Research vessel “Vilnius” with a scientific group onboard took part in the international ecosystem survey in Northern Seas
28 May 2021

Research vessel “Vilnius” with a scientific group onboard took part in the international ecosystem survey in Northern Seas

The survey was aimed to estimate the biomass and abundance of immature juveniles of Atlantic-Scandinavian herring to make a reliable assessment of the spawning stock recruitment of this fish.

Traditionally, the survey was carried out in water areas of ​​the Norwegian and Barents Seas by the vessels of five participants: Russia, Norway, Iceland, the Faroe Islands and Denmark (in respect of the EU). The scientists from the Polar Branch of “VNIRO” onboard the Russian research vessel covered a survey area of ​​about 80 000 square nautical miles in the Barents Sea. This water area is the biggest one where the survey for herring juveniles has been carried out in the last 20 years. The total length of the survey route was over 4 000 nautical miles. The research program that was arranged by the ICES Working Group of International Pelagic Surveys (WGIPS) has been implemented completely.During the research cruise, 88 oceanographic stations were taken (47of them were taken according to the WGIPSresearch plan), someoceanographic stations were taken twicein the Kola Section. The scientists have collected samples of plankton from 86stations to assess its biomass in the survey area (as well as from 47 stations according to the WGIPS research plan). 62 sampling hauls were performed to identify fish species from acoustic records, to make the stock assessments and collect samples on biology, parasitology and ichthyopathology.

On the basis of the data collected, the scientistshave revealed thatjuveniles of Atlantic-Scandinavian herring from the 2016-2018 year classes which occurred in a high abundancein catches taken during the survey for bottom fish species in February-March 2021, almost entirelymigratedin April from the Barents Sea to recruit the spawning stock in the Norwegian Sea.This early migration of herring from older age groups wasmost particularly caused bya sudden warming andincreased solar activity in the early April, which is likely to be confirmed during the surveyto be conducted by foreign vessels in May and during theinternational ecosystem survey in the Norwegian Sea in summer.

There is a positive dynamics in the capelin stock condition that was registered by acoustic equipment and that was observed in catches almost in the entire survey area.The bulk of the catches was made up of herring fromthe 2020 year-classthat will be able to recruitthe fishing stockabundantly in 2022. The abundanceof capelin in the survey area exceeded20 billion specimens.

Three-spined stickleback occurred in catches taken nearthe Russian territorial waters.This species in high densitiesmigrated to theinletsof the Kola Peninsula to spawn. In the area wheredense concentrations of three-spined stickleback were detected, there werealso abundant marine mammals feeding on this fish.

The results from the joint stock assessments made by all the Parties who participated in the international ecosystem survey in the Northern Seas will be available following a post-cruise ICES meeting to be held in mid-June 2021.

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