The management and protection of Ukrainian sturgeons during wartime

1 Introduction

Sturgeons (family Acipenseridae) are among the oldest fish species (1). These bone-cartilaginous fish (Chondrostei) have survived for over 200 million years, including through at least two mass extinctions (2, 3). According to the World Wide Fund for Nature (WWF) and the Food and Agriculture Organization of the United Nations (FAO), six species of sturgeon inhabit or inhabited until the end of the last century the Ukrainian waters (4–6). Conserving them is a key task in Ukraine today to prevent their extinction (7–9). Ukraine is located in the eastern part of Europe, bordering the Black Sea and the Sea of Azov. It is one of the few remaining places in Europe where sturgeons spawn and migrate along major rivers entering both seas, which also represent important feeding areas (10). Notably, the Russian sturgeon (Acipenser gueldenstaedtii), beluga (Huso huso), stellate sturgeon (Acipenser stellatus) and sterlet (Acipenser ruthenus) still spawn in the Lower Danube (10, 11). Sterlet have formed isolated populations in the upper reaches of the Dniester and Desna rivers, which are important areas for conserving these endangered species (12). The Atlantic sturgeon (Acipenser sturio) and the ship sturgeon (Acipenser nudiventris) were formerly present in Ukrainian waters but have been extinct for decades (13).

The migration routes of sturgeon in the river systems and territorial waters of Ukraine are a key element of their life cycle for both anadromous (sea to river) and potamodromous (fresh water only) species. Spawning takes place in the upper reaches of rivers, while feeding sites are located in both rivers and marine waters. Until the mid-20th century, five species of anadromous sturgeon were spawning in the basins of the Danube, Dnipro, Don, Southern Bug and Dniester rivers, as well as in a number of rivers in the Azov region (Figure 1). Some populations covered distances of up to 2,000 km to reach their spawning grounds.

The diverse migration patterns of these species ensured genetic diversity and population resilience, but anthropogenic interventions have reduced these patterns by 50–90%, turning sturgeons into vulnerable species listed in the Red Data Book of Ukraine (14, 15). Modern research, particularly genetic and telemetry studies, confirms the existence of these populations. However, restoring river connectivity is essential if these sturgeons are to be able to complete their life cycle (16).

Sturgeon species worldwide are now on the verge of extinction due to poaching, overfishing, dam construction, environmental damage and climate change (1, 3, 5, 7–10, 12, 13, 15, 17). The regulation of rivers in the 1930s–1950s disrupted sturgeon spawning migration routes in the Azov–Black Sea region (14). As a compensatory measure, large-scale ranching programs were established to release juveniles into the lower sections of rivers. However, excessive fishing in the 1980s and 1990s led to a catastrophic decline in Ukrainian sturgeon stocks. Today, wild populations are on the verge of extinction, having declined by 99% over the past 25 years (13, 18). Currently, sturgeons of wild origin in the northwestern part of the Black Sea are primarily of Danube origin. In the eastern Black Sea, the Rioni River in Georgia is the main remaining sturgeon spawning river (19). In the southwestern part of the Black Sea, the Sakarya River in Turkey was one of the few rivers where sturgeon populations were still reproducing until the early 2010s, when a series of dams destroyed the remaining habitats and prevented access to the middle section of the river (Figure 1) (10).

Since gaining independence in 1991, Ukraine has recognized sturgeons as a valuable resource and developed an industry around them. Aquaculture, which includes hatchery production for conservation as well as subsequent stocking and restocking, has significant potential to replenish sturgeon populations as part of restoration programs (4, 5). However, Russia’s aggression against Ukraine since 2022 has jeopardized the conservation of wild populations and the gradual growth of sturgeon aquaculture. Due to the ongoing war between Russia and Ukraine, artificial breeding and restocking are being carried out only to a very limited extent. Furthermore, monitoring wild populations in Ukrainian territorial waters is difficult under the current conditions. Based on this review, we present the current situation and address the recommendation for the future conservation of Ukrainian sturgeon populations are provided for the future.

This review addresses the historical development of sturgeon populations, the current situation under wartime conditions, and attempts to provide an outlook for the management of Ukrainian sturgeon stocks in the postwar period. Naturally, this comes with certain limitations. Due to the political upheavals of the past, the available data is fragmentary and was collected using different methods, making comparisons difficult. Unfortunately, the effects of the ongoing war also cannot yet be definitively assessed. This further complicates the formulation of recommendations for the postwar period. Nevertheless, despite these limitations, we are attempting to assess the situation of the various sturgeon species in Ukraine and to provide recommendations for current and future management.

2 Historical assessment of the sturgeon population

During the Soviet period (1920–1991), the assessment of sturgeon populations in Ukraine’s territorial waters was integrated into the state fishery management system. This was coordinated by the Interdepartmental Ichthyologic Commission (established in 1949) and the Scientific Advisory Council on Sturgeons (established in 1972). Scientific assessments were primarily based on scientific data collected by fishery research institutes and incorporated commercial catch data for the Azov–Black Sea basin.

Key assessment tools included annual trawl surveys, conducted twice a year in spring and autumn. Bottom trawls of up to 25 meters along the seabed were used. During these surveys, which covered the entire open sea area via station grids, the number of sturgeon species caught per unit effort (CPUE) was recorded to estimate relative abundance and assess population structure. Another important source of scientific data was coastal observation points, which operated permanently using standard sets of nets to collect data on migrating, spawning sturgeon populations. Combining the direct (area-based) abundance estimation method with the bio-statistical method (based on the analysis of biological [size, age, sex, fecundity] and statistical [fishing intensity, by-catch] data) provided a comprehensive tool for assessing and forecasting sturgeon stocks. Annual statistics on commercial catches were collected and integrated for population abundance prediction (20, 21).

