NOAA Teacher at Sea
Lacee Sherman
Aboard NOAA Ship Oscar Dyson
June 6, 2018 – June 28, 2018
Mission: Eastern Bering Sea Pollock Acoustic Trawl Survey
Geographic Area of Cruise: Eastern Bering Sea
Date: June 16, 2018
Weather Data from the Bridge at 18:30 on 6/17/18:
Latitude: 57° 09.7 N
Longitude: 166° 26.4 W
Sea Wave Height: 3-5 ft
Wind Speed: 10 knots
Wind Direction: 345°
Visibility: 8 knots
Air Temperature: 7.2° C
Water Temperature: 7.8° C
Barometric Pressure: 996.8 mb
Sky: Grey and slightly foggy
Science and Technology Log
In the fish lab, after the haul is sorted out, a sample of each species are randomly selected to undergo additional measurements and data collection. One of the primary pieces of information needed is the lengths for about 300 pollock per haul. The length of the pollock is important because larger fish have larger internal organs. The internal organ that matters most to this survey is the size of the swim bladder since this is what give us the echo that can be picked up by our acoustic transducers.
According to the NOAA Ocean Service, “If fish relied solely on constant swimming to maintain their current water depth, they would waste a lot of energy. Many fish instead rely on their swim bladder, a dorsally located gas-filled organ, to control their stability and buoyancy in the water column. The swim bladder also functions as a resonating chamber that can produce and receive sound, a quality that comes in handy for scientists locating fish with sonar technology.”
To process a trawl sample, the pollock are put into baskets and weighed. One basket is selected at random to obtain the lengths and weights of individual fish. 30-35 Fish are selected for otolith samples (ear bones) that can be used to age the fish. These fish are also inspected to look for the sex of the fish and their maturity stages. There are 5 different maturity stages for pollock: immature, developing, pre-spawning, spawning, and spent. Since the fish already needs to be cut open for this process, we will sometimes look at the stomach contents of the fish as well to see what they are eating. Based off of stomach contents, one of the main food sources for pollock in the Bering Sea this summer are euphausiids, or krill.
In addition to trawl samples, we also are taking samples of Euphausiids with a special tool called a Methot net. Four Methot samples will be taken on each leg of this research survey. A Methot net includes a sturdy metal frame of a set circumference with a net attached to the back. The net is a very fine mesh (small holes), so that the small euphausiids don’t escape. A flow meter is attached that measures the volume of water that is going through the net.
The euphausiids are a very important component of the marine food web in the Bering Sea. Euphausiids eat very small phytoplankton and zooplankton, so they are omnivores. Pollock eat the euphausiids, and then the pollock are eaten by marine animals such as seals, orcas, large cod, and even larger pollock. Humans also eat pollock, often in the form of imitation crab meat and the fish filet sandwiches from fast food chains.
Once the Methot net has come back on the ship at the end of the haul, a scoop (sub-sample) of them is taken and counted. Fish larvae and anything else that is not euphausiids is taken out and counted separately and then we go to work counting to get a total number of euphausiids from our sample. In our small sub-sample of .052 kg, our count was 1,110 euphausiids. Based off of the total haul weight of 2.12 kg, we are able to estimate the total number of euphausiids for this haul to be 45,251. This number is calculated based off the total number and weight of our sub-sample, compared to the total weight of the Methot haul.
Personal Log
I finally saw Orcas!! All of the running around on the ship was worth it! We always seem to be heading in opposite directions so I have seen mostly just dorsal fins, but I’ll take it! One morning I finally saw them from a closer distance and was able to see the white patch near the eye. I feel like I will be remembered by everyone on the ship as the “crazy whale-obsessed teacher,” but I can live with that.
One of the side experiments happening on the ship looks at the survival rate of fish caught on traditional fishing lines versus fish caught in trawl nets. One pollock had been caught and all of us on the ship decided the name should be Jackson Pollock. Jackson survived for a few days, but didn’t last past 6/15/18. The next day six new fish were put into the tank after a trawl catch, and after 24 hours, only two were still alive.
NOAA Careers and Unexpected Learning Opportunities
I have been trying to talk to everyone on the ship about how they first got interested in this type of work and exactly what their role is for day to day operations. There are so many different career options that can allow you to live on ships and be involved with scientific research.
The past few days I have spent time trying to learn as much as I can about everything related to the ship. I spent time speaking with Commanding Officer (CO) Michael Levine and Ensign (ENS) Sony Vang about their ship and land assignments and the requirements of the NOAA Corps. ENS Vanessa Oquendo showed me how some of the ship’s controls work. They are regularly focused on navigation (on a paper chart and electronically), and communication with other ships about positioning, weather, and the speed and direction of the ship. There is a lot to consider and to maintain 24/7.
Getting the nets in and out of the water is a very complicated process and involves many different ropes, chains and weights. I noticed this really cool type of knot that seemed to undo itself, so I asked one of the Deck Crew members, Jay Michelsen to teach me some cool ship knots. I learned how to make: bowline knots, flying bowline knots, cow hitch knots, daisy chains, double daisy chains, and a way to finally wrap up headphones so that they won’t tangle themselves.
Matthew Phillips and Scientist Mike Levine taught me how to fillet a fish which will be useful since I enjoy cooking so much! I will no longer be intimidated to buy fish whole. We got some practice on a spare cod that we caught and a few rockfish.
One of the licensed engineers, Becca Joubert, gave me a tour of the engine room and I was able to see the engines, winches, rudder, water filtration systems, and the repair shop. I didn’t realize that fuel was held in different tanks, but it works best that way because of safety and because it helps to distribute the weight all around the ship better.
Did You Know?
The NOAA Ship Oscar Dyson was named after a commercial fisherman named Oscar Dyson. There is a smaller boat on board named the Peggy Dyson after his wife, who would broadcast the weather forecast twice a day every day to local ships as well as personal announcements and important sports scores.
Things to Think About:
Dolphins and Orcas eat a variety of fish, squid, and sometimes other marine mammals, while large whales such as blue whales and humpbacks mostly rely on krill as their main food source. Why would such large marine mammals feed primarily on tiny krill?
Since there is a relationship between pollock and euphausiids, as the number of pollock grows, what is a reasonable prediction about the number of euphausiids?