CROATIAN FAUNA 2009 - ADRIATIC STURGEON

Adriatic Sturgeon - Latin Acipenser naccarii Bonaparte, 1836. Foreign names: Adriatic Sturgeon (English); Adriastör (German); Storione del Naccari (Italian) The Adriatic Sturgeon is an endemic species of the Adriatic Sea and the sub-Adriatic rivers. Its habitats are the rivers of northern Italy and in Croatia it is found in the river mouths of the rivers flowing into the Adriatic Sea. It is more common in the northern Adriatic and ranges along the eastern Adriatic coast all the way to Albania. It is a rare species. The Adriatic Sturgeon may grow up to 2000 mm in length and reach the weight of 25 kg, although it is usually considerably smaller. Its body is elongated and spindle-shaped and is not covered with scales but with bony plates or scutes, extending along the body in five rows. Hence the name of the subclass, Chondrostei, chondrosteans. Their back is olive-green and brown, the sides are lighter in colour and their belly is white. The top of the head is a projecting wedge-shaped snout, broad and relatively short, and with the rounded tip. The Adriatic Sturgeon has a small inferior, i.e. subterminal moth (mouth posterior to the tip of the snout). The lips are meaty and the lower one is interrupted in the middle. Adult sturgeons are toothless and in the young ones they are stunted. Their eyes are small and poorly developed, so that their barbels are important tactile organs for the detection of food on the river bottom. The barbels are found on the lower side of the snout, closer to its tip rather than to the mouth. The first rays of pectoral fins are strong and bony. The dorsal fin is located far on the back and the caudal fin is asymmetric (heterocercal). The Adriatic Sturgeon feeds on invertebrates from the bottom and small fishes. The Adriatic Sturgeon is an anadromous species: it lives in the sea and migrates to fresh water (rivers) to breed. It is a long-living species that grows slowly. In the beginning it grows rather fast and at the end of its second year it reaches about 0.5 m in length and weighs approximately 1 kg. However, to reach 1 m in length and the mass of 8 to 9 kg, it takes another 10 years. The males are capable of reproduction between the age of six and eight years, and the females between the age of eight and twelve years. It spawns in the spring, from March to May. The female spawns once in two to four years and the male once a year or every second year. After hatching the young fishes migrate to the sea, where they grow up. There is few information about the biology of this species. The flesh of the Adriatic Sturgeon is used for food but their roe is not processed into caviar. The Adriatic Sturgeon is a demersal species inhabiting freshwater, brackish water and seawaters of the Adriatic. It lives in the sea, at places with silty or sandy bottom. It mostly stays close to the river mouths, up to a depth of 40 m, although it sometimes goes deeper. The Adriatic Sturgeon is threatened by the pollution of watercourses and partition of rivers, which prevents their migrations. Another great problem is overfishing of still growing fishes. It occurs very rarely in the nature and the populations are slowly growing. According to the IUCN Red List, this species is Critically Endangered (CR) in Croatia. Pursuant to the existing protection based on the law, the Adriatic Sturgeon is a strictly protected species. The international protection documents mentioning this species are the Bern Convention (Convention on the conservation of European wildlife and natural habitats) (Appendix II), the Washington Convention (The Washington Convention on International Trade of Endangered Species of Wild Fauna and Flora – CITES) (CITES II) and the European Habitats Directive (the Council Directive on the conservation of natural habitats and of wild fauna and flora (Appendix II and V).