Working group on international deep pelagic ecosystem surveys (WGIDEEPS; 2nd Report; outputs from 2021 meeting)

The Working Group on International Deep Pelagic Ecosystem Surveys (WGIDEEPS) plans and reports on the international hydroacoustic-trawl surveys on pelagic redfish in the Irminger and Norwegian seas. During the 2021 meeting attended by Germany, Iceland, Norway, and Russia, the working group reported on the results from the pelagic redfish (Sebastes mentella) survey conducted in the Irminger Sea and adjacent waters in June-August 2021.
The trawl-acoustic survey on pelagic redfish in the Irminger Sea and adjacent waters was carried out by Russia only. In December 2020, the Marine and Freshwater Research Institute (MFRI) in Iceland informed the group that Iceland would not participate in the survey in June/July 2021. No specific reasons were given for the withdrawal. The participation of Germany was cancelled as well in the end of April due to technical problems. A bilateral agreement with financial compensation between Russia and Germany was reached, providing that Russia should take over the German part of the survey. Since the Russian and the German survey parts had to be carried out one after the other, the survey was extended from June to August 2021.
The survey area this year represented the minimum area required for perception of the state of redfish shallower and deeper than 500 m. About 242 000 NM2 were covered, encompassing the northeastern (subarea A) and southeastern (subarea B) survey area and part of the southwestern (subarea E) survey area. As relative survey indices, a biomass of 490 000 t was estimated at depths shallower than deep scattering layer (DSL) by hydroacoustic measurements, about 352 000 t within the DSL, shallower than 500 m by a trawl method, and 154 000 t deeper than 500 m by the trawl method. For the redfish at depths shallower than 500 m, the observed biomass by of 842 000 t was the highest since 2005. The reason for this significant increase may be due to an incoming strong recruitment of Sebastes mentella most likely from the NAFO area, combined with favourable oceanographic conditions. The present results at depths shallower than 500 m show continuation of biomass increase which has been for the first time indicated in subarea A in 2018. For the redfish deeper than 500 m, the estimated biomass of 154 000 t is the lowest observed biomass since the beginning of the time-series. Concentrations of redfish deeper than 500 m were mostly distributed in the northeastern part of the survey area over Irminger Basin.
WGIDEEPS recommends that the survey should be continued with at least three vessels to cover the distribution area of redfish in the area. Additionally, the working group recommends that more nations should participate in the next surveys and that chartering of additional vessels and cost sharing should be considered as an alternative to direct participation.