The Sturgeon
THE PROTAGONIST OF CAVIAR
The genetic secret of sturgeon
LIVING FOSSILS
On the basis of their chromosome complement, sturgeon can be divided into two broad groups: diploids and tetraploids. A fundamental genetic distinction that reveals a great deal about the extraordinary evolution of these most ancient of fish.
But what does this actually mean?
Sturgeon represent a particularly fascinating case, as many species are naturally characterised by polyploidy, meaning that they possess a higher than normal number of chromosomes. This genetic peculiarity is one of the distinguishing traits of their long evolutionary history.
From an evolutionary standpoint, sturgeon are considered true “living fossils”. According to a study published in the scientific journal Nature Ecology & Evolution, their genomic diversification dates back some 345 million years. Despite the passing of geological eras, their outward appearance has remained remarkably close to the original, as has much of their genetic heritage.
To investigate this extraordinary evolutionary stability, geneticists analysed the DNA and proteins of the sterlet sturgeon Acipenser ruthenus. The results showed that the evolution of its proteins has proceeded with exceptional slowness, at a rate comparable to that of such ancient species as sharks and coelacanths, present in the oceans for over 300 million years.
The genetic analysis further revealed that the sterlet sturgeon underwent a complete genome duplication around 180 million years ago. For this reason it is not considered diploid but tetraploid: it possesses four copies of its chromosomes instead of the two normally found in most animal species.
A characteristic that makes sturgeon not only protagonists of fine gastronomy, but also authentic living treasures of the planet’s evolutionary history.
Sturgeon: origin and characteristics
HABITAT AND CHARACTERISTICS
Sturgeon are often described as “prehistoric fish”, as their evolutionary origin dates back some 200–250 million years. They have a largely cartilaginous skeleton, an elongated, robust body and five longitudinal rows of bony scutes, particularly evident in young specimens and progressively less pronounced with age. The body surface is also covered with small ganoid scales.
The skull is characterised by bony plates arranged in a mosaic and by a rostrum, whose shape and length vary from species to species. The mouth, set on the underside, is protrusible and toothless in adult specimens, adapted to feeding on the riverbed.
Sturgeon show a marked predisposition to hybridization, a phenomenon observed in the wild between species sharing the same habitats and breeding periods. Growth is slow and sexual maturity late: it is generally reached at around 8 years in the Siberian sturgeon, between 10 and 12 years in the white and Danube sturgeon, and at around 18-20 years in the beluga sturgeon.
Sturgeon are found in the cold and temperate waters of the northern hemisphere. Most species are anadromous: they live mainly in a marine environment and ascend rivers to reproduce in fresh water.
Their life cycle unfolds between coastal waters, where most of their growth takes place, and river environments, reached by migrations that can be very long, in order to lay their eggs on gravel or sandy substrates. Some species, such as the Siberian sturgeon Acipenser baerii, are instead exclusively freshwater fish.
There are also so-called “landlocked” populations, isolated upstream of natural or artificial barriers, which have adapted to live and reproduce entirely in fresh water. Such is the case of the white sturgeon Acipenser transmontanus, a species that generally leads a solitary life, except during the winter and breeding periods, when it gathers in small groups on the riverbed.
Sturgeon feed mainly on benthic organisms such as worms, small crustaceans and molluscs, which they locate thanks to their sensory barbels and draw in through their distinctive protrusible mouth. The beluga sturgeon Huso huso may also include small fish in its diet.
A prehistoric giant to be protected
THE STURGEON
Considered a true “living fossil”, the sturgeon is one of the most ancient fish species on the planet. Present on Earth for over 250 million years, it has crossed geological eras with its original appearance almost unchanged, making it an extraordinary living testimony to prehistory.
Celebrated for its prized meat and above all for its precious eggs — the renowned caviar — the sturgeon was for decades the victim of intensive, indiscriminate fishing. Between the 1980s and 1990s, growing worldwide demand caused a drastic collapse in wild populations, bringing this species to one of the highest risks of extinction in the world. Faced with an increasingly critical situation, the international community heeded the alarm raised by biologists and environmentalists.
Since 1998 the sturgeon has been officially listed among the species protected by the CITES Convention
(the Washington Convention on International Trade in Endangered Species of Wild Fauna and Flora).
Fishing quotas were initially introduced by species and by country; subsequently, from 2009, any form of fishing of wild sturgeon was prohibited. Until that time the market had been supplied almost exclusively by caviar from the wild sturgeon of the Caspian Sea. In order to preserve the species without giving up the production of caviar, sturgeon farms then spread rapidly throughout the world.
Authenticity, protection and awareness
TRACEABILITY AND CERTIFIED QUALITY
To ensure the safeguarding of the species and the transparency of the market, CITES has established an international register of companies authorised to produce and package caviar. These businesses must comply with strict control and traceability protocols, including the obligation to apply non-reusable labels to the primary and secondary containers of the product.
Every package must bear a CITES identification code containing precise information on the sturgeon species, on the origin of the product (wild or farmed), on the establishment code, on the country of provenance, on the year of production and on the batch or import certificate. A system that is essential to guaranteeing authenticity, safety and legality along the entire supply chain, from the birth of the fingerling to the sale of the caviar.
Despite strict international regulations, poaching and the illegal caviar trade unfortunately continue to represent a real threat to the survival of the sturgeon. On the black market or through unauthorised channels, it is still possible to come across supposed “wild caviar” sold under the counter at seemingly attractive prices.
Behind offers that are too good to be true, however, there often lie products of poor quality or even counterfeits: caviar that is excessively salty owing to poor storage, eggs from other fish species such as lumpfish, or imitations made from coloured potato paste.
Particular care should also be taken with purchases made while travelling abroad, especially in Russia or in the countries of Eastern Europe, where caviar is often offered as a gastronomic souvenir. Beyond the need to maintain the cold chain correctly during transport, many are unaware that the regulations allow the import of a maximum of only 125 grams of caviar per person. For larger quantities, a specific CITES import permit must be obtained.
For this reason it is essential to rely exclusively on reputable, qualified retailers, able to guarantee the certified provenance of the product and the transparency of the entire production chain. Being informed is essential, for consumers and industry operators alike: possessing or trading caviar without the correct CITES documentation carries very severe penalties.
Italian law provides, for anyone trading in, purchasing, importing or exporting sturgeon eggs without adequate certification, penalties that may extend to imprisonment from six months to one year or fines of between 20,000 and 200,000 euro (Art. 2, Law 150/92).
Behind every package of authentic caviar there lies not only a luxury product, but also a delicate balance between gastronomic tradition, sustainability and the protection of one of the most ancient and fascinating creatures on our planet.
