A new report from May has shown a decrease in the index of Norwegian-Icelandic herring of 13%
A preliminary report on the results of an international expedition from last May in the Norwegian Sea and adjacent sea areas is now available.
One of the main objectives of the expedition is to assess the volume and distribution of Norwegian-Icelandic herring and other pelagic species. In addition, the state of the ocean and the ecosystem are examined, including temperature and levels of conflict.
The expedition is organised within the International Working Group of the Marine Research Council (ICES).
Participants in the mission as well as the research vessel Arni Fridriksson, were research vessels from Norway, the Faroe Islands, Denmark and Russia. As the expeditionary section of the Barents Sea, which focuses on young herring, has been delayed, the results of that section will be added to the report in August.
Norwegian-Icelandic herring in May of this year was at its highest density in the southwest sea where the 2013 cohort (7 years) was dominant, and in the eastern region where the 2016 cohort (3 years) was predominant (Figure 1). The Herring Total Index for Herring was 4.25 million tonnes compared to 4.9 million tonnes in 2019, a decrease of 0.62 million tonnes (13%). The indices of recent years have fluctuated slightly, but overall they show a fairly stable population size (Figure 2).
The 2016 cohort was in the largest number (57%) and biomass (41%). His index at the age of four is higher than the large cohort of 2004, which puts the size of the 2016 cohort in context (Figure 3). In the coming years, the 2016 cohort can therefore be expected to become even more prominent in the biomass of the stock.
The blue whiting was found offshore on most of the entire study area if it is separated east of Iceland in the cold East Iceland stream. The highest density was on the southern part of the study area as well as with the Norwegian continental shelf.
This expedition does not cover the entire stock, and especially the adult stock. The results, however, give evidence of the size of new cohorts. The total geothermal index for blue whiting was estimated at 390,000 tonnes, down by 26% from last year. The highest was measured by the 2019 cohort (32.5%) and its index is of the same magnitude as the cohorts of 2013-2015 and 2019 at the same age, but they have proven to be large.
There was a slight decrease between years in the quantity indices for the entire study area, with the exception of the area east of Iceland where there was a slight increase (Figure 4). In the middle and eastern parts of the region, the indices are below the 1995-2019 average. On the other hand, in the northern part of the region, where the highest values were traditionally, the indices are close to the historical average.
The sea temperature was similar to or just above the average of the last 25 years at 0-200 m depth in the western part of the sea area but below the average in the warmer sea east and south (Fig. 5). At a depth of 200-500 m, the temperature was below and above average. Figure 5. Sea temperature (left) and temperature deviation from the average of 1995-2019 (right) at 50-200 m depth in May 2020.[/caption]
These results, and in particular the herring measurements, will be used, among other things, at the ICES meeting at the end of August. where the stock size assessment and advice of these pelagic fish stocks is carried out. More on the results of the expedition can be found in the preliminary report.