Page 157 - Dedola2011

l. INTRODUCTION
The introduction of allochthonous species in marine habitats is a traditional practice in
aquaculture, particularly when fisheries are depleted due to the overexploitation of
native species (see e.g. Breber, 1985; Pellizzato et al. , 1989). However, this method can
often pose serious risks (e.g., local extinction, hybridization) to indigenous species,
particularly when farming is performed without separation ofthe farmed area from
natural biotopes (see Wonham and Carlton, 2005). The introduction ofthe Manila clam
Ruditapes philippinarum (Adams and Reeve, 1850) (Bivalvia: Veneridae) to Europe in
the 1970s and 1980s (Gosling, 2003) from its native habitat on the West coast ofthe
Pacific from Russia to the Philippines serves as a paradigm for such a phenomenon.
Since then, the Manila clam has rapidly spread along European coastlines, becoming the
main contributor to local clam fisheries. The Manila clam was released in the North-
East Adriatic in the 1980s (Breber, 1985) to counter the dramatic depletion of severa}
native species due to overexploitation ami/or pollution (Savini et al., 2010). In the
Adriatic, the Manila clam progressively occupied the ecologica} niche of the indigenous
European grooved carpet shell, Ruditapes decussatus L., 1758, which led to the
extinction of local populations (Jensen et al. , 2004).
In 2008, severa! specimens of R. philippinarum were found in the Gulf of Olbia (North-
East Sardinia). This species has now become abundant (Cannas et al., 2009) and has
established the first recorded population of Manila clams in Sardinia. The introduction
ofthis species was likely the result ofthe 'accidental ' release ofadult individuals a few
years earlier due to careless management by fishery operators that were conducting
legai stabulation processes in the town ofOlbia (Cannas, pers. comm.; Cristo, pers.
comm.).

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Gìan Luca Dedola: ANALISI DELLA VARIABILITÀ GENETICA DI PATELLA FéRRUGINEA, PATEL.LA UL l'SSIPONENSIS (MOLLUSCA: GASTROPODA) E PINNA
NOBILIS (MOLLUSCA: BIVALVIA): lLCONTRJBUTO DEl DATI MOLECOLARl ALLA CONSERVAZIONE DI SPECIE MINACCIATE- Tesi di douorato in Scienze
della natura e delle sue risorse • indiri7.zo BK>logi.a Ambientale, Università degli Studi di Sassarl