Squalus acanthias
The spiny dogfish (*Squalus acanthias*) is the most common representative of the order Squaliformes in European waters and the only shark species consistently encountered in the Pontic basin. Although an active predator, it does not pose a danger to humans, being a small-sized species that prefers deeper and colder waters. It is a fish with fascinating biology, characterised by remarkable longevity and an unusually long reproductive cycle, factors that however make it very sensitive to commercial fishing pressure.
It has a fusiform and hydrodynamic body, grey-blue on the dorsal side, often dotted with small white lateral spots, and whitish on the ventral side. The distinctive morphological element is the two sharp, horny spines located in front of each dorsal fin, which serve as a defence mechanism against larger predators. The eyes are large, adapted for low light, and the mouth is ventral, equipped with sharp teeth arranged in multiple rows.
It is a cosmopolitan species, adapted to temperate waters on continental shelves. In the Danube Delta area, its presence is limited to the marine sector in front of the river mouths (Chilia, Sulina, Sfântu Gheorghe), where it enters in search of food when salinity conditions are high. It generally prefers sandy or muddy substrate, active at depths ranging from 10 to over 200 metres in the Black Sea.
The spiny dogfish is an opportunistic and gregarious hunter, often moving in large groups, sometimes separated by sex. Its diet consists predominantly of small pelagic fish such as anchovy, sprat and horse mackerel, but it does not refuse marine invertebrates such as crabs or cephalopods. It has an extremely fine olfactory sense, being able to detect traces of blood or mechanical vibrations from considerable distances.
Reproduction in this species is ovoviviparous, with embryos developing inside the female for almost two years (the longest gestation period among vertebrates). At the end of this period, the female gives birth to 2-11 live young, fully formed, measuring approximately 20-30 cm. Due to late sexual maturity (approx. 12-15 years) and the small number of young, the capacity for population recovery is extremely low.
The species is classified as Vulnerable (VU) on the IUCN list, especially due to intensive fishing for its meat (marketed under various names) and for its liver oil rich in vitamin A. In the Black Sea, although not a main target as in the Atlantic, it is frequently caught accidentally in trawl nets or in turbot seines. Sustainable management of this species is essential for maintaining trophic balance in the Pontic marine ecosystem.