Northern Ireland, like many other nations, has made high-level commitments to improving marine management and conserving biodiversity through the development of a representative network of marine protected areas (MPAs). However progress to fulfil commitments was found to be hampered by complex governance, poor interdepartmental cooperation and lack of political will. Stakeholder participation is a vital component of MPA planning and implementation, and the successes of MPA designation is greatly affected by fisher buy-in and compliance. This Thesis presents a novel participatory mapping method, which was used to directly engage fishers in the development of quantitative pre-planning data on their spatial access priorities. Data on the perceptions of fishers' and their thoughts on marine management, including MPA site suggestions, were also gathered. Stakeholder engagement and the incorporation of stakeholder data should facilitate the development of MPA planning solutions that have a reduced negative impact on stakeholders. This assertion was tested with the fisher-derived data. Multiple MPA planning scenarios were developed and the benefit of incorporating both quantitative and qualitative fisher data was clearly demonstrated on planning solutions. A novel approach of transparent inclusion of stakeholder MPA suggestions into decision-support software was also proposed. MPAs and fisheries face increasing competition for space from emerging ocean uses. Building upon previous strategic conservation planning-based approaches to ocean zoning, planning scenarios were developed to simultaneously optimise space allocations for MPAs, renewable energy generation and fisheries. The approach enabled explicit assessment of the trade-offs between competing uses, which should help increase the transparency and defensibility of planning decisions. It was also established that co-location of marine industries can significantly affect both the cost and the spatial configuration of marine planning solutions. The use of the insights and tools developed in this Thesis should contribute to improved MPA planning processes and help reduce the amount of conflict associated with planning solutions.