Working Group on Mackerel and Horse Mackerel Egg Surveys (WGMEGS)

The Working Group on Mackerel and Horse Mackerel Egg Surveys (WGMEGS) is responsiblefor the planning, data collection, and data analysis of the ICES triennial mackerel and horsemackerel egg surveys. This report focuses on the Terms of Reference that are directly involvedwith the execution of the mackerel and horse mackerel egg survey (MEGS) in 2019.The results of the two Workshops on Egg staging, Fecundity and Atresia in Horse mackerel andMackerel (WKFATHOM) (12–16 October 2018, Bremerhaven, Germany and 9–12 November2018, IJmuiden, The Netherlands) were discussed, with the subsequent enhancements and recommendationsproposed during these workshops outlined in the workshop report (ICES, 2018a)incorporated into both of the WGMEGS manuals (ICES, 2019a), (ICES, 2019b).Planning for the 2019 survey was fine-tuned. Although the broad planning of the 2019 surveywas undertaken during the 2018-planning meeting and reported in the 2018 WGMEGS report,amendments to the provisionally agreed plan required additional intersessional refinements.The settled plan for the 2019 survey has been included as an annex in the latest version of theWGMEGS Manual for the Mackerel and Horse Mackerel Egg Surveys (ICES SISP 6, 2019a). In2019, the survey once again faced significant challenges with regards to its ability to provideadequate geographical and temporal coverage given the limited vessel resources at our disposal.After their withdrawal from the MEGS survey in 2016, Norway re-joined the survey in 2019,however Iceland withdrew its participation in early 2019. Also, contrary to the first survey plan,which was published with the 2018 WGMEGS report (ICES 2018b), Denmark was not able toparticipate. The resulting gaps in the survey plan were mitigated by the inclusion of additionalsurveys undertaken on commercial vessels. In 2019, Portugal, Spain (IEO and AZTI), Ireland,UK/Scotland, the Netherlands, Germany, the Faroe Islands, and Norway participated in the eggsurvey.In 2019, the survey was split into six sampling periods. Due to a delay in starting the Portuguesesurvey it was decided to move the start date of period 2 in the southern area earlier into Januaryand to incorporate the 9a survey into period 2. The final, sixth period ended in late July. Waterswest and southwest of the Iberian Peninsula were surveyed in period 2 only. The Cantabrian Seawas sampled in periods 3 – 5 while Biscay was sampled in periods 2 to 6. The Celtic Sea andwaters west of the British Isles were sampled in periods 2 to 7, and the vast oceanic waters northand northwest of Britain towards Iceland and into the Norwegian Sea were sampled in periods5 and 6.Mackerel daily egg production was highest in period 4, (April), for the western component, whilefor the southern component the maximum was observed in period 3. Total mackerel egg production(provisional, southern and western component combined) was 1.64 × 1015. Provisionalfecundity estimate was 1142 egg per gram female, resulting in an SSB index of 3.1 × 106 tonnes.For the Western stock of horse mackerel, highest mean daily egg production was estimated duringthe final sampling period 7. For almost all sampling periods, egg production in this specieswas much lower than observed during previous egg surveys. Total annual egg production forwestern Horse mackerel was 1.78 × 1014.