Tursiops truncatus 

Scope: Mediterranean
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Cetartiodactyla Delphinidae

Scientific Name: Tursiops truncatus
Species Authority: (Montagu, 1821)
Infra-specific Taxa Assessed:
Regional Assessments:
Common Name(s):
English Common Bottlenose Dolphin, Bottle-nosed Dolphin, Bottlenosed Dolphin, Bottlenose Dolphin
French Dauphin souffleur, Grand dauphin, Souffleur, Tursiops
Spanish Delfín Mular, Pez Mular, Tursión
Tursiops gephyreus Lahille, 1908
Tursiops gilli Dall, 1873
Tursiops nuuanu Andrews, 1911
Taxonomic Notes: All bottlenose dolphins around the world were previously recognized as T. truncatus, but recently the genus has been split into two species: T. truncatus and T. aduncus (the smaller Indo-Pacific Bottlenose Dolphin – Wang et al. 1999, 2000a,b). However, the taxonomy of bottlenose dolphins is confused, due to geographical variation, and it is very possible that additional species will be recognized in the future. For example, two forms in the North Atlantic, an offshore and a coastal form, are distinguishable on the basis of morphology and ecological markers (e.g., Mead and Potter 1995), have fixed genetic differences and, therefore, eventually may be assigned to different species (Leduc and Curry 1997, Hoelzel et al. 1998, Reeves et al. 2003).

Bottlenose dolphins in the Black Sea are recognized as a subspecies possessing morphological differences from Atlantic and Pacific dolphins (Barabasch-Nikiforov 1960, Geptner et al. 1976). The Black Sea subpopulation is also differentiated genetically from other bottlenose dolphins in the eastern and western Mediterranean and the northeastern Atlantic (Natoli et al. 2005), and the available evidence (Birkun 2006) supports recognition of the subspecies T. t. ponticus.

Assessment Information [top]

Red List Category & Criteria: Vulnerable A2cde (Regional assessment) ver 3.1
Year Published: 2012
Date Assessed: 2009-11-18
Assessor(s): Bearzi, G., Fortuna, C. & Reeves, R.
Reviewer(s): Hammond, P. & Perrin , W.
This subpopulation qualifies for listing as Vulnerable based on criterion A2cde.

Generation time for this species is estimated as 23 years (Taylor et al. 2007). Therefore, three generations from 2009 would go back or forward 69 years, to ca. 1940 and ca. 2078, respectively.

In northern portions of the Mediterranean basin, there is a well-known history of intentional killing, including extensive extermination campaigns conducted until at least the early 1960s, and there has been (and continues to be) substantial incidental mortality in fishing gear (A2d). It is not possible, however, to make robust estimates of either kind of mortality for other than short time periods and limited areas within the total subpopulation range. There is strong evidence that overfishing of dolphin prey has resulted in a form of habitat loss and degradation and likely also in a decline in area of occupancy (A2c). Other factors, such as disturbance by marine traffic, may be contributing to those processes. High levels of contamination by pollutants are another source of concern (A2e). Of the identified threats, only the extermination campaigns have ceased.

According to literature from the 19th century, “dolphins” were abundant throughout Mediterranean coastal waters. On the northern side of the basin, the animals were mostly seen as vermin, and one of the main concerns of fishery managers from the late 18th century onwards was to develop and deploy new means of killing the largest possible number of dolphins. Conflict with fisheries was reportedly acute in several areas of Spain (A. Aguilar, pers. comm.), France, Italy, and former Yugoslavia (today’s Slovenia, Croatia, Serbia and Montenegro), where thousands of animals were killed for bounties (Bearzi et al. 2004). Bottlenose and Common Dolphins were the main targets of the extermination campaigns in Mediterranean coastal areas. Numbers of Bottlenose Dolphins in some areas where they were formerly high are now lower, and this pattern can reasonably be extrapolated to other areas in the northern part of the basin. Given this, a reduction in population size of more than 30% since 1940 is suspected. Thus, the main drivers to justify a listing of Vulnerable are (a) the extensive extermination campaigns in the northern part of the western basin that ceased in the 1960s followed by (b) more recent bycatch in fisheries and prey depletion in a number of areas as well as generalized deterioration in quality of habitat (see ‘Threats’ section). It is suspected that even though substantial recovery may have occurred as the culling came to an end several decades ago, the other threats that have developed and increased in recent decades have either kept numbers down or slowed recovery so that the population is still at least 30% below its 1940 level. This extrapolation from a small number of areas to the rest of the Mediterranean, for much of which there is little or no information on the status of Bottlenose Dolphins, represents a precautionary rather than evidentiary interpretation of evidence. As explained in the March 2010 Guidelines for Using the IUCN Red List Categories and Criteria, version 8.0 (sections 3.2.3, 3.2.4 and 3.2.5 in particular), assessors are encouraged to ‘adopt a precautionary but realistic attitude, and to resist an evidentiary attitude to uncertainty when applying the criteria’.