Following the establishment of fish hatcheries between the 1950s and 1980s, monitoring programs increasingly focused on hatchery-based reproduction and stocking outcomes. One key metric was the returning rate of adult fish at national level from restocking in territorial waters, which ranged from 0.01% to 1.8%.

Since the post-Soviet period began in 1992, the assessment and forecasting of the status of the sturgeon population has been carried out by the Institute of Fisheries and Marine Ecology of Ukraine (until 2021), the Southern Research Institute of Marine Fisheries and Oceanography (until 2013), and the Odessa Centre of the Southern Research Institute of Fisheries and Oceanography (until 2021). While research on sturgeons in the Sea of Azov remained more or less systematic and regular, research in the Black Sea became much more difficult due to financial constraints when organizing large-scale studies. Regular trawl surveys ceased and data on Black Sea sturgeon populations became fragmentary (22, 23).

In the Lower Danube, the Institute of Marine Biology of the National Academy of Sciences of Ukraine carries out sturgeon research within the framework of the research programs ‘Program of research catches for studying the state of aquatic bioresources of the lower Danube basin’ and ‘Program of research catches for studying the ichthyofauna and benthic ichthyocenoses of the Odessa Bay and the surrounding waters of the Black Sea’, as well as international projects (24, 25). To collect and analyze primary material in the Lower Danube, bycatch of adult sturgeon is recorded using various floating nets (mesh size 18–55 mm) throughout the year. During the post-spawning period, bycatch of young sturgeon is recorded using a 6.5 mm bottom trawl net in various parts of the Danube Delta.

To study the migration routes and behavioral characteristics of sturgeons in the river, acoustic telemetry using stationary receiver stations is currently being used effectively (12).

Collecting genetic samples of fish from the region at the Institute of Marine Biology of the National Academy of Sciences of Ukraine will enable future assessment of the genetic structure of sturgeon.

3 Historical migration routes of sturgeons within the river systems and territorial waters of Ukraine

Sturgeons use the Azov and Black Seas as feeding grounds, foraging in shallow coastal waters before migrating into rivers to spawn after reaching sexual maturity. In the Black Sea basin, about 40% of the coastline is accounted for by Ukraine’s territorial waters. The extensive shallow coastal waters therefore play a substantial role in providing feeding grounds for sturgeons throughout the Black Sea. Traditionally, the spawning migrations focused on large rivers such as the Danube, Dnipro and Don, where historical spawning grounds were located in the rapids (26). In the Danube basin, Ukraine controls significant estuarine sections, such as the North Arm of the Danube Delta (an area of about 5,800 km²). The most extensive historical sturgeon migration reached Bavaria from the Black Sea, and several other spawning sites were located in the Middle and Lower Danube (27).

In the Danube basin, spawning migration of sturgeons occurs in spring (March–May), as well as in autumn for early spring spawning. These migrations reached densities of up to 10,000 individuals per km² in the lower reaches (28). However, the construction of the Iron Gates 1 (1972) and 2 (1984) dams on the river at rkm 865 interrupted the spawning migration, blocking about 65% of the route. This has led to a significant reduction in populations. Nevertheless, there are still spawning grounds on the Lower Danube where beluga (H. huso), stellate sturgeon (A, stellatus), sterlet (A. ruthenus) and Russian sturgeon (A. gueldenstaedtii) spawning has been confirmed (10, 11, 29).

The Dnieper River system (2,201 km long) was also an important site for historical sturgeon migration from the Black Sea. Sturgeons migrated here to Kyiv and even further upstream to Belarus (around 2,000 km) (23, 30). The main sturgeon spawning grounds were located in the lower reaches of the Dnieper River. Until the 1950s, Russian and ship sturgeon performed anadromous migrations in spring (April–June), spawning in the rapids near Zaporizhzhia. Densities of 5–15 thousand individuals per year were reached in the lower reaches (31). The sterlet, a potamodromous species, migrated in tributaries such as the Desna and the Pripyat for local spawning and inhabited mainly the middle reaches of the Dnieper above the city of Kyiv (15).

In the Dnieper basin, the construction of cascade dams blocked up to 80% of the spawning grounds (32). The first Dniepro HES dam was built near Zaporizhzhia between 1927 and 1932. This resulted in the loss of the Dnieper rapids, which were important for spawning. The next dams to be built were the Kakhovka dam (1950–1956) above the city of Kherson and the Kremenchuk dam (1954–1960), followed by the Dniprodzerzhynsk dam (1956–1964), the Kyiv dam (1960–1968) and the Kaniv dam (1963–1975) (4, 12, 23, 30). After the completion of the Kakhovka dam, the historical spawning grounds were almost completely lost. The area suitable for sturgeon spawning shrank to 75–90 km, and significant artificial changes to the Dnieper basin’s hydrological regime over time made even this area unsuitable for effective sturgeon spawning (33). Consequently, all beluga spawning grounds, around 80% of Russian sturgeon spawning grounds, and over 90% of stellate sturgeon spawning grounds were lost (34). The current situation regarding the presence and reproduction of sturgeon populations in the Dnieper River remains unclear due to ongoing military operations in the area (35).

In the Dniester River basin, sturgeons migrated to spawn in the Dniester’s tributaries and floodplains (36, 37), even utilising the upstream reaches near Mohyliv-Podilskyi. Following the regulation of the Dniester’s main channel by the Dubosarska dam in 1954, the most effective spawning grounds were found in the Lower Dniester (12). However, by the end of the 1990s, these sites had effectively been eliminated due to the overgrowth of the spawning grounds with aquatic vegetation and Dreissena mussels. Small spawning grounds remained in the lower reaches of the river, but the conditions for spawning there were suboptimal (38). Consequently, sturgeon lost their commercial value in the Dniester.

