Assessment of reserve effect in a marine protected area: the case study of the Professor Luiz Saldanha Marine Park (Portugal)

Dissertação de mest., Biologia Marinha (Ecologia e Conservação Marinhas), Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2011

The Professor Luiz Saldanha Marine Park (PLSMP) is located in the central region of Portugal (Arrábida coast), comprising 38 km of coastline. It was established in 1998 and in August 2005 specific management measures were implemented. Three protection levels were established: Total – human activities not allowed; Partial - some fishing allowed with some gears (octopus traps, jigging, handline); Complementary - fishing allowed with vessels under 7m length and licensed to operate within the marine park. To monitor the reserve effect, in terms of abundance, biomass and also community composition, experimental fishing trials with trammel nets on soft bottoms have been conducted since 2007 (depths between 10 – 45m). The individuals caught were identified to species level, measured to the nearest mm and released when alive. The data (species abundance and biomass) were analyzed both with univariate and multivariate methods, allowing the comparison between the three protection levels. The data analysis showed higher values of Catch per Unit Effort (CPUE) in number and in weight for the Partial and Total protection areas when compared to the Complementary, where fishing with nets is allowed. Also the biodiversity indices (Margalef and Shannon-Wiener) showed higher values in these two areas. The multivariate analysis (ANOSIM) supports the previous results, in the sense that the communities from Partial and Total sections were found to be significantly different from the one found in the Complementary area. The SIMPER analysis showed that the bastard sole Microchirus azevia and the toadfish Halobatrachus didactylus are important contributors for the distinction of these communities. It was noticed that in assessing the reserve effect, the benefits of protection is differed from species to species. The analysis at the species level was important in the detection of trends that are probably related with the implemented protection measures. Namely the species Chelidonichthys lucerna, M. azevia and Raja clavata showed abundance increases from the first analyzed period (Aug. 2007 - Aug. 2009) to the second (Aug. 2009 - Aug. 2010), after the full implementation of the marine park. Besides the increase in abundance, C. lucerna and M. azevia also registered an increase in the median total length. Overall, the results suggest that the Partial and Total protection areas are important for several soft bottom species. The importance of protection level was confirmed by Gaussian GAM models, for both sandy and muddy bottom. This analysis also revealed water temperature as an important predictor of CPUE in weight. The results obtained include the first signs of a reserve effect concerning the soft bottoms of the Prof. Luiz Saldanha Marine Park. The protection measures, mainly the restriction on the use of trammel and gill nets, seem to benefit some bottom associated species. To better understand the reserve effect on the biodiversity and abundance of soft bottom communities, further sampling should be considered.