So how do they work?
With a 3-meter iron rod (beam) holding open the net, the beam trawl is deployed off the stern at each station. Two floats keep the trawl from sinking too far down while two sensors measure depth, temperature (microbathy thermograph) and how much it accelerates through the water (bottom contact sensor). Those sensors help calculate the area of the benthic region covered in square kilometers along with the amount of biomass of fish and invertebrates caught. The haul then gets sorted and a subsample of all species are frozen for fish diet analysis, taxonomy, and voila! Off to the next station!
Excitement was in the air as our first beam trawl splashed through the surface from beneath. For five minutes the trawl had traveled on the mysterious benthos. Juvenile arctic cod and Bering flounder, invertebrates such as brittle stars, snails and snow crab underneath the coordinates of 72°30’ N, 165 ° 15’ W were revealed from a coat of mud. Three researchers have traveled far from their home country to gain more specific knowledge about the organisms living in this section of the Chukchi Sea. Their experience with the waters in other parts of the world is a helpful contribution to a greater understanding of this ecosystem.
Aleksey Somov, a Fish Biologist from Vladivostok Russia, has made several expeditions with the Pacific Fisheries Research Center. His research allows him to partake in international cooperation with his specialist degree in ecology. The main regions of his study are located in the Bering Sea and with his knowledge he can now compare results he may find here in the Chukchi Sea. He would like to understand the differences in how marine communities change with latitude, with different kinds of water masses, types of sediments, and temperature changes. A few of his favorite things to do are to process fish from our trawls, especially the beam trawl; later he will compare them to his work in the western Chukchi Sea on the age and population status of these fishes. He is learning a lot about the different types of trawls used in this survey and the species of fish found in our Arctic Ocean.
Another Russian colleague of ours is Igor Grigorov, from Moscow, Russia. As a Fish Biologist, this is his fourth survey. His work allows him to collaborate internationally not only with the USA but also with Japan, South Korea and China. He is working on his PhD on skates, studying their age, distribution and other fundamental biology. The Russian Research Institute of Fisheries and Oceanography (VNIRO) Laboratory of the Pacific Ocean has sent him on quests near the Kuril Islands studying pacific saury and the RACE 2016 groundfish survey on the eastern Bering Sea. The diversity of species found in northern Chukchi Sea does seem a bit smaller than his previous surveys, but he is gaining quality experience determining the fish and invertebrates, spending hours working with our team with keen focus.
With expert hands, the otolith (ear bone) and stomach contents of “age 0” Arctic Cod can be retrieved to determine age and diet. Samples are also taken back to the lab to determine caloric content (which then determines fat content) and fatty acids are analyzed to understand the food web these fishes occupy. The information retrieved from these tiny creatures will help settle questions regarding their contribution to the marine food web and how the retreating sea ice may potentially affect their nutrition.
Nataliya Kuznetsova is a trophic ecologist with the TINRO Center in Vladivostok, Russia. She has taken part in a number of surveys with the Alaska Fisheries Science Center conducting integrated ecosystem research in the eastern Bering Sea. The Bering Aleutian Salmon International Survey (BASIS) was her first experience, starting in 2003, and she has been coming annually through 2007. While taking part in the surveys, Natalia collects zooplankton samples using a “Juday” net, a vertical tow with a small mesh net from surface to near bottom and back. She is processing the zooplankton samples from this net during the survey to give us an idea of the zooplankton species composition in the Chukchi Sea. Natalia also conducts on board diet analyses of the fishes we are collecting in the mid-water nets, and has found that the age-0 Arctic cod are feeding on small copepods and crabs (or zoea). All in a day's work!