NOAA Teacher at Sea
Aboard NOAA Ship Oscar Dyson
July 4 – 22, 2014
Mission: Annual Walleye Pollock Survey
Geographical Area of Cruise: Bering Sea North of Dutch Harbor
Date: Sunday, July 6th, 2014
Weather Data from the Bridge:
Wind Speed: 6 kts
Air Temperature: 8.6 degrees Celsius
Weather conditions: Hazy
Barometric Pressure: 1009.9
Latitude: 5923.6198 N
Longitude: 17030.6395 W
Science and Technology Log
Part One of the Survey Trawl: Getting Ready to Fish
Today is my second day aboard the Oscar Dyson. We are anxiously waiting for the echosounder (more information on echosounder follows) to send us a visual indication that a large abundance of fish is ready to be caught. The point of the survey is to measure the abundance of Walleye Pollock throughout specific regions in the Bering Sea and manage the fisheries that harvest these fish for commercial use to process and sell across the world. The Walleye Pollock are one of the largest populations of fish. It is important to manage their populations due to over-fishing could cause a substantial decrease the species. This would be detrimental to our ecosystem. The food web [interconnecting food chains; i.e. Sun, plants or producers (algae), primary consumers, animals that eat plants (zooplankton), secondary consumers, animals that eat other animals (pollock), and decomposers, plants or animals that break down dead matter (bacteria)] could be altered and would cause a negative effect on other producers and consumers that depend on the pollock for food or maintain their population.
The main food source for young pollock is copepods, a very small marine animal (it looks like a grain of rice with handle bars). They also eat zooplankton (animals in the plankton), crustaceans, and other bottom dwelling sea life. On the weird side of the species, adult pollock are known to eat smaller pollock. That’s right, they eat each other, otherwise known as cannibalism. Pollock is one of the main food sources for young fur seal pups and other marine life in Alaskan waters. Without the pollock, the food web would be greatly altered and not in a positive way.
How do we track the pollock?
Tracking begins in the acoustics lab. Acoustics is the branch of science concerned with the properties of sound. The acoustics lab on board the Oscar Dyson, is the main work room where scientists can monitor life in the ocean using an echosounder which measures how many fish there are with sound to track the walleye pollock’s location in the ocean. They also use the ships’s GPS (Global Positioning System), a navigation system, to track the location of the NOAA vessel and trawl path.
What is sonar and how does it work?
Sonar (sound ranging & navigation; it’s a product of World War II) allows scientists to “see” things in the ocean using sound by measuring the amount of sound bouncing off of objects in the water. On this survey, sonar images are displayed as colors on several computer monitors, which are used to see when fish are present and their abundance. Strong echoes show up as red, and weak echoes are shown as white. The greater the amount of sound reported by the sonar as red signals, the greater the amount of fish.
How does it work? There is a piece of equipment attached to the bottom of the ship called the echosounder. It sends pings (sound pulses) to the bottom of the ocean and measures how much sound bounces back to track possible fish locations. The echo from the ocean floor shows up as a very strong red signal. When echoes appear before the sound hits the ocean floor, this represents the ping colliding with an object in the water such as a fish.
The scientists monitor the echosounder signal so they can convey to the ships’s bridge and commanding officer to release the nets so that they can identify the animals reflecting the sound. The net catches anything in its path such as jellyfish, star fish, crabs, snails, clams, and a variety of other fish species. Years of experience allows the NOAA scientists the ability to distinguish between the colors represented on the computer monitor and determine which markings represent pollock versus krill or other sea life. We also measure the echoes at different frequencies and can tell whether we have located fish such as pollock, or smaller aquatic life (zooplankton). The red color shown on the sonar screen is also an indicator of pollock, which form dense schools. The greater amount of red color shown on the sonar monitor, the better opportunity to we have to catch a larger sample of pollock.
Once we have located the pollock and the net is ready, it is time to fish. It is not as easy as you think, although the deck hands and surveyors make it look simple. In order to survey the pollock, we have to trawl the ocean. Depending on the sonar location of the pollock, the trawl can gather fish from the bottom of floor, middle level and/or surface of the ocean covering preplanned locations or coordinates. Note: Not all the fish caught are pollock.
The preplanned survey path is called transect lines with head due north for a certain distance. When the path turns at a 90 degree angle west (called cross-transect lines) and turns around another 90 degree angle heading back south again. This is repeated numerous times over the course of each leg in order to cover a greater area of the ocean floor. In my case we are navigating the Bering Sea. My voyage, on the Oscar Dyson is actually the second leg of the survey, in which, scientists are trawling for walleye pollock. There are a total of three legs planned covering a distance of approximately 6,200nmi (nautical miles, that is).
