Page 17 - Invasive_Species_2013

shrimp Metapenaeus monoceros. On the other hand, their assemblages, particularly erect and canopy-forming algae,
spread has almost completely eliminated populations of the shifting the original habitat to one dominated only by
native penaeid prawn Melicertus kerathurus in those areas. low-lying and turf-forming algae (Sala et al., 2011).

Other non-native species such as ascidians, corals, jellyfish
or fishes are also expanding their distributional ranges from
other seas across the Mediterranean. Occasional sudden
blooms, like those of the comb jelly Mnemiopsis leidyi or the
nomadic jellyfish Rhopilema nomadica, have adversely
affected beach tourism in some areas, blocked water intake
pipes in ports and other coastal developments, and clogged
fishing nets thereby reducing catches.

Current numbers of alien fish species established in MPAs
are unknown (Fig. 8 a, b) as much of the information gathered
relates to coastal areas but not specifically to MPAs. Most
introductions into the Mediterranean have entered through
the Suez Canal, spreading through the Levantine basin and
causing profound changes in coastal communities. Invasive
fish species have produced significant ecological and
socio-economic impacts in the invaded environments,
causing large changes in the native communities of fish and
other species. The case of Kas-Kekova MPA off Turkey’s
south-western Lycian coast is a clear example of these
impacts. Here two invasive herbivorous fish species from the
Red Sea (Siganus luridus and S. rivulatus) are responsible for
creating and maintaining underwater barren grounds
composed solely of bare rock and patches of crustose
coralline algae. The grazing pressure by both fish populations
has severely reduced the composition and biomass of algal Percnon gibbesi. Photo: C. Suárez - OCEANA

(b)
(a)

Fig. 7. (a) Presence of the decapod Percnon gibbesi in Mediterranean MPAs. Data collected from published and unpublished sources;
(b) Percnon gibbesi observations in the Mediterranean Sea. From Katsanevakis et al., 2011.

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