Assessment of commercial and recreational fishing effects on trophic interactions in the Cap Roux area (north-western Mediterranean)

Assessing both direct and indirect effects of fishing, i.e. effects extending to two or more trophic levels, is becoming a key issue in restoration ecology. The present study compared the Cap Roux no-take area (NW Mediterranean) with the surrounding non-protected areas. Direct effects of fishing were investigated using experimental net fishing and underwater visual census (UVC) specifically to survey species targeted by commercial fishing and angling. Indirect effects of fishing were deduced from predation and density of sea urchins. Observations showed higher biomass and abundance (from catch rates) inside the MPA and differences in size composition (from UVC). The effect of protection from fishing was rapid, with differences apparent within 5 years of protection, and was most evident for highly targeted fish. Rates of predation on two species of sea urchin (Paracentrotus lividus and Arbacia lixula) were dependent on protection level and season. This pattern was consistent with the presence of large Diplodus spp., known sea urchin predators, observed inside the reserve only in winter. However, the density of the sea urchins did not differ between the MPA and adjacent fished areas. Copyright (c) 2012 John Wiley & Sons, Ltd.