Report of the Working Group on Mackerel and Horse Mackerel Egg Surveys (WGMEGS)

The ICES Working Group on Mackerel and Horse Mackerel Egg Surveys (WGMEGS), chaired by Gersom Costas (IEO, Spain) and Matthias Kloppmann (TISF, Germany), met at the Marine Institute, Dublin from 9–13 April 2018, to plan the Mackerel and Horse Mackerel Egg Survey in 2019 and finalize results of the 2017 North Sea mackerel egg survey. The nations participating in the 2019 Northeast Atlantic (NEA) MEGS sur-vey will be Portugal, Spain, Scotland, Ireland, The Netherlands, Norway, Denmark, Germany, Iceland and the Faroe Islands. The main aim of the survey is to relate the number of freshly spawned eggs found in the water to the number of females having produced these eggs. Knowing the fecundity of the females and sex ratio provides an estimate for the spawning-stock biomass.The 2019 survey will be based on seven regular sampling periods (Section 5). Norway announced that it will re-join the survey in 2019. In addition, Denmark disclosed that they will participate in 2019 and probably also in the 2020 North Sea MEGS, provided the necessary ship time is granted by their administrative bodies. The 2010 and 2013 surveys pointed to progressive forward shifting of peak spawning, the 2016 NEA MEGS pointed to a return to the traditional spawning peak in May, but much further North than anticipated. In contrast, spawning in the southern areas remained compar-atively low during the whole 2016 spawning season. Additional information, however, collated from spring surveys undertaken in 2017 (Section 5.10) point towards an in-crease of spawning activities in the South to levels observed before 2016 but also to a continuation of spawning at the northern boundaries of the enlarged survey area.The return of Norway and possibly the return of Denmark would be extremely helpful to be able to plan a full coverage of the survey area in 2019. The survey plan will be further elaborated during the course of 2018 and an updated survey plan will be pre-sented after WKFATHOM.In 2019, the MEGS survey will continue as an AEPM survey; however, as with the sur-veys in 2013 and 2016, the intention will be to also carry out intensive DEPM sampling during expected peak spawning periods of both species in an attempt to calculate a DEPM SSB estimate. The periods highlighted as being the likely peak spawning peri-ods are periods 3 and 4 for mackerel and period 6 and 7 for western horse mackerel. Fecundity analysis will be conducted by Norway (IMR), the Netherlands (Wageningen Marine Research), Scotland (MSS), Ireland (MI) and Spain (IEO and AZTI).The WKFATHOM staging and fecundity workshops will take place during October in Bremerhaven (egg identification and staging) and in November in IJmuiden (fecundity and atresia). These workshops are essential to maintain the quality assurance of the mackerel and horse mackerel egg surveys and it is strongly advised that participating analysts attend these workshops. Final amendments to the egg survey /fecundity sam-pling planning schedules will be made during these workshops and distributed among all survey participants. The revised and finalized survey plan will be published in the second interim report of WGMEGS in September 2019