In the Southern Bug basin, migrations were local; sturgeon spawned near Voznesensk, 100–200 km from the sea, until the 1950s. Again, the construction of a dam on the river in the 1970s reduced the accessible section of the river to 30 km (39). Currently, there is no information about sturgeon spawning migrations to the Bug River.

As a result of the regulatory works, access to historic spawning sites in the Black Sea tributaries of Ukraine has been eliminated (Table 1).

Table 1. Chronology of dam construction on sturgeon migration routes.

*The dam was decommissioned in 1999, and instead the Oleksandrivska Dam (No. 13) began operating on the Southern Bug River.

According to the latest data from WWF Ukraine, some spawning sites on the major rivers of the Black Sea basin remain accessible despite the construction of dams (33). The available migration corridors comprise approximately 863 km on the Danube, 355 km on the Dniester and 93 km on the Dnieper (33).

The Don and Kuban rivers, which enter the Sea of Azov, were also an important habitat for beluga, Russian sturgeon and stellate sturgeon. While stellate sturgeon mainly spawned in the Kuban, Russian sturgeon and beluga almost exclusively reproduced in the Don River. Sterlet inhabited both rivers. Until the 1960s, belugas migrated upstream in the Don for distances of up to 1,000 km, but the construction of dams on both rivers between 1951 and 1974 blocked their migration routes, resulting in a catastrophic decline in natural sturgeon populations. Construction of the dams on the Don River began with the Tsimlyanska dam, which was commissioned in 1952 (around 300 km from the river’s mouth). By 1970, three more low-head dams had been built on the Don, reducing the accessibility of the spawning grounds for sturgeons to zero. On the Kuban River, the transformation of the water regime began with the commissioning of the Fedorovska dam in the 1960s (140 km from the river’s mouth), followed by the creation of the Krasnodar Reservoir (40, 41).

The construction of dams on the Don and Kuban rivers from 1951 to 1974 led to the catastrophic deterioration of sturgeon spawning conditions. Around 80% of Russian sturgeon spawning grounds, over 90% of stellate sturgeon spawning grounds and all major beluga spawning grounds were lost. Following the construction of the dams, migration routes were reduced by 70%, with migrations now limited to estuarine areas of 10–50 km. Telemetry data records only the return of 5–10% of released juveniles (15, 16).

3.1 The status of sturgeon populations in the Sea of Azov basin

After the Caspian Sea, the Sea of Azov was the region with the second-largest sturgeon catch worldwide in the last century (4, 14). Throughout the history of exploiting sturgeon stocks in the Azov Sea, the fishery has relied on three species: Russian sturgeon, stellate sturgeon and beluga. The sterlet, a freshwater species, was less commercially important and was mainly used as a food source by local communities.

Statistical data on sturgeon catches in the Azov–Black Sea basin dates back to the mid-19th century. The highest catches were recorded during this period in the Azov Sea basin. Up to 7,500 tons of sturgeon were harvested in the waters of the Don and its estuary, and up to 5,000 tons in the waters of the Kuban River and delta. The total annual sturgeon catches in the Azov basin reached 16,000 tonnes (30). A progressive decline in fisheries then began as a result of overfishing and the deterioration of natural spawning grounds. By 1913, catches had fallen 10–12-fold, dropping to approximately 10% of previous records. By the mid-1930s, the annual catch of Azov sturgeon reached 6,500–7,300 tonnes. During the Second World War, catches of sturgeon in the Sea of Azov decreased again, reaching 1,100–1,200 tons per year. By 1952–1953, the annual sturgeon catch had fallen to 3.2–3.3 thousand tons (42).

Alongside restrictions on fishing timing, areas and methods introduced in the 1950s and 1960s, and the development of commercial reproduction methods for all sturgeon species, populations steadily increased by the end of the 1960s (4, 30).

Until 1975, the most numerous species in the Azov Sea basin was the stellate sturgeon, comprising up to 80% of the total biomass, while Russian sturgeon accounted for 17% and beluga for about 3%. Subsequently, the species composition reversed, and from the 1980s onwards, Russian sturgeon became the dominant species in the Sea of Azov due to massive releases from hatcheries (43, 44). In 1988, population assessments in the Sea of Azov resulted in an estimated of 17.6 million sturgeons, comprising 14.1 million. Russian sturgeon, 3.4 million stellate sturgeon and 54,000 belugas (Figure 2), predominantly originating from hatchery releases.

Following the collapse of the USSR in the early 1990s, poaching escalated significantly. According to joint Ukrainian-Russian research data, the total abundance of sturgeon was estimated to be 16.1 million individuals in 1992, of which 4.47 million were adults/sexually mature. By 1996, this figure had fallen to 6.1 million, and by 1999 it had dropped further to 4.45 million, of which only 419 thousand were mature fish (20, 45). Different estimates suggest that, in the late 1990s, the illegal catch of all sturgeon species in the Black Sea and Azov basins was 6–10 times higher than the legal fishery (46, 47).

The efficiency of the artificial reproduction of sturgeon in the Sea of Azov basin increased so much that, between 1956 and 1997, sturgeon farms raised 450 million stellate sturgeon and 412 million Russian sturgeon. From 1980 to 1985 alone, these farms produced almost 40 million young sturgeon annually for release into the wild. Since the early 1970s, over 90% of the sturgeon population has consisted of hatchery fish and mature fish have made up around 95% of the catch (48). By 1986, the proportion of fish originating from hatcheries in the sturgeon and stellate sturgeon populations was estimated at 90–95% and 80–85%, respectively (49). However, the scale of beluga reproduction was insufficient to maintain the species’ commercial importance. Beluga fishing was banned in 1985, and the species was listed in the Red Data Book of Ukraine in 1994 (15).

