download pdf

Mediterranean and Black Sea Cetacean Red List Assessment
Tursiops truncatus
chemicals.
1) Excessive fishing pressure is a growing concern worldwide and is having profound direct and indirect
impacts on Mediterranean ecosystems (Sala 2004). In the Mediterranean there is an acute lack of historical
data and fisheries statistics are generally incomplete and unreliable (Briand 2000, 2003). Nonetheless, it is
acknowledged that unsustainable fishing has led to dramatic ecological changes and caused the decline of
many fish stocks, including key bottlenose dolphin prey (Caddy 1997; FAO 1997, 2000). Nutritional stress
may be a factor in the low density of bottlenose dolphins in several Mediterranean areas (Bearzi et al. 1999,
2005b, 2006). Conversely, density is high where prey is abundant (e.g. in the Amvrakikòs Gulf, Greece,
where dolphin density is an order of magnitude higher than in the overfished waters of the nearby island of
Kalamos; Bearzi et al. 2005a, 2006).
2) Incidental mortality in fishing gear – particularly trammel and set gillnets, but also drift gillnets – is a
frequent occurrence, and in some Mediterranean areas the rates have almost certainly been unsustainable
(e.g. Silvani et al. 1992). Bycatch in trawl nets appears to be relatively uncommon in most Mediterranean
areas. However, high mortality in bottom trawls has been reported from the coast of Israel (Goffman et al.
1995). Dolphins also die incidentally in purse seines and longlines (Bearzi 2002), but the relative importance
of mortality from these gear types on Tursiops at the basin level is probably low. Interference with coastal
fisheries (“depredation”) can result in animals being shot, harpooned or harassed (Bearzi 2002; Gazo et al.
2004) although such retaliation probably occurs less frequently now than in the past when dolphins were
regarded as vermin and systematically persecuted (Bearzi et al. 2004). Intentional killing may still be a
serious problem in areas where acute conflict exists. However, depredation or damage to fishing gear by
the dolphins does not necessarily always lead to open hostility towards them. Attitudes towards dolphins
along the Mediterranean coasts vary greatly according to cultural, religious or other factors (e.g. see Bearzi
2005).
3) Contaminant levels, particularly of organochlorine compounds, in Mediterranean bottlenose dolphins are
very high compared to levels reported from other areas (Corsolini et al. 1995; Aguilar et al. 2002; Fossi and
Marsili 2003) and are a concern due to their potential effects on reproduction and health (Fossi and Marsili
2003). At concentrations similar to or lower than those detected in Mediterranean animals, compounds such
as PCBs have been associated with reproductive disorders and immune-system suppression in bottlenose
dolphins from other populations (Lahvis et al. 1995; Schwacke et al. 2002; Hall et al. 2005). Although
organochlorine contamination is decreasing in some areas (Tolosa et al. 1997), levels in Mediterranean
cetaceans remain exceptionally high (Aguilar and Borrell 2004).
In addition to the main threats listed above, mass mortality (die-offs), direct disturbance from boating
activities, and noise represent potential threats at local scales. Die-offs appear to have affected bottlenose
dolphins to a lesser extent than other Mediterranean species such as the striped dolphin (Aguilar and Raga
1993). However, bottlenose dolphins elsewhere have experienced mass mortality (Lipscomb et al. 1994;
Duignan et al. 1996; Birkun et al. 1998). As mass mortality may be partly related to the animals’ weakened
immune systems induced by exposure to xenobiotics or by stress from poor nutrition (Aguilar and Borrell
1994; Calzada et al. 1996; O’Shea and Aguilar 2001), the risk to bottlenose dolphins in the Mediterranean
is considered high. Direct disturbance by recreational boating is another potential threat (Lusseau 2003;
Constantine et al. 2004) that has been poorly investigated in the Mediterranean. The number of recreational
boats was correlated with avoidance of certain areas by dolphins in the north-eastern Adriatic during the
summer (Fortuna submitted).
Conservation measures
National protection status
National protection status varies according to country. Bottlenose dolphins are legally protected as a
species in some countries and as “cetaceans” or “marine mammals” in others. In some States, bottlenose
dolphins are not given specific protection as a species or by virtue of their inclusion within an order or
class of animals, but they may gain some protection through broad legislation that applies to the marine
environment or nature in general.
Various kinds of marine protected areas exist or have been proposed throughout the Mediterranean. Although
not always specifically intended for bottlenose dolphins, the following measures, once implemented, could
contribute to their conservation:
• Pelagos Sanctuary, a 90,000 km 2 cetacean sanctuary in the Corsican-Ligurian Basin, created in
Annex 3: Regular Species
69