Working group on mackerel and horse mackerel egg surveys (WGMEGS)
The Working Group on Mackerel and Horse Mackerel Egg Surveys (WGMEGS) is responsible for the planning, data collection, and data analysis of the ICES triennial mackerel and horse mackerel egg surveys. This report focuses on the Terms of Reference that are directly involved with 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 and Mackerel (WKFATHOM) (12–16 October 2018, Bremerhaven, Germany and 9–12 November 2018, Ĳmuiden, The Netherlands) were discussed, with the subsequent enhancements and recommendations proposed 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 survey was 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 the WGMEGS Manual for the Mackerel and Horse Mackerel Egg Surveys (ICES SISP 6, 2019a). In 2019, 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 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 to participate. The resulting gaps in the survey plan were mitigated by the inclusion of additional surveys 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 egg survey. In 2019, the survey was split into six sampling periods. Due to a delay in starting the Portuguese survey it was decided to move the start date of period 2 in the southern area earlier into January and to incorporate the 9a survey into period 2. The final, sixth period ended in late July. Waters west and southwest of the Iberian Peninsula were surveyed in period 2 only. The Cantabrian Sea was sampled in periods 3 – 5 while Biscay was sampled in periods 2 to 6. The Celtic Sea and waters west of the British Isles were sampled in periods 2 to 7, and the vast oceanic waters north and northwest of Britain towards Iceland and into the Norwegian Sea were sampled in periods 5 and 6. Mackerel daily egg production was highest in period 4, (April), for the western component, while for the southern component the maximum was observed in period 3. Total mackerel egg production (provisional, southern and western component combined) was 1.64 × 1015. Provisional fecundity 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 during the final sampling period 7. For almost all sampling periods, egg production in this species was much lower than observed during previous egg surveys. Total annual egg production for western Horse mackerel was 1.78 × 1014.