Note on population structure: although this listing treats the Bottlenose Dolphins throughout the entire Mediterranean Sea as a single unit, separate subpopulations probably exist in some areas, e.g., the Adriatic Sea, where the species has declined dramatically (quite likely by at least 50%) over the past 50 years (Bearzi et al. 2004, 2008). Other geographically distinct subpopulations are known to reside within relatively small semi-closed basins such as the Amvrakikos Gulf in western Greece (400 km²), where they exhibit specialized behaviour and feeding habits (Bearzi et al. 2008a). Therefore, the listing of Mediterranean Bottlenose Dolphins as a single subpopulation should not be interpreted to mean there is no further subpopulation structure within the region.

Geographic Range [top]

Range Description:Bottlenose Dolphins are widely distributed throughout the Mediterranean Sea. Although historically their distribution may have been continuous, at least in coastal waters, it is now marked by gaps with low densities that may be either natural or the result of anthropogenic effects (e.g., intensive exploitation, whether deliberate or indirect; habitat degradation or loss). Range includes inshore, coastal and offshore waters to near the continental slope.

Bottlenose Dolphins occur in most coastal waters of the basin and have been reliably reported in the waters of Albania, Algeria, Croatia, Cyprus, France, Gibraltar (U.K.), Greece, Israel, Italy, Montenegro, Morocco, Slovenia, Spain, Tunisia and Turkey.  They occur regularly around many of the region’s offshore islands and archipelagos (Bearzi et al. 2008). Many of the Mediterranean areas inhabited by these dolphins are subject to intensive human use, e.g. the straits of Gibraltar, Bonifacio, and Messina, and the gulfs of Lion, Genoa, and Trieste. Within their overall range, gaps with very low densities of animals have been documented, e.g., in the north-western Ligurian Sea (France and Italy) and in the north-western Gulf of Vera (Spain). Variation in density is likely related to several factors, including a) habitat characteristics and b) local availability of suitable prey. The effects of past extermination campaigns (Bearzi et al. 2004) and a variety of ongoing threats probably have contributed to the patchiness of the current distribution of Bottlenose Dolphins across the region.

Countries occurrence:
Albania; Algeria; Bosnia and Herzegovina; Croatia; Cyprus; France; Gibraltar; Greece; Israel; Italy; Lebanon; Libya; Malta; Monaco; Montenegro; Morocco; Serbia (Serbia); Slovenia; Spain; Syrian Arab Republic; Tunisia; Turkey
FAO Marine Fishing Areas:
Mediterranean and Black Sea
Additional data:
Range Map:22563-3

Population [top]

Population:Total population size is unknown but may be in the low 10,000s based on observed densities in areas that have been surveyed (Bearzi et al. 2008). Further subpopulation structure exists and may require future assessments at a finer geographical scale. Further genetic analysis with samples from areas not yet included are strongly recommended.

A declining trend is inferred, refering specifically to the time since the early 1940s (i.e., over the last three generations). It is uncertain whether the subpopulation is still declining and if so, at what rate.

