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- Modelling spatial and temporal scales for spill-over and biomass exportation from MPAs and their potential for fisheries enhancementPublication . Pérez-Ruzafa, Ángel; Martín, Ernesto; Marcos, Concepción; Zamarro, José Miguel; Stobart, Ben; Harmelin-Vivien, Mireille; Polti, Sandrine; Planes, Serge; García-Charton, José Antonio; González-Wangüemert, MercedesMarine protected areas (MPAs) are considered as a tool for marine conservation and sustainable fishery resource management. Improvements in fishery yields should take place via the spill-over of individuals from the reserve. In general, it has been demonstrated that MPAs affect the density and biomass of the organisms within them, however, little evidence has been found in order to assess the exportation of individuals across their boundaries. In this study, a simple model involving population growth, harvest, and the diffusion coefficient for individuals was used to explore the effects of protection on populations inside the reserve and the spill-over of individuals to the fished area. The model showed that biological responses inside marine reserves appear to develop quickly, reaching mean levels within a short (1–5 year) time period. Mean population abundance is always higher inside the reserve and highlights the effectiveness of protection, particularly when there is strong fishing pressure outside the reserve. However, reserves smaller than 2000 m radius show significantly lower levels of abundance inside than larger sites. Large MPAs (i.e. about 2000 m in radius) offer nearly the maximum capacity for recovery (close to 100% of the system carrying capacity) and nearly the maximum flux of individuals per unit boundary length. Very large MPAs (i.e. larger than 6000 m in radius) could be a guaranteed means of providing resilience in order to prevent population crises, with the added advantage that the flux of individuals is slightly higher at larger distances from the boundary. However, in practice they provide no further advantage towards increasing the density of individuals or the exportation of biomass, and a network of smaller MPAs could be more beneficial, both from the point of view of conservation and of benefits to fisheries.
- Effects of fishing protection on the genetic structure of fish populationsPublication . Pérez-Ruzafa, Ángel; González-Wangüemert, Mercedes; Lenfant, Philippe; Marcos, Concepción; García-Charton, José AntonioMarine reserves have been identified as an important tool in the management of fishery resources and their number is increasing rapidly, most of them being on islands. However, knowledge on the real effect of protection from fishing on the genetic structure of populations, the spatial scales involved, or the suitability of islands as reserves in terms of connectivity, is scarce. This paper analyses the effects of fishery protection on the genetic structure of populations of Diplodus sargus, a target species, in protected and non-protected areas of the western Mediterranean. Populations studied showed high genetic variability at spatial scales from 101 to 103 km. Protected areas have significantly higher allelic richness. The lower levels of heterozygosis and higher heterozygote deficit showed by islands compared with coastal areas makes clear the importance of considering the connectivity processes when designing a MPA.