Critically Endangered
Adriatic sturgeon
Acipenser naccarii
Adriatic sturgeon is a ray-finned fish in the family Acipenseridae (order Acipenseriformes) — Acipenser naccarii, recorded as Critically Endangered.
Appearance
The rostrum is tendentially conical and rather short (1/3 of the head), the head is broad and rounded at the apex, with a protractile mouth that lower lip is thin with a central cleft, and four barbels (circular section) that are closer to the tip of the snout than they are to the mouth. The series of longitudinal scutes are five: dorsal (1 series, 10–14 scutes), lateral (2 series, one per side, 30–42 scutes each) and ventral series (2 series, one per side, 8–11 scutes each). The dorsal fin has no spines and 36 to 48 soft rays, and the anal fin has 24 to 31 soft rays.
The Adriatic sturgeon reaches a maximum length exceeding 2 m (6.6 ft). The published maximum weight was 25 kg (55 lb), but large wild fish recently caught were evidently exceeding 40 kg (88 lb).
Range and habitat
The Adriatic sturgeon can be found in freshwater and marine environments, among them estuaries and brackish water. Historically it was to be found in the Adriatic Sea and the rivers flowing into it on either side. In 1932 its range in the sea was reported to be from Venice and Trieste to Greece and Corfu.
Pins are Wikidata “endemic to” fields. Orange dots, when present, are GBIF occurrence tiles — survey bias included.
Diet and breeding
During spring months mature fish migrate to the upper part of the rivers, then they lay eggs from April to June in deep and oxygenated waters, on gravelly substrates at a depth of 2–10 m (10–30 ft), with a current velocity of 0.8 m/s (2.6 ft/s) at least. Water turbulence is very important for the reproductive success of sturgeons, since it avoids egg stress, aggregation of the eggs, anoxia, parasites, and predators.
Adriatic sturgeons tend toward an opportunistic feeding, swallowing substrate together with prey and organic matter, among them small decaying carrions. In the rivers they mainly eat gammarids, diptera larvae and oligochaetes, sometimes small fish, that they suck up with their toothless, funnel-like mouths. Considering the present invasion in the Po and other rivers of the allochthonous Corbicula sp., probably these freshwater clams are now an important prey.
In crisis
The main threat that Adriatic sturgeons face is damming, that involves the fragmentation of the habitat and prevents trophic and spawning migrations. The only suitable remaining habitat for spawning were in the vicinity of the confluence of the River Po with some of its tributaries. During the 20th century, overfishing on adults and above all immature sturgeons was another important cause of the decline of the wild stock of A. Naccarii.
Despite it is now a protected species, illegal fishing by poachers is presently one of the main threat in the Po basin (for example,,), particularly harmful when smaller fish are taken before they have reached maturity and reproduced at least once. Illegal capture with giant lift nets placed close to the estuaries can be a big threat, as well as commercial fishing in the sea and lagoons.
CITES lists this taxon on Appendix II. Confirm the current appendix on the CITES checklist.
Adriatic sturgeon is Critically Endangered on this catalog because that is the IUCN category stored on Wikidata. Confirm the official criteria and any later count on iucnredlist.org.
Sources
Written for this catalog from the English Wikipedia article on Adriatic sturgeon, Wikidata item Q376480. Family and order context is original field-guide writing about the group, not a copied assessment of this one species. Wikipedia text is CC BY-SA. Not an IUCN assessment. Counts, when quoted, can change — confirm them on the recovery programme and on iucnredlist.org.
