Literature and osteological collections unambiguously confirm that Common Dolphins were widespread and abundant in much of the Mediterranean Sea until the late 1960s, and that their decline occurred relatively quickly (Bearzi et al. 2003; and see references contained therein). Today, Common Dolphins remain relatively abundant in the westernmost portion of the basin, the Alboràn Sea. There are sparse records off the coast of Algeria where, however, survey coverage has been limited. Possibly isolated groups are present around Sardinia and Corsica, particularly off their western coasts (Bearzi et al. 2003). Common Dolphins are seen in the early summer in the south-eastern Tyrrhenian Sea off the island of Ischia (Mussi et al. in press). The species is also present in the Sicily Channel, with larger groups being observed around Malta (Vella in press). Common Dolphins can be found in portions of the eastern Ionian Sea, particularly around the island of Kalamos (Politi and Bearzi in press), and in the Gulf of Corinth (Frantzis and Herzing 2002). Sighting and stranding data indicate a regular presence of Common Dolphins in the Aegean Sea, particularly in the Thracian Sea, Northern Sporades, the southern Evvoikos Gulf, the Saronic Gulf, and the Dodekanese (Frantzis et al. submitted). Otherwise, these dolphins are rare in, or completely absent from, Mediterranean areas where information is available (Bearzi et al. 2003). Mediterranean regions where Common Dolphins have apparently vanished include the Adriatic Sea, Balearic Sea, Provençal basin, and Ligurian Sea. Population Trend
There is no basin-wide estimate of abundance for Common Dolphins in the Mediterranean Sea. Line-transect ship surveys of the Alboràn Sea in 1991?1992 produced an estimate of 14,736 (CV=0.38; 95% CI=6,923?31,366), with a density of 0.16 dolphins per km², but no estimates were made for this species elsewhere in the western Mediterranean due to the low number of sightings (Forcada and Hammond 1998). Vella (in press) combined data from ship and aerial surveys conducted between 1997?2002, and obtained a density estimate of 0.135 dolphins per km² (CV=0.28; 95% CI=0.066?0.290) in the area around the Maltese islands. Around the island of Kalamos in the eastern Ionian Sea, the mean sighting frequency was 0.016 groups per km (or 0.11 dolphins per km) in the years 1993?2000, but in 2001?2002 there was a significant decrease to 0.007 groups per km (or 0.04 dolphins per km) (Student?s t=4.88, p<0.001). The number of individuals encountered in this area has decreased continually, and many individuals that used to be seen regularly until 1996 have disappeared (Bearzi et al. 2003).
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