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Mediterranean and Black Sea Cetacean Red List Assessment
Stenella coeruleoalba
in Spain, Italy and France alone, but the toll was undoubtedly much higher because these countries
represent only a fraction of the Mediterranean coastline known to have been affected (Bortolotto et al.,
1992; Aguilar and Raga, 1993). The primary cause of the die-off was a morbillivirus infection (Domingo et
al., 1990), but PCBs and other organochlorine pollutants with potential for causing immunosuppressive
effects were suggested to have triggered the event and/or enhanced its spread and lethality (Aguilar and
Borrell, 1994).
Tissue levels of organochlorine compounds, some heavy metals and selenium are high and exceed
threshold levels above which detrimental effects commonly appear in mammals (Aguilar, 2000). Blubber
concentrations of DDT (an agricultural pesticide) and PCB, the two main organochlorine pollutants, show
a slowly declining trend in the last two decades (Aguilar and Borrell, 2005) but are still high. An association
has been reported between high PCB levels and the presence of unusual luteinized cysts in the ovaries of
Mediterranean striped dolphins (Munson et al., 1988).
The diet of striped dolphins includes commercial fish and cephalopod species (Pulcini et al., 1993; Blanco
et al., 1995), so the widespread depletion of fishing resources in the Mediterranean has the potential to
affect striped dolphin numbers by reducing the availability of food for them.
Conservation measures
No specific measures have been taken for the conservation of striped dolphins in the Mediterranean Sea,
although generic protection laws for cetaceans exist in many range states.
One area where the species is relatively abundant is the Marine Sanctuary for Cetaceans in the Corso-
Ligurian Basin, declared by the Governments of Italy, France and Monaco. Apart from this, because the
striped dolphin is an oceanic species, most existing protected areas are of no use for its conservation.
Establishment of offshore protected areas through international agreements similar to that for the Ligurian
Sea should be encouraged. A governmental initiative in Spain to identify areas of special interest for the
conservation of cetaceans led to recommendations but no implementation thus far. Better management
and enforcement is needed in existing protected areas and additional initiatives should be undertaken in
more Mediterranean countries, especially in the eastern portion of the basin.
Pelagic driftnets have been prohibited in Spain and their use has been limited by EU regulations since
2002. However, a reduced Italian fleet still fishes with such gear in an unregulated manner (Pace et al.,
2005), as does a large Moroccan fleet and the French tonnaille vessels (Imbert et al., 2001, 2002; Tudela
et al., 2005). All of these operations are known to cause substantial cetacean mortality. Driftnets should be
eliminated from the region or, at a minimum, existing regulations on that gear need to be strictly enforced.
Most Mediterranean countries have regulations prohibiting direct takes, and these too need to be enforced
more rigorously.
Control of pollution, particularly that by organochlorine compounds, has begun to take hold in the last
two decades and pollutant levels are decreasing. However, existing laws and control should be further
enforced and striped dolphin populations should be monitored to assess trends and geographical variation
in tissue levels. There is a particular need for sampling in the southern and eastern Mediterranean.
The population was quantified in the western Mediterranean immediately after the 1990 die-off. Abundance
should be monitored to assess changes in abundance through time, particularly to assess recovery from
the die-off.
Occurrence of ovarian cysts should be monitored in the population and their potential impact on
reproduction should be investigated.
Diet should be studied through stomach content and isotopic analyses to assess overlap with commercial
fisheries.
Stranded dolphins should be monitored for establishing prevalence of morbillivirus infection.
Annex 3: Regular Species
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