Distribution and population structure of deep‐dwelling red coral in the Northwest Mediterranean |
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| Authors: | Michela Angiolillo Andrea Gori Simonepietro Canese Marzia Bo Cristina Priori Giorgio Bavestrello Eva Salvati Fabrizio Erra Michael Greenacre Giovanni Santangelo |
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| Institution: | 1. III Dipartimento Tutela degli Habitat e della Biodiversità Marina, Istituto Superiore per la Protezione e Ricerca Ambientale (ISPRA), Roma, Italy;2. Departament d'Ecologia, Universitat de Barcelona, Barcelona, Spain;3. Dipartimento di Scienze della Terra, dell'Ambiente e della Vita, Università degli Studi di Genova, Genova, Italy;4. Dipartimento di Biologia, Università degli Studi di Pisa, Pisa, Italy;5. Istituto Nazionale di Oceanografia e Geofisica Sperimentale, Trieste, Italy;6. Universitat Pompeu Fabra, Barcelona, Spain |
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| Abstract: | Commercially harvested since ancient times, the highly valuable red coral Corallium rubrum (Linnaeus, 1758) is an octocoral endemic to the Mediterranean Sea and adjacent Eastern Atlantic Ocean, where it occurs on rocky bottoms over a wide bathymetric range. Current knowledge is restricted to its shallow populations (15–50 m depth), with comparably little attention given to the deeper populations (50–200 m) that are nowadays the main target of exploitation. In this study, red coral distribution and population structure were assessed in three historically exploited areas (Amalfi, Ischia Island and Elba Island) in the Tyrrhenian Sea (Western Mediterranean Sea) between 50 and 130 m depth by means of ROV during a cruise carried out in the summer of 2010. Red coral populations showed a maximum patch frequency of 0.20 ± 0.04 SD patches·m?1 and a density ranging between 28 and 204 colonies·m?2, with a fairly continuous bathymetric distribution. The highest red coral densities in the investigated areas were found on cliffs and boulders mainly exposed to the east, at the greatest depth, and characterized by medium percentage sediment cover. The study populations contained a high percentage (46% on average) of harvestable colonies (>7 mm basal diameter). Moreover, some colonies with fifth‐order branches were also observed, highlighting the probable older age of some components of these populations. The Ischia population showed the highest colony occupancy, density and size, suggesting a better conservation status than the populations at the other study locations. These results indicate that deep dwelling red coral populations in non‐stressed or less‐harvested areas may diverge from the inverse size‐density relationship previously observed in red coral populations with increasing depth. |
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| Keywords: |
Corallium rubrum
deep sublittoral zone demographic structure Mediterranean Sea precious corals ROV imaging |
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