Preliminary results of fisheries research in the East Siberian Sea at the RV «Professor Levanidov» in September 2019

Abstract

The results of complex research carried out in the East Siberian Sea on board of RV “Professor Levanidov” in September 2019 are presented. The formation of positive air temperature anomalies over the sea, the expansion of the zone of river flow influence in the central and southeastern parts of the shelf, and an abnormal decrease in sea ice cover were noted. Arctic water masses and the waters of the East Siberian Sea were dominant on the shelf. At depths of more than 180 m, waters of Atlantic origin were well traced by salinity more than 34.5 ‰, positive temperature and silicon content less than <10 μM. Photosynthesis processes were limited by nitrogen, whose concentrations in the photic layer were reduced to analytical zero. Summer phase of phyto- and zooplankton development was observed in most of the sea. The main contribution to the total biomass of mesoplankton was made by copepods and chaetognaths. Plankton biomass on the inner shelf was twice as high as on the outer shelf. The average benthic biomass in trawl catches was 15 kg per mile, of which up to 74 % was echinoderms and 9 % crustaceans.17 fish species from 6 families were registered in trawl catches. The dominant species was the polar cod Boreogadus saida found in small numbers almost everywhere at depths 33 to 250 m with bottom temperatures from –1.7 to 0.47 °C, kept sparse, without forming dense aggregations. Maximum concentrations were observed in the southeastern part of the study area. High intensity of fish feeding was noted. Diets of polar cod and snailfishes (Liraridae) consisted mostly of hyperiids, gammarids, and copepods. The diet of capelin Mallotus villosus was dominated by copepods. Polychaetes and gammarids formed the bulk of the diet of sculpins (Cottidae). Microplastics are found in small quantities in the southeastern and central part of the sea only. Tissue samples were collected for population-genetic analysis, DNA‑barcoding studies, and analysis of aquaDNA.

Species Composition, Abundance, Distribution Features and Size Characteristics of Fish of the Genus Liparis (Cottiformes: Liparidae) in the East-Siberian and Laptev Seas

“…Frequency of occurrence and spatial distribution. During the study period, gelatinous snailfish was the most common species of the genus Liparis in the Laptev and East Siberian seas which was reported earlier (Andriyashev, 1954;Chernova, 1991;Orlov et al, 2020aOrlov et al, , 2020b. Specimens of this species were found in 22.4% of catches in the Laptev Sea, in 24.7% in the East Siberian Sea (Table 2).…”

“…It should be noted that L. laptevi is included in the list of species composition of the genus Liparis in the East Siberian and Laptev seas according to the results of the trawl survey in 2019. (Orlov et al, 2020a(Orlov et al, , 2020b.…”

“…Representatives of the genus Liparis are one of the significant structural elements of the Arctic ichthyofauna (Karamushko, 2013), although their diversity in the Arctic seas of Russia is limited by a few species (Table 1). Four of them, L. bathyarcticus Parr, 1931, L. fabricii Krøyer, 1847, L. laptevi Popov, 1933and L. tunicatus Reinhardt, 1836, are currently reported for the East Siberian and Laptev seas (Andriyashev, 1954;Chernova, 1991Chernova, , 2018Orlov et al, 2020aOrlov et al, , 2020b. General information about these fish can be found in a number of summary works (Andriyashev, 1954;Able and McAllister, 1980;Chernova, 1991Chernova, , 2013aChernova, , 2013bParin et al, 2014).…”

“…Global temperature rise has a significant impact on the Arctic, which has already led to a 50% reduction in the area of ice cover from 2002 to 2017 (Kwok, 2018). First of all, the changes affected shallow shelf seas, including the Laptev and East Siberian Seas, which made it possible to conduct studies in areas previously inaccessible to bottom trawling (Chernova, 2015;Glebov et al, 2016aGlebov et al, , 2016bOrlov et al, 2020aOrlov et al, , 2020bSyomin and Zimina, 2020). This study presents the results of analysis of catches taken during large-scale trawl surveys in the above seas in 2014 and 2017.…”

Walleye Pollock Gadus chalcogrammus, a Species with Continuous Range from the Norwegian Sea to Korea, Japan, and California: New Records from the Siberian Arctic

“…The data presented here clearly indicate that the few records of walleye pollock in the North Atlantic have their origin from the North Pacific, and its range extends almost continuously from the coast of Norway in the North Atlantic to the coasts of Korea, Japan, and California in the North Pacific. Walleye pollock has not yet been found in the East Siberian Sea, since research there is extremely rare and limited in that area [85,86]. However, the discovery of walleye pollock in the East Siberian Sea, in our opinion, is a matter of the near future.…”