Long term spatial and temporal variability in catches of common spiny lobster Palinurus elephas (Fabricius, 1787) in Corsica (NW Mediterranean): fisheries trends, biological trends or both?

The small-scale fishing fleet of Corsica (France, NW Mediterranean) is mostly composed of small artisanal boats. The common spiny lobster, Palinurus elephas, is the most valuable of all caught species. As a result, it is the main target of most fishermen during the 7-months fishing season. Populations of this species seem to decrease since the 1950's. The aim of this study was to understand if this decline could be linked with overfishing, or if other biological, ecological or climatic factors could explain this population drop. To achieve this goal, we combined 1) a meta-analysis of all data concerning fishing effort and captures in published and grey literature and 2) an on-board monitoring program that started in 2004. Using obtained data, we followed fleet structure, fishing effort and captures evolution from 1950 to 2011. Our results point out an important capture decrease during the 20th century. This trend started during the 1950’s and 1960’s, when trammel nets replaced traditional wood traps. A micro-regional analysis revealed that exploitation intensity widely varied among different areas around the island. Moreover, landings and catch rates showed important spatial and temporal variations. This could be caused by changes in recruitment rates. However, recruitment processes of this species are still poorly understood. Improving our knowledge of common spiny lobster life cycle will likely lead to a more comprehensive and efficient assessment of Corsican stocks of this species.