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Spondylus spinosus Bursatella leachi Chama pacifica Crepidula fornicata
Brachidontes pharaonis Crassostrea gigas Musculista senhousia Xenostrobus securis
Pinctada radiata Ruditapes philippinarum Aplysia dactylomela

Introduction from the Atlantic
Introduction from the Red Sea
Maritime traffic
Aquaculture

Fig. 6. Potential introduction pattern of alien molluscs and presence in MPAs.

More than 200 alien marine molluscs have been recorded carpet shell Ruditapes philippinarum. The spectacular
off the Mediterranean coast. Most of them are of Indo-West invasion of these exotic species in some lagoon environments
Pacific origin and are believed to have entered the such as the Thau lagoon (south-western France) has altered
Mediterranean through the Suez Canal (Zenetos et al., the ecosystem to such a degree that these species have
2012). They display a distinct migration pattern beginning become an important part of the biomass and diversity of the
along the Mediterranean coast of Israel, moving north to the lagoon flora and fauna (Boudouresque et al., 2011).
south coast of Turkey and Cyprus before entering the
Aegean Sea and pushing westwards towards Malta, Italy Similarly, invasive alien crustaceans can have severe
and elsewhere (Fig. 6). negative impacts on native ecosystems. They may
completely change native communities through alteration
Aided by factors such as transport on or in ships (in hull of trophic interactions, interference competition, disease
fouling and ballast waters) and introduction through transmission or habitat modification (Snyder and Evans,
aquaculture activities, mollusc invasions are common in 2006). For example, Percnon gibbesi, probably the most
many Mediterranean coastal marine ecosystems, especially invasive decapod species found in the Mediterranean to
bays and estuaries. The Asian date mussel Arcuatula date, has spread rapidly in the region and reached a number
(Musculista) senhousia, for example, is an ecologically of MPAs (Fig. 7), forming thriving populations in a very short
important global invader that has invaded estuaries in the space of time. Its feeding habits (it consumes primarily algae
Mediterranean. These mussels can form dense aggregations but also other crabs, polychaetes, gastropods, crustaceans
2
of up to 170,000 mussels per m on mudflats, altering the and jellyfish) may affect the structure of benthic
habitat, reducing the diversity of large invertebrates, communities, particularly algal assemblages, and it may
inhibiting the growth of seagrasses, and decreasing the compete with native species for food and shelter
abundance of suspension-feeding bivalves (Munari, 2008). (Katsanevakis et al., 2011). In addition, eight species of alien
penaeid prawns have been recorded in the Mediterranean
Some coastal lagoons have also suffered significant (Galil, 2007). Their introduction into the Mediterranean
alterations to their native communities, particularly through through the Suez Canal has created a lucrative parallel
the effects of bivalves introduced through aquaculture, such industry for Levantine fisheries, in particular for species like
as the American oyster Crassostrea gigas or the Japanese the Kuruma prawn Marsupenaeus japonicus or the speckled

Monitoring Marine Invasive Species in Mediterranean MPAs: A strategy and practical guide for managers 13