Bottlenose Dolphin
Tursiops truncatus (Montagu, 1821)
Tursiops tursio Fabricius.: Kovachev, 1925: 7.
Order Cetacea
Family Delphinidae
Conservation status: in Bulgaria: Vulnerable VU [D1]; International: IUCN-DD, BeC-II, HD.
General distribution. Practically in all oceans and seas of the moderate and tropical latitudes. The Black Sea population inhabits the coastal regions as a typical benthic form and is rarely found far into the sea at depths of more than 200 m [1; 2].
Distribution and abundance in Bulgaria. The problem of the taxonomic status of the Black Sea population as a separate subspecies is disputable [1], but a genetic isolation of this population has been established. This is the most rare Black Sea dolphin [1], which is a result of its way of living near the shore, its large size and low fertility [3]. The recent observations at the Bulgarian Black Sea coast are mostly made in its northern part. Two to five groups of 5-12 animals each were observed some 10-17 miles off cape Galata in the winters of 1992-5. In the autumn and in the spring they move 3 – 10 miles off the coast [4]. In 2004 separate bottle-nosed dolphins were seen near Kaliakra, Balchik and Byalata laguna (N. Davidkov, personal communication). 4 corpses washed ashore were registered between Pomorie and Sinemorets in 2003 [5]. The data about numbers are insufficient. In 1997 along the Turkish caost 485 bottle-nosed dolphins were counted, and in 1998 – 468 individuals [6]. Up to about 40 dolphins were counted in 1992, 1993 and 1994 during the autumn-winter season, in the region of Varna bay [ 4].
Habitats. The bottle-nosed dolphin is benthos-eating and hence, in practice, a shore form [1].
Biology. 10 species of fish have been registered in the food of the bottle-nosed dolphin (apart from benthic, during the seasonal fish migrations it also feeds on pelagic fish – anchovy, the Pontic shad). It lives for 25-30 years. Pregnancy lasts for 12 months. It gives birth to 1 young. The lactation period is 4 - 17 months. The females reach sexual maturity at the age of 5-6 years and later, the males at the age of 8-12 years [7;1].
Similar species. Larger than the other two bottle-nosed dolphins (an average length of 2.30 m). It differs in its habitus from the ordinary dolphin by the clear (sharp) border between the colour of the back and the belly [1].
Negative factors. Until the 80s, industrial fishing. Nowadays, the severe degradation of the Black Sea ecosystem; pollution of the waters; disturbance, poaching and catching for dolphinaria [2; 7; 8].
Conservation measures taken. Strictly protected according to the Biological Diversity Act. Included in the Bulgarian Red Data Book of 1985.
Conservation measures needed. Implementation of a common strategy for control over the activities in the Black Sea, guaranteed preservation of appropriate aquatories, monitoring [8].
References. 1. Kleinenberg, 1956; 2. Simmonds, 2003; 3. Birkun et al., 1999; 4. Stanev, 1996; 5. Peshev et al., 2005; 6. Dede, 1999; 7. Birkun, 2002; 8. Notarbartolo di Sciara, 2002.
Author: Nikolai Spassov
