The Norwegian research trip 2021 produces significantly lower mackerel catches. Underwater photos mackerel in the Svalbard zone mackerel ecosystem cruise 2021 on “Eros”. (Photo: HI)
The great mackerel and ecosystem research trip carried out by the Norwegian Institute of Marine Research has concluded for 2021.
The main impression is significantly lower mackerel catches during this year’s cruise compared to last year. There is no indication that the mackerel has migrated to or grazed in the Barents Sea this year, writes research leader Leif Nøttestad.
Significantly lower mackerel catches were caught during this year’s mackerel ecosystem cruise with “Eros” and “Vendla” compared to last year’s cruise.
In total, the two Norwegian vessels performed 145 standardized 30-min trawl hauls with about 5 knots of towing speed in the upper water masses (0 to 35 meters) for mackerel.
The centre of gravity of the mackerel this year was found further south in the Norwegian Sea and younger mackerel in the North Sea. The distribution of mackerel in northern waters was actually greater this year, but catches were significantly lower within the mapped distribution area compared with last year.
“We also failed this year to establish the zero line for mackerel in the northwesternmost sea areas. This is partly due to delays related to bad weather. In addition, we spent extra unforeseen time on acoustic mapping and station work to cover for missing mapping of a new foreign research vessel. There is no indication that the mackerel has migrated in and grazed in the Barents Sea this year,” writes Leif Nøttestad.
Less wind, better weather
After a long period of demanding conditions in the Norwegian Sea with delays, the weather and wind conditions in the last part of the mackerel ecosystem cruise have mainly been good. We have had solid progress and good working conditions for acoustic recordings, station work and trawling on board Eros and Vendla. It is difficult to assess the extent to which poor weather conditions with dominant northern and westerly winds may have had a negative effect on catch rates for mackerel during the voyage.
Colder in the west-northwest
Preliminary temperature measurements indicate that there have been some colder surface temperatures in the western / north-western parts of the Norwegian Sea during this year’s mackerel ecosystem cruise compared with last year. Nevertheless, the western distribution of mackerel in ex. The Jan Mayen area has been slightly further west this year than last year. This is primarily due to the fact that mackerel have grazed in even colder sea areas down to 4.5-5.5 ° C in these sea areas compared to last year. That said, the mackerel catches on board the Vendla and Eros have generally been significantly lower also in the northern sea areas during this summer’s mackerel ecosystem cruise compared with last year’s survey.
NVG herring and blue whiting
The main impression is that there have also been lower acoustic blue whiting registrations during this year’s cruise compared to last year, and very little blue whiting in the western and north-western parts of the Norwegian Sea.
“We must analyze the data that includes all participating vessels and nations before we can say anything more about the stock estimate itself,” says Leif.
“There have also been scattered acoustic herring recordings with sonar and sonar. The largest concentrations during the second part of the cruise have been in the north-eastern Norwegian Sea and south-eastern part of Jan Mayen. It is also clear that some NVG herring have been above the so-called acoustic blind zone in the upper 10-15 m of the water column, based on simultaneous sonar registrations and trawl catches of herring near the surface. We also return to this year’s stock index for NVG herring, after we have analyzed all the acoustic and biological data from all the vessels that have been involved in the cruise.”
Lump fish and salmon
“We have marked a total of about 160 lump fish of various sizes in the Norwegian Sea on board the two Norwegian boats. Both adult Atlantic salmon and smaller post-smolt have been caught in the central and northern Norwegian Sea as far north as 75 ° N for a number of biological, ecological and genetic studies,” notes Leif.
Fewer marine mammals observed
The observations of marine mammals on board the Eros and Vendla were dominated by fin whales, minke whales, humpback whales, white-tailed dolphins and killer whales.
“We saw fewer marine mammals this year than last year, but this is probably largely related to significantly worse weather and observation conditions this year compared to last year. We had longer periods of sea fog that almost made visual observations of marine mammals almost impossible,” writes Leif.
Many performed research assignments
“Throughout the cruise, we have collected a number of otoliths (ear stones) and genetic samples for new methods for separating different herring populations. There has also been a separate systematic collection program and thorough investigations of the parasite Kudoa thyrsites which gives “jelly mackerel” and quality of the mackerel.
We also collect more than two full freezers with mackerel samples from all over the Norwegian Sea for use in the development of a new method for genetic identification of the mackerel’s stomach contents,” says the Norwegian scientist.
The way forward
All available data from all vessels and nations will now be compiled after the end of the voyage. In the next two weeks, a key research task will be to analyze all the data from all the vessels that have participated in the mackerel ecosystem cruise this year and calculate this summer’s stock index for the mackerel stock based on the standardized swept area trawling.
Then a so-called international post cruise meeting will be held from 20 to 25 August. There the combined Institutes of Marines will perform quantity measurement and come up with updated stock indices from the cruise for all three major pelagic fish stocks; mackerel, NVG herring and blue whiting. Furthermore, the central ICES WGWIDE meeting where the international stock calculations for our most important pelagic fish stocks will be carried out, will take place from 26 August to 01 September.
The actual stock advice from ICES, including the mackerel council for 2022, will be published on 30 September.