In the 1990s, massive and organized illegal fishing, as a result of insufficient fishery control, had a devastating impact on the sturgeon stocks that were maintained through releases. From 1994 to 2000, the average annual scale of illegal sturgeon fishing in the Sea of Azov was estimated to be at least ten times higher than the official catch (30). During this period, the official catch decreased from 1,200 to 200 tonnes (see Figure 3).

According to data from the Institute of Fisheries and Marine Ecology, the stellate sturgeon population was estimated to comprise 0.6 million individuals of all age classes by the end of 2000, while the Russian sturgeon population was estimated to comprise 3.3 million individuals. The 2022 IUCN re-assessment found that the Russian sturgeon remains the most abundant species of sturgeon in the Sea of Azov. The stellate sturgeon is regularly observed, albeit in declining numbers (15). As of 2021, the Russian sturgeon population in the Sea of Azov was estimated to be at least 700,000, while the stellate sturgeon population was estimated to be below 100,000. The majority of these fish now originate from fish farms on the Don and Kuban rivers (14, 30). Despite stocking of these species in its tributaries, there have been no recent records of beluga in the Sea of Azov (50). Since Ukraine lost access to the Sea of Azov due to Russia’s occupation of Ukrainian territories adjacent to the sea in 2022, it has become impossible for Ukrainian scientists to conduct population assessments.

3.2 Status of sturgeon populations in the Black Sea basin

The status of sturgeon stocks in the Black Sea during the 20th century was similar to that in the Sea of Azov. The Lower Danube and the north-western part of the Black Sea are the main feeding areas for sturgeons in the Black Sea. Up to 90% of the Black Sea sturgeon populations were found in the northwestern part, primarily in Ukrainian water bodies (4, 23). As in the Sea of Azov, the most common species are the Russian sturgeon and the stellate sturgeon.

The only natural spawning in the north-western Black Sea is taking place in the Danube (12, 23). According to the results of bottom trawl (51, 52) conducted in February–March on the wintering grounds between 1981 and 2002, the number of Russian sturgeon increased from 1981 to 1993 but then began to decline. Conversely, the calculated number of stellate sturgeon remained relatively stable at approximately 1.5 million individuals until 1994 (Figure 4).

By the late 1990s and early 2000s, these numbers had gradually declined to fewer than 0.5 million individuals. The number of juvenile belugas fell from around 400,000 to 100,000, remaining relatively stable at between 100,000 and 150,000 until 2002. However, the total number of sturgeon has continuously decreased since 1994, reaching 2 million in 1998 and 1.5 million by 2002 (23). A notable trend in the Danube sturgeon population was the increased presence of stellate sturgeon compared to Russian sturgeon after 1993–1994. This shift has recently made stellate sturgeon the dominant species in this part of the Black Sea. The main reason for this phenomenon is likely to be the overfishing and poaching of sturgeon after this period. This has resulted in stellate sturgeon becoming increasingly dominant, accounting for almost 75% of the total population.

Hatchery production is key to maintaining sturgeon populations in the Black Sea tributaries of Ukraine. The hatcheries capture adult fish during their spawning migration in the lower reaches of rivers for breeding purposes. Of these fish, the Russian sturgeon remained the most numerous (23). The sterlet population has become relatively stable in the lower reaches of the Danube due to lower fishing pressure on this species in the Danube region (11, 12). Before 2022, Ukrainian sturgeon releases for population support took place every year in the Black Sea region. These were mostly Russian sturgeon and sterlet fingerlings.

According to official statistics, the total catch of the three sturgeon species in the Black Sea basin in Ukraine increased from 19 tons in 1992 to 211 tons in 2002, before dropping significantly to 0.42–0.43 tons in 2004–2005 (Figure 5) (23).

This sharp decline is evidence of a deterioration in the status of the fish population, caused by insufficient reproduction and intensive, mostly illegal, fishing. Following the collapse of the USSR, uncontrolled fishing of sturgeon intensified significantly in the north-western part of the Black Sea, particularly in the fish’s wintering grounds. By 1995, the estimated catch had reached around 600 tonnes, 12 times higher than the official catch of all Black Sea countries combined. However, this figure was probably even higher, as the calculations did not cover the sturgeon fishing areas or take into account losses of fish at sea through bycatch (23, 30).

Today, all sturgeon species are in an extremely desolate state (53). The beluga, Russian sturgeon, stellate sturgeon and sterlet in the Dnipro and Dniester basins have lost all commercial importance (1, 7, 17). Nevertheless, poaching remains a significant problem, particularly at the mouth of the Danube and in the Black Sea (54, 55).

3.3 Legal protection efforts

Prohibiting commercial sturgeon fishing in the Black Sea is an important step towards conserving stocks. Notably, Georgia banned commercial sturgeon fishing in the early 1970s, and Turkey has prohibited it for over 15 years since 2010. Other countries that have banned commercial sturgeon fishing include Ukraine (since 2000), Romania (since 2006), and Bulgaria (since 2011). Today, any commercial fishing of Black Sea sturgeon is prohibited. According to Ukrainian legislation all the sturgeon species caught by the aimed fishing or as a by-catch, must be released back into the water, regardless of whether they are alive or dead. These matters are monitored and enforcement is under the supervision of national authorities, in particular the Ministry of Environmental Protection and Natural Resources. Research is also carried out by scientists on board commercial fishing vessels, where bycatch sturgeon are determined and measured and then released back into the water (24). In Serbia, until 2019, the minimum fishing measure for taking a sterlet was above 40cm, however, due to the population decline, it is included in the permanent sturgeon fishing ban (10, 27).

Since 1998, sturgeon fishing and trade have been strictly controlled and regulated by several international agreements. In 1994, the Ukrainian National Red Data Book listed the sterlet, beluga, Atlantic sturgeon and ship sturgeon, whereas the Russian sturgeon and stellate sturgeon were first listed in 2009 (15). Ukraine became a member state of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) in 1999. The existing system of prohibitions and the requirement to release sturgeon from catches has ensured their migration to the Danube for natural spawning (34).

