Marine Protected Areas: Reserve effect or natural variability? The Patagonian octopus case

Abstract

Population characteristics can be influenced by specific factors of the habitat and the natural variability of populations can confuse the effect related to protected environments. This study compares the demographic characteristics of Octopus tehuelchus in three coastal environments: two Marine Protected Areas (San Antonio Bay -SAB- and Islote Lobos -IL-) and a traditional fishing zone (El Fuerte -EF-). Weight frequency distributions, sex ratio and recruitment were monthly compared between the three intertidal zones. O. tehuelchus was smaller in IL, where fishing intensity is lower or null, and reached the largest sizes in the main fishing area of EF and within SAB (where there is no regulation and a mid-high fishing intensity). The sex proportion in SAB and EF was 1:1 all along the year. Although the proportion of mature females in IL was higher, the highest recruitment was observed in EF (the traditional fishing ground). These new data suggest that previous studies, which reported that Marine Protected Areas have positive effects for O. tehuelchus populations, can no longer be supported, and highlight the importance of understanding and quantifying the magnitude and range of natural variability in each environment when assessing the effectiveness of Marine Protected Areas.