More than 1960 species of animals have been found in the Black Sea. These animals include many Mediterranean species that are thought to be unable to fully adapt to the living conditions of the Black Sea.
Fish and mammals are actively moving from the Sea of Marmara to the Black Sea. Some of them remain in it, retaining their ability to reproduce, while others enter only for a certain period of time to find food and then return back to the Sea of Marmara to breed. There are about 180 species of fish in the Black Sea: mackerel, blacktip shark, duck, dragon fish, large lionfish, storm-petrel and three species of dolphin. Until the second half of the 20th century, monk seals on the verge of extinction also lived in the Black Sea.
Planktonic marine organisms that cannot swim are transported by currents. They are introduced through the currents of the Bosphorus Strait, after which the majority heads for the water surfaces. As a result, they are dispersed to different parts of the sea. In the Black Sea, the seabed fauna arriving from the Mediterranean gradually occupies the entire shelf area.
As the temperature of the Black Sea is relatively lower than that of the Mediterranean, Mediterranean inhabitants who prefer to be cold have settled there, such as species of North Atlantic origin. For example, among the marine sponges that live in the Black Sea, 82.8% are North Atlantic and only 17.2% are endemic to the Mediterranean.
About 20% of the Mediterranean fauna have migrated and settled in the Black Sea. Today, the transit of Mediterranean animals in the Black Sea continues. New immigrant species from the USA, Western Europe, Japan and other coastal areas are constantly being discovered.
The Black Sea ecosystem harbours many shellfish. Among the 90 or so species of shellfish, the main species is the Black Sea Mussel (Mytilus galloprovincialis), inhabiting a variety of rocky biotopes from surface cliffs to depths of 50-60 metres. This mussel is one of the most active filterers of seawater passing through its brachial filter, trapping plankton and detritus on which the mussel feeds. Its population has been severely declining as a result of the opening of the food chain in the Black Sea ecosystem and the introduction of invasive species such as crayfish (Rapana thomasiana).
The Black Sea ecosystem is home to many crustaceans. Among the approximately 90 species of shellfish, the main species is the black abalone (Mytilus galloprovincialis), which lives in various rock biomes from the rock surface to depths of 50 to 60 metres. This mussel is one of the most active filterers .Through its bronchial filter it traps plankton and debris from which the mussel feeds. Due to the opening up of the food chain in the Black Sea ecosystem and the introduction of invasive species (such as Rapana thomasiana), its population is in sharp decline.
About 17.8% of the fish in the Black Sea are usually freshwater and breed in neighbouring rivers. Among them are representatives of the carp and thorny orders. They can tolerate a certain degree of water salinity, so they try to use food resources in coastal marine areas. Some species of sturgeon and trout also belong to this category. The latter live in typical marine conditions, but to breed and lay eggs they migrate to rivers (anadromous species). The next smallest group (10.7%) is represented by the Pontic relict type. This is a combination of herring and duck, some of which are carrageenan as well as harip. The most abundant species come from the sea and the ocean.
They represent 71.5% of the Black Sea fish. This group includes typical Mediterranean endemic species and Red Sea species such as greenlings and minnows. Among them are some of the Boreal-Atlantic relics such as the newt and flounder . Other growing fish are fish that have been introduced or have appeared in the Black Sea due to changes in the composition of animals, plants and phytoplankton. These are small tuna, batfish and hake recorded in recent years.