The role of the Ukrainian-Russian Bilateral Commission on Fisheries in the Azov Sea should also be noted. Established under intergovernmental and interagency agreements, the commission coordinated the joint efforts of Ukraine and Russia in studying Azov Sea sturgeons and genetic monitoring of artificial reproduction from the first years after the dissolution of the USSR (56). However, the Commission’s role diminished rapidly following Russia’s aggression against Ukraine in 2014, ceasing altogether in 2022. Today, Russia still reports on the Sea of Azov sturgeon populations through artificial reproduction (41). Nevertheless, while the current status and extent of the natural reproduction of Azov sturgeon populations is unclear.

In 2017, Ukraine and Romania’s environmental services reached an agreement to jointly protect sturgeons and record violators in the Danube’s coastal zones (57, 58). In the same year, Ukraine implemented Directive 92/43/EEC concerning the conservation of natural habitats, wild flora and fauna (see Table 2) (59, 60).

Table 2. Sturgeon conservation activities in Ukraine in chronological order.

Special attention should be given to the efforts of WWF Ukraine. Since the launch of the ‘LIFE for Danube Sturgeons’ project (project Nr. LIFE15 GIE/AT/001004) (58), which ran from 2016 to 2021, numerous measures have been taken to improve the protection of sturgeons in Ukraine. These include a market survey to control the trade in sturgeon meat and caviar, and awareness campaigns for the public and fishing communities, particularly in Vylkovo (Odessa region), focusing on the need for sturgeon conservation and the creation of alternative income sources to sturgeon fishing. Volunteer patrols have been established on the basis of the Danube Biosphere Reserve to protect sturgeons during migration (‘Sturgeon Watchers’) in the lower reaches of the Danube (61, 62). Due to the war, these activities are currently not possible in this form on the other Ukrainian sturgeon rivers. Legislative and executive authorities from the Ministry of Environmental Protection, the State Service of Ukraine for Food Safety and Consumer Protection, the State Commission for the Red Data Book of Ukraine and the National Police and Border Guard Service have undergone training (63). Additionally, research institutes and various experts from Lower Danube states have been brought together.

The most significant outcome of these efforts was the implementation of the 2021–2030 Action Plan for the Conservation and Reproduction of Sturgeon Populations, approved by the Ministry of Environmental Protection and Natural Resources (Order No. 391 of 28 December 2020) and executed by the Fisheries Agency of Ukraine in 2020 (64, 65). Over the past five years, this plan has driven the organization of systematic sturgeon research within national and international projects of the National Academy of Sciences and the National Academy of Agrarian Sciences of Ukraine. During this time, problems associated with artificial reproduction have been assessed, and priority steps have been identified to strengthen the role of fish hatcheries in supporting sturgeon populations in Ukraine (66). Unfortunately, military aggression by the Russian Federation is limiting the implementation of important steps aimed at taking active measures to replenish and restore the capacity of sturgeon hatcheries destroyed by the war.

The Danube Biosphere Reserve, a protected wetland area in the Danube Delta, which holds the status of the UNESCO Biosphere Reserve, has proposed a series of measures to protect sturgeon populations in the Black Sea basin. These measures included introducing fishing regulations, which led to changes in fishing equipment and locations, and became mandatory not only for the Danube, but for the whole of Ukraine where sturgeons inhabiting open waters (67). For the past 15 years, the Danube Biosphere Reserve has taken various annual measures to protect sturgeon as part of improvements to the ‘Fishing Regimes in the Black Sea Basin’. In 2023, these measures were finally enshrined in the ‘Fishing Rules in the Black Sea Basin’ (68). These measures included introducing fishing regulations, which led to changes in fishing equipment and locations, and became mandatory not only for the Danube, but also for the rest of the country. Since 2017, restrictions have been introduced on the height of driftnets in the Danube River. These driftnets should not exceed 6 m in height; an outer mesh wall with a minimum mesh size of approximately 200 mm was permitted. The thread thickness used in the inner and outer netting was also limited to 1.2 mm to prevent the use strong sturgeon-targeting nets. These restrictions were intended to reduce the capture of adult sturgeons in strong nets and may have contributed to the protection of the spawning stock (12). Furthermore, since 2018, the use of fixed nets with a mesh size greater than 45 mm has been prohibited for non-specialized fishing in the entire pre-mouth coastal or lower river section of the Danube River, covering an area of 24.2 thousand hectares. These nets had previously contributed to sturgeon bycatch. Since 2020, the minimum mesh size in herring nets has increased from 28 mm to 32 mm, which may reduce this year’s bycatch of YOY sturgeon (22). Starting in May, these sturgeon migrate downstream during their downstream migration from the Danube River into the sea (12, 22).

