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similar copepod species composition in coastal, between the islands and pelagic areas
because the coastal species widespread to offshore environment. The highest diversity
peak is coincident with the chlorophyll maximum (40-80 m depth). Here, the presence
of epipelagic or mesopelagic copepod species could be attributed to great food
availability such to allow them to coexist. The secondary diversity peak at 150-200 m
could be explained by a more equal abundance distribution between species, though
species number and abundances are less greater than upper layers. In the area between
the islands, the presence of mesopelagic species (such as the genera Aetideus,
Heterorhabdus, Haloptilus and Eucalanus) in the sub-surface interval (40-60 m) could
suggest an ingression of pelagic water between these islands. The occurrence of rare
species (Aetideus armatus, Augaptilus longicaudatus, Chiridius poppei, Euchirella
messinensis) in the 200-300 m layers of the most offshore station, could increase
heterogeneity between these layers and could be determined by the LIW influence,
identified by the salinity maximum (S>38.77). On the whole, there are no substantial
differences in species composition and zonation pattern between this area and the other
neighbouring parts of the Mediterranean Sea and there is a clear uniformity of copepod
populations, as confirmed by many authors (Champalbert, 1996; de Puelles et al.,
2003). However, there are evident differences in the relative importance of some species
with boreal or subtropical character. O. atlantica, considered as a boreal species, was
more abundant than O. plumifera in the Egadi Islands Archipelago, and the subtropical
species Farranula rostrata occurred with relative scarce abundances in this area but it is
dominant from Sicily Channel (Siokou-Frangou et al., 1997). This could confirm the
more boreal character of the Egadi Archipelago area.

REFERENCES

Astraldi G., Bacciola D., Borghini M., Galli C., Lazzoni E. & Picco P. 1996.
Circolazione superficiale lungo la sezione Sicilia-Sardegna. Atti 11° Congresso
AIOL: 93-101.

Carli A.M., Bruzzone C.L. & Sarà R. 1973. Studio dello zooplancton di superficie
raccolto alle Isole Egadi (Sicilia) nel periodo Maggio-Luglio 1970. Bollettino di
Pesca, Piscicoltura e Idrobiologia, 28(2): 339-359.

Champalbert G. 1996. Characteristic of zooplankton standing stock and communities in
the Western Mediterranean Sea: Relation to hydrology. Scientia Marina, 60(2):
97-113.

Colantoni P., Ligi M., Morsiani M.P. & Penitenti D. 1993. Morphology and recent
sedimentary evolution of the western sicilian continental shelf. Geological
development of the sicilian-tunisian platform. UNESCO Reports in Marine
Science, 58: 93-98.

Fernandez de Puelles M.L., Gràs D. & Hernandez-Leon S. 2003. Annual cycle of
zooplankton biomass, abundance and species composition in the neritic area of the
Balearic Sea, Western Mediterraean. Marine Ecology, 24(2): 123-139.

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