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Mediterranean and Black Sea Cetacean Red List Assessment
Tursiops truncatus
Israeli
Mediterranean
coast (Israel)
Ionian Sea
(Greece)
Amvrakikos Gulf
(Greece)
Central Adriatic Sea
(Kornati & Murtar
Sea, Croatia)
North-eastern
Adriatic Sea
(Kvarneric, Croatia)
North-eastern
Adriatic Sea
(Kvarneric, Croatia)
North-eastern
Adriatic Sea
(Kvarneric, Croatia)
North Adriatic Sea
(Gulf of Trieste,
Slovenia)
- inshore
1999-
2004
-
85
-
480 inshore
1993-
2003
2001-
2005
- 48
400 inshore
0.38 152 -
136-
186
300 inshore 2002 - 14
800 inshore
1990-
2004
- 120
1,000 inshore 1997
113
0.06
2,000 inshore 2003
102
0.05
600 inshore
2002-
2004
0.08 47
Information on status and trends of the subpopulation is fragmentary because of the evident substructure
and the diversity of the monitoring efforts and the fisheries with dolphin bycatch. The only Mediterranean
area with quantitative historical information that can be used for direct calculation of trend and present
status is the northern Adriatic Sea. There, bottlenose dolphin numbers likely declined by at least 50%
over the past 50 years, largely as a consequence of historical killing, followed by habitat degradation
and overfishing (Bearzi et al. 2004). For other parts of the northern Mediterranean, e.g. Spain, Italy and
southern France, the available information on removals and trends in abundance is less precise and
clear but suggests similar trends (Silvani et al. 1992; reports by workshop participants). A decline in
abundance of about 39% was observed in a limited area of the north-eastern Adriatic between 1995 and
2003 (Fortuna submitted). The nature and extent of by-catch and other threats vary with region, but the
overall pattern leads to the suspicion that the basin population has been reduced by at least 30% over
the last 60 years. In recent years, as suggested by sightings and strandings, gaps have appeared in a
formerly continuous distribution along the Mediterranean coast of Spain, indicating a reduction in the area
of occupancy (reported by workshop participants).
Habitat and Ecology
Bottlenose dolphins in the Mediterranean are commonly regarded as coastal/inshore animals (Notarbartolo
di Sciara and Demma 1997; Gannier 2005). However, they are regularly found in deep waters near the
continental slope in the Alborán and Balearic seas (Forcada et al. 2004; Cañadas and Hammond in press)
and in continental-shelf offshore waters of the Adriatic Sea and Tunisian plateau (Bearzi et al. 2004; Ben
Naceur et al. 2004).
The mean size of bottlenose dolphin groups varies according to location, from typically small numbers in
coastal waters (Bearzi et al. 1997; Ben Naceur et al. 2004) to larger numbers in pelagic waters (Forcada
et al. 2004; Cañadas and Hammond in press). Coastal bottlenose dolphin groups average 7 individuals,
whereas the mean size of offshore groups is about 35. Association with other cetacean species is
uncommon, except in the Alborán Sea (Cañadas et al. 2002).
Mediterranean bottlenose dolphins are catholic feeders with a preference for demersal prey (Blanco et al.
2001). In coastal waters they can spend up to 5% of their time following trawlers (Bearzi et al. 1999). They
also sometimes forage around fish-farm cages or take fish from gillnets (Lauriano et al. 2004; Diaz et al.
2006).
Threats
Owing to their occurrence in coastal waters, bottlenose dolphins are regularly exposed to a wide variety
of human activities. Those in the Mediterranean were subjected to hunting until the 1960s (Bearzi et al.
2004). The main threats in recent times include: 1) reduced availability of prey caused by overfishing
and environmental degradation; 2) incidental mortality in fishing gear; and 3) toxic effects of xenobiotic
Annex 3: Regular Species
68