Following a submission of two reports from 26 European environmental non-governmental or-ganisations (NGOs) to the European Commission (DG MARE) concerning the introduction of emergency measures to mitigate bycatch of common dolphins in the Bay of Biscay and harbour porpoises in the Baltic Sea, ICES established the Workshop on Emergency Measures to mitigate BYCatch of harbour porpoise in the Baltic Sea and common dolphin in the Bay of Biscay (WKEM-BYC). WKEMBYC was tasked to build on the work conducted by WGMME and WGBYC to as-sess the emergency measures proposed by the NGOs, explore alternative measures, and suggest emergency measures that are necessary to ensure a satisfactory conservation status of these stocks. The work of WKEMBYC was based on the examination of the information provided by NGOs, as well as the work conducted by WGMME 2020 and WGBYC 2020 under ToR E and ToR G respectively. The population of harbour porpoise in the Baltic Proper is considered to be critically endangered and its abundance is 497 individuals (95% CI 80–1091). At least 5–10 individuals might die from bycatch every year. A Potential Biological Removal (PBR) limit for the Baltic Proper harbour porpoise was estimated at 0.7 animals per year. Data from the North Sea and the Celtic Sea showed that the highest bycatch rate for harbour porpoise was in gillnet and trammel net fish-eries (GNS and GTR). Data from 2016 to 2018 from Bay of Biscay bycatch rates are highest in midwater pair trawls ( PTM). Harbour porpoises are also caught in bottom and midwater otter trawls (OTB, OTT and OTM). The three proposed emergency measures by NGOs aiming at a reduction of bycatch numbers are not sufficient for the protection and recovery of the Baltic Proper harbour porpoise popula-tion, therefore WKEMBYC recommended adjustments.. The proposed monitoring actions by NGOs would increase the knowledge of the harbour porpoise population. The common dolphin is one of the most abundant cetacean species in European waters. The appropriate scale at which to evaluate the population status of common dolphins occurring in the Bay of Biscay is the European Atlantic Assessment Unit, where its abundance is estimated to be 634 286 (CV=0.307). In 2017 and 2018, the mortality due to bycatch inferred from French strandings in the Bay of Biscay and Western English channel at large was respectively estimated at 9300 [5800; 17 900] and 5 400 [3400; 10 500] common dolphins. In the Bay of Biscay and the Iberian Coast, the mean annual bycatch estimated from at sea observations for 2016–2018 across all métiers amounted to 3973 (95% CI 1998–6599) dolphins. PBR was calculated as 4926 individ-uals per year. Comparing bycatch estimates obtained from strandings with PBR suggests recent estimates (2017–2019) were higher than the PBR limit. Removing bycatch in the January–March winter period reduces the estimated bycatch to a small proportion of the total, and much lower than the calculated PBR. WKEMBYC considered that the NGO proposed closure of all fisheries of concern in the Bay of Biscay from December to March was expected to significantly reduce bycatch of common dol-phins. However, suggestions of alternative closures needed to be further explored and the use of ‘pingers’ needed to be considered.