Estimating marine protected area network benefits for reef sharks.
Abstract
Animal movement has direct applications in spatial management and conservation planning, yet it is rarely taken into account for the design of natural protected areas. For instance, reef shark species are thought to benefit from marine protected area networks, even though their movement behaviour remains poorly characterized. Poor understanding of species' movements implies that the benefits of MPA networks for species' populations are still widely unknown.To understand the consequences of movement behaviour for protection, we modelled movements of three reef shark species' (Carcharhinus albimarginatus, C. amblyrhynchos and C. leucas) with distinct levels of reef association using real passive-acoustic telemetry data. The model simulates if individuals are protected or unprotected by their movements in a system of reef patches in a network of MPAs. Model parameters that control individuals' movements were estimated from acoustic telemetry data. To estimate benefits for species we monitored longevity and time spent in protected habitats across all scenarios of reef protection, fishing intensity (11 values for each) and protection of high or low suitability reefs (a reef-dependent factor that attracts sharks to reside in it) for populations of 1,000 individuals per species. The time individuals spent in protected reefs increased linearly with protection until it levelled off after 50%-80% of reefs protected (78% C. amblyrhynchos, 72% C. albimarginatus and 52% C. leucas, at 100% protection). Individuals' life span decreased exponentially with fishing intensity. Reef protection only mildly counteracted life span lost to fishing. Protecting highly suitable reefs increased time spent in protected reefs, optimal protection was reached at a lower number of reefs protected, and life expectancy was higher with protection of highly suitable reefs.Synthesis and applications. Our framework can be applied to many studies using passive-acoustic telemetry to track animal movements. Protected area networks benefit species highly attached to protected sites. To increase benefits of marine protected area networks for all species (with low and high degrees of reef attachment) we need to understand the use of reef-adjacent areas, dispersal routes and characterize reef suitability for multiple species.