Riccardo Cattaneo-Vietti

The red coral populations of the gulfs of Naples and Salerno: human impact and deep mass mortalities

Abstract The existence of deep red coral (Corallium rubrum) banks in the gulfs of Naples and Salerno (South Tyrrhenian Sea, Mediterranean Sea) is well known in historical records due to the heavy coral harvesting that occurred during the 19th and 20th centuries, by both trawling gears and scuba diving. In 2010 and 2012, during two Remotely Operated Vehicle (ROV) surveys on board of the Research Vessel (R/V) Astrea, red coral banks were detected in 16 of the 25 visited localities, between 45 and 150 m depth. Seven of these banks, located in the inner part of the Gulf of Naples, were already explored in 1918 by a scientific survey reporting the occurrence of red coral. Healthy populations (densities > 90 colonies m−2) were present only around the coasts of the Phlegrean Islands (Ischia and Procida Islands). Very low densities (< 5 colonies m−2) or the absence of coral were recorded in all other sites of the Gulf of Naples (including all historical re-visited banks), and a variable percentage of dead colonies was observed. This evidence suggests a huge state of stress likely favoured by the hydrodynamic conditions in the Gulf, enhancing water pollution and sedimentation rate. Finally, the documented high fishing pressure plays a major role in the hard-bottom communities’ degradation. A recent mass mortality episode was also recorded along the Amalfi coast, around Li Galli Islands (Gulf of Salerno), at a depth range between 80 and 100 m, where the mortality affected 80% of the largest colonies, estimated to be around 70 years old. Several possible reasons for this mortality have been hypothesised, such as the formation of local down-welling currents inducing an unusual drop of the thermocline, or sudden warm water emissions (sulphur springs) in an area characterised by important volcanic activities, or local landslides generating turbidity currents along the steep slopes.

An overexploited Italian treasure: past and present distribution and exploitation of the precious red coral Corallium rubrum (L., 1758) (Cnidaria: Anthozoa)

Abstract The aim of this paper is to supply an overview of all historical and recent knowledge on landings, fishing and geographic distribution of the red coral banks along the Italian coasts in order to make a contribution to the conservation and future management of this resource. Along the Italian coasts, the banks have been exploited for millennia, using non-selective trawling gear that was banned in Europe in 1994. Today, harvesting is allowed only by scuba divers and regulated by specific laws. We examined 153 years of history of coral fishing in Italy, from Unification (1861) to 2014. Data about the coralline fleets and the amount of coral landings were recorded for the considered span of time. From a quantitative point of view, the coral fishing in Italy in the last 150 years has been dominated by the sub-fossil coral reservoirs from the Sciacca Banks (Sicily Channel), where an extraordinary amount of 18,000 tons was collected in 34 years (1875–1888 and 1893–1914). This amount represents about 90% of all red coral harvested along the Italian coast in the last 150 years. Excluding this period, the average annual yield was initially around 100 tons, decreasing to 28 tons 100 years later, therefore demonstrating a severe overexploitation of the resource. The great part of the deep red coral banks was abandoned because harvesting was no longer profitable. Nevertheless, quantitative data suggest that red coral banks, even though overexploited, are still widespread along Italian coasts, mainly in shallow waters. These banks show a remarkable persistence although with a generalised shift towards smaller colony sizes and higher density. The time span necessary in recovering the pristine structure, following the end of the fishing activities, appears very long and the populations of several areas might be unable to re-colonise the old and overexploited banks.