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The Workshop on Unavoidable Survey Effort Reduction 2 (WKUSER2) focused on best-available approaches that can minimize information loss and ensure continuity in survey time series when unavoidable changes to survey effort occur. WKUSER2 recognised that reductions, reallocations, or increases in survey effort present similar set of problems, and therefore concentrated on all aspects of survey effort changes. The workshop reviewed available research, current practices, and recommended future directions on four key topics: (i) key elements of flexibility of a survey, (ii) why and how to combine data from different sources (e.g. surveys, fishery sampling) and deal with survey gaps, (iii) how to configure estimation and simulation models, and (iv) review existing tools and technology to evaluate consequences of survey effort changes.Road maps were developed for the key topic areas i, ii, iii, and iv, whenever possible, to assist scientists and survey managers in making decisions on how to evaluate and mitigate the impact of survey effort changes on data and advice quality. Many tools are available or are being developed for that purpose, but the group recognized two important needs during the workshop: i) defining clear objectives and priorities of a survey, which are essential to properly evaluate con- sequences of survey changes; and ii) making all tools accessible, reproducible, and transparent to benefit the whole community. This requires organisational and cultural shift to create support systems that ensure the development and sustainability of such tools in the future.

This is the final report of the European Commission funded research project "DRuMFISH" (service contract n° EASME/EMFF/2014/l.3.2.4/ SI2.721116). The main aim of the project was to develop models and strategies for providing advice for mixed fisheries that account for: (i) fishing mortality ranges consistent with MSY, (ii) all fish caught being landed, and (iii) significant components of the marine fish ecosystem lacking key biological information. In order to meet this aim, DRuMFISH delivered a review of assessment approaches for data-poor stocks, extended mixed fisheries simulation frameworks to include data-poor stocks. The assessment approaches and simulation frameworks were implemented in 7 case studies. These case studies were mixed fisheries in the Baltic Sea, the North Sea, the Celtic Sea, the Bay of Biscay, the Western Mediterranean, the Adriatic Sea, and the Aegean Sea. Within the case studies, 35 data-poor stock assessments were done. These assessments provided exploitation status of data-poor stocks. Different harvest control rules were subsequently tested for their expected yields and stock biomasses from the mixed fisheries in the simulation frameworks. Now that data-poor stocks can be incorporated with in the mixed fisheries simulation frameworks, the design of new management plans can account for data-poor stocks in mixed fisheries.