The current status of bottlenose dolphins




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AC18 Inf. 2
(English only/ Seulement en anglais/ Únicamente en inglés)


The current status of bottlenose dolphins


(Tursiops truncatus)

in the Black Sea
By Alexei Birkun, Jr.


January 2002




ACCOBAMS

Agreement on the Conservation of Cetaceans of the Black Sea, Mediterranean Sea and contiguous Atlantic area




M. Würtz

ACCOBAMS interim Secretariat

16, Bd. de Suisse

MC-98000 MONACO


The current status of bottlenose dolphins (Tursiops truncatus) in the Black Sea



Alexei Birkun, Jr.
Laboratory of Ecology and Experimental Pathology, S.I. Georgievsky Crimean State Medical University,

Lenin Boulevard 5/7, Simferopol 95006, Ukraine; AlexeiBirkun@home.cris.net



1 Introduction

The Black Sea biodiversity in general and the fauna of Black Sea marine mammals in particular are rather confined owing to inherent peculiarities of this basin including the high degree of geographical isolation of the sea, its low water salinity and quite severe environment, as well as because of a large amount of hypoxic and anoxic waters below 100-250 m. Three species of cetaceans – the harbour porpoise (Phocoena phocoena), the short-beaked common dolphin (Delphinus delphis) and the common bottlenose dolphin (Tursiops truncatus) – and one pinniped species – the Mediterranean monk seal (Monachus monachus) – crown the trophic pyramid of the Black Sea as top predators which have no natural enemies in this basin (Kleinenberg, 1956; Geptner et al., 1976; Jefferson et al., 1993).


In the last three decades, Black Sea biodiversity has been seriously damaged due to the human-associated degradation of the sea proper and its drainage basin (Zaitsev and Mamaev, 1997). The species composition of most marine communities was modified with the explosive expansion of some organisms and the depression of many others. The Mediterranean monk seal has disappeared almost completely from the subregion (Kiraç and Savaş, 1996; Öztürk, 1999). Black Sea dolphins and porpoises, drastically affected by commercial direct killing continued till the early 1980s, are exposed to modern anthropogenic threats which cause the deterioration of habitats, the depletion of food resources and adversely impact cetacean population health.
The bottlenose dolphin population is known as the smallest Black Sea cetacean population which is negatively influenced by various anthropogenic impacts (Klinowska, 1991; Birkun et al., 1992; Birkun and Krivokhizhin, 1996 b). This population is protected by long list of international and national legislative acts, but practically its conservation status is far from perfection. The aim of this review is a critical evaluation of existent knowledge on Black Sea bottlenose dolphins with special respect to their taxonomic position, distribution, abundance, important threats and survival potentialities.

2 Taxonomy

The bottlenose dolphin is a single representative of the genus Tursiops and one of two Delphinidae species in the Black Sea (Table 1). For the first time it was recorded in this basin under the name Delphinus tursio by Rathke (1837). Fifty-five years later, Ostroumov (1892) has confirmed its presence and attributed it to the species Tursiops tursio Fabricius. Then, within taxonomic revision of Black Sea cetacean fauna conducted by Barabasch-Nikiforov (1940), local bottlenose dolphin was designated as the subspecies Tursiops truncatus ponticus. The author compared his own research data (1,450 individuals and 19 skulls were measured) with few publications on the Atlantic bottlenose dolphin and, as a result, has adduced four morphological peculiarities as diagnostic markers of the Black Sea subspecies:

(a) lesser body length (120-310 cm; 225 cm on average);

(b) some difference in typical coloration;

(c) short-cut beak with relatively more wide basis; and

(d) lesser number of teeth (from 74 to 90 in both jaws).


Table 1 – Taxonomic position of the Black Sea bottlenose dolphin





Latin name

English name

Order:

Cetacea Linnaeus, 1758

Cetaceans

Suborder:

Odontoceti Flower, 1867

Toothed whales

Family:

Delphinidae Gray, 1821

Dolphins

Genus:

Tursiops Gervais, 1855

Bottlenose dolphins

Species:

Tursiops truncatus (Montagu, 1821)

Common bottlenose dolphin

Subspecies (?):

Tursiops truncatus ponticus Barabasch, 1940

Black Sea bottlenose dolphin

The proposed new taxonomic position of the Black Sea bottlenose dolphin immediately excited strong objections from some cetologists (e.g., Zalkin, 1941). Later, Kleinenberg (1956) has examined 21 skulls and 50 carcasses which were 155-310 cm long with the mean length of 275 and 233 cm in mature males and females, respectively. He strictly criticized the preceding standpoint (Barabasch-Nikiforov, 1940) and recognized above features (especially, coloration, beak measurements and teeth number) as insufficient and unreliable criteria for the subspecies determination. However, he measured only two skulls of bottlenose dolphins from other (unspecified) sea(s). Of course, that was not enough for accurate comparative morphometric investigation.


No indisputable evidence, supporting either Barabasch-Nikiforov’s or Kleinenberg’s viewpoint, was reported during last 45 years. Nevertheless, in spite of persistent unsolved controversy, existing de jure and de facto, this animal is mentioned as the “rare endemic subspecies” in many publications belonging to subsequent authors originated mainly from the former USSR (Tomilin, 1957, 1983; Barabasch-Nikiforov, 1960; Geptner et al., 1976; Anonymous, 1985; Birkun and Krivokhizhin, 1994; Sokolov and Romanenko, 1997).
Thus, precise genetic and biometric studies are needful to remove a vagueness of Black Sea bottlenose dolphin’s taxonomic status. The use of subspecies name cannot be recommended unless and until it will be proved by certain data.

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