Mediterranean Bottlenose Dolphins are genetically differentiated from those inhabiting the contiguous eastern North Atlantic Ocean and Scottish waters.  Based on nuclear and mitochondrial DNA analyses, distinct populations have been identified across the Black Sea and the Mediterranean Sea (Natoli et al. 2005). The genetic analysis of 145 samples along a continuous distributional range from the Black Sea to the eastern North Atlantic (16 samples from the Black Sea, 74 from the Mediterranean Sea, 35 from the eastern North Atlantic and 20 from Scotland) found population structure with boundaries that coincided with the transitions between different types of habitat. The different zones can be characterized by ocean floor topography and by features such as surface salinity, productivity and temperature. Five populations were identified: Black Sea, eastern Mediterranean, western Mediterranean, eastern North Atlantic and Scottish. The Black Sea population showed the highest differentiation from other populations. Significant genetic differentiation was observed between populations from the eastern and the western Mediterranean. The boundary between the western Mediterranean and the eastern North Atlantic was the weakest observed, although the two populations still showed significant genetic differentiation.  Despite the lack of obvious physical barriers, the eastern North Atlantic and the Scottish populations also showed genetic differences. There was genetic evidence of directional emigration of females at the extreme of the range although neither sex showed a strong bias for greater dispersal (Natoli et al. 2005). Population structure of Bottlenose Dolphins around the Iberian Peninsula was investigated through isotopic signatures and organochlorine pollutant loads in tissues of stranded animals from Catalonia, Valencia and the Balearic Islands and adjacent Atlantic waters (Huelva and Portugal; Borrell et al. 2006). Significant differences in stable isotopes of carbon (13C/12C) and in PCB congener profiles indicated that dolphins from the Atlantic and the Mediterranean do not intermingle.  In the Mediterranean, dolphins from Catalonia and Valencia were indistinguishable, suggesting a common distribution area. However, dolphins from the Balearic Islands differed from those of mainland Spain in their DDT/PCB ratio and from all the other sample groups in their PCB congener profiles, suggesting that the deep waters between the Balearic Islands and the Peninsula represent an effective barrier for the species (Borrell et al. 2006). Evidence of population structure also has been found in other Mediterranean delphinids, including Short-beaked Common Dolphins (Delphinus delphis) (Natoli et al. 2008), Striped Dolphins (Stenella coeruleoalba) (Fossi et al. 2004, Gaspari et al. 2007b) and Risso’s Dolphins (Grampus griseus) (Gaspari et al. 2007). These findings suggest not only that the more obvious physical boundaries such as the Strait of Gibraltar (minimum width about 45 km and sill depths less than 145 m) and the Turkish Straits system (Dardanelles minimum width about 450 m and sill depths less than 55 m) represent barriers to the movement of individuals, but also that the much wider Sicily Channel (143 km and sill depths less than 200 m), oceanic features such as the Almería-Orán front (Tintoré et al. 1988) and more generally differences in habitat characteristics tend to limit the movements of Bottlenose Dolphins (Natoli et al. 2005).

There is no basin-wide estimate of numbers and the most reliable information comes from a few local studies  (Bearzi et al. 2008). Useful information on past and present occurrence also comes from stranding records from Algeria, Croatia, France, Greece, Italy, Malta, Morocco, Spain, and Tunisia (however, a stranded carcass is not necessarily indicative of the dead animal’s having lived nearby). Virtually nothing is known for large portions of the south-eastern part of the basin (Bearzi et al. 2008c). Most studies in coastal waters are limited to areas of 400 to 1,000 km² and probably do not even cover the entire ranges of the groups under study.  Relatively recent, broad-scale shipboard surveys (4,000–80,000 km²) showed that in some Mediterranean areas Bottlenose Dolphins are present both near shore and offshore, and densities can range between four and 20 animals per 100 km² (Ben Naceur et al. 2004, Forcada et al. 2004, Cañadas and Hammond 2006, Gómez de Segura et al. 2006, Bearzi et al. 2008c). Studies tend to focus on areas of relatively high dolphin density, although study site preferences also may depend on logistical and other considerations. Although the total population size in the Mediterranean remains uncertain, it unquestionably exceeds the threshold level for red listing as Vulnerable under the D criterion.

Indirect but convincing evidence of dolphin abundance in historical times can be found in early accounts describing interactions with fisheries and systematic attempts to exterminate dolphins (including Bottlenose Dolphins) in Mediterranean coastal waters (Bearzi et al. 2008).

