Rov-based ecological study and management proposals for the offshore marine protected area of cap de creus (nw mediterranean)

Aiming to improve the conservation status of the European seas, the Marine Strategy Framework Directive (MSFD) was adopted in 2008, establishing a general framework for all EU countries in the field of marine environmental policy. The MSFD enforces all Member States to adopt an adaptive management strategy in their territorial waters grounded on (1) an ecosystem-based approach, (2) the creation and management of Marine Protected Areas (MPAs) as essential tools to reach a (3) previously designed Good Environmental Status (GES), to which they must evolve as the result of (4) policy measures that would only be enforced after the launching of a (5) monitoring program based on (6) previously selected indicators/parameters. In the case of the Spanish State, the MSFD was legally transposed as a state law in year 2010, leading to the designation of 10 new offshore MPAs. One of these 10 areas, evaluated under the framework of the Life+ Indemares project, sets the spatial limits of this PhD thesis: the offshore area of Cap de Creus. This thesis begins by evaluating the structure of the megabenthic invertebrate assemblages present on the continental shelf and submarine canyon based on 60 underwater video transects performed by a Remotely Operated Vehicle (ROV) and a manned submersible. 9 different assemblages were identified: (A) shelf assemblage with Eunicella cavolini; (B) soft-bottom shelf assemblage with pennatulaceans; (C) soft-bottom assemblage with Sabella pavonina; (D) sandy bottom shelf assemblage with Leptometra phalangium; (E) deep shelf and shelf-break assemblage with Lanice conchilega; (F) cold-water coral assemblage with Madrepora oculata; (G) ‘Roche du large’ assemblage with sponges; (H) slope assemblage with Cerianthus membranaceus; and (I) aggregation of the brittle star Ophiothrix fragilis. Depth, current speed and substrate type were identified as the main factors determining the spatial patterns observed at the scale of the study area, although fishing intensity played a predominant role in the soft-bottom areas of the shelf, where fishing is known to occur. This information was used to elaborate predictive distribution maps of benthic assemblages using the algorithm Random Forest. Increasing levels of bottom trawling intensity had a negative impact on species richness, diversity, and also on the structure of the community dwelling on the continental shelf. Based on the response of key megafauna species to increasing levels of fishing effort, 4 species were chosen as indicators for a monitoring program. A detailed monitoring protocol together with quantitative baseline data is provided in order to assess the future evolution of the benthic ecosystem once management measures are put in practice. The proposed protocol extensively describes the sampling methodology to be applied at sea, the video analysis, the processing of the data and the interpretation of the results. Two fish assemblages were identified in the video images: (A) shelf assemblage with highly-mobile small-sized fishes (Trisopterus spp., Serranus cabrilla, triglidae and Scorpaena species) and (B) canyon assemblage with less mobile and larger fishes (Helycolenus dactylopterus, Lepidopus caudatus, Conger conger and Phycis phycis). The low number of fishes identified in the ROV footage made us very pessimistic with their use in the monitoring protocol as indicators of fishing activity. Finally, this thesis provides the amount of marine litter accumulated on the seafloor of the study area. The results of this PhD thesis have to be considered an attempt to simplify the implementation of the MSFD in offshore areas by providing the necessary tools to implement an ecosystem-based approach to management using imaging techniques, which should lead to a continuous monitoring of the benthic ecosystem, as demanded by the MSFD.