Military operations have significantly restricted fishing areas. For example, since 2022, fishing has been prohibited year-round in the 22–31 km straight arm of the Kiliya Delta branch of the Danube. For safety reasons, the commercial fishing season for all species has been restricted and, since 2022, fishing has only been permitted during daylight hours. Consequently, this has also reduced the bycatch of sturgeon (22). It is important to emphasize the need for continued scientific research on sturgeons during hostilities. Thus, the Institute of Marine Biology of the National Academy of Sciences of Ukraine (NASU) has developed a scientific program entitled ‘The Program for the Creation of a Genetic Collection of Biological Material Aimed at Establishing a Reference Genetic Database of Sturgeon Species in the Lower Danube and the North-Western Part of the Black Sea for 2025–2030’. This program was approved by the Director of the State Institution ‘Institute of Marine Biology’ of the National Academy of Sciences of Ukraine on 25 March 2025.Permission has been granted from the Ministry of Environmental Protection and Natural Resources to conduct a lifetime collection of tissue samples (fin samples) of species listed in the Red Book of Ukraine. A key part of this research involves establishing a genetic sample collection of sturgeon species in the region at the State Institution ‘Institute of Marine Biology of the NAS of Ukraine’. This work is being carried out as part of the Action Plan for the Conservation of Sturgeons in Ukraine for the period 2021–2030. The plan was approved by Order No. 391 of the Ministry of Environmental Protection and Natural Resources of Ukraine on 28 December 2020. These steps are the precondition for the future assessments of the genetic structure of these populations. In 2025, genetic material was collected as part of field research and transferred to the Leibniz Institute for Zoo and Wildlife Research in Berlin, Germany, in accordance with an agreement on scientific and technical cooperation and official CITES permits. While the war continues, research will be conducted in Germany, where Ukrainian scientists will receive further training in sturgeon species identification and trade control techniques. According to the WWF’s 2022 report (69), Ukraine’s law enforcement agencies have become more transparent, actively reporting cases of sturgeon seizures and bycatch on their websites and social media. Nevertheless, some data exist that provide insight into these illegal activities. A total of 82 cases of poaching and illegal trade were recorded in Ukraine between 2016 and 2022 (70). A total of 47.4 kg of caviar and 779 kg of sturgeon were seized during this period. Most of these cases (33%) occurred in the Odessa region, which has the greatest access to the Black Sea and the Danube Delta (see Figures 6, 7) (71, 72). In addition, there is also evidence for poaching in the Dnipro River (see Figure 8). Therefore, control must be improved and harmonized to fulfil the legislative and executive authorities’ goal of stopping sturgeon-related crime (54, 58, 73–75).

A new EU-funded project called ‘LIFE Boat for Sturgeon’ has recently been launched, in which ten partners from the Danube range countries Austria, Romania, Bulgaria, Hungary, Slovakia, Slovenia and Ukraine are collaborating to stabilise populations of sturgeons until 2030 (63).

3.4 Conservation attempts

Given the critical decline in sturgeon populations, the release of fish originating from controlled reproduction is necessary to maintain the populations in Ukrainian waters. To compensate for the loss of sturgeon stocks in the Azov Sea basin during the Soviet era, artificial breeding and the release of fish into natural water bodies were initiated.

Until 2009, both state and private Ukrainian fisheries sectors took adult sturgeons were harvested from the Sea of Azov for broodstock (30). After the sturgeon was listed in the Red Book of Ukraine in 2009, the fish farming for restocking of natural populations was paralyzed due to the lack of mature fish, as harvesting wild sexually mature sturgeon was significantly complicated. Obtaining the permits to catch a species listed in the Red Book is a complicated, bureaucratic, and expensive process that has become even more difficult under wartime conditions. Consequently, none of the private farms were able to obtain a permission to catch sturgeon anymore. Government activities of artificial sturgeon reproduction in the Black Sea basin are still ongoing, although on a small scale. These reproductions are based on previously caught specimens (14, 76).

Genetic control of reproduction under these conditions has become a top priority (49). In the late 1990s, the direction of genetic monitoring of artificial reproduction of natural sturgeon populations began to develop in Ukraine as well: The Laboratory of Genetic Research, established at the Azov Center of YugNIRO in Berdyansk (76), joined sturgeon genetic research. Unfortunately, access to the genetic research laboratory established at the Azov Centre of YugNIRO was lost due to Russian aggression. The laboratory is currently abandoned due to the Russian occupation.

However, efforts to support sturgeon stocks in Ukrainian river basins have not been very successful. Before the collapse of the Soviet Union, mass production of sturgeon in the Sea of Azov was carried out solely by Russian state farms. Private companies produced only a small number of sturgeon: around 4–5 million fingerlings per year (76). Following the economic crisis that followed the collapse of the Soviet Union, significant negative changes were seen in sturgeon farming, mainly due to a decrease in the number of skilled farmers and decline in sturgeon stocks, as well as the economic and technical difficulties faced by fish farms (30). From 2005 to 2015, the number of young fingerlings bred commercially for release into the Sea of Azov continued to decline. Due to the tense military situation in south-eastern Ukraine after 2014 and the associated economic difficulties, replenishment of natural reserves from the Ukrainian side has completely ceased (Figure 9).

The most important state sturgeon hatchery was built in the lower region of the Dnipro River in 1984. The hatchery was designed specifically to reproduce sturgeon for stocking to the Black Sea basin (30). It is the only hatchery in Ukraine that effectively reproduces beluga, Russian, and stellate sturgeon. In recent years, it has also reproduced sterlet because their populations are declining rapidly (14). The hatchery produces more than 1.5 million juveniles annually (76). Since 1984, approximately 65 million juveniles have been released into Ukrainian waters entering the Black Sea (Figure 10).

In June 2023, the Dnipro Sturgeon Production and Experimental Fish Reproduction Hatchery was affected by the demolition of the Kakhovka Dam. At the time, the farm had 15,800 Russian sturgeon, sterlet, stellate sturgeon, beluga and non-native paddlefish in its stock. The flooding of the breeding ponds resulted in the fish escaping (Figure 11) (77). Following the collapse of the dam in 2024-2025, sturgeons have been recorded fairly regularly in the vicinity of Zaporizhzhia, including confirmed sightings of adult sturgeons. However, the most important broodstock for release programs have probably been lost forever.

Recently, the World Sturgeon Conservation Society appealed to all those involved in sturgeon conservation in Ukraine to support the rebuilding of the hatchery. As of November 2025, the area remains an active military zone.

Between 2020 and 2021, two private farms — the ‘Odesa Sturgeon Complex’ on the Lower Danube and ‘Ishkhan’, located in the Chernivtsi region on the Upper Dniester — began restocking natural waterways with native sturgeon species (76, 78, 79). However, the capacity of these private farms cannot make up for the production loss of the destroyed state farm.