The only Mediterranean area with quantitative historical information that can be used to infer population trends over time scales of more than a couple of decades is the northern Adriatic Sea. There, Bottlenose Dolphin numbers likely declined by at least 50% in the second half of the 20th century, largely as a consequence of deliberate killing initially, followed by habitat degradation and overfishing of prey species (Bearzi et al. 2004). For some other parts of the northern Mediterranean, e.g. Italy and southern France, the available information is less precise but suggests similar trends (Blanco and González 1992, Borrell et al. 2000). In an area off southern Spain where the species has been studied intensively, abundance estimates have shown variability but no trend since the early 1990s (Cañadas et al. 2006).
Current Population Trend:Decreasing
Additional data:
Number of mature individuals:10000

Habitat and Ecology [top]

Habitat and Ecology:

Bottlenose Dolphins in the Mediterranean are often regarded as predominantly ‘coastal’ or ‘inshore’ animals but this designation may be misleading as they can be encountered in continental shelf and shallow plateaux waters at any distance from the coast (Bearzi et al. 2008). They inhabit a wide variety of habitats including continental shelf waters, lagoons and enclosed seas, and the waters surrounding islands and archipelagos (Bearzi et al. 2008). In the Alborán and Balearic Seas they occur across the entire shelf, along the shelf edge and in deep waters of the continental slope, and in productive waters 200–500 m deep (Cañadas et al. 2002, 2005, Forcada et al. 2004). In the Strait of Gibraltar, at or near the western limits of what is defined here as the Mediterranean region, Bottlenose Dolphins occur mainly in water 200–600 m deep, over steep slopes (de Stephanis et al. 2008). In Greek waters they are found in coastal areas, straits, gulfs, semi-closed eutrophic waters, and steep coasts with no continental shelf (Frantzis et al. 2003, Bearzi et al. 2005, 2008).

The size of Bottlenose Dolphin groups varies according to biogeographic region, prey availability, activity and other factors. Most encounters have been with groups of fewer than ten individuals (Bearzi et al. 2008). Associations with other cetacean species are uncommon, although in some areas mixed aggregations with Short-beaked Common Dolphins (Delphinus delphis) and Long-finned Pilot Whales (Globicephala melas) have been observed (Bearzi et al. 2008).

In Mediterranean coastal waters Bottlenose Dolphins target primarily demersal prey during feeding sessions characterized by dives lasting 3–5 min and occasionally up to 8 min, depending on water depth (Bearzi et al. 2008). Reported prey items include demersal species such as European Hake (Merluccius merluccius), European Conger (Conger conger), Red Mullet (Mullus barbatus), Striped Red Mullet (Mullus surmuletus), Common Cuttlefish (Sepia officinalis), Common Octopus (Octopus vulgaris) and a variety of other bony fishes and molluscs (Bearzi et al. 2008). As most studies have relied on stomach contents from stranded animals, inferences may be subject to bias (Barros and Clarke 2002). In some Mediterranean areas Bottlenose Dolphins also feed on Clupeidae or other epipelagic prey (Bearzi et al. 2008).

In the Mediterranean Sea, predation is regarded as a minor cause of mortality. Bottlenose Dolphins, as well as other small Mediterranean delphinids, are preyed upon occasionally by sharks, principally Great White Sharks (Carcharodon carcharias) but also several other species (Fergusson 1994, Morey et al. 2003). The numbers of large sharks have declined drastically in Mediterranean waters over the past century (Ferretti et al. 2008) and this may have reduced predation pressure considerably.  Other potential dolphin predators, such as the Killer Whale (Orcinus orca) and the False Killer Whale (Pseudorca crassidens), are rare in the Mediterranean (Notarbartolo di Sciara 1987, Reeves and Notarbartolo di Sciara 2006).
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):23
Movement patterns:Nomadic

Use and Trade [top]

Use and Trade: Live cetaceans from the wild are captured for ‘dolphin-assisted therapy’ (Marino and Lilienfeld 2007) or for research purposes. ‘Takes’ of Bottlenose Dolphins are prohibited in most Mediterranean riverine States by national legislation or international agreements (Bearzi et al. 2008). However, live captures (and any mortality and social disruption associated with capture operations) still occur occasionally (Bearzi et al. 2008).