Trawling is where we release a large net into the sea located on the stern (the back of the boat). Trawling is similar to herding sheep. The fish swim into the net as the boat continues to move forward, eventually moving to the smaller end of the net. Once the sonar screen (located on a computer monitor) shows that we have collected a large enough sample of pollock, the deck hands reel the net back on board the boat.
We have caught the fish, now what? Stay tuned for my exciting experience in the wet lab handling the pollock and other marine wild life. It is most certainly an opportunity of a lifetime.
What an adventure!
I was lucky enough to spend a day exploring Dutch Harbor, Alaska before departing on the pollock survey across the Bering Sea. It took me three plane rides, several short lay-overs and and a car ride to get here, a total of 16 hours. There is a four hour time difference between Dutch Harbor and Dover, Delaware. It takes some getting used to, but definitely worth it. The sun sets shortly after 12:00 midnight and appears again around 5:00 in the morning. Going to sleep when it’s still daylight can be tricky. Thank goodness I have a curtain surrounding my bed. Speaking of the bed, it is extremely comfortable. It is one of those soft pillow top beds. Getting in and out of the top bunk can be challenging. I haven’t fallen yet.
During my tour through the small town of Dutch Harbor, I have encountered very friendly residents and fishermen from around the world. I was fortunate to see the U.S. Coast Guard ship Healy docked at the harbor. What a beautiful vessel. Dutch Harbor has one full grocery store (Safeway) just like we have in Delaware, with the exception of some of the local Alaska food products like Alaska BBQ potato chips. They have a merchant store that sells a variety of items ranging from food, souvenirs, clothing, and hardware. They have three local restaurants and a mom and pop fast food establishment. One of the restaurants is located in the only local Inn the Aleutian hotel, which also includes a gift shop. Dutch Harbor is home to several major fisheries. Dutch Harbor is rich in history and is home to the native Aleutian tribe. I took a tour of their local museum. It was filled with the history and journey of the Aleutian people. While driving through town, I got a chance to see their elementary and high school. They both looked relatively new. Dutch Harbor is also home to our nation’s first Russian Orthodox Church. Alaska is our 50th state and was purchased from Russia in 1867.
One of the coolest parts of my tour was walking around the area known as the “spit”. The “spit” is located directly behind the airport. I’m told it is called the “spit” because the land and water are spitting distance in length and width. We walked along the shoreline and discovered hundreds of small snails gathered around the rocks. We also found hermit crabs, starfish, sea anemones, jellyfish, and red algae. We saw red colored water, which is a bloom or a population explosion of tiny algae that get so thick that they change the color of the water.
Another animal in abundance in Dutch Harbor is the bald eagle. There is practically one on every light post or tall structure. Often the bald eagles are perched in small groups. Watch out: if you walk too close to a nesting mother, she will come after you. They are massive, regal animals. I never get tired of watching them.
Did You Know?
Did you know that Alaska’s United States Coast Guard vessel has the ability to break through sea ice?
This is especially helpful if you want to study northern areas, which are often ice covered, in the winter, and to assist a smaller boat if it gets trapped in the ice.
Did you know that scientists set time to Greenwich Mean Time (GMT) which is the time in a place in England?
This reduces confusion (e.g. related to daylight savings, time zones) when the measurements are analyzed.
Meet the Scientist:
Leg II Chief Scientist Dr. Alex De Robertis
Title: NOAA Research Fishery Biologist (10 years)
Education: UCLA Biology Undergraduate Degree
Scripps Institute Oceanography San Diego, CA PhD.
Newport, Oregon Post Doctorate work
Born in Argentina and moved to England when one-year old.
Lived in Switzerland and moved to Los Angeles,CA at the age of 13.
Currently lives in Seattle, Washington, and he has two kids aged one and five.
Responsible for acoustic trawl surveying at Alaska Fisheries Science Center
Was able to help with the Gulf of Mexico oil spill clean-up using the same echo sonar used on trawl surveys.
What is cool about his work:
He enjoys his work, especially the chance to travel to different geographic locations and meet new people. “You never know what you are going to encounter; there is always a surprise or curve ball, when that occurs you adjust and just go with it”.
In the near future, he would love to see or be part of the design for an autonomous ocean robot that will simplify the surveying process.
He has been interested in oceans and biology since a small boy. He remembers seeing two divers emerge from the sea and was amazed it was possible.