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Black Sea dolphin - Yunus Karadeniz

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  •   Written by Giuliana
  • Category: Logbook

In the Black Sea live 3 species of dolphins: the bottlenose dolphin (Tursiops truncatus ponticus), the common dolphin (Delphinus delphis ponticus) and harbor porpoises (Phocaena phocaena relicta).
The dolphins that live in the Black Sea are genetically and morphologically distinct from other dolphin populations in the western and northeast Mediterranean sea, so that they are recognized as endemic subspecies found anywhere else.

It is estimated that in the early '50s in the Black Sea lived over a million of dolphins, and over the years they have been decimated by the many campaigns of commercial fishing. In fact, between 1958 and 1966 it was slaughtered more than 440,000 common dolphins, while more than 365,000 have been killed in the previous 12 years.
Since 1966, given the high risk of extinction, the Black Sea is a non-dolphin fishing. This has led to some recovery and, although the current population size is unknown, it is estimated to be made up of tens of thousands of individuals.
The recorded cases of deaths of dolphins are of accidental and due mainly to the depletion of the sea that is deprived of the main prey (sardines and anchovies) from overfishing, to eutrophication of the waters, to the presence of fishing nets and diseases caused by pollution of their environment.

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The Black Sea - Summary
• Nearly 87% of the Black Sea is completely anoxic (oxygen-free) and contains high concentrations of hydrogen sulfite: this derives from geological events that have occurred in it, from its particular shape and from its specific water balance (strong isolation from the ocean, deep waters - with a maximum of 2,212 m in the center - a large catchment area and a large number of tributaries).
• The pelagic and benthic organisms are largely absent.
• The high diversity of habitats provides favorable conditions for the invasion of alien species.
• The composition and structure of marine communities are constantly changing as a result of the reduction in population of some species and the expansion of others.
• Generally, in undisturbed natural conditions, the diversity of the fauna of the Black Sea is about three times less than that of the fauna of the Mediterranean.
• The threats to the endemic and relict species of the study area are made by increased salinity, due in turn to inappropriate management of water resources and pollution of the brackish coastal lakes and estuaries, especially in the Sea of ​​Azov.
• Primary production is increased due to eutrophication and the number of species declined. These changes, caused by fishing practices not adequate, they hit fish stocks; there was a change in favor of small pelagic species such as anchovy and sprat.
• The deterioration of some marine habitats and the lack of standards for the regulation of the introduction of alien species - such as through the ballast water of navigable - have meant that these have spread, with a change in the balance of ecosystems marine native. This problem is growing in the basin of the Sea of ​​Azov, which has stimulated the search for effective countermeasures to combat undesirable species, which have become sedentary and dominant in the food chain.
• Over-exploitation of fish stocks, in combination with the invasion of the comb jelly Mnemiopsis, has caused the collapse of the stock of anchovy in the Black Sea and the disappearance of the most valuable species of fish. Today is not yet in place a reserve management of fish stocks sufficiently adequate and integrated.
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Source: "The Black Sea" - Authors: Yu.P. Zaitsev - B.G. Alexandrov - N.A. Berlinsky (Institute of Biology of the Southern Seas) - Zenetos A. (National Centre for Marine Research, Greece)

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