Results of the Icelandic part of the International Ecosystem Summer Survey in Nordic Seas (IESSNS) in July 2021 on R/V Árni Friðriksson

Abstract

The Marine and Freshwater Research Institute (MFRI) has participated in the International Ecosystem Summer Survey in Nordic Seas (IESSNS) every summer since 2010. The aim of IESSNS is to monitor the pelagic ecosystem, 0‐500 m depth, including measurements of nutrients, primary production, temperature, salinity, zooplankton, and abundance and geographical distribution of mackerel (Scomber scombrus), blue whiting (Micromesistius poutassou), herring (Clupea harengus) and lumpfish (Cyclopterus lumpus). In summer 2021, the Icelandic part of IESSNS was conducted July 5‐26, on R/V Árni Friðriksson, and covered Icelandic waters except the southeast area which was covered by vessels from Faroe Islands and Norway. Survey transects were 4322 nautical miles and 315 stations were sampled. Mackerel was caught at 41% of surface trawl stations located inshore southeast of Iceland and in the Norwegian Sea. A few specimens were caught west, north, and southwest of Iceland. Compared to 2020, mackerel had a larger distribution range east of Iceland, but density was lower. Surface temperature, 10 m depth, ranged from 2.0 °C to 11.6 °C, and was highest south of Iceland and coldest in the Denmark strait. Mesozooplankton dry weight ranged from 3.6‐35.0 g*m‐2 and there was no distinct spatial pattern. Despite favorable temperature and prey conditions west and southwest of Iceland mackerel was not present. The survey estimates abundance index for Norwegian spring‐spawning herring and its distribution north and northwest of Iceland was similar to observations in previous years. Blue whiting was present along the shelf edge south of Iceland where no fish was measured last year. 0‐group blue whiting was caught at five surface trawl stations which has not occurred since 2011. In total 451 lumpfish were tagged and released at 49 stations distributed around the island.