Based on data from scientific fishing activities financed by WWF, juveniles of Russian, stellate and sterlet sturgeons, as well as beluga sturgeons, were found in the lower Danube and Dniester rivers in 2023 and 2024 (12, 80, 81). However, there is no data indicating whether these sturgeons resulted from stocking programs in Ukraine or natural reproduction. In 2024, WWF Ukraine was developing recommendations for conserving and restoring natural sturgeon populations (82, 83).

3.5 Aquaculture

There is no doubt that sturgeon aquaculture can contribute significantly to the survival of sturgeons. Increasing the supply of sturgeon meat and caviar through aquaculture reduces the demand for wild sturgeon and its products (84, 85). Intensive development of the sector began at the national level in the mid-20th century, peaking in 1988 with the production of 146 tonnes of sturgeon (86). However, production has steadily declined since the dissolution of the Soviet Union in 1991, with overall production reaching just 37 tonnes in 1991 (87).

As of 2021, Ukraine had 20 sturgeon farms. Most sturgeon are raised in the Zaporizhzhia, Cherkasy, Odessa, Kherson, Chernivtsi and Kyiv regions. The leading sturgeon farms in Ukraine are: Osetr and Bester (both in the Kyiv region), Chernihivrybhosp (in the Chernihiv region), the Ukrainian Service Enterprise (in the Kyiv region), Fortuna-XXI (in Kyiv), Kind Fish (in the Kyiv region), the Odesa Sturgeon Complex (in the Odesa region), the Ishkhan Farm (in the Chernivtsi region), the Oasis Bisan (in the Mykolaiv region), the Aquasvit Group of Companies, the Aqua Top (both in the Odesa region), the Research and Production Centre Forel (in the Volyn region), the Irkliyivskyi fish hatchery (in the Cherkasy region), Brig LTD (in the Zaporizhzhia region), Biosula (in Kyiv), Olesia (in the Kherson region), Mercury (in the Vinnytsia region), Micron (in the Dnipropetrovsk region) and the Khotymyr Agricultural Fish Farm (in the Ivano-Frankivsk region).]. The Russian sturgeon, the beluga, the sterlet, the stellate sturgeon and the Siberian sturgeon (A. baerii), the American paddlefish (Polydon spathula), the beluga-sterlet hybrid (Bester) and the Russian-Siberian sturgeon hybrid are cultivated for commercial purposes in aquaculture. All of these species of sturgeon are reared in ponds, as well as in recirculating aquaculture systems (RAS), cages and pools (14, 30, 76).

According to the latest FAO data, approximately 100 tonnes of the total national sturgeon products have been produced annually in Ukrainian aquaculture over the past decade (4, 14, 76). Before the war, Ukraine’s demand for sturgeon products was only met by around 30% (88). This left a 70% gap in the market for sturgeon aquaculture in Ukraine. Caviar consumption increased by around 41% in the space of a year (from 2020 to 2021), peaking in 2021. According to forecasts, this increase in consumption was expected to continue in the coming years (89).

Exports of sturgeon products gradually and noticeably increased from 2014 to 2021. The highest export growth rates were recorded in 2015, when exports increased by 104%. However, from 2018 to 2021, exports failed to regain momentum. In terms of value, the largest markets for Ukrainian exported sturgeon caviar were the United States, the United Arab Emirates and Switzerland, accounting for 55% of total exports together (90). Ukraine announced a 48% increase in imports of sturgeon caviar over six consecutive years, culminating in 2021. The highest growth rates were recorded in 2018, when imports increased by 283%. China was the main supplier of sturgeon caviar to Ukraine, accounting for 84% of total imports. It is difficult to predict how the aquaculture sector will develop further under the current war conditions. According to the Fisheries Agency, the number of fully functioning aquaculture enterprises in Ukraine has fallen below the 50% threshold, and sturgeon production is likely to decline by a similar amount (91, 92). Notably, the European Union has announced that it will provide comprehensive support and assistance to Ukrainian aquaculture after the war. The FAO assumes that the recovery and restoration of aquaculture, particularly sturgeon farming, will take at least five years (5, 93–95). Following Russia’s invasion of Ukraine in 2022, the Ukrainian sturgeon aquaculture industry suffered a massive downturn. According to data from the State Scientific Institution ‘IRGEMO’, the number of Ukrainian exporters of sturgeon products (mainly edible caviar) fell fivefold between 2022 and 2025.

4 Discussion

Sturgeons are an integral part of Ukraine’s natural heritage and are flagship species of freshwater biodiversity. The rapid growth of human economic activity and the construction of dams in the 20th century significantly disrupted sturgeon migration routes and spawning habitats (96). Despite an official prohibition, the protection of sturgeons is low due to a lack of law enforcement, while poaching and illegal fishing pose significant threats to their populations. Reasons for this include the issue being given low priority due to a lack of awareness of the impact of illegal fishing, as well as a lack of personnel and technical resources. Corruption is also a contributing factor (97–99). Control of poaching in former Soviet Union countries was ineffective and the responsible authorities were often engaged in illegal fishing activities (100). According to data collected by WWF, Ukrainian fisheries officially caught around 49 thousand tons of sturgeon between 1927 and 2001. Poaching amounted to 5,000 tonnes per year in the 1990s, decreasing to 30 tonnes per year by 2016 (33). The problem persists to this day.

