Multidisciplinary and multiscalar approach for a sustainable management of Red Coral (Corallium rubrum,L.1758) from the island of Sardinia (West Mediterranean Sea)

Abstract

Red Coral, Corallium rubrum (L.1758), is an important socio-economic resource for the Mediterranean community and the island of Sardinia, due to its great commercial value. Since 1979, regional law regulates colonies harvesting for its correct management and conservation. Nevertheless, all available data that provided the scientific base for the actual law, came from landing data obtained from fishermen, leaving huge lacks of knowledge in terms of investigated areas (and relative geological features) and representativeness of the state of the stock. In this work we report an example of multidisciplinary and approach, both biological and geological, for an unprecedented multiscalar mapping of red coral colonies that can provide important improvement in its conservation. A Geological survey (“MaGIC” project, Marine Geohazard along Italian Coasts) using Multibeam, Side Scan Sonar and Sparker 500J was conducted in Summer 2009, providing a detailed data coverage of two key areas of South Sardinia continental shelf San Pietro Island and Cape Carbonara. Data collected during the survey were integrated with CARG project (Official National Italian Geological Cartography). This Geomorphological analysis provided a usefull guideline to define and map harvesting areas and planning the further ROV survey. The Biological R.O.V survey was carried out in Summer 2011; more than 2000 photos were Geo-referenced to the multibeam map of the bottom, and examined using CPCe (Coral Point Count with Excel extensions) Software in order to create a database on the abundance and morphometry of colonies. Colonies were divided in 3 categories: Ramified, non ramified and dead colonies. For the morphometric database, the basal diameter and maximum height of the colony was measured along with number and type of ramifications. The population structure was also calculated for better describe the status of the stock. This mapping approach has allowed scientist to discover new banks of coral that can could be harvested in a short/long- time period in less known areas as well as a better overview of sites already used for harvesting. Morphological adaptations of Red coral colonies to environmental features can be evaluated thanks to to the multibeam references. In conclusion these data can provide the new scientific base for a local-based specific regulation for C.rubrum harvesting