Diversity of the reef fish community within and outside a fishing zone in the marine protected area of Balandra Bay (La Paz, Mexico)

The establishment of marine protected areas (MPAs) is the most widely used tool for protecting marine biodiversity. However, many of these areas have no active controls, leaving place for illegal fishing and thus failing to achieve their objectives. This illegal fishery can negatively impact the ecosystem by targeting some fish species which can have cascading trophic effects. In regions where governmental authorities do not have the means to conduct active controls, collaboration with local population is essential. This situation is present in the Bay of La Paz in Mexico. There, the multi-use MPA of Balandra includes fishing and no-fishing areas. San Rafaelito is a no-fishing zone, where numerous ecotourism activities take place, while in La Gaviota artisanal and sport fishing are permitted. Thanks to ecotourism activities in San Rafaelito, this area could benefit from the almost permanent control by the population, and this could increase the effectiveness of this area. Here, we studied the effect of the absence of fishing on reef fish communities, controlled by ecotourism. Specific richness, composition of assemblages, total biomass, as well as the biomass and the density of fish targeted by fishery were compared between the two sites. The total biomass, biomass and the density of large individuals of targeted species were significantly higher at San Rafaelito. More specifically, the biomass and density of large individuals of parrotfish (Scaridae) and groupers (Serranidae Mycteroperca rosacea) were significantly higher at San Rafaelito. The lower biomass and density of large piscivores and herbivores at La Gaviota may affect the reef ecosystem functioning. Indeed, the key roles of herbivory and bioerosion operated by Scaridae as well as the top-down control achieved by predatory Serranidae could be reduced at this site. Accordingly, our work revealed the effectiveness of the San Rafaelito no-fishing zone, unlike multi-use areas such as La Gaviota.