Working group on mackerel and horse mackerel egg surveys (WGMEGS)

The ICES Working Group on Mackerel and Horse Mackerel Egg Surveys (WGMEGS) coordi-nates the mackerel and horse mackerel egg surveys in the Northeast Atlantic (NEA) and the mackerel egg survey in the North Sea. This report focuses on the execution, and results, of the surveys (MEGS) conducted during 2022.

In 2022, the survey once again faced significant challenges with regards to its ability to provide adequate geographical and temporal coverage, given the limited vessel resources at its disposal. In 2022, Portugal, Spain (IEO and AZTI), Ireland, UK/Scotland, the Netherlands, Germany, the Faroe Islands, and Norway participated in the egg survey in the western and southern areas. Denmark and UK/England, with some additional assistance from Norway, surveyed the North Sea as a single-pass DEPM survey. This is the first time in many years that both the Atlantic and North Sea surveys have been conducted in the same year.

WGMEGS notes that the expansion of recent surveys during periods 5 and 6 occurred again in 2022. While the northern and western boundary was not contained, the number of eggs being missed in this area would not contribute significantly to the overall SSB calculation. Due to dif-ficulties encountered by the Irish survey in period 6 this area was not surveyed.

Mackerel daily egg production was highest in period 5 for the western component, while for the southern component the maximum spawning intensity was observed in period 3. Total mackerel egg production for southern and western components combined was 2.093 * 1015 eggs. The real-ised fecundity estimate was 1268 egg per gram female, resulting in an SSB index of 3.565 * 106 tonnes.The total 2022 Daily egg production (P0tot) for mackerel in the North Sea was 0.691*1013 eggs/day, a 50% decrease in egg numbers reported during the 2021 survey.

For the Western stock of horse mackerel highest mean daily egg production was estimated dur-ing period 6. Spawning was very low throughout all survey periods, with an obvious peak oc-curring in period 6. Total annual egg production for western Horse mackerel was 5.51 * 1014, a 310% increase on 2019. In addition, P0tot and SSB was calculated using DEPM for western horse mackerel. The total Daily egg production for 2022 was 0.186*1013 eggs/day resulting in an SSB index of 891 * 106 tonnes.

For the Southern stock of horse mackerel, the peak spawning period was estimated to be in Jan-uary- February. The Total Egg Production estimated for the 2022 survey was 5.18 x 1011 eggs/day, 37% lower than the estimate for the survey in 2019. Adult parameters to estimate SSB couldn’t be obtained for the present report.