Molecular studies strongly suggest that Russian Sturgeon (Acipenser gueldenstaedtii) is very closely related to Persian Sturgeon (Acipenser persicus), and it may be the case that these two taxa are conspecific. However, this is still under discussion, and currently they are treated as two separate species.

Russian Sturgeon is extremely rare in the Black Sea basin, with natural populations having been reduced by >90% over the last three generations. This is attributed to overharvesting and loss of habitat; spawning and nursery sites have been lost due to dam construction. The only, exception seems to be in the lower Rioni, where some spawning may still occur, but individuals are rare. The Caspian basin has lost 70% of spawning grounds since the 1950s, mainly due to hydroelectric power stations. Flow regulation of the Kuban has led to the loss of 140,000 ha and damming of the river Don removed 68,000 ha spawning ground (CITES 2000).

The population migrating to the Danube, where it was heavily overfished and poached, seems to have vanished in the last is considered to have become extirpated within the next 10 years. The Caspian populations are also under massive pressure from overfishing and loss of spawning habitats. Most migrating spawners are poached, and most of the remaining fish only spawn once during their lifetime. This decline is predicted to continue as illegal fishing at sea and in rivers, for caviar and meat, will soon result in the extinction of the remaining natural wild population. In the immediate future, the survival of this species depends on stocking, which has to be improved to address outbreeding depression.

The species is assessed as Critically Endangered due to a population size reduction of more than 80% over the last three generations (approximately 143 years). This is based on approximately 90% decline in global catches of the species within just 15 years, despite large levels of stocking (average global catch from 1992 to1999 was 1,531.75 tonnes, reduced to 175.37 tonnes from 2000 to 2007); a 92.5% decline in estimated spawning stock biomass in the Volga between 1961–1965 and 1998–2000; an 88% decline in the average number of spawners entering the lower Volga between the 1962–1975 average to the 1992–2002 average; and a decline in the Juvenile Production Index from the Romanian Danube.

This species is known from the Black, Caspian and Azov seas, where it once spawned in all larger tributaries. In the Black Sea, local ecomorphs that have been described as subspecies A. gueldenstaedtii colchicus (Marti 1940) or alternatively as A. persicus colchicus (Arthyukin and Zarkua 1986). This ecomorph ranges from the Danube and the rivers of northern Turkey to the Georgian rivers occurring in the rivers Enguri, Rioni, Tskhenistskali, Coruh, Yesilirmask, Kizilirmak and Sakarya as well as in the Danube. Genetically, no secure method exists to distinguish this subspecies from A. gueldenstaedtii yet. In the Rioni it is reported to be the prominent form in the catches and on the spawning grounds (Guchmanidze 2009). Recent investigations in the Rioni in 2019 and 2020 confirmed its ongoing reproduction here (Scheele, pers. comm.) while in the Sakarya River the last confirmed reproduction dates back to 2008. Only fragments of a spawning population are remaining in the Danube (last confirmed natural reproduction in 2006) with very few individuals entering the river annually.

In recent years in the Caspian Sea catchment, reproduction of A. gueldenstaedtii is described only in the Volga and Ural rivers on a regular basis. Occasionally the species spawns in other rivers in the range. Individuals originating from stocking programs are released in the northern tributaries of the Black Sea, the Caspian Sea (except Ural) and in the Sea of Azov.

Considering the long lifespan of the species, it cannot be excluded that mature, wild-born individuals from these rivers still persist in the Azov, Black or Caspian seas, but these seem to spawn irregularly or do not spawn successfully any more.

The wild, native populations of A. gueldenstaedtii have undergone a major decline, which is currently continuing. Despite many release programs, introducing millions of fingerlings annually, several populations are now on the verge of extinction and major populations have actually been lost recently. Extinction of the species (in the wild) is expected within the next decade if there is no major breakthrough in conservation efficiency.  

According to FAO fisheries statistics (FAO 2009) global catches fell from 4,250 tonnes in 1992 (first available catch data) to 67 tonnes in 2007 (last available catch data), a decline of 98% in 15 years. The average catch from 1992 to 1999 (8 years) was 1,531.75 tonnes, whereas the average catch from 2000 to 2007 (8 years) was 175.37 tonnes, a decline of 88.5%.  

