The Black Sea is home to sharks, though not the large, predatory species found in other oceans. Its unique characteristics limit the types of sharks that can inhabit it, leading to a distinct population adapted to these specific conditions.
Identifying Black Sea Sharks
The most prevalent shark species in the Black Sea is the Spiny Dogfish (Squalus acanthias). This bottom-dwelling, highly migratory shark is relatively small, typically reaching lengths of up to 1.5 meters and weighing around 10 kilograms. Its name derives from its pointed snout and the sharp, venomous spines in front of its two dorsal fins.
Spiny Dogfish primarily feed on small schooling fish, such as Black Sea sprat, European anchovy, and whiting, and also consume invertebrates like shrimp and crab. While the Spiny Dogfish is the most common, other species have been sighted. The Small-Spotted Catshark (Scyliorhinus canicula), a nocturnal hunter of mollusks, crustaceans, and small fish, occasionally appears in the Black Sea. The Common Thresher Shark (Alopias vulpinus), known for its elongated tail used to stun prey, is another species rarely confirmed in these waters.
The Black Sea’s Unique Environment
The Black Sea possesses distinct oceanographic features that significantly influence its marine life, including shark populations. It is the largest meromictic basin globally, meaning its water layers do not mix easily. This results in a strong stratification where a lighter, fresher surface layer sits atop a denser, saltier deep layer. The surface salinity is comparatively low, around 17-18 parts per thousand (‰), contrasting with the Mediterranean Sea’s approximately 35‰.
Below a depth of 150 to 200 meters, the Black Sea’s waters are anoxic, meaning they are completely devoid of oxygen. This anoxic zone also contains high levels of hydrogen sulfide, making it inhospitable for most complex marine organisms. Only about 13% of the Black Sea’s total volume, specifically the shallower, oxygen-rich surface waters, can support marine animals and algae. These conditions restrict the habitat for sharks and other fish to the upper, oxygenated layers, limiting the diversity and size of species that can thrive there.
Human Encounters and Safety
Encounters between humans and sharks in the Black Sea are exceedingly rare, and attacks are virtually non-existent. The prevalent Spiny Dogfish is not considered aggressive towards humans. While these sharks do possess spines that can inflict painful punctures or scratches if mishandled, primarily due to venomous glands at their base, they do not actively attack swimmers or divers.
The small size and non-aggressive nature of the resident shark species contribute to the Black Sea’s reputation as a safe swimming destination. Unlike other oceanic regions where larger, more formidable shark species are present, the Black Sea’s unique environmental conditions prevent such species from establishing a permanent presence. Any larger sharks that might enter from the Mediterranean Sea through the narrow Bosporus Strait typically do not venture far into the Black Sea due to its lower salinity and anoxic deep waters.