Small MPAs do not protect cuttlefish (Sepia officinalis)

Marine reserves have been widely implemented as tools for biodiversity conservation and fisheries management, amongst other goals. A large number of empirical studies have focused on their effects on reef fish populations. Yet, few studies have looked at their effectiveness on semelparous species such as cephalopods, in spite of their commercial importance in many coastal regions across the globe. In this study we combine behavioural (biotelemetry) and demographic (experimental fishing) data to understand the effects of the Luiz Saldanha Marine Park (LSMP) on local populations of cuttlefish, Sepia officinalis. We used a beyond-BACI design to analyze the possible effect of the implementation of a no-take area on the abundance and biomass of this species and acoustic telemetry data to assess its site fidelity and movements within the study area. Results indicate that there was no detectable effect of the implementation of the no-take area on the abundance or biomass of cuttlefish. We found evidence that acoustically tagged adult cuttlefish leave the reserve a few days or weeks after tagging. The fact that cuttlefish have low site fidelity inside the reserve and large movements across and beyond the study area explains why there is no increase in the population inside the MPA. These results suggest that small coastal marine reserves such as the LSMP are not effective in providing long term protection to cuttlefish populations and, probably, those of other short-lived, highly mobile cephalopods.