NOAA Teacher at Sea
Aboard NOAA Ship Oscar Dyson
July 19 – August 8, 2019
Mission: Midwater Trawl Acoustic Survey
Geographic Area of Cruise: Gulf of Alaska (Kodiak to Yakutat Bay)
Weather Data from the Gulf of Alaska: Lat: 58º 50.39’ N Long: 150º 14.72’ W
Air Temp: 14.2º C
Today we had the chance to sail up into Resurrection Bay on the Kenai Peninsula and it was beautiful! In general, transects, or lines the boat collects acoustic information along, run perpendicular to the Gulf of Alaska shelf because that is where pollock are most likely found. Luckily for us, a few of them travel up into bays along the coast and give us a welcomed change of scenery from the open ocean.
Why do we survey in bays when pollock are usually open water fish? Well, during the winter, pollock sometimes aggregate to spawn (reproduce) in bays and those areas are documented by the scientists. In the summer, scientists want to see if there are still any pollock present in those areas. Unfortunately, we do not have time to survey all of the bays and so just a few are selected. For this leg, after the next couple of days back on the shelf, we will head up into Prince William Sound, which I am really looking forward to seeing.
While following the transects up into Resurrection Bay, it was fun to see sailboats, fishing boats, helicopters and float planes rushing around us. To my surprise, I also saw masses of RV campers through the binoculars when looking at town. I learned that Seward is a popular place for people to visit from Anchorage and other areas for summer vacations and fishing opportunities. As for those of us on the boat, we also enjoyed the summer weather while sailing through. The sun was shining and it seemed that everyone took a moment to step outside, make a few phone calls home (we had service for a bit!) and soak up the warm weather. All in all, I think everyone feels re-energized going into our final 10 days at sea.
Science and Technology Log
We stopped to fish near the mouth of Resurrection Bay and found mostly age 1 and 2 pollock, along with a few adults. This shows us that pollock do utilize both the bay and the shelf areas during their lifecycle. Afterwards, we headed back out into the gulf and fished with a net called a Methot net.
A Methot net is a different kind of net that is specialized to catch Euphausiids (krill). In addition to collecting data on pollock, scientists also collect data on Euphausiids (krill). The net used to collect krill is a bit different than the one used for pollock. There are no pocket nets along the side and instead of the end of the net being mesh, there is a small canister that the net filters krill into. Once we haul in the net, it is time to sort and collect data on the catch, just like the pollock trawls.
It has been back to regular fishing trawls since then, along with comparison trawls. A comparison trawl is when we fish twice over the same area using two different nets. This year, the scientists decided to replace the old survey net with a newly designed one that is a little bit smaller and easier for the deck crew to deploy. Now they need to compare the two nets to make sure the newer net is catching the same species and size of fish. Darin was explaining to me that they have to do approximately 25 comparison trawls on this survey and will continue comparisons during the winter survey as well. If all goes according to plan, they will permanently replace the old net next summer.
On one of our trawls the other day, we caught a lot of rockfish. Lucky for us, rockfish is a species we can keep and eat on the boat. We are not allowed to keep salmon, crab, halibut or herring since they are prohibited species. You are only allowed to keep those species if you have a special permit. While I wish we could eat the others, rockfish is also really tasty!
Did You Know?
There is an incinerator on NOAA Ship Oscar Dyson that burns all of our trash from the boat so that we don’t have to keep it aboard for the whole trip. Also, nothing is thrown overboard, not even food scraps. When I was taking a look yesterday, the temperature was over 800 degrees Celsius. Diesel fuel is used as fuel initially, followed by burning sludge from the boat once it gets hot enough. All leftover ash gets put into bins and discarded when back in port.
Thanks for following along!
P.S. We go up and watch the sunrise everyday…it is beautiful out here!