The Norwegian Institute of Marine Research has issued their preliminary report from mackerel ecosystem survey 2022

The Norwegian Institute of Marine Research has issued their preliminary report from mackerel ecosystem survey 2022

The international mackerel ecosystem cruise in the North-East Atlantic in the summer of 2022 was carried out with six vessels from five countries in less than five weeks from 1 July to 3 August 2022.

The main purpose of the cruise is to produce an annual age-based abundance measurement index with uncertainty estimates for North-East Atlantic mackerel. A standardized pelagic trawl method (swept-area) is used to obtain a quantity index and spatial distribution of the mackerel stock in relation to other numerous pelagic fish stocks.

The stock index is included in the stock calculations for the mackerel stock in accordance with the conclusions from the method revisions in ICES in 2017 and 2019.

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The international mackerel ecosystem cruise has been conducted annually for 13 years from 2010 to 2022.

Another important purpose of the cruise has been to establish a new time series of quantity index for both coal mullet and Norwegian spring-spawning herring (NVG). This is done by implementing standardized transect-based acoustic methods for quantity estimation in combination with pelagic trawling based on acoustic recordings. The time series of the population indices for blue whitingand NVG herring is now seven years long (2016-2022).

The trip mapping that was included in the calculations for the mackerel quantity index was 2.9 million km2 in 2022, which is 32 percent larger than the mapping in 2021. The trip mapping was increased in western areas (Icelandic and Greenlandic waters) compared to 2021. Furthermore, 0, 28 million km2 mapped in the North Sea in July 2022, but these stations have not yet been used in the calculations of the mackerel index.

The quantity index increased by 43 percent for biomass and 43 percent for quantity (number of individuals) compared to 2021. The most numerous year classes in 2022 were the 2020, 2019, 2010 and 2011 year classes, respectively. The internal consistency between the different year classes increased compared to 2021, especially for 5-8 year-old mackerel, when the 2022 index was included in the time series (2010, 2012-2022).

The mackerel is still most widespread in the Norwegian Sea. The mackerel was more widespread in the west than in the last two years. The mackerel appeared more in clumps in 2022 compared to 2021, especially at two trawl stations in the cruising area.

A preliminary estimate suggests that total biomass of blue whiting registered during IESSNS 2022 was 2.1 million tons, which is similar to 2021 (2.2 mill tons). Estimated stock abundance (ages 1+) was 27.2 billion compared to 26.2 billion in 2021. Age 1 and 2 respectively, dominated the estimate in 2022 as they contributed to 44% and 33% (abundance) and 30% and 33% (biomass), respectively. The group considered the acoustic biomass estimate of blue whiting to be of good quality in the 2022 IESSNS as in the previous survey years.

As in previous years, there was overlap in the spatio-temporal distribution of mackerel and herring. This overlap occurred between mackerel and North Sea herring in the North Sea and partly in the southernmost part of the Norwegian Sea. There were also some overlapping distributions of mackerel and Norwegian spring-spawning herring (NSSH) particularly in the western, north-western part of the Norwegian Sea.

Other fish species also monitored are lumpfish (Cyclopterus lumpus) and Atlantic salmon (Salmo salar). Lumpfish was caught at 71% of surface trawl stations distributed across the surveyed area from southwestern part of Iceland, central part of North Sea to southwestern part of the Svalbard. Abundance was greater north of latitude 72°N compared to southern areas. A total of 60 North Atlantic salmon were caught in 38 stations both in coastal and offshore areas from 61°N to 76°N in the upper 30 m of the water column. The salmon ranged from 0.028 kg to 4.1 kg in weight, dominated by post-smolt and 1 sea-winter 4 individuals. We caught from 1 to 6 salmon during individual surface trawl hauls. The length of the salmon ranged from 15 cm to 74 cm, with the highest fraction between 20 cm and 30 cm.

Satellite measurements of sea surface temperature (SST) in the Northeast Atlantic in July 2022 show that parts of central Norwegian Sea and areas east and north of Iceland were slightly cooler than the long-term average for July 1990-2009. The northern regions of the Nordic Seas were slightly warmer than the average while the East Greenland Current was cooler that the long-term average. The SST in the Irminger Sea and Iceland Basin were slightly warmer than the average.

The zooplankton biomass varied between areas with a patchy distribution throughout the area. In the Norwegian Sea areas, the average zooplankton biomass was at similar level as last year, slightly lower in Icelandic waters, and higher in Greenlandic waters.

The acoustic results on Norwegian spring-spawning herring and blue whiting presented in the cruise report are preliminary and have not yet been finalized and properly quality checked. A final cruise report from the IESSNS 2022 will be available at the same time as the ICES WGWIDE report will be available on 30. September 2022.

The findings summarised by researcher and survey coordinator Leif Nøttestad

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Norwegian HI issues preliminary report from mackerel ecosystem survey 2022

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