NOAA Teacher at Sea
Jessica Cobley
Aboard NOAA Ship Oscar Dyson
July 19 – August 8, 2019
Mission: Midwater Trawl Acoustic Survey
Geographic Area of Cruise: Gulf of Alaska (Kodiak to Prince William Sound)
Date: Saturday, July 20th, 2019
Weather Data from Kodiak, AK: 4:00am Lat: 57.79° N Lon: 152.4072° W Temp: 56 degrees F.
Personal Log
Good morning! It is currently 4:30am on Saturday, July 20th and I have just woken up for my first shift on the boat. So far, I have met scientists Abigail McCarthy and Troy Buckley, who will be working the day shift with me. I also met Ruth, an intern from the University of Washington and my bunkmate. It will be nice to have someone else on board who is also new to the experience!
Before talking about work, I’d like to share what we got up to in Kodiak before departing on the cruise. One thing to note – Chief Scientist Darin Jones explained that because this is the 3rd leg of the survey and the scientists are taking over from the previous group, we do not have any set up or calibration of equipment to do. If this had been leg 1 of the survey, the free days in port would have been spent doing those jobs. Lucky us!
After unpacking everything in our state rooms (bunks), we quickly set out to explore Kodiak. In two and a half days, were able to see a lot! Wednesday night, some friends of mine in town took us for a stroll on Near Island, followed by a yummy dinner at Noodle Bar.
Thursday morning, team building began with a run to Safeway and Walmart for all last minute necessities. The teacher in me couldn’t resist a fresh pack of sharpie markers and colored pencils. 🙂 In the afternoon, we walked along Spruce Cape where we picked a TON of blueberries and found the largest barnacle I have ever seen.
After a short recoup back on the boat, Darin and Abigail were ready for an evening surf session at Fossil Beach. This beach is the farthest south you can access by road in Kodiak and the drive was BEAUTIFUL. Prior to the trip, I hadn’t looked up any pictures of Kodiak and so the treeless green mountains, cliffy coastlines and herds of cows were exciting to see. Once at the beach, we jumped in the ocean, watched a successful surf session and finished our team building with a fire and dinner on the beach.
Science and Technology Log:
In just a few days of being here, I have already learned a lot about the workings of the ship and what we will be busy doing for the next three weeks. Here is a preview.
To begin, science shifts run from 4am – 4pm and 4pm – 4am. Throughout this entire time, acoustic data is being collected and read. Acoustic data is gathered by sending out sound waves from a transducer box attached to the bottom of a centerboard underneath the boat. The sound waves reverberate out and bounce off of anything with a different density than water. In the picture below, you can see a bold line on the screen with smaller dots above. Take a look and see if you can identify what the line and dots might represent.
If you thought the big bold lines on each screen were the seafloor, you were correct! Most of the little dots that appear above the sea floor are fish. Fish are identified from the sound waves bouncing off of their swim bladders. Swim bladders are the “bags” of air inside fish that inflate and deflate to allow the fish to raise and lower itself in the water column. Air has a different density compared to water and therefore shows up in the acoustics data.
What is this acoustic data used for? There are 2 primary parts. The first is to identify where schools of fish are located and therefore areas well suited for collecting fish samples. The second is to calculate the total biomass of pollock in the water column by combining acoustics data with the actual measurements of fish caught in that same area. More specifics to come as I take part in the process throughout the survey.
Did You Know?
On this survey, scientists do not catch/survey fish at night (when it is dark). The reason? At night, bottom dwelling species come up off the seafloor at night to feed. During the day they settle back down on the seafloor. The scientists are primarily interested in catching pollock, a mid water species, so they fish during daylight hours.
Updates to come later in the week. It is time for me to join the scientists and get ready process our first catch!
Cheers, Jess
