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Fisheries research in the Chukchi Sea at the RV «Professor Levanidov» in Au-gust 2019: some preliminary results
Authors: Orlov А.М., Benzik А.N., Vedishcheva Е.V., Gafitsky S.V., Gorbatenko К.M., Goryanina S.V., Zubarevich V.L., Kodryan К.V., Nosov М.А., Orlova S.Yu., Pedchenko А.P., Rybakov М.О., Sokolov А.М., Somov А.А., Subbotin S.N., Taptygin М.Yu., Firsov Yu.L., Khleborodov А.S., Chikilev V.G.
Number of views: 276
Oceanographic, planktonic, trawl and acoustic surveys were conducted in the Chukchi Sea in August 2019
at the research vessel “Professor Levanidov”. The hydrological and hydrochemical regime was formed under
the influence of the spread of Pacific waters coming through the Bering Strait; East Siberian desalinated
waters — from the west along the coast and to the north of Wrangel island; and waters of Arctic origin. North
of 73°30′N, waters of Atlantic origin with characteristic temperatures higher 0 °C and salinity over 34.5‰
were observed at the depths mainly from 180 m to the bottom, which were clearly traced in the distribution
of bottom temperature, salinity and hydrochemical characteristics. The oxygen saturation of water in the
surface layer within the entire studied area exceeded 100%, the maximum values — in the pycnocline
layer (158%). The processes of photosynthesis were limited by mineral nitrogen, the onset of summer
was evidenced by its minimum in the surface layer. Mesoplankton biomass was high with predomination
of chaetognaths and copepods, euphausiids were second in rank; in the southern part of the sea biomass
was twice as high as in the north. In the northern part, there was an intense phytoplankton bloom, a large
number of nauplias and copepodites of the early stages of development, which formed a spring complex.
In the southern part, low concentrations of phytoplankton observed, copepods were represented by older
age groups, which is typical for the spring-summer period. The catch was dominated by the Tanner crab,
accounting for about 50%. Sea stars and the brittle stars were of secondary importance, with polychaetes,
sponges and gastropods to a lesser extent. 44 species of fish were found in the catches, and representatives of
the families Cottidae, Zoarcidae, Liparidae, Gadidae, Pleuronectidae, and Agonidae dominated. The biomass
of large walleye pollock was 890 thousand tons, that of polar cod 117 thousand tons, and Bering flounder 42
thousand tons. According to acoustic data, the abundance and biomass of pollock within the survey area was
242 million inds. and 398 thousand tons, polar cod — 9349 million inds. and 206 thousand tons, respectively.
The daily ration of a large pollock varied from 3.4% to 4.7%, and that of polar cod from 2.5 to 9.4% for a
different-sized fish. Of the marine mammals, the grey whale was most often found near the Bering Strait,
while walruses and polar bears were observed in the northern part of the sea.