NOAA Teacher at Sea
Emily Cilli-Turner
Aboard NOAA Ship Oscar Dyson
July 24 – August 11, 2018
Mission: Pollock Acoustic-Trawl Survey
Geographic Area of Cruise: Eastern Bering Sea
Date: August 6, 2018
Weather Data from the Bridge:
Latitude: 58 04.81 N
Longitude: 174 06.88 W
Wind Speed: 6.88 knots
Wind Direction: 275.19 (NW)
Air Temperature: 10.0 C
Barometric Pressure: 1013.2 mb
Visibility: 6 nautical miles
Sea Wave Height: 4 feet
Sky: Overcast
Science Log
While the techniques written about in the previous blog post ensure that when we use the trawling nets we mostly catch pollock, there is usually a small amount of by-catch in each haul. By-catch means ocean life other than pollock (the desired catch) that we bring up in a haul using the trawling net. This post will focus on some of the creatures that I have seen in the catches during my time on NOAA Ship Oscar Dyson.
Principal species of interest:
Pollock: The scientific name for these pollock (known as Alaska pollock or walleye pollock) is Gadus chalcogrammus. We often catch many different ages of pollock, from age 0 pollock up to large adult pollock and these range in length from a few centimeters up to about 62 centimeters. Pollock is most of what we catch, and they are easy to identify by their three dorsal fins and speckling. Pollock mainly eat euphausiids and copepods, but also sometimes eat the age 0 pollock.
By-catch species:
Chum Salmon: Chum salmon (Oncorhynchus keta) is one of the five types of salmon and lives for about 6 years on average. Like all salmon, they are spawned in freshwater and then migrate out to the ocean. Once they return to the freshwater and spawn, they die about two weeks later. They mostly eat zooplankton and insects, but have been known to eat comb jellyfish as well.
Jellyfish: We see several types of jellyfish in each catch, but we mainly see the Northern Sea Nettle (Chrysaora melanaster). We have also seen Northern Sea Nettle swimming near the surface before sunrise when we are pole fishing for pollock. The word melanaster translates to “black star,” which you can identify in the pattern on the bell of this jellyfish. The bell diameter can reach up to 12 inches and the tentacles can grow as long as 10 feet. As climate change has warmed the surface temperatures of the Bering Sea, the population of Northern Sea Nettle is increasing. Northern Sea Nettles mostly eat zooplankton, but sometimes also eat pollock!
Smooth Lumpsucker: Smooth lumpsuckers (Cyclopterus lumpus) are named so because of an adhesive disc on their underside that helps them suction onto the ocean floor. These fish spend most of their time on the bottom of the ocean and are not particularly good swimmers. The roe (eggs) of the lumpsucker is a delicacy in Scandinavia.
Flatfish: Alaska Plaice & Yellowfin Sole: We have also caught two types of flatfish during my time aboard the ship: yellowfin sole (Pleuronectes aspera) and Alaska Plaice (Pleuronectes quadrituberculatus). These peculiar looking fish can be identified by having both eyes on top of their head. When they are spawned, these fish have eyes on either side of their head, but as they get older the eyes migrate to be on the same side. These fish mainly reside on the ocean floor, where they eat polychaetes and amphipods, such as worms and mollusks.
Capelin: The capelin (Mallotus villosus) is a small fish in the smelt family reaching a length of about 10 inches. It feeds mainly on plankton and krill. The most interesting thing about capelin is their smell; if you put their scales close to your nose you will smell cucumbers!
Personal Log
While the weather since boarding the NOAA Ship Oscar Dyson has largely consisted of some high winds and big swells, there have been one or two nice days in the Bering Sea. On these days, we have taken the opportunity to go outside. On one particularly nice day where the sun was shining, there was a mini corn-hole tournament on the deck. After thinking that my time on the ship was the least amount of time spent outside during the summer, this was a nice way to spend the after-dinner time.
I am also grateful for NOAA scientists Mike Levine and Darin Jones, who have made me feel like an expert in the fish lab. At this point, I know more about pollock than I ever thought I would. In the fish lab, I primarily am responsible for measuring the length of the pollock sample. However, Mike and Darin have also taught me about pollock anatomy and how to tell if a pollock is male or female. I have also become good at extracting the otoliths, which involves a precise cut of the pollock. For a person with almost no experience working with biological specimens, much less fish, I finally feel like a useful part of the team.
Did You Know?
The Bering Sea is an extremely important fishing location and the United States catches over $1 billion of seafood here each year.
