Marine protected areas (MPAs) are increasingly viewed as an important management tool within a suite of policy alternatives to reduce, prevent and/or reverse on-going declines in marine biodiversity.The overall aim of this thesis was to test the efficacy of MPAs as a conservation measure, particularly focusing on partially protected areas which have received less attention than fully protected areas. An evidence-based approach, combining a rigorous assessment of the literature through ‘systematic review’ methodology, with field studies of fishing gear restriction areas in the UK was undertaken to examine the biological effects of partially protected areas on biotarelative to fully protected areas and open access fished areas. The syntheses of available evidence included in the systematic review suggested that while partially protected areas significantly enhanced density and biomass of fish relative to open access areas, fully protected areas yielded significantly higher biomass of fish within their boundaries relative to partially protected areas. The positive response to protection was primarily driven by target species. Theeffects of life history and ecological traits on the response of fish species to fully and partially protected areas were further examined using mixed effects modelling. Fish maximum body size, adult habitat preference and the exploitation status of the species were significantly related to the magnitude of response to full and partial protection.These results highlighted the importance of incorporating species information in the design of new MPAs, whichensuresthat protection is provided at spatial scales relevant to the species in need of conservation.
Fishery closed areas, where fishing with bottom-towed gear is prohibited but fishing with static gear is permitted are amongst the commonest examples of MPAs in the UK. Underwater camera surveys were conducted at Cardigan Bay Special Area of Conservation (SAC), the Modiolus Box within the Pen Llŷn a’r Sarnau SAC, Skomer Marine Nature Reserve and the Port Erin closed area in the Isle of Man to examine the response of epibenthic invertebrate communities toprotection from bottom fishing. Benefits from protection were observed for three of these MPAs and the magnitude of response was generally higher for the target species such as scallops and for sessile, fragile taxa such as hydroids, bryozoans and sponges. Two key environmental characteristics that influenced the effect of protection were the intensity of fishing at the control unprotected areas and the level of natural disturbance from waves and tides. Overall, theresults showedthat partially protected areas are a valuable spatial management tool particularly in areas where exclusion of all extractive activities is not a socio-economically and politically viable option. The findings also highlight the importance of considering the physical nature and dynamics of the environment, the nature of the species concerned and past and present level of fishing intensity throughout the designation process of MPAs, so as to avoid negative impacts on fisheries and limited conservation benefits.