Structure of planktonic community in the southern part of the Chukchi Sea in summer period

Results of plankton and oceanographic surveys conducted by Pacific Fish. Res. Center (TINRO) in the southern Chukchi Sea in August-September of 2003, 2007, 2008, and 2010 are presented. Plankton samples were collected by Juday BSD net (mesh size 0.168 mm) from the layer 0-200 m or 0-bottom on the shelf with towing velocity 0.7-1.0 m/s. The samples are processed according to standard techniques accepted in TINRO (Volkov, 1996). The net phytoplankton biomass varied in the range 80-1683 mg/m3, with mean value 728.0 mg/m3 (the surveys were conducted mostly in the period of phytoplankton bloom, with exclusion the year 2008 when its biomass was insignificant). It was usually heightened in two areas: in the southeastern Chukchi Sea influenced by water advection from the Bering Sea and in the waters of the Siberian Coastal Current entered to the western Chukchi Sea. The zooplankton biomass had a tendency to increase year by year because of increasing of all species groups abundance, in particular Chaetognatha. Species structure of zooplankton was rather stable, with permanent 3-4 dominant species with summary portion > 50 % of total biomass, though some year-to-year changes of their percentage were observed. These changes, as well as spatial differences of the species structure, are linked with water exchange and depend on water transport through the Bering Strait and the western boundary of the Chukchi Sea and distribution of the entered waters, which improve productivity of the southern Chukchi Sea and enrich its fauna

Results of multidisciplinary survey in the Laptev Sea in August-September, 2015

Data on oceanographic conditions and species composition of plankton, benthic and demersal fish and invertebrates are presented, obtained in the complex survey over the external shelf of the Laptev Sea in August-September 2015. The zooplankton abundance was low, with only local increases up to 400 mg/m3. Species diversity of fish and nekton invertebrates in the bottom trawl catches was low, too: 26 fish species and 2 species of cephalopods. Mean biomass of fish was estimated as 4.3 t/km2 (in total 132. 103 t within the surveyed area of 30,500 km2). All fish species were distributed sparse. Arctic cod was the most abundant and occurred over the whole surveyed area, with large-sized fish dominating at the bottom and medium-sized (9-15 cm) fish - in the pelagic layer, other commercial species were greenland halibut and deepwater redfish caught on the continental slope. Bottom invertebrates in trawl catches were presented by 6 species of shrimp and 12 taxonomic groups of different rank, with predominance of starfish, brittle stars and sponges; gastropods were represented by 11 species, with Neptunea heros dominating by mass (42 %). Macrobenthos in samples of the bottom sampler was presented by 20 taxonomic groups, with predominance of polychaetes, bivalves and sipunculoids

Results of complex surveys in the East Siberian Sea in August 2015

Data on oceanographic conditions, composition of plankton communities, benthic and demersal fish and invertebrates in the southern East Siberian Sea are presented by results of the complex survey conducted in August 2015, The bottom trawl survey assessed 10 species of fish and 3 species of jellyfish with total biomass 1900 t. Arctic cod Boreogadus saida dominated absolutely in the benthic ichthyocenose (60.6 % of the total biomass). Besides, 3 species of shrimps, 1 crab species, 4 species of gastropods, and 6 other taxonomic groups of macrobenthos including starfish and isopods were found in trawl catches, with the average biomass of macrobenthos 41.7 kg/km2. In the bottom samples of macrobenthos, 12 taxonomic groups were presented, with predominance of bivalves, polychaetes, isopods, and amphipods (summary 95 % of the total biomass)