The Black Sea, a semi-enclosed body of water, is home to sharks, though the species and potential danger differ significantly from other oceanic environments.
Shark Species Present
The most common shark species is the Spiny Dogfish (Squalus acanthias), also known locally as “Katran.” These bottom-dwelling sharks are migratory and most abundant during spring and summer. Spiny Dogfish typically average between 70 to 100 centimeters (28-39 inches) in length, though females can grow larger, reportedly up to 180 centimeters (71 inches). Their diet primarily consists of small schooling fish, such as sprat, whiting, and anchovy, along with invertebrates like shrimp and crab. Spiny Dogfish are known to hunt in packs and possess two dorsal fins, each with a sharp, venomous spine used for defense.
Another species, the Small-Spotted Catshark (Scyliorhinus canicula), inhabits sandy, gravelly, and muddy seafloors, occasionally found in the upper slopes and shelves. This nocturnal hunter typically reaches a maximum size of about 100 centimeters (40 inches). Its diet is varied, including mollusks, crustaceans, seaworms, and small fish. The Common Thresher Shark (Alopias vulpinus) also inhabits the Black Sea, though rarely. This larger species, which can grow up to six meters (20 feet) long, uses its elongated, whip-like tail to stun prey like anchovies and shad. The Tope Shark (Galeorhinus galeus), also known as the School Shark, is globally distributed in temperate seas and is present in the Black Sea. Tope sharks can grow to nearly two meters (6.6 feet) long and are opportunistic feeders, consuming fish such as sardines, flatfish, and even smaller sharks and stingrays, along with invertebrates.
Safety and Unique Marine Environment
Sharks in the Black Sea pose a very low threat to humans. Incidents are extremely rare, and they are not considered dangerous to swimmers. The Spiny Dogfish, for instance, is not a serious threat, and its venomous spines are only a risk if the shark is provoked or handled improperly. Larger, more dangerous shark species, such as the Great White or Bull Shark, do not typically inhabit the Black Sea.
The Black Sea’s unique environment significantly limits shark diversity and abundance compared to other oceans. A key factor is its lower salinity. Surface waters average between 17 and 18 parts per thousand (ppt), roughly half that of typical ocean waters. This lower salt content creates an environment inhospitable for many marine species, including most sharks requiring higher salinity.
Furthermore, the Black Sea features an extensive anoxic, or oxygen-depleted, deep-water layer. Below depths of approximately 70 to 150 meters (230 to 500 feet), there is virtually no dissolved oxygen. This condition creates a vast “dead zone” where most complex marine life cannot survive, effectively restricting the habitable zone for fish and other organisms to the upper, oxygenated layer. This severely limits the available habitat and prey base for larger predatory sharks, which need ample oxygen and a rich food source to thrive. The limited prey in the oxygenated upper layer, combined with these unique conditions, contributes to the low number and non-aggressive nature of sharks.