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Mediterranean and Black Sea Cetacean Red List Assessment
Stenella coeruleoalba
DNA analysis yielded 27 haplotypes, none of which was shared between the two areas, thus supporting
differentiation (García-Martínez et al. 1995).
Sub-population structure: Inside the Mediterranean there is some clinal variation in body size suggestive
of population structure and/or restriction in gene flow between areas (Calzada and Aguilar, 1995); this
appears to be confirmed by significant differences in tissue pollutant levels between Spain and Italy
(Monaci et al., 1998). Gaspari (2004) considered dispersal range sufficiently limited between populations
across the Mediterranean, and possibly between inshore and offshore populations within the Ligurian Sea,
to make differentiation feasible.
Generation time: Generation time for this dolphin population has been estimated as 22 years for females
(Calzada et al., 1996; Calzada et al., 1997) and 20 for males (Calzada et al., 1996). It is therefore
appropriate to use the default value for small delphinids of 20 years (see main text of workshop report).
Range and population: Although overall the striped dolphin is the most abundant cetacean in the
Mediterranean, both in the eastern and the western basins, it is not found at uniform densities. It typically
shows a preference for highly productive, open waters beyond the continental shelf (Notarbartolo di Sciara
et al., 1993; Forcada et al., 1994; Frantzis et al., 2003; Gannier, 2005). Two strandings were recorded in
the Marmara Sea in 1990s (Öztürk et al., 1999).
Reliable abundance estimates are available only for the western basin and most of them refer to the period
immediately or soon after the 1990-1992 die-off:
Western Mediterranean excluding the Tyrrhenian Sea (1991): 117,880 (95%CI=68,379-214,800) (Forcada
et al., 1994)
Balearic Sea (1991): 5,826 (95%CI=2,193-15,476) (Forcada and Hammond, 1998)
Gulf of Lions (1991): 30,774 (95%CI=17,433-54,323) (Forcada and Hammond, 1998)
Ligurian Sea (1992): 14,003 (95%CI=6,305-31,101) (Forcada et al., 1995)
South Balearic area (1991): 18,810 (95%CI=8,825-35,940) (Forcada and Hammond, 1998)
Alboran Sea (1991): 17,728 (95%CI=9,507-33,059) (Forcada and Hammond, 1998)
Central coast of Spain (2000-2002): 15,778 (95%CI=10,940-22,756) (Gómez de Segura et al., 2006)
Habitat and Ecology
Oceanic, with a preference for highly productive, open waters beyond the continental shelf. Particularly
abundant in the Ligurian Sea, the Gulf of Lions, the waters between the Balearic Islands and the Iberian
Peninsula, and the Alborán Sea.
Threats
In the past, striped dolphins were hunted for use as bait for shrimp traps and longlines. Despite being
prohibited, catches with this aim continue in at least southern Spain and probably other areas.
Incidental captures in pelagic drift nets have been a major source of mortality all over the western
Mediterranean in the past. These nets are still being used by at least Italian, Greek and Moroccan vessels,
resulting in extensive dolphin mortality. The Spanish driftnet fishery in the Alborán Sea reportedly killed
145-183 striped dolphins per season in the early 1990s (Silvani et al., 1999); this fishery was halted in
1995 but the nets were transferred to Moroccan boats, which continue operating and have been estimated
to kill more than 3,600 dolphins (striped and common, combined) in the Alborán Sea per year (Tudela et al.
2005). The Italian drift net (spadare) fishery is estimated to have killed thousands of striped dolphins per
year through at least the early 1990s (Di Natale, 1992, 1995); although fishing effort has declined, mortality
is still observed in Italian waters. The French thonaille drift net fishery has been estimated to take about
180-472 striped dolphins per season (Imbert et al., 2001). Reports from other fishing activities are sparse
and collected non-systematically, but they indicate that striped dolphin mortality in at least pelagic purseseines,
longlines and gillnets is widespread and likely significant (Di Natale and Notarbartolo di Sciara,
1994). To this should be added a certain number of direct catches for human consumption or for use as
bait, which continue in several Mediterranean countries (SGFEN, 2001).
In 1990-1992 a die-off devastated the whole Mediterranean population; > 1000 carcasses were examined
Annex 3: Regular Species
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