PhD thesis abstract:
Marine protected areas (MPAs) can allow the recovery of species heavily exploited elsewhere. MPAs can also provide benefits to outer fished areas through ‘spillover’ of both juveniles and adults. Fisheries enhancement may also take place in outer areas via egg/larval export from MPAs. Little information is available, from this perspective, on the potential of MPAs to export propagules (i.e. eggs and larvae) as well as about the movement patterns of juvenile fish stages (i.e. settlers and post-settlers). Information on spatial connectivity and dispersal is crucial to understand the degree to which MPAs may 1) sustain fish stocks within their borders and/or in outside fished areas, and 2) possibly replenish other MPAs within an effective network. Using different techniques (visual census, otolith microstructure and microchemistry analysis, lagrangian models) we investigated the potential of Torre Guaceto MPA (TGMPA, Apulia, SE Italy) as an effective “source” of larvae/juveniles of the white sea bream (Diplodus sargus sargus) by assessing dispersal patterns and related connectivity at both larval and post-settlement stages.
Results showed that TGMPA hosts high densities and biomass of spawners, that would potential drive to an high eggs/larval production able to replenish both TGMPA itself and the unprotected area down-current, where high densities of post-settlers were recorded. Dispersal of larvae and post-settlers occurred over up to 100-200 and 30 km, respectively, providing evidence for spatial connectivity between TGMPA and outer sites (and vice versa). This multidisciplinary investigation is one of the few providing evidence for spatial connectivity and dispersal of coastal fish in the Mediterranean environment, focusing on the potential role of an MPA as an effective ‘source’ of fish eggs, larvae and juveniles. Analogous data from a number of relevant marine species would be crucial to effectively design MPA networks adapted to the specific geographic context.