Evaluation of impact of artificial reefs on artisanal fisheries: need for complementary approaches

Abstract

In a general context of fisheries decline due to overfishing and to other phenomena such as climate change, it appears to be crucial to implement a sustainable management of natural resources by finding a balance between conservation and exploitation purposes. Artificial reefs (ARs) have recently become one of the existing management tools, often in combination with fishing quotas or marine protected areas. To evaluate the effectiveness of the studied ARs, different methods have been used: (i) visual census by SCUBA diving (AR scale), (ii) fisheries landings survey (local scale) and (iii) external fish tagging (regional scale). Underwater visual census (UVC) showed a significantly higher species richness and density in ARs than in the control site. Abundance, biomass and LPUE data (Landings Per Unit Effort) issued from artisanal fisheries landings survey were not significantly different around the AR system from other fishing grounds of the French Catalan coast. The tagging experiments on Diplodus sargus suggested that the connectivity of demersal fish populations must be taken into account to evaluate the influence area of ARs and thus their indirect impacts on artisanal fisheries. The present study highlights the interest of combining methods covering different spatial scales in order to evaluate direct and indirect impacts of ARs on artisanal fisheries. Methods for the evaluation of AR efficiency are discussed.