Gwenael Cadiou

The spring and summer distribution of adults and larval fish stages of Sparids and Scorpaenids was studied in two sites in the western Mediterranean. Fish adults and larvae of those two taxa were identified and sorted according to their life stages in order to study their distribution and develop suitable habitat maps. Study areas were located on French coastal waters, the “Côte Bleue” Marine Park (CBMP) has an east-west orientation with substratum dominated by Posidonia beds and the Marine Reserve of Cerbe’re-Banyuls (MRCB) runs north-south and is dominated by rocky substrates. Generalised Additive Models (GAM) combined with Geographic Information System (GIS), were used to model the suitable habitats for fish larvae and adults. During spring months, waters exhibit low Sea Surface Temperatures (SST), low Photosynthetically Active Radiation (PAR), high values of Sea Surface Chlorophyll-a concentration (Chl-a), and mostly negative values of Sea Level Anomaly (SLA) indicating anticyclonic eddies. During summer months, waters have higher values of SST, lower values of Chl-a and positive values of SLA indicating cyclonic eddies. The results revealed different environmental responses in the distribution of fish adults and larvae in the CBMP and MRCB. Suitable habitats for adult were mainly dependent on the substrate types (Posidonia meadows and sand) and they were found close to the coast, whereas fish larvae were dependent on environmental cues (Chl-a, SLA, SST) with a sparse spatial distribution.

Marine biodiversity is threatened by human impact. Though few marine species are regarded as being extinct due to Man, many species are critically endangered (e.g. the monk seal Monachus monachus), endangered (e.g. the Mediterranean giant limpet Patella ferruginea) or vulnerable, i.e. dwindling rapidly, although not threatened with extinction in the immediate future (e.g. the large mollusk Pinna nobilis). There are also threats to ecosystems (ecodiversity), such as, in the Mediterranean, the Lithophyllum byssoides rim and the seagrass Posidonia oceanica meadow. Marine Protected Areas (MPAs) were initially established to protect biodiversity via the removal of human exploitation and occupation. However, since the 1970s, the notion of MPA has moved on to a more general concept of nature conservation, then to a more dynamic one of nature management, within the framework of sustainable development. Today, the aims of MPAs are therefore sixfold: nature conservation, public education, reference areas for scientific research, tourism, export of fish eggs, larvae and adults to adjacent areas and finally management of the various uses of the sea (e.g. commercial fishing, recreational fishing, pleasure boating and tourism) in such a way that they do not conflict with each other or with conservation aims. Mediterranean MPAs, especially the Port-Cros National Park, illustrate the fact that they are rather characterized by the management of human activities than by a set of prohibitions and that there is no negative interaction between biodiversity conservation and artisanal fishing (i.e. small-scale commercial fishing), at least in the way it is done (i.e. with additional constraints to general regulations: mesh size, prohibition of trawling and longlining, etc.). Consequently, MPAs are generally of benefit to the economy (e.g. commercial fishing and tourism industry), not only within MPAs but also in adjacent areas. They therefore constitute a powerful tool for integrated coastal management.