Threats [top]

Major Threat(s): Owing to their occurrence in coastal waters, Bottlenose Dolphins in the Mediterranean are exposed to a wide variety of human activities. Whilst intentional killing was likely the most important cause of mortality until the 1960s (Bearzi et al. 2004, 2008), important ongoing threats include incidental mortality in fishing gear and the reduced availability of key prey caused by region-wide overfishing and environmental degradation. Additional potential or likely threats include the toxic effects of xenobiotic chemicals, epizootic outbreaks, direct disturbance from boating and shipping, noise, and the consequences of climate change. It is worth noting that this same array of known and potential threats applies to riverine, estuarine and coastal cetaceans in many other parts of the world as well (e.g., Reeves et al. 2003).

Fishery-related mortality
Due to their opportunistic behaviour and predominantly coastal occurrence, Bottlenose Dolphins in the Mediterranean are at risk of entanglement in many types of fishing gear. In addition to incidental mortality, depredation and damage caused by dolphins to fishing gear may result in animals being shot or harassed in retaliation (Di Natale and Notarbartolo di Sciara 1994). Incidental mortality of Bottlenose Dolphins has been reported from Algeria, Croatia, France, Greece, Israel, Italy, Malta, Morocco, Spain, Tunisia, and Turkey (Bearzi et al. 2008). Bycatch in set nets reportedly is frequent in coastal waters throughout the basin (Di Natale and Notarbartolo di Sciara 1994, Díaz López 2006, Brotons et al. 2008). Significant mortality also was reported in pelagic driftnets off Morocco, Spain, Malta, Italy and Turkey (Di Natale and Notarbartolo di Sciara 1994, Di Natale 1995). Few attempts have been made to assess the impact of fishery-related mortality on local populations of Bottlenose Dolphins, and the actual magnitude of bycatch and retaliation events is unknown in most cases (Bearzi et al. 2008). However, the available studies and circumstantial evidence for local populations raise serious concern, suggesting that annual fishery-induced mortality is locally unsustainable in at least some cases (e.g. Brotons et al. 2008). Data from strandings can be informative with regard to the occurrence and relative scale of bycatch. Along the Italian coasts in the years 1986–2005, Bottlenose Dolphins were the second most numerous species classified as bycaught after the Striped Dolphin (301 and 71 records, respectively; Podestà 2007). Of 694 Bottlenose Dolphins stranded in Italy during the same period, 71 (11%) showed signs of bycatch (Podestà 2007). Of a total of 21 Bottlenose Dolphins stranded in France in 2003, eight reportedly had been bycaught (Dhermain 2003). Signs included specimens gutted, missing peduncles or fins, obvious net scars, and/or ropes tied to the tails. These percentages are likely underestimates, considering that the majority of the remaining carcasses were in an advanced state of decomposition and therefore signs, if present, would not necessarily have been observable. Bycatch in trawl nets appears to be infrequent in most Mediterranean areas, but may be locally significant. For instance, of 67 Bottlenose Dolphins found dead stranded or adrift along the coasts of Israel between 1993 and 2004, 26 (39%) were judged to have been taken in trawl nets (Feingold et al. 2005). Bottlenose Dolphins have not been reported entangled in fish farm gear in the Mediterranean, except when anti-predator nets (mesh size 15 cm) are deployed (Díaz López and Bernal Shirai 2007). The overall frequency of intentional killing (see ‘Past culling campaigns’) has drastically declined over the years, due in part to protective legislation in most Mediterranean countries. However, targeted kills still occur in certain areas (e.g. Tudela 2004, Gazo et al. 2008). In addition to killing in retaliation for damage to fisheries, killing with harpoons or guns for local consumption of meat was reported as recently as the early 1990s in the Ligurian and Tyrrhenian seas, notwithstanding legal protection (Di Natale 1991, Di Natale and Notarbartolo di Sciara 1994). Such occurrences seem to have become rare in more recent times. The illegal use of dynamite for fishing in several Mediterranean areas (e.g. Reynolds et al. 1994, Tudela 2004) represents another fishery-related threat to Bottlenose Dolphins. Though impact at the basin level is probably low, it may be significant locally and a few Bottlenose Dolphin deaths suspected to have been caused by explosives have been reported.