A recent study found that around 16% of the caviar and sturgeon sampled in Ukrainian markets was mislabeled or came from poached fish (55). This number represents the minimum level of poaching; the exact extent is unclear due to the nature of the crime. A market survey revealed ongoing demand for wild sturgeon products, such as caviar. This is alarming because demand for these products puts pressure on wild populations (101, 102). This persistent may contribute to continued poaching pressure and suggests that consumers do not fully accept aquaculture products (69, 70, 101). The sale of caviar in violation of national and international law calls into question the effectiveness of control activities. Insufficient controls undermine the future of the Ukrainian sturgeon populations. Therefore, improving control of the sturgeon trade is urgent. An important condition for aquaculture farms should be the strict, constant implementation of CITES requirements for selling their products on the domestic market and for export (103, 104). Equally important is the constant monitoring of compliance with these requirements by state regulatory authorities. In the case of caviar, inspections usually only verify the accuracy of labelling and the completeness of CITES codes. However, recent investigations have demonstrated that forensic methods must be employed to verify declarations (105, 106).

Raising public awareness of the dire situation of the Ukrainian sturgeon populations is therefore crucial for their survival. Awareness campaigns should focus on the historic importance of the sturgeon fishery and caviar trade, as well as the causes of the decline in wild populations. These campaigns should raise public concerns about the possible extinction of sturgeon and encourage public support for conservation efforts. Public participation especially of local communities is an essential key element of any successful conservation program.

Genetic monitoring has become a top priority for the artificial reproduction of natural sturgeon populations, given the increasing proportion of farmed fish within them. However, a recent assessment of the genetic composition of the sterlet population in the upper Danube found that a significant proportion (around 23%) are of Volga origin (48). This makes it difficult to maintain the purity of the populations (107, 108). Therefore, to prevent illegal trade, maintain genetic purity and control stocking programs, the regular application of state-of-the-art genetic methods is necessary to ensure stock integrity. Including sturgeons in the Red Book of Ukraine has enabled strict adherence to the requirements for their protection. However, in the field of artificial reproduction, there has been a shortage of high-quality broodstock for the restocking of natural populations. Therefore, the process of obtaining permits for the extraction of sturgeons from natural water bodies requires revision and adaptation.

But these measures alone do not address the problem of natural reproduction. Stocking may only be a temporary solution that allows time for habitat recovery; it does not solve the main problem of habitat restoration. This can be seen in Dabry’s sturgeon (A. dabryanus) in the Yangtze River in China. Millions of fingerlings are released there every year, but there is no natural reproduction (109). It is also important to note, that as a result of the war, a fairly large section of the Dnieper River is now flowing freely, as it did in the past. This could eventually make the area favorable for sturgeon and re-open historic spawning grounds. Intensive discussions are already taking place about the future of sturgeon populations in connection with the government’s plan to rebuild the Kakhovka Dam. The government’s decision should take into account the security of the water supply, environmental protection and the restoration of the ecosystem, including the valuable former sturgeon habitats (110, 111). One way to effectively mitigate the impact of dam construction would be to build fish migration structures and create conditions that allow for natural reproduction, thus preserving and restoring the reproductive migration of sturgeons and other species. Between 1979 and 1983, attempts were already made to create artificial spawning grounds for lithophilous fish species on the Dniester River. Unfortunately, these projects were not successfully implemented (12).

When considering the option of reconstructing the Kakhovka reservoir, one option is to dam only the south-eastern, shallower part of the reservoir. If this option is chosen, the resulting dam section with the appropriate depth and currents necessary for creating artificial sturgeon spawning grounds would measure approximately 12 km in length (82). Specialists at the Institute of Hydrobiology of the National Academy of Sciences of Ukraine have developed methods for creating artificial sturgeon spawning grounds and have extensive experience in preparing technical conditions for various types of fishway that could be used to restore sturgeon migration routes in Ukraine. However, recent studies indicate that population fragmentation with limited migration through facilitation structures leads to the genetic degradation of subpopulations (16, 112, 113). An alternative option for environmental restoration is to dismantle the dams, which would ensure the long-term survival of the sturgeon population. This would free up a significant area of the riverbed for the restoration of sturgeon spawning migration routes and grounds. However, such long-term prospects require a more detailed study of the flow characteristics and riverbed conditions before and after the dismantling of dams.

In light of the current situation and Russia’s military aggression, which has resulted in the loss of many types of economic, scientific and environmental activities, the protection of sturgeons also hinges on ending the war and restoring Ukraine’s territorial borders.

5 Conclusions

The current state of sturgeon populations in Ukraine is extremely unfavorable. This is due to several factors, including poaching, river damming, environmental destruction, pollution, climate change and, more recently, the war between Ukraine and Russia. The historical migration routes of sturgeon in Ukraine demonstrate their critical dependence on river connectivity; anthropogenic barriers have led to a sharp decline in their numbers. The Danube is the only Ukrainian river with reported natural spawning. In 1999, Ukraine joined CITES and began cooperating with other international organizations to protect and restore sturgeon populations. Despite the war, Ukrainian scientists are continuing their field research to obtain population data, but they need to increase the scale of their work. Today, Ukraine still needs to improve its national legislation to ensure effective enforcement and develop control mechanisms to stop wildlife crime. To control the illegal trade in sturgeon and prevent the uncontrolled stocking of non-native species, it is essential to create conditions in Ukraine that allow for the control of products on the market. Ideally, a joint laboratory specializing in wildlife forensics and stocking control would be established in collaboration with other Black Sea countries. However, this can only be the second step; priority must be given to building up resources for the reproduction and rearing of broodstock, while simultaneously re-naturalizing the habitat for spawning.

In recent years, support for open-water populations has been achieved through the release of fish from private farms, thanks to state funding and the efforts of WWF. The destruction of the Kakhova Dam has resulted in the loss of sturgeon broodstocks, which is detrimental to both sturgeon conservation and aquaculture. Effective legislative and technical prerequisites must currently be established to facilitate the formation of a high-quality sturgeon broodstock. To preserve the unique genetic adaptations of the different river systems, we recommend taking special care of them by:

• introducing a system to control and trace fish