Background The Celtic Sea is a rich ecosystem that extends from the edge of the Atlantic continental shelf. It encompasses deep water features such as seamounts and canyons, as well as varied coastal habitats such as tidal estuaries and rocky reefs. These features and habitats support a wealth of biodiversity, including cold-water corals, sharks, cetaceans, and commercially-important fin and shellfish species. Like oceans and seas globally, the health of the marine ecosystem in the Celtic Sea region is under significant threat from a variety of external pressures, including climate change, fisheries, chemical pollution, shipping, construction and dredging, coastal development and tourism. Implementation of the ecosystem approach, involving all aspects of the ecosystem including human activities, is widely advocated as the solution to reversing damage to the marine environment. Objectives The PISCES project aimed to increase the capacity of stakeholders to apply the ecosystem approach and communicate it more widely through the process of collaboratively-developed guidelines. Therefore, the project worked closely with stakeholders from several EU Member States to test collaborative methodologies for implementing the ecosystem approach in the Celtic Sea. The project applied a demonstration approach, with the aim of producing new guidance for effective delivery of the ecosystem approach; promoting its results to the wider marine community; and contributing to improved policy and governance for other sub-regions and regional seas in EU maritime waters. The goal, by the end of the project, was for relevant marine stakeholders in the Celtic Sea region to have a greater shared understanding of the ecosystem approach towards integrated marine management, with agreed mechanisms in place for the implementation of the ecosystem approach in the context of relevant EU marine policies, such as the Marine Strategy Framework Directive (MSFD). Results The initial phase of the PISCES project involved identifying relevant stakeholders and increasing their knowledge of marine policy and the ecosystem approach. A key group of 30 stakeholders was primarily engaged, representing seven different sectors in England, Wales, Ireland, France and Spain, including the fishing and shipping industries. Stakeholder engagement was an ongoing activity throughout the project. p>A key objective of the project was the production of guidelines as a mechanism for the practical implementation of the ecosystem approach in the context of EU marine policy. These guidelines were produced primarily through a series of five workshops with stakeholders. In the final stages there was a detailed review process, during which 102 stakeholders contributed to at least one step of guideline development. The guidelines were endorsed by stakeholders as a representation of their commitment to sustainable cross-sectoral management through the ecosystem approach. The PISCES guidelines have relevance for all marine sectors and activities in Europe and include recommendations for sea-users and governments on the role they can play in implementing the ecosystem approach through the Marine Strategy Framework Directive (MSFD). The fact that the guidelines were developed by multi-sectoral stakeholders gives them added relevance and resonance with all marine sectors. The recommendations in the guidelines, and also the stakeholder engagement process, can be applied to other marine regions in Europe by stakeholders and national and EU governments. The PISCES project developed a communications strategy to ensure that different target audiences could be effectively reached, with the project website playing a central role. Project stakeholders wanted to feel that the information they supplied through the project was used to influence the implementation of marine policy in the Celtic Sea. Improved communication with government decision-makers was therefore an important objective delivered by the project. Government advocacy plans were developed for each country. In the final phase of the PISCES project, a comprehensive outreach and dissemination programme was undertaken. The PISCES team and their key stakeholders communicated with more than 11 000 people across Europe, over 2 000 of these at 27 conferences in the last six months of the project. The guidelines have been widely cited and referred to in stakeholder networks, conferences, government meetings, reports and communications. PISCES has also provided government policy-makers with a better understanding of the potential benefits of greater stakeholder participation in implementation of marine policy, and what the expectations of stakeholders are. The UK government has pledged to develop an MSFD-specific stakeholder engagement strategy, a key PISCES recommendation. Government stakeholders also confirmed that they will draw on the PISCES guidelines when implementing the MSFD (e.g. in developing the programme of measures) and during marine planning (e.g. the UK Marine Management Organisation). PISCES has also helped to catalyse international cooperation in the Celtic Sea, particularly via improved exchange between industry sectors. There is also evidence of increased exchange and discussion between national governments (UK, Ireland and France) and within the Commission (e.g. DG ENV and DG MARE) on related issues, as a result of PISCES advocacy. Moreover, PISCES has widely championed the concept of transnational multi-sector stakeholder forums, which are increasingly acknowledged as key to enabling effective collaboration at the regional seas-level. A final evaluation survey showed that 92% of the stakeholders surveyed found the guidelines to be useful; 85% felt PISCES made it easier to talk about the ecosystem approach; and 89% felt more comfortable talking with others about how it fits within the MSFD. PISCES demonstrated how stakeholders can add value at each step of policy implementation, through assisting in monitoring, data collection, testing measures and providing social and economic evidence. Ultimately this may lead to greater compliance with the MSFD and other activities that positively impact the marine environment. Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).