Prey depletion
Overfishing is having profound direct and indirect impacts on Mediterranean ecosystems (Sala 2004) and it has contributed significantly to dramatic ecological changes, including decline of dolphins and other megafauna (Bearzi et al. 2008) and caused the decline of many fish stocks (Caddy and Griffiths 1990, De Walle et al. 1993, Stanners and Bourdeau 1995, Garcia et al. 2005). Some of the Mediterranean fish stocks that have been either ‘overexploited’ or ‘fully exploited’ include important bottlenose dolphin prey (Bearzi et al. 2008, 2010). Reduced carrying capacity (i.e., fewer prey available) due to overfishing was proposed as one explanation for the low densities of Bottlenose Dolphins in the Adriatic and Ionian Seas. Conversely, Bottlenose Dolphin densities tend to be high in areas where prey is still abundant (Bearzi et al. 2008).

Contamination by xenobiotics
Contaminant levels, particularly of organochlorine compounds, in Mediterranean Bottlenose Dolphins are very high compared to the levels reported for Bottlenose Dolphins in some other areas (Corsolini et al. 1995, Marsili and Focardi 1997, Aguilar et al. 2002, Fossi and Marsili 2003, Wafo et al. 2005, Borrell et al. 2006, Borrell and Aguilar 2007, Storelli et al. 2007). At concentrations similar to or lower than those documented for Mediterranean Bottlenose Dolphins, compounds such as PCBs or PAHs have been associated with reproductive disorders, immune-system suppression and neoplasia (Lahvis et al. 1995, Reddy et al. 2001, Schwacke et al. 2002, Jaber et al. 2005, Hall et al. 2006). Although organochlorine contamination is decreasing in some areas, levels in Mediterranean Bottlenose Dolphins remain high (Tolosa et al. 1997, Aguilar and Borrell 2004, Borrell and Aguilar 2007, Storelli et al. 2007). Monitoring of toxic chemicals, risk assessment and intervention protocols therefore represent important precautionary measures (Schwacke et al. 2002, Fossi and Marsili 2003, Jaber et al. 2005, Porte et al. 2006). Various and sometimes high levels of heavy metals have been found in stranded bottlenose dolphins from the Mediterranean (e.g. Leonzio et al. 1992, Frodello et al. 2002, Roditi-Elasar et al. 2003, Lahaye et al. 2006).  The effects of these metals at the population level are unknown.

Epizootic outbreaks
Epizootic outbreaks appear to have affected Bottlenose Dolphins to a lesser extent than other Mediterranean delphinids, such as the Striped Dolphin (Aguilar and Raga 1993, Van Bressem et al. 1993). Morbillivirus infections have been reported in a Bottlenose Dolphin stranded on the Mediterranean coast of Israel in 1994 (Tsur et al. 1997) and another stranded in Mauritania (Atlantic coast of West Africa) in 1988 (Van de Bildt et al. 2001). Bottlenose Dolphins elsewhere have experienced mass mortality from such outbreaks, e.g. in Black Sea waters (Birkun et al. 1998, Birkun, 2006) and on the Atlantic coast of the United States, where more than half of one local population may have died (Lipscomb et al. 1994, Duignan et al. 1996, Schulman et al. 1997).  As epizootic phenomena may be related to immune-system compromise induced by exposure to xenobiotics and/or by stress from poor nutrition (Aguilar and Borrell 1994, Calzada et al. 1996, O’Shea and Aguilar 2001), the risk of disease outbreaks in Bottlenose Dolphins in the Mediterranean may be considerable.

Boat traffic and acoustic disturbance
There has been a great expansion of recreational boat traffic and shipping in the Mediterranean in recent decades (Dobler 2002) but the potential for resultant behavioural disruption and habitat loss has been investigated only to a limited extent. Permanent or temporary avoidance of one Mediterranean area by Bottlenose Dolphins as a consequence of a large seasonal increase in boat traffic was reported in coastal waters of Croatia (Fortuna 2006). Similar negative effects have been reported from other places around the world (Allen and Read 2000; Lusseau 2004, 2005; Bejder et al. 2006). The noise from various human activities in addition to boating/shipping - e.g. seismic surveys, dredging, drilling, underwater explosions, and the use of military or other sonars – is also a cause for concern (Richardson et al. 1995, Nowacek et al. 2007).

Climate change
Some of the effects of global warming have become dramatically apparent in recent years (IPCC 2007). Climate change has the potential to affect a range of biological processes and cause significant shifts in marine and other biota (e.g., Peñuelas et al. 2002, Parmesan and Yohe 2003, Diaz-Almela et al. 2007). Increased seawater temperature has been observed in Mediterranean deep (Bethoux et al. 1990) and surface waters (Metaxas et al. 1991, Bethoux and Gentili 1996) and there is increasing evidence of biological responses to such warming (e.g., Francour et al. 1994, Diaz-Almela et al. 2007). Effects of climate change on cetaceans, often mediated via changes in prey abundance and distribution, have become apparent in several non-Mediterranean areas (Learmonth et al. 2006, Simmonds and Isaac 2007) and similar effects may be occurring in Mediterranean waters (Azzellino et al. 2008, Cañadas and Hammond 2006). At present, however, it is impossible to predict the net effect of climate change on Bottlenose Dolphins – either in the Mediterranean Sea or elsewhere.

Live capture
The removal of live cetaceans from the wild – whether for captive display, for ‘dolphin-assisted therapy’ (Marino and Lilienfeld 2007) or for research purposes – is equivalent to incidental or deliberate killing, as the animals brought into captivity or killed during capture operations are no longer available to help maintain their wild populations (Reeves et al. 2003). ‘Takes’ of Bottlenose Dolphins are prohibited in most Mediterranean riverine States by national legislation or international agreements (Bearzi et al. 2008). However, live captures (and any mortality and social disruption associated with capture operations) still occur occasionally (Bearzi et al. 2008).

Conservation Actions [top]

Conservation Actions: Several of the existing laws and treaties in force today (reviewed in Bearzi et al. 2008) could provide a potentially solid framework for the conservation of Bottlenose Dolphins and for the protection of their habitat in the Mediterranean region. Unfortunately, implementation and enforcement of those instruments have not been consistently effective. Actions taken to date have not been adequate to maintain a ‘favourable’ status of Bottlenose Dolphin populations (as advocated by the EU Habitats Directive) or to prevent further population decline. Tangible actions to protect Bottlenose Dolphins and other Mediterranean cetaceans have been surprisingly few, especially if one considers the large number of existing laws, regulations and agreements that have been in place for years and even decades (Bearzi et al. 2008).

About a hundred national Marine Protected Areas (MPAs) of different types, sizes and purposes have been established in Algeria, Croatia, Cyprus, France, Greece, Israel, Italy, Lebanon, Malta, Monaco, Morocco, Slovenia, Spain, Syria, Tunisia and Turkey, but specific measures for cetacean conservation are rarely included in their management plans. A notable exception is the 87,000 km² cetacean sanctuary created in 1999 by France, Italy, and the Monaco Principality in the Corso-Ligurian-Provençal Basin (the ‘Pelagos Sanctuary’; Notarbartolo di Sciara et al. 2008). In addition, three years of provisional protection (from July 26th, 2006) were granted to the waters east of the islands of Losinj and Cres (Croatia) following a proposal for the creation of a special zoological reserve for dolphins. However, that period has expired and so far no protection measures have been enforced. If appropriately managed, MPAs could contribute to Bottlenose Dolphin conservation by preserving their prey and habitat, reducing the risks of mortality in fishing gear, providing refuge from noise and other types of disturbance, raising awareness, stimulating research and facilitating exchange of information (Hoyt 2005). However, levels of enforcement are often low and many of the existing Mediterranean MPAs merely represent ‘paper parks’ (Bearzi 2007, Guidetti et al. 2008). Other types of action that can provide direct or indirect benefits to Bottlenose Dolphins include area-, season-, or fishery-specific reductions in fishing effort, changes to fishing gear or fishing practices to reduce incidental mortality, curtailment of inputs of toxic pollutants, and boating regulations.

Citation: Bearzi, G., Fortuna, C. & Reeves, R. 2012. Tursiops truncatus. The IUCN Red List of Threatened Species 2012: e.T22563A2782611. . Downloaded on 19 August 2017.
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