The preliminary report on the international mackerel and ecosystem survey in the summer of 2023 in the Northeast Atlantic has been published. Photo HI
Researchers from Havforskningsinstitutt (HI) have summarised most of the findings from this year’s mackerel and ecosystem survey.
The preliminary survey report from this year’s mackerel-ecosystem survey is available now, but the findings summarised by researcher and survey coordinator Leif Nøttestad who writes:
The international mackerel and ecosystem survey in the summer of 2023 in the Northeast Atlantic was conducted with five vessels from four countries from July 1 to August 3, 2023.
The main purpose of the annual survey is to provide an index of the amount of mackerel in the Northeast Atlantic, in different age groups.
The mapping of mackerel covered 2.3 million square kilometres; 21 percent smaller than last year. This is mainly due to the fact that Greenland did not participate in this year’s survey.
Furthermore, 0.28 million square kilometres of the North Sea were also mapped this year, but this time series (2018-2023) is not yet included in the mackerel index.
About the Survey
The precision of this year’s mackerel population indices from the survey was good, with little uncertainty compared to 2022. This is due to the fact that we did not have individual large mackerel catches in the trawl nets this year (maximum 5.7 tonnes), compared to last year. In the previous year, we had two trawl stations with mackerel catches of around 20 tonnes each.
The quantity index from the survey was reduced by 42 percent in total weight (biomass), and 39 percent in terms of number of individuals compared to 2022.
The most numerous year classes during the 2023 survey were the 2020- and 2019-year classes.
Mackerel is still most abundant in the Norwegian Sea, but its distribution has significantly decreased over the past decade. This is primarily true for the western areas, especially in the Greenlandic and Icelandic waters, as well as in the northernmost regions of the Norwegian Sea.
Mackerel were more widely distributed to the east and northeast during the 2023 survey compared to 2022. Mackerel also appeared less clustered in 2023 compared to 2022.
The zero line, where mackerel were no longer found, was reached this year for the first time for the entire survey area. It was north of 60°N.
Overlap between Herring and Mackerel
As in previous years, there was overlap in the spatial and temporal distribution of herring and mackerel.
The overlap was between mackerel and North Sea herring in parts of the North Sea, and between mackerel and Norwegian spring-spawning herring in the northern parts of the Norwegian Sea.
Lumpfish, Capelin, Arctic Cod, and Salmon
Among other fish species, lumpfish, capelin, Arctic cod, and Atlantic salmon were also mapped.
Lumpfish were caught in 76 percent of the surface trawl hauls from southwestern parts of Iceland, central parts of the North Sea to the southwestern part of Svalbard. The quantity was greater north of 72°N compared to southern areas.
Hundreds of Lumpfish were tagged by researchers during this year’s survey, which should contribute to increased knowledge about the species’ distribution and migration.
Capelin were caught in surface trawls at 29 stations along the cold fronts: north of Iceland, north and northwest of Jan Mayen, northwest of Bear Island, and west of Svalbard. There were more trawl stations with capelin catches in the west and north of Jan Mayen compared to previous years.
Arctic cod were caught in larger areas north and northeast of Iceland compared to all previous years in the time series.
A total of 62 Atlantic salmon were caught at 24 stations in both coastal and open waters from 62°N to 74°N in the upper 30 metres of the water column. The trawl catches yielded between 1 and 12 individuals.
The salmon weighed between 84 grams and 2.7 kg and were dominated by post-smolts that had come from the rivers in the spring, and salmon that had spent a year at sea.
Environment and Plankton
The western and northwestern sea areas were considerably colder in 2023 compared to 2022 based on direct measurements from the upper water masses.
The East Iceland Current pushed cold water masses further east and southeast compared to previous years. This likely influenced the distribution and migration of mackerel to become more eastern and northeastern this year compared to last year.
Satellite measurements of sea surface temperature indicated that the central parts of the Norwegian Sea were somewhat warmer than the long-term average for July 1990-2009.
The Irminger Sea and the Icelandic Basin also showed slightly warmer temperatures than the long-term average.
The amount of zooplankton varied between areas, with clusters distributed throughout the entire survey area. The average amount of zooplankton was larger in the Norwegian Sea and Icelandic waters in 2023 compared to 2022.
Blue Whales near Jan Mayen
Opportunistic whale observations were conducted on board the two Norwegian vessels and the Faroese research vessel.
A total of 1078 marine mammals were observed, representing 10 different species, during the survey. The most dominant areas (hotspots) were along the continental slope west and north of Jan Mayen, and in the southwestern and western parts of Svalbard.
Fin whales and humpback whales dominated among the baleen whales. A total of eight blue whales were observed in the western and northern parts of Jan Mayen.
Groups of killer whales dominated in the southern and northeastern parts of the Norwegian Sea, overlapping with mackerel, which they were likely preying on.
Results for Norwegian spring-spawning herring and capelin coming soon
In the current preliminary survey report, the results for herring or capelin are not included.
The final survey report, including these results, will be available in late September.