Sturgeons belong to the order Acipenseriformes, which includes two families Acipenseridae (sturgeon) and Polyodontidae (paddlefish). Most of the 27 Acipenseriformes species are extremely threatened, with 25 species being included in the IUCN Red List of Threatened Species, of which 17 are classified as endangered or critically endangered.
The high economic value of sturgeon (products), mainly of caviar, along with the failure to implement sustainable fisheries management, and the loss of spawning grounds, have resulted in population declines over the last decades. A large portion of the global caviar trade is thought to be illegal, sometimes even believed to prevail over legal trade by several times. For example police and customs services of EU Member States seized over 12 tonnes of illegal caviar in the EU between 2000 and 2005 [1].
On the international level, in response to the dramatic sturgeon population decline and with the aim of ensuring that trade of sturgeon products is sustainable and not threatening the survival of the species, all species of sturgeon and paddlefish have been listed in the Appendices of CITES [2] since 1998. Two species – the Common or Baltic Sturgeon Acipenser sturio and the Shortnose Sturgeon Acipenser brevirostrum – are listed in Appendix I of the Convention, prohibiting any international commercial trade. All other species are listed in Appendix II, whereby international trade is regulated by governments through a system of permits.
The European Union, as the world’s largest importer of caviar, has taken various measures to combat illegal caviar trade, and adopted in 2006 a regulation [3] fully implementing the universal labelling system for caviar agreed upon under CITES. In the attempt to significantly strengthen control and enforcement, the regulation requires that all caviar containers, regardless of size and no matter whether the caviar is imported, repackaged or to be exported, bear a specific label specifying the source of the caviar, the year of harvest and certifying that it is legally harvested, in line with CITES Resolution Conf 12.7. Moreover, all re-packaging plants for caviar in the EU have to be licensed and registered.
However to enforce the regulation of legal trade and prevention of illegal trade, independent control technologies and the development of a standardized identification system for parts and derivates of Acipenseriformes are urgently required [4]. Such a system should be capable of:
- Identification at the species-level of Acipenseriformes products including caviar;
- Population identification;
- Source identification (wild versus aquaculture);
- Age determination of caviar because strict timeframes govern its international trade.
At the International Sturgeon Enforcement Workshop in 2006, which had been organised by the European Commission, DNA technology was identified as highly valuable in support of points 1 to 3. Most sturgeon products can nowadays readily be identified to the species level by analysis of the mitochondrial cytochrome b gene. However there are the following closely related species that are not identifiable using this method: Russian (A. gueldenstaedtii) - Persian (A. persicus) - Siberian (A. baerii) - Adriatic (A. naccarii) sturgeon, Green Japanese (Acipenser medirostris) – Sakhalin (Acipenser mikadoi) sturgeon, and three species of sturgeons within the genus Scaphirhynchus (Scaphirhynchus albu - Scaphirhynchus plathorhynchu - Scaphirhynchus suttkusi). Reasons for the failure of differentiation by cytochrome b analysis include biogeographic history and/or hybridization among species either in nature or due to hatchery practices and release [5], stressing the importance to move towards an understanding about population structure and dynamics. This study aimed to introduce Single Nucleotide Polymorphisms (SNPs) in support of a standardized identification system as defined above. As a first step, on an inter-species level, it focused on the development of SNPs for species differentiation between Russian (A. gueldenstaedtii), Persian (A. persicus), Siberian (A. baerii) and Adriatic (A. naccarii) sturgeon. The rationale for the project was to enable the application of DNA markers to the regulate the trade in caviar of wild and farmed origin and to support the management of wild and hatchery stocks of sturgeon in Caspian Sea range states.
[1] European Commission IP⁄06⁄611, 15⁄05⁄2006 (See "Documents" section).
[2] CITES: Convention on International Trade in Endangered Species of Wild Fauna and Flora.
[3] COMMISSION REGULATION (EC) No 865/2006 of 4 May 2006 laying down detailed rules concerning the implementation of Council Regulation (EC) No 338/97 on the protection of species of wild fauna and flora by regulating trade therein. (see "Documents" section).
[4] Proceedings of the International Sturgeon Enforcement Workshop to Combat Illegal Trade in Caviar (27-29 June 2006; Brussels, Belgium; - See "Documents" section).
[5] Ludwig, A. (2008) Identification of acipenseriformes species in trade. Journal of Applied Ichthyology, 24 (SUPPL. 1), pp. 2-19.