Fishery closures and marine protected areas are increasingly being used as tools to achieve sustainable fisheries. The “plaice box”, a gear restriction area in the North Sea that was established to reduce the bycatch of undersized plaice ( Pleuronectes platessa ), is considered ineffective because there has been a shift in the distribution of juvenile plaice to the waters that remained open to bottom trawlers. Here we examine the hypothesis that bottom trawling benefits the small benthic invertebrates that form the food source for plaice and that the plaice box had a negative impact on food production for plaice. A size-based model of benthic communities indicates that the production of prey was low without trawling and maximal in areas that are trawled once to twice a year. Therefore, bottom disturbance may improve the feeding conditions for species that feed on small invertebrates. As plaice aggregate at the locations with the highest benthic biomass, this may explain the observed redistribution to areas outside the plaice box. We conclude that the plaice box may not have been the most appropriate measure to protect plaice from discarding and that the species’ ecology should be considered when choosing the most appropriate management measure to achieve an objective.

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Piet, G.J 1 ., Boon, A 2 . Jongbloed, R 1 ., van der Meulen, M 2 ., Tamis, J 1 . van der Wal, J.T 1 .Teal ,L SummaryThis development of the framework and approach for a Cumulative Effects Assessment (CEA) is based on a literature review. From this we adopted several definitions that guided this development.• A CEA is understood as "a systematic procedure for identifying and evaluating the significance of effects from multiple sources/activities and for providing an estimate on the overall expected impact to inform management measures. The analysis of the causes (source of pressures and effects), pathways and consequences of these effects on receptors is an essential and integral part of the process".• Cumulative effects are "the incremental impact of the action when added to the other past, present and reasonably foreseeable actions". In this approach we only consider a (cumulative) effect significant if it has an impact on a relevant ecosystem component.Therefore our framework and approach for a CEA is based on all human activities that may have a potential impact on any relevant (from a policy perspective) ecosystem component at an appropriate spatio-temporal scale.The literature also identified some key challenges that need to be addressed for CEA to evolve into a consistent, appropriate tool to assist decision-making. These challenges included• A clear distinction of the receptor-led CEA from the dominating stressor-led Environmental Impact Assessment (EIA) approaches and• Enabling CEA to provide ecosystem-relevant information at an appropriate regional scale.Therefore this CEA is explicitly developed to be a receptor-led and fully integrated framework, i.e.involving multiple occurrences of multiple pressures (from single and/or different sources) on multiple receptors, as opposed to other existing approaches dealing with only a subset of those pressures or receptors, hence our use of the phrase iCEA for integrated CEA. As a proof of concept for this iCEA we selected one receptor, the ecosystem component marine mammals.From the literature review we adopted (and slightly modified) a risk-based framework for defining and undertaking cumulative effects assessments which is aligned to the work in the OSPAR IntersessionalCorrespondence Group on Cumulative (ICG-C) Effects and the ICES Working Group on IntegratedAssessments of the North Sea (WGINOSE), thereby ascertaining this framework and approach is wellplaced within ongoing international North Sea initiatives. Furthermore, the CEA framework in this study should contribute to national North Sea policymaking, with a specific focus on the Marine Strategy framework Directive (MSFD). This literature review is presented in Chapter 1.Our iCEA framework consists of four phases each corresponding to a chapter in this report:1. Conception. This is where purpose and scope are defined (see Chapter 2). 3. Execution (importance). Here we establish the relative importance of each impact chain using a risk-based approach that calculates "Impact Risk", i.e. the contribution of...

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