Russian Sturgeon is now very rare in the Danube and has only occured as single individuals in recent years. No reproduction seems to have taken place in the last decade (Danube Sturgeon Task Force pers. comm. 2019). Romanian catch data (Danube) show that in 2002, 3,726 kg were caught; in 2003, 1,499 kg; in 2004, 440 kg; and in 2005, 37 kg, showing a 99% decline in just four years (Paraschiv et al. 2006). A juvenile production index (evidence of breeding) for the Danube (Romania) also shows a decline: catch per unit effort (CPUE) was just over 0.7 in 2000, < 0.2 in 2001, 0.3 in 2002, 0 in 2003, < 0.1 in 2004, 0.1 in 2005, 0 in 2006, < 0.05 in 2007 and 0 in 2008. (CPUE = number of Young of the Year + number of <1-year-olds caught from natural recruitment captured in an 80 m net over 6 hours (Suciu, pers. comm. 2008; Paraschiv et al. 2006, Knight et al. 2010). More recent data are unavailable due to the complete ban of fishing throughout the entire distribution area and the lack of sufficient monitoring.

So far, no genetic marker has been described to separate A. gueldenstaedtii and A. persicus with security. Haplotypes and genotypes of both species form one clade, including A. gueldenstaedtii colchicus (A. Ludwig, pers. comm.). Genetically, A. gueldenstaedtii and A. persicus are rather populations of one species than separate species. Therefore, additional scientific evidence is necessary to finally solve this question. So far the classification in two different species is maintained due to the morphological differences described.

Despite many conservation stocking programs (releasing millions of fingerlings), the populations are now almost at the verge of extinction and major populations have been lost recently (Danube). Extinction (in the wild) of this species is expected within the next decade if there is no major breakthrough.

In the Volga, 30 million fingerlings are released annually. In the northern Caspian Sea, about 80% of juveniles originate from artificial reproduction, while about 20% are believed to come from natural spawning. The stock in the Rioni is small, and now the species might only infrequently spawn here. However, due to the large levels of stocking (particularly in Russia and Iran), the exact population sizes of wild fish are unknown. In recent years, Iran stopped stocking. According to CITES (2000) Russia released 25 million fingerlings annually into the Volga in 1979–1980, 35 million in 1981–1985, 40.8 million in 1986–1990, 42 million in 1991–1995, and 28 million in 1996–1998; Iran released 300,000 fingerlings in 1994, which increased nearly every year to 960,000 in 1999. Despite this level of stocking, fisheries catches still declined.

According to FAO fisheries statistics (FAO 2009) global catches fell from 4,250 tonnes in 1992 (first available catch data) to 67 tonnes in 2007 (last available catch data), a decline of 98% in 15 years. The average catch from 1992 to 1999 (8 years) was 1,531.75 tonnes, whereas the average catch from 2000 to 2007 (8 years) was 175.37 tonnes, a decline of 88.5%.  

Data from the Caspian Sea (Khodorevskaya et al. 2009) catches were between 6,000 and 9,000 tonnes per year in the 1960s, rising to a peak of around 14,500 tonnes in the late 1970s–early 1980s, then declining to fewer than 1,000 per year from 2000 to 2008. The estimated spawning stock biomass in the Volga has also drastically declined, from 13,200 tonnes (1961–1965) and 22,200 tonnes (1966–1970), to 1,000 tonnes (1996–1997) and 1,000 tonnes (1998–2002). The average number of spawners (1,000 individuals) passing fishery zones to the spawning grounds in the lower Volga (per year) has declined by 88% from the average recorded over 1962–1975 to the average recorded over 1992–2002. Romanian catch data (Danube) shows a catch of 3,726 kg in 2002; 1,499 kg in 2003; 440 kg in 2004; and 37 kg in 2005, showing a 99% decline in just four years (Paraschiv et al. 2006). A Juvenile Production Index (evidence of breeding) for the Danube (Romania) also shows a decline: CPUE was just over 0.7 in 2000, < 0.2 in 2001, 0.3 in 2002, 0 in 2003, <0.1 in 2004, 0.1 in 2005, 0 in 2006, < 0.05 in 2007 and 0 in 2008 (CPUE = number of Young of the Year - number of <1-year-olds caught - from natural recruitment captured in one netting (Suciu, pers. comm. 2008, Paraschiv et al. 2006, Knight et al. 2010). More recent data are not available due to the complete ban of fishing throughout the entire distribution area and the lack of sufficient monitoring.

Marine habitat for this species includes shallow coastal and estuarine zones. In freshwater, it occurs in deep parts of large rivers with moderate to swift current. Russian Sturgeon spawns in strong currents (1–1.5 m/s) in large and deep rivers on stone or gravel bottom.

This species has anadromous and freshwater populations; the freshwater populations that existed in the Danube and the Volga are both now probably extinct. It has a complicated pattern of spawning migrations, which include spring and autumn runs. Individuals migrating in spring enter freshwater just before spawning; they tend to spawn in lower reaches of rivers (320–650 km in the unregulated Ural). Individuals migrating in autumn overwinter in rivers and spawn the following spring further upstream (900–1,200 km in the Ural).

Males reproduce for the first time at 8–13 years, females at 12–16 years of age. Females reproduce every 4–6 years and males every 2–3 years in April–June, when the temperature rises above 10 °C. The generation length used for the 2009 Red List assessment was 10–16 years, however this was an underestimate (based on age at first maturity). Generation length has been recalculated for this reassessment. Using the calculation Age of first reproduction + [z * (length of the reproductive period)] (IUCN Standards and Petitions Committee 2019), with z=0.6, average generation length is 47.6 years; three generations is therefore estimated as approximately 143 years for this species. Today, in the Caspian Sea, almost all the mature fish in the population are first-time spawners and are caught illegally during their first spawning event.

Larvae drift with the currents. Juveniles then move towards shallower habitats, before migrating to the sea during their first summer. They remain at sea until they reach maturity. The Russian Sturgeon feeds on a wide variety of benthic molluscs, crustaceans and small fish.

Within its large range, Russian Sturgeon faces many threats, with overexploitation and dams being the major threats. These threats have been ongoing for decades. Most spawning sites have been lost due to dam construction. The Caspian basin lost 70% of spawning grounds since the 1950s, mainly due to the construction of hydroelectric power stations; the Ural is now the only river in the basin with unregulated flow and also holds the largest global population of this species. Flow regulation of the Kuban River has led to the loss of 140,000 ha, and damming of the river Don has removed 68,000 ha of spawning ground. For example, in the middle section of the Danube, the annual catch dropped from 14,636 kg in 1983 to 1,636 kg in 1985 (a decline of just under 90%), this is believed to be due to the construction of the Iron Gate II dam which was constructed in 1984, blocking access to the upstream spawning grounds for the species (CITES 2000).

In the Caspian Sea and Sea of Azov, the illegal sturgeon catch for all species was evaluated to be 6–10 times the legal catch (CITES 2000). Bycatch is a threat to the species in both marine and freshwater habitats.

Artificial reproduction and stocking have turned out to be insufficient to stop the decline. While wild populations are lost, ex situ stocks have gained importance and there are several captive stocks of Russian Sturgeon. As these are not only kept for conservation purposes but also for ranching and aquaculture, genetic pollution is an increasing threat. Fish from different populations are moved to different locations (e.g. Caspian stocks moved to Sea of Azov) and different species are hybridised, either on purpose or accidentally, in fish farms. This genetic pollution bears a high risk that the species becomes completely lost in the wild and captive stocks, as well as wild fish originating from stocking, are impacted by hybridisation; the pure species may go extinct unnoticed.

This was a major commercial species, fished for caviar and meat, but its importance is now reduced due to its drastic decline and the resulting catch prohibitions. The species is reared in aquaculture, either as a pure species or as hybrids.

This species is fully protected in all range countries where it occurs or occurred, but the fisheries ban is insufficiently enforced.

As the major threats to Russian Sturgeon—illegal fishing and dams—have not been addressed sufficiently, artificial reproduction and stocking are the only means to prevent the species from full extinction in the wild. Priority should be given to combat illegal harvest and implement habitat restoration measures to improve natural reproduction, while releases based on genetic plans are recommended to be continued to maintain the species.

Fish lifts and artificial spawning grounds have been constructed in parts of the Caspian and Black Sea region only (CITES 2000). The effectiveness of these varies widely between sites.

This species is listed by the Bern Convention, the EU Fauna-Flora-Habitat Directive and the CITES Appendix II, and it is included in the Pan European Action Plan. Gene bank development for of live individuals and as well as cryopreservation is are ongoing in several range countries.