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

Abstract

In September 2019, the R/V “Professor Levanidov” carried out comprehensive studies in the Laptev Sea from 140 ° to 110 ° E at depth range of 60–950 m. High positive anomalies of air and surface water temperatures were noted up to + 2 + 3 °C and +1.5 °C respectively with an abnormally low sea ice cover. Cold Arctic and desalinated waters of the river flow dominated in the upper 200 m layer. Atlantic waters were traced in the layer from 180–300 m to the bottom, and their core — at a maximum temperature of + 1.6 + 1.92 °C at 240–280 m. By the time of the survey, the active vegetation of phytoplankton had finished. Oxygen saturation in the almost the entire surface layer was below 100 %. Primary production was limited by mineral nitrogen concentration. Low concentrations of phosphates, nitrates and silicates in the intermediate waters indicated the penetration of Atlantic waters. The average biomass of plankton on the shelf was 239,8 mg/m3, on the slope — 374,2 mg/m3. Copepods and chaetognaths with considerable contribution of hyperiids and euphausiids dominated in plankton by weight. The bulk of zooplankton was large organisms, while small and medium fractions were 22 and 10 %. Brittle star, starfish, and shrimp dominated in trawl benthos. 25 demersal fish species of 14 families were found in bottom trawl catches. Zoarcidae, Liparidae and Gadidae were the most diverse. Polar cod was recorded along the entire route with highest concentrations in Atlantic waters at depths of 217–460 m. Copepods dominated in the diet of Polar cod juveniles, while that of adults was supplemented by large pelagic crustaceans and fish with high level of cannibalism. Greenland halibut was found along the entire continental slope at 270–750 m while the largest catches were in its central and western parts. The increase of halibut number and occurrence was due to the wide distribution of Atlantic waters on the slope. The main component of its diet was Polar cod.

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

“…3, Figure 3), sagittal otoliths are clearly visible in the stomach. In shape, they certainly belong to a representative of the family Gadidae [69], most likely to the polar cod Boreogadus saida, which is the most abundant fish in this area [55,[70][71][72][73].…”