. I really enjoyed this project as it blended my passion for alternative energy with my love for getting out on the water. This project won the WOW Award at the Florida Solar Energy Center’s Energy Whiz Olympics!
Now, I am incredibly excited about the opportunity to sail aboard the NOAA Ship Oscar Dyson out of Dutch Harbor, Alaska! This will officially be the furthest north I have ever traveled! As we experience climate change, particularly in areas near the poles where the effects of climate change are more dramatic, it is important to study these changes and how they affect economically important species such as the Alaskan or Walleye Pollock (Theragra chalcogramma). Walleye Pollock is said to be the largest remaining supply of edible fish in the world, and is the fish used in high quality breaded and battered fish products, fish sticks, and surimi(also known as “imitation crabmeat”). Many fast food restaurants commonly use Walleye Pollock in their fish sandwiches. It is important that this fishery be monitored and maintained so that harvest remains sustainable. I hope that I may enlighten my students about their impacts on the environment when they decide what they will eat so they may become more conscientious consumers.
I am getting ready to head out to sea and am really looking forward to working with the scientists on board the NOAA Ship Oscar Dyson! While my blog will be geared towards my AP Environmental Science students, I hope that people of all ages will follow me along my journey as I learn about the science behind maintaining a sustainable fishery. I also hope to inspire my own students, and others, about the career opportunities in STEM associated with NOAA. Stay tuned!