Some Dolphins Observations In The North-western Part Of The Black Sea
Some Dolphins Observations in the North-Western Part of the Black Sea
S.G. Bushuev1, V.P. Savusin2
1Odessa Branch Institute of biology of southern seas, National
Academy Sciences of Ukraine
2State ecological inspection of the Black Sea, Ministry of ecology and resources of Ukraine, Odessa
All three species of dolphins, living in the Black Sea, are represented in a North-Western part of sea (NWBS): common dolphin (Delphinus delphis ponticus), bottlenose dolphin (Tursiops truncatus ponticus) and harbour porpoise (Phocoena phocoena relicta).
The character of dolphin’s separate species distribution in this region practically is not investigated. Dolphins never organized here such dense congestions, as in east part of the sea, at shores of Crimea and in region of Kertch strait. Therefore their specialized hunting in NWBS practically was failed. In passing for want of catching a fish here was extracted up to 1000 animals per one year, which were handed over on processing on Otchakov, Kherson, Vilkov and Odessa fishing plants (Salnikov, 1967). Unfortunately, even the statistics of catching on dolphins species was not conducted, not speaking about the detailed biological analysis of the caught animals.
On data\’s of airinvestigation which have been carried out in 1950-60 years, the number of dolphins in NWBS varied hardly depending on a season. It was marked, that their number in area was increased noticeably since May till July - August (in that time the gradual movement of jambs to North Haven place), and then again decreased by October (Salnikov, 1967). For want of it was informed about "dolphins generally", without separation by species, though, apparently, it was taken into account in main the common dolphins, as the most mass pelagic trade species. It’s unknown how have been changed number and distribution of rather settled, "coastal" species - bottlenose dolphins and harbour porpoise, Taking into account information about biology of these two species, it is possible to assume, that in NWBS there should be resident subpopulations of bottlenose dolphins and harbour porpoises, is
probable remaining here on wintering. The common dolphins staying here carry a seasonal nature. Common dolphins used and (though and in a smaller measure) use now NWBS mainly as feeding area. Their emerging is connected with migrations in summer period to the North-Western shelf anchovy, herring, jack mackerel and formation dense feeding congestion\’s of a sprat. Rather weak dolphins assimilation of so highly productive area is possible to explain by feature of Black Sea common dolphins biology, which inclined to avoid of areas with muddy, polluted and low salinity waters (Freiman, 1951).
On data\’s of airinvestigation the small groups of dolphins (up to 50-100 individuals and on occasion up to 1000 individuals) have been met in NWBS in 1950-60 years. The aggregate number of dolphins in area changed from several thousands up to several tens thousands of heads. Certainly, the researches have been oriented in main on the account of common dolphins; that’s why bottlenose dolphins and, especially, harbour porpoises number have been hardly underestimated. N.E. Salnikov (1967) had allocated 5 main areas of dolphins concentration in warm period of a year: Danube, Tuzlov, Tendrov, Djarilagach and Tharkhankut.
Since last years in the Black Sea a significant aggravation of ecological circumstances took place. Most hardly situation had become complicated in its North-Western part. Growth of contamination and eutrophication of marine waters caused a periodic formation extensive hypoxygenous zones on the North-Western shelf, violation of general balance of ecosystem, sharp decrease of production fodder zooplancton and benthos, fisheries production. Migrations to NWBS of a mackerel, pelamida, lufar, jack mackerel were practically stopped completely. In the beginning of 90-th years the number of mass pelagic planctonophagus – anchovy (one of main fodder objects of all three species Black Sea dolphins) was considerably reduced in an outcome of outburst of development inadvertent installer ctenophora Mnemiopsis leidyi. In this connection the marine mammals number in NWBS area have been reduced.
As the accounts of dolphins were not carried out from the middle of 80-th years, it is possible to judge decrease of their modern number in NWBS only on indirect data: a diminution of number of observations in the sea and cases of observations from a shore, decrease of observable groups sizes (now groups of 30-50 individuals are considered as large, and the groups of more significant sizes practically were not marked), insignificant number of known cases of dolphins by-catches in fishery instruments, finding stranded at coast dead dolphins.
On data of State ecological inspection of the Black Sea and Odessa branch IBSS for the last year in NWBS only 7 cases of stranded dolphins detection have been registered (3 bottlenose dolphins -1 in a delta of Danube, 1 on Bugaz spit and 1 near Kinburn spit; 3 common dolphins - 2 on Tuzla spit and 1 on a beach of Odessa; 1 harbour porpoise - on a beach of Odessa). In Crimea and on Caucasus the number of stranded dolphins on 1 km of coast is much higher, than in NWBS (Glazov, Lyamin, 2000; Krivokhizhin, Birkun, 2000). Strangely enough, that in the current year fishery inspections had not registered any case of by-catches dolphins in fishing instruments, whereas by Turkish sources it is known, that the death of dolphins (first of all porpoises) during fishing of flatfish and sharks in NWBS carries a mass character (Ozturk, 1999).
By results of coastal observations and 2 ship expeditions conducted in July-August 2000 on vessels "Ukraine" (State ecological inspection) and "Octopus" (Odessa branch IBSS) have been fixed availability of seasonal congestion\’s of common dolphins by number 30-50 individuals in areas of Tuzla spit, Djarilgach island and Dniester bank. The groups of bottlenose dolphins by 4-8 individuals have been marked in area of Tendra spit and in east part of Karkinitsky gulf.
It is necessary to mark, that the incidental sketchy observations can not give integral submission about modern condition of dolphin populations and character of its distribution in NWBS. These information becomes extremely important both for an evaluation of ecosystem qualitative condition, and for development and realization of effective measures directed on dolphins protection, as all Black Sea cetacean are placed in the Red book of Ukraine, European Red list, the International Red book IUCN and are protected by a number of the multilateral international legal acts.
Within the framework of the scientific-practical program of study, protection and the restorings marine mammals of the Black and Azov seas "Dolphin", authorized by Ministry of ecological security of Ukraine per 1999, Odessa branch IBSS and State ecological inspection of the Black Sea planned to reinstate realization of dolphins registration survey and to develop a system of the collection of information about marine mammals in NWBS, including monitoring of stranded dolphins and record-keeping of incidents of dolphins by-catches.
References
1. Glazov D.M., Lyamin O.I. Observations of stranded dolphins on the Black Sea coast of Caucasus // Materials of Int. Sci. Conf. Marine mammals of Holarctic.- Arkhangelsk, 2000.-P. 87-90.
2. Krivokhizhin S.V., Birkun A.A. Experience of systematic study of stranded cetaceans and by-catches of the Black Sea // Ibid.- Arkhangelsk, 2000.-P.198-202.
3. Salnikov N.E. Cetaceans (Cetacea) // In: Biology of a North-Western part Black Sea.- Kiev: Nauk. dumka, 1967.- P. 235-40.[In Russian]
4. Freiman S.Yu. Dolphins of the Black Sea- Simferopol: Crimizdat, 1951.-29p.[In Russian]
5. Ozturk B. Cetacean and the Impact of Fisheries in the Black Sea //Bull.Accobams.- Monaco, 1999.- N 2.- P.11-2.
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