The WKBYC workshop was held to address three advice requests from the European Commission to the Working Group on Bycatch of Endangered Species. To address these issues DGMARE requests ICES to consider the following: 1 ) Assess the extent to which current fishery monitoring schemes, including inter alia those conducted under the DCF and Regulation 812/2004, provide an acceptable means of assessing the nature and scale of cetaceans and other protected species bycatch. Consider alternative means and other sources of data that could be used to improve our understanding of the conservation threat posed to cetaceans and protected species by bycatch in European fisheries. 2 ) Advise on how Annex II of Regulation 812/2004 defining technical specifications and conditions of use Acoustic Deterrent Devices could be best revised in light of technical and scientific progress in this field. 3 ) Based on the methodology used and the estimates of bycatch limits (take limits) generated by region at WKREV812 and other relevant analyses, propose effective ways to define limits or threshold reference points to by-catch that could be incorporated into management targets under the reformed CFP. Limits or threshold reference points should take account of uncertainty in existing bycatch estimates, should allow current conservation goals to be met, and should enable managers to identify fisheries that require further monitoring, and those where mitigation measures are most urgently required. In response to the first request: ICES compared the coverage of current sampling under the DCF and the EU Regulation 812/2004 programmes with known abundances of cetaceans (and approximate indications of abundances of other protected species), with an index of bycatch vulnerability and with minimum estimates of fishing effort by métier. Métiers/areas were identified where the risk to populations of certain species (groups) being adversely affected was greatest, and where coverage of the present monitoring schemes was relatively poor. Second request: ICES also approached a small number of underwater acousticians and manufacturers of ADDs and asked them for their views on how Annex II of Regulation 812/2004 could be best revised. A number of existing ADDs are effective in reducing harbour porpoise bycatch, but the full bounds of the technical specifications between an effective and an ineffective ADD are not known. The group recommends that rigorous experiments are needed to demonstrate the effectiveness of new ADDs, while prescriptive constraints are unhelpful. ICES bases its advice for an >80% reduction in bycatch on the results of all the successful pinger experiments listed by Dawson et al. (2013), with >95% being the standard level of confidence for scientific studies. Third request: the group considered that the existing procedures to establish limits and reference points (CLA, PBR, and 1.7%), has been reviewed several times in the past decade. The WKBYC notes the recommendations made by the WGMME (2013), particularly that the Catch Limit Algorithm (CLA) approach is recognized as the most appropriate method to set limits on the bycatch of cetaceans and that explicit conservation and management objectives for managing interactions between fisheries and cetacean populations should be adopted at a European level.