[Note: It has been agreed that territorial waters of all six
Habitat and Ecology
IUCN Red List Assessment
Red List Category
Red List Criteria
The Black Sea Short-beaked Common Dolphin subspecies, D. d. ponticus, is assessed as Vulnerable based on criterion A2cde. There is no estimate of overall population size but preliminary data for some parts of the basin suggest that it is currently at least several 10,000s, and possibly 100,000.
Generation time was not estimated for this subspecies but was assumed to be approximately 15 years following Taylor et al. (2007). Three generations therefore would be about 45 years.
The past 45-year period (three generations) includes circumstances that are relevant to criterion A, as follows:
(1) Large directed takes occurred during the years 1962-1983 before the ban on small cetacean hunting was declared in Turkey in 1983. Within that 22-year period, the total number of common dolphins killed was at least 159,000-161,000 but certainly greater because that range of values does not take account of catches in Romania (1962-66) or Turkey (before 1976 and after 1981) (see “Threats”).
(2) A mass mortality event of unknown cause occurred in 1990, involving at least 100s of dolphins.
(3) A mass mortality event caused by morbillivirus infection occurred in 1994, again involving at least 100s of animals.
(4) The Black Sea environment overall (including common dolphin habitat) and many of its indigenous animal populations (including common dolphin prey) have been increasingly degraded from the 1970s to the present, with a likely peak in the devastation caused by overfishing and habitat deterioration (including pollution and explosive growth of populations of invasive species) in the late 1980s–early 1990s. These processes, taken together, have led to severe declines in prey populations.
A reduction in common dolphin population size of more than 30% (the threshold for Criterion A2cde) was inferred from a simple simulation in which the population was assumed to increase at a constant 4% per year and the direct removals were as indicated in paragraph (1) above. This simulation showed that a decline of about 36% in the last three generations would be required for the current population size to be about 100,000. Although the current population size may be larger, there is also reason to believe that the post-1962 removals were considerably larger than indicated.
Directed killing ceased in 1983 but degradation of habitat, prey depletion and epizootics have continued and these factors are not well understood.
The population size is unknown. Region-wide estimates based on strip transect surveys in the
Line transect surveys have been conducted recently to estimate common dolphin abundance in a few parts of the range (see Table 1 in attached PDF). The survey areas are small relative to the total range of the subspecies. Results suggest that current population size is at least several 10,000s, and possibly 100,000 or more.
By the mid 1960s, the population was depleted due to long-running overexploitation, which involved the killed of many 100,000s of common dolphins in the mid-20th century (IWC 1983; see “Threats”). The directed takes continued until 1983 when cetacean hunting finally ceased in
Last century, the population was depleted because of directed takes. The total number of animals killed is unknown, but it was estimated that before the mid 1950s common dolphins comprised 94.8% of the total number of Black Sea cetaceans killed and processed in the former
Reduced prey availability has been considered an ongoing major threat to D. d. ponticus since the late 1980s (Bushuyev 2000). Of two mass mortality events that killed unknown but certainly large numbers of common dolphins in winter–spring 1990 and summer–autumn 1994 (Krivokhizhin and Birkun 1999), the latter was recognised as being the result of a morbillivirus epizootic (Birkun et al. 1999). However, both die-offs coincided with a drastic decline in the abundance of both principal prey species, anchovy and sprat, which has been blamed on overfishing, eutrophication (e.g. water hypoxia) and the explosive increase of the introduced ctenophore Mnemiopsis leidyi (Zaitsev and Mamaev 1997). The total commercial catch of anchovies declined by 12-fold (from 468,800 tonnes in the 1987-88 fishing season to 39,100 tonnes in 1990-91), while landings of sprat fell by a factor of nearly eight (from 105,200 tonnes in 1989 to 13,800 tonnes in 1993) (Prodanov et al. 1997). This correlation between large die-offs of
Other known threats (bycatch in pelagic trawls, parasitic invasions) are of secondary importance (at least at present).
The species D. delphis is listed globally as Least Concern by IUCN. At the same time, the Mediterranean population is listed as Endangered (see Bearzi et al. 2003), and concerns regarding the Black Sea population were expressed in the IUCN/SSC 2002-2010 Conservation Action Plan (Reeves et al. 2003).
Commercial killing of Black Sea common dolphins, as well as other Black Sea cetaceans, was banned in 1966 in the former
The Strategic Action Plan for the Rehabilitation and Protection of the
On a national level,