|Scientific Name:||Acipenser naccarii|
|Species Authority:||Bonaparte, 1836|
|Taxonomic Notes:||Based on mitochondrial DNA analysis no molecular marker has been found to differentiate between this species and Acipenser gueldenstaedtii. Research is still ongoing.|
|Red List Category & Criteria:||Critically Endangered A2bcde; B2ab(i,ii,iii,iv,v) ver 3.1|
|Assessor(s):||Bronzi, P., Congiu, L., Rossi, R., Zerunian, S. & Arlati , G.|
|Reviewer(s):||Smith, K., Pourkazemi, M. & Suciu, R.|
In Italy the wild population is most likely extinct as the species almost totally depends upon stocking and there is no evidence of spawning from stocked or wild individuals (the last known natural spawning probably occurred early 1980s). The few animals occasionally captured in the wild are probably from aquaculture origin and were probably released in the last few years. However, there is a slim chance that wild individuals still exist. The population on the eastern Adriatic are also probably extinct in the wild, there is no evidence of natural reproduction since 1990 in Albania. However, there also is a slim chance that wild individuals still exist there.
The species is assessed as Critically Endangered (Possibly Extinct) under criterion A2, on the basis of an estimated population decline of greater than 80% (possibly 100%) in the past three generations (60 years). This population decline is based on a decline in the extent of occurrence (EOO), area of occupancy (AOO), and catch data, and was caused by over-harvesting (both legal and illegal), loss of access to spawning grounds (dams), and pollution (industrial and agricultural).
The remaining potential suitable spawning grounds are restricted to very few areas in the Po River with an AOO of less than 10 km² (one location). There may still be some wild individuals left, but it is unknown how many there may be; potentially there are less than 250. Without continuous re-stocking the survival of this species is doubtful as continued successful reproduction in the wild can no longer be confirmed.
For the EU 27 region, the species is also assessed as Critically Endangered (Possibly Extinct) (CR(PE) A2bcde;B2ab(i,ii,iii,iv,v)).
|Range Description:||This sturgeon was present exclusively in the southern part of Europe. Apparently it is restricted to the Adriatic Sea area, and in particular to the fresh waters of the northern part of Italy and the eastern coasts of the Adriatic Sea.
Historically the species was present in the sea from Venice and Trieste, to Greece and Corfù (Berg 1932); and in the Venetian lagoons during fall (Faber 1883). It was recorded in the rivers Adige, Brenta, Bacchiglione, Livenza, Piave, Tagliamento, and Po (and its affluents); once it was recorded up to Turin (Festa 1892); at Carignano and Carmagnola (Delmastro 1982); and in the Po delta (Tortonese 1989, Paccagnella 1948, D'Ancona 1924, Pavesi 1907); in the Ticino and Adda rivers (Bernini and Nardi 1989, 1990); along the Albanian coasts (Filipini et al. 1956); and Croatia (Mrakovic et al. 1995), Bosnia-Herzegovina and Montenegro (Lake Skadar). It was last recorded from Albania in 1997 in the Buna River (Ludwig et al. 2003). There is evidence that the species was previously found in Greece (Economidis 1973) but it is no longer known there. It was reintroduced to Greece (Pascos et al. 2003) but there is no evidence that it has established a viable population. There have been conflicting opinions regarding its presence in Spain.
At present, as a consequence of a recovery plan carried out by several public institutions from 1990 to 2007, specimens have been recorded in the Po River and its inflow rivers (Ticino, Adda, Oglio, Mincio), and in the rivers Adige, Livenza, Piave, Tagliamento. The Isola Serafini Dam on the middle of the Po River, prevents the migratory movements of the downstream populations into the upstream part of the river. There is no evidence available for natural spawning of wild or released individuals.
Possibly extinct:Albania; Croatia; Greece; Italy; Montenegro; Serbia (Serbia)
|Range Map:||Click here to open the map viewer and explore range.|
Artificial reproduction in fish farms has been effective and successful since 1988 (Arlati et al. 1988), and the species is continuously restocked in Italy. However, there is no evidence to confirm successful reproduction in the wild. The presence of natural populations in Italy cannot be excluded completely because of some sporadic catches of individuals of possible wild origin. Spawning has not been recorded at suspected spawning grounds over the past 15 years. A land-locked population seems to be present in the river Ticino but it remains unclear whether the occasionally caught individuals originate from escapees or stockings.
A genetic comparison between Italian and Albanian samples collected some decades ago showed a high level of diversification and suggested that the different populations should be considered as distinct conservation units (Ludwig et al. 2003).
The species was reintroduced to Greece (Pascos et al. 2003), but there is no evidence that it has established a viable population. It is considered as regionally extinct in Croatia, Albania and Montenegro.
Of approximately 2,000 specimens of A. naccarii fished in the Po River and sold at the fish market between 1981 and 1988, more than 80% of the specimens weighed less than 3.5 kg, having been taken before the reproductive phase (Rossi et al. 1991).
|Habitat and Ecology:||The Adriatic Sturgeon lives in large rivers where, in the past, reproduction occurred from May to July. It is a long-lived, anadromous species, living mainly in the rivers. It spawns in freshwater after a marine period of growth during which it remains near the shore (at the mouths of the rivers) at a depth of 10–40 m. The upstream migration into Italian rivers occurs during the first months of the year (Paccagnella 1948, D'Ancona 1924). It occurs over sandy or muddy bottoms. The only remaining suitable spawning areas for this species are at the confluence between the Po River and its tributaries (Adda, Ticino etc).|
|Use and Trade:||Pure A. nacarii are not traded much; it is used more to produce hybrids with other sturgeon species, which are traded. Subsistence catches of this species for food is illegal.|
|Major Threat(s):||Overfishing (both legal and illegal), and in particular of pre-reproductive sized fish, threatens this species. It is also threatened by the creation of barriers to its migratory routes, which reduce its reproductive success; and fragmentation of populations, particularly by dams for hydropower on the Po River (Isola Serafini's Dam, Piacenza). Water pollution, the Allee effect, and competition for habitats with allochthonous species (Silurus glanis) also threaten the future survival of this sturgeon.|
The species A. naccarii is listed in Annex 2 of the Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora of community interest whose conservation requires the designation of special areas of conservation. This species was also listed on CITES Appendix II in 1998.
Together with other sturgeon species that once were present in Italy (A. sturio and Huso huso), the capture of the species is forbidden by law in the regions of the Padana valley, Lombardia, Emilia Romagna and Veneto.
Artificial reproduction in fish farm (ex-situ) is effective and has been successful since 1988, from an original population caught from the wild in the 1970s and from F1, and the species is continuously restocked in Italy. However, there is no evidence to confirm continuing reproduction in the wild.
A recovery plan for this species has been carried out by several public administrations since the early 1990s, with scientific research and restocking actions of about a total of half millions of specimens of different size reintroduced in the public waters (rivers Adda, Oglio, Piave, Po). The last part of the plan was supported also by a Life project.
A project for a fish passage allowing to the fish to overcome the Isola Serafini's dam is under evaluation by the public authority. This project was proposed in occasion of the building of a new and bigger navigation lock close by the old one on the Po river, in the Province of Piacenza.
|Citation:||Bronzi, P., Congiu, L., Rossi, R., Zerunian, S. & Arlati , G. 2013. Acipenser naccarii. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 03 August 2015.|
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