The results indicate that marine protected areas are having a significant effect on the biomass of herbivorous fishes in the Caribbean, which especially indicates their importance as a refuge for larger fish. The importance of even small MPAs is accentuated by the results showing that certain terminal phase fish are only found within MPAs. The coral reef communities were also more stable inside the MPAs due to the larger percent coral cover, increased fish stock, and lower algal cover. This study adds significant support to the need to maintain or increase the amount of MPAs to help preserve coral reef communities.
Kopp et al. (2010) examined whether small, established marine reserves could effectively sustain a coral reef ecosystem by enhancing the fish stocks and limiting macroalgae growth. The authors studied two marine protected areas (MPAs) around the island of Guadeloupe, one located around Ilets Pigeon and one in the bay of the Grand Cul-de-Sac Marin, and five non-protected reefs for comparison with the protected reefs. Surveys of the fish and benthic communities revealed that although the mean number of individuals per 100 m2 was about the same in MPAs as in non-MPAs, the mean biomass of herbivorous fishes was significantly larger inside MPAs, indicating the presence of larger fish in the MPAs. The study also reported a significantly lower cover of macroalgae in the MPAs than in the non-protected areas, and a significant negative correlation between benthic macroalgal cover and herbivorous fish biomass. Though there was no evidence in the study of the benefits of MPAs extending over their boundaries, they were shown to increase fish biomass and manage macroalgal cover, which contributed significantly to sustaining coral reef ecosystems. — Rachel King
Kopp, D., Bouchon-Navaro, M., Mouillot, D., Bouchon, C., 2010. Herbivorous fishes and the potential of Caribbean marine reserves to preserve coral reef ecosystems. Aquatic Conservation: Marine and Freshwater Ecosystems 20, 516–524.
Within the two MPAs studied, five reef sites were sampled between 1 and 10 m in depth, and the five non-protected reef sites were also sampled between these depths. Visual surveys of fish were performed twice in both the dry and rainy seasons using a 150 x 2 m transect, which provided estimates of fish abundance in terms of density and biomass. Fish were identified to the species level and their length recorded in 5 cm size classes for fish fewer than 20 cm and in 10 cm classes for fish larger than 20 cm. The biomass of fish was estimated using weight-length relationships from the literature. For scarid fish, the phase (initial or terminal) was also noted. While the fish survey was conducted, the benthic community composition was estimated by recording the types of benthic organisms present at every meter along the 150 m transect.
To analyze the collected data, the authors used a canonical analysis of principal coordinates (CAP), which allows a constrained ordination to be performed on the basis of any distance. The response of the whole fish assemblage in the MPAs was analyzed, followed by examining each species. Benthic cover between MPAs and non-protected areas was compared and a correlation between benthic cover and herbivorous fishes was found using the non-parametric Spearman rank correlation coefficient.
The mean number of individuals per 100 m2 in the MPAs (87.4±22.3 (SE)) was very close to the value outside the MPAs (86.3±22.3 (SE)). This pattern was also observed for the number of scarid fishes inside and outside the MPAs. However, both the total assemblage of fish and scarid fish showed a larger biomass inside the MPAs. Although a few species had higher abundances outside the MPAs, most had larger numbers and biomass inside the reserves and therefore indicated a significant reserve effect on those species. The size class of species also differed significantly between the two types of areas. Large adults of three species, Scarus vetula, Sparisoma rubripinne, and S. viride, that were also in their terminal phase were only found within MPAs, and Acanthurus bahianus only had medium-sized individuals present within MPAs. The results also showed that the mean percentage of terminal males was 22% inside MPAs, whereas it was only 10% outside the reserves. Significant correlations were also found between coral cover and the biomass of large herbivorous fishes, biomass of large herbivorous fishes and macroalgal cover (negative correlation), and macroalgae and algal turf (negative correlation).