Human predation along Apulian rocky coasts (SE Italy): desertification caused by Lithophaga lithophaga (Mollusca) fisheries

Human predation along Apulian rocky coasts (SE Italy): Desertification caused by Lithophaga lithophaga (Mollusca) fisheries Fanelli, G | Piraino, S | Belmonte, G | Geraci, S | Boero, F* Marine ecology progress series. Oldendorf [MAR. ECOL. PROG. SER.]. Vol. 110, no. 1, pp. 1-8. 1994. The date mussel Lithophaga lithophaga is a Mediterranean boring mollusc living in calcareous rocks. Its populations are intensely exploited by SCUBA divers, especially in southern Italy. Collection is carried out by demolition of the rocky substratum, so that human predation on date mussels causes the disappearance of the whole benthic community. The impact of this activity along the Apulian coast was evaluated by 2 surveys carried out by SCUBA diving inspection of the Salento peninsula. The Ionian coast of Apulia, from Taranto to Torre dell'Orso (Otranto), was surveyed in 1990 and in 1992 by 2 series of transects (from 0 to 10 m depth, 2 km from each other), covering 210 km. Observations were transformed into an index of damage, ranging from 0 (no damage) to 1 (complete desertification). 159 km of the inspected coast are rocky. The first survey (1990) allowed us to estimate that a total of 44 km was heavily affected by this human activity (the index of damage ranging between 0.5 and 1), whereas the second survey showed heavy damage along a total of 59 km. This increase in length was accompanied by a high increase in the index of damage along parts of coast that were less intensely exploited in 1990 than in 1992. The second survey (1992) was extended to 90 km of the Adriatic coast of Apulia (from Otranto to Torre S. Sabina, Brindisi), with 47 km of rocky coast and a total of 10 km heavily affected by date mussel fishery. Date mussel collection is one of the most destructive human activities along the Apulian coast and it has long-term effects because sea urchin grazing probably prevents recolonization of barren areas. Rarefaction of the resource due to overexploitation and habitat destruction caused rapid 'evolution' of the techniques of predation, with an increase in searching efficiency achieved by the use of underwater vehicles. Similar impacts of date mussel collection have been recorded in other parts of the Italian coast, especially Campania and Sardinia, and it is possible that such situations are common, but still undetected, in other areas of the Mediterranean.