This week fisheries scientists from the Faroe Islands, Iceland and Norway met to analyse and coordinate results from a joint mackerel survey that was conducted earlier this summer. As earlier reported on the MRI website, the investigations were carried out onboard four vessels from Iceland, the Faroes and Norway during the period 1 July through 10 August 2012. The main aim was to map the distribution and abundance of mackerel and other pelagic in the Northeast Atlantic while undertaking feeding migrations to northern waters in addition to investigate ocean conditions and productivity of the area. R/V Árni Friðdriksson participate for the fourth time in this annual joint mackerel survey and this year all vessels were using a recently developed and standardised pelagic trawl for the entire survey area.
The mackerel abundance in the survey area was estimated based on standardised trawls at regular intervals (Figure 1). In total it was estimated that 5.1 million tons of mackerel was occurring in the survey area, thereof 1.5 million tons or 29% within the Icelandic EEZ see (Table 1) and (Figure 2). In a survey conducted by the same three parties in 2011 the total estimated biomass was 2.7 million tons, while in 2010 the total estimate was 4.8 million tons, respectively. The total area surveyed in 2012 was 1,530 thous. square km, compared to 1,060 in 2011 and 1,750 thous. square km in 2010. The between-year differences in area coverage is regarded as the main reason for different estimates in the three years.
Although the results are not as yet used by ICES (International Council for the Exploration of the Sea) to estimate the total stock size of mackerel, the investigations confirm like the results in earlier years, an extensive northerly distribution of mackerel during summer. They also confirm that the oldest mackerel has the greatest migratory range in the eastern North Atlantic in summer, while the greatest concentrations were found farthest to the west and north in the survey area.
Overlap of distribution between mackerel and Atlanto-Scandian herring was mainly in the Norwegian Sea and to the east of Iceland (Figure 1). In the eastern part of the survey area, the herring abundance was low. Acoustic index for the Atlanto-Scandian herring gave a biomass estimate of 7.2 million tons, which means a continued decline in the stock size as predicted by ICES.
The greatest densities of calanoid copepods (most important food for mackerel) was west off Iceland where the mackerel was also in greatest concentrations. In other areas the copepod abundance was relatively low as it has been in recent years.
The sea surface temperature in the North Atlantic was in general above the long-term average. This applied in particular to the area southwest of Iceland while the sea surface temperature in the southwest Norwegian Sea north of the Faroes was slightly lower than in recent years. Further analyses of the data collected during this joint survey will take place in the coming months.
Also attached here is summary of the report of the meeting of the scientists of the participating countries in English.
Cruise report from the coordinated ecosystem survey (IESSNS) here