Weighing of a partial sample with 5.4 tonnes of mackerel in the final haul on “Kings Bay” in the Svalbard zone during the 2020 International research cruise. (Photo: Leif Nøttestad / HI)
The researchers from the various countries have now compiled the results from the 2020 International Research Cruise cruise in a final report.
The international mackerel and ecosystem cruise in the Northeast Atlantic lasted just over four weeks from 1 July to 4 August 2020. A total of six vessels from Norway, Iceland, the Faroe Islands, Greenland and Denmark participated.
In the annual cruise, the researchers use a specially designed trawl over fixed course lines to get a picture of how much mackerel there is in the sea. The result is one of several important indices that researchers use to estimate the size of the mackerel stock – which in turn is used to provide quota advice for the species.
Never measured more mackerel on the cruise
“This year’s cruise estimate for mackerel is the highest we have ever registered in the years the cruise has gone,” says international cruise coordinator Leif Nøttestad.
He presented the results to the International Council for the Exploration of the Sea ICES ‘working group WGWIDE on Thursday 27 August.
-“We did not find mackerel in Greenlandic waters and a strong reduction in Icelandic waters. At the same time, there is an increase in central and northern parts of the Norwegian Sea,” he says.
The mackerel plays the main role, but the researchers also measure a number of other species and environmental factors. Here are some highlights from the scientific cruise report :
Found more mackerel than last year
The trawl cruise’s stock index for mackerel is measured 7 percent higher in tonnes compared with last year. The most numerous year classes were 2010, 2016, 2011, 2013 and 2014 ranked in order.
The geographical survey was close to 3 million square kilometers in 2020, corresponding to 2017-2019. In addition, 0.26 square kilometers were mapped in the North Sea in July. This is the third year that the North Sea has also been mapped in the cruise, but the results from this are not used in the cruise index yet.
The zero limits in distribution (where there are no fish) were found in most mapped areas with the exception of in the north-western part of the Norwegian Sea, towards the Fram Strait west of Svalbard. Here, mackerel continued to be outside the cruise’s coverage area, but the researchers believe that this has not significantly affected the cruise index for the mackerel stock.
The mackerel was less lumpy within the cruise area and had a prominent distribution in the central and northern parts of the Norwegian Sea in 2020 compared with previous years. At the same time, there is correspondingly less mackerel in western areas of the Norwegian Sea.
Nvg herring is also registered on the cruise
The index for the total amount of Norwegian spring-spawning herring registered on the cruise was 24 percent higher in 2020 than in 2019.
The increase was related to the 2016 year class, which is now entering the cruise area strongly. The four-year-olds are the largest age group in the herring population – they make up 33 per cent in tonnes. But these fish are still to be found in the northwestern part of the Norwegian Sea, mainly.
The 2013 class is distributed in all herring areas in the cruise, and makes up 22 percent of the population.
Smaller but more blue whiting
The total amount of tonnes of blue whiting registered on this year’s cruise was 11 percent lower than the 2019 cruise.
The one-year-olds dominated the estimate in 2020 in tonnes and in number. Good numbers of recruiting “zero-year-olds” were also observed during the cruise this year, but it is still uncertain to what extent they will contribute to the fishable stock in the future.
Herring and mackerel overlap
As in previous years, mackerel and herring overlapped in the southern and southwestern parts of the Norwegian Sea.
The herring from 2016 also enters together with the mackerel in the central and northeastern parts of the Norwegian Sea.
In the eastern Norwegian Sea between 62-67 ° N, mackerel was present, but not herring. Herring, on the other hand, were found alone north of Iceland.
Older and younger herring were separated by larger herring east and north of Iceland and in the southern Norwegian Sea. Young herring stood in the northeastern Norwegian Sea.
Roe biscuits, salmon and zooplankton
Of other fish species, roe biscuits and Atlantic salmon were also mapped. Roe biscuits were caught in 74 percent of the surface trawl tails from Cape Farvel, the southern tip of Greenland to the western parts of the Barents Sea.
Several hundred roe deer were tagged to provide more knowledge about the migration pattern of the species.
A total of 54 Atlantic salmon were caught in 30 stations in both coastal and open sea areas from 60 ° N to> 77 ° N in the upper 30 meters of the water column. It was post-smolt of 100-200 grams and single-sea winter salmon of 1-2 kilos that dominated the catches.
The amount of zooplankton was sharply reduced from 2018 to 2020 in both Greenlandic and Icelandic waters.
In the Norwegian Sea, the amount of zooplankton measured on the cruise has been relatively stable in recent years.