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aquaculture and aquarium trade. The Suez Canal, as a pathway of non indigenous
species, is believed to be responsible for the introduction of 493 alien species into
the Mediterranean; approximately 11% being invasive (55 species) with, only 270 of
these species are definitely classified as Lessepsian immigrants. Of these 270
Lessepsian immigrants, 71 consist of casual records while 175 are successfully
established, 126 out of them (including 17 invasive ones) are limited to the Eastern
Mediterranean Sea, whereas the others are progressively spreading in the
neighbouring Marine Strategy Framework Directive subregions (Zenetos et al., 2012).

Figure 3. Geography of the Mediterranean Sea with the main routes of species range expansion. Bold
capital abbreviations correspond to the main Mediterranean subregions (ALB: Alboran Sea; NWM:
North Western Mediterranean; TYR: Tyrrhenian Sea; ADR: Adriatic Sea; ION: Ionian Sea; AEG: Aegean
Sea; LEV: Levantine Basin) and adjacent seas (ATL: Atlantic Ocean; BLA: Black Sea; RED: Red Sea). Italic
abbreviations correspond to some remarkable Mediterranean locations (Gib: Gibraltar Straits; GoL:
Gulf of Lions; Sue: Suez Canal). Temperatures correspond to winter–summer mean sea-surface
temperatures. Arrows represent main routes of species range expansion according to their origin:
Mediterranean natives (orange), Atlantic migrants (green) and Lessepsian migrants (red). (Lejeusne et
al., 2010).

Shipping is blamed directly for the introduction of 12 species only, whereas it is
assumed to be the only pathway of introduction (via ballasts or fouling) of further
300 species. In addition, for approximately 100 species shipping counts as a parallel
possible pathway along with the Suez Canal or aquaculture. (Zenetos et al., 2012).
Lessepsian species decline westwards, while the reverse pattern is evident for ship-
mediated species and for those introduced with aquaculture. There is an increasing
trend in new introductions via the Suez Canal and via shipping (Zenetos et al., 2012).
Increase in trade, tourism and maritime activities have provided new and
enhanced pathways for the spread of marine non indigenous species through
shipping. Shipping has been reported to be responsible for the introduction (either
among hull fouling or in ballast waters) of 54 NIS until 1950. The current rate (based
on the last decade) of ship-mediated non indigenous species in the Mediterranean is
one new species every six weeks. (Zenetos et al., 2012). In the Western
Mediterranean Sea, shipping remains the most prominent pathway of introductions.