In situ rare long term observations of the dogtooth grouper Epinephelus Caninus in artificial reefs recently immersed in the National Park of the Calanques (north-western Mediterranean sea, France)

Abstract

In winter 2017, biomimetic designs of porous concrete artificial reefs (Ragues® modules of 3 m in height for 12 tons in weight) targeting different high-value and apex rocky species such as groupers were immersed between-19 and-22m in the National Park of the Calanques (French Mediterranean coast-43° 12.679' N / 5° 23.485' E) as part of an experimental ecological restoration project called REXCOR. Still ongoing, the main objective of the REXCOR project is to evaluate the capacity of innovative designs of artificial reefs to restore altered ecological functions of the rocky coastline (shelter, breeding, feeding, nursery grounds) historically impacted by the sewage outflow of the city of Marseilles (second largest town in France). During the first summer after their deployment, one specimen of the Dogtooth Grouper, Epinephelus caninus, (Valenciennes, 1843) estimated to 65 cm was observed by scubadivers during three consecutive months (June, July and August 2018) and then in December 2018 inside the artificial reefs. Thanks to photoidentification and to the analysis of the different morphologic characteristics, it was determined as a unique individual. The specimen was a gravid female estimated between four to more than eight years old. To our knowledge, this is the first documented record of high site-fidelity (at least 7 months) for E. caninus found in Northwestern Mediterranean coastal habitats. This could represent a first positive cue to undertake a larger project of ecological restoration. It is also the first record in the National Park of the Calanques since its creation in 2012 and the first record in artificial reefs in France, especially at such a low depth despite the presence of others important artificial reefs sites in this area.