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

Abstract

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 carned 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 l ] , 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 knl 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 lncrease 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 Carnpania and Sardinia, and it is possible that such situations are common, but still undetected, in other areas of the Mediterranean.

Ecology and diversity of Mediterranean hard-bottom Syllidae (Annelida): a community-level approach

“…Indiscriminate illegal fishing of the date mussel Litho phaga litho phaga has occurred on the Southeast Italian coast, especially in recent decades; the procedure involved the mechanical removal of macrobenthos on calcarenitic rocky bottoms, and although it is now more effectively controlled, it resulted in widespread desertification (barrens) that is still evident (Fanelli et al 1994). The Marine Protected Area (MPA) of Torre Guaceto (south Adriatic Sea) is much less affected by desertification, probably due to the top-down control of the protected ichthyofauna on grazers inducing a positive cascading effect on the sessile macrobenthos (Guidetti 2006).…”

Relative growth and reproductive cycle of the date mussel Lithophaga lithophaga (Linnaeus, 1758) sampled from the Bizerte Bay (Northern Tunisia)

“…Some other studies focused on the impact of harvesting and overexploitation on marine ecosystem and Mediterranean rocky coasts (Fanelli et al 1994;Parravicini et al 2009). Besides the important ecological role of L. lithophaga in recent ecosystems, its fossils have been used in paleoecological and paleogeographic studies for dating some geological periods and indicating submergence phases (Gilli and Audra 2004;Ballèvre and Lardeux 2005).…”

Settlement and juvenile habitat of the European spiny lobster <i>Palinurus elephas</i> (Crustacea: Decapoda: Palinuridae) in the western Mediterranean Sea

“…They are extracted from the rock by demolishing it, with the consequent destruction of the habitat and the associated benthic community (Russo and Cicogna, 1992;Fanelli et al, 1994). Date mussel extraction undoubtedly leads to a decrease in the availability of the suitable settlement microhabitat for P. elephas.…”

“…Date mussel extraction undoubtedly leads to a decrease in the availability of the suitable settlement microhabitat for P. elephas. Additionally, date mussels are longlived and have very low growth rates (Kleeman, 1973;Galinou-Mitsoudi and Sinis, 1997) and their exploitation may rapidly become unsustainable (Russo and Cicogna, 1992;Cuccu et al, 1994;Fanelli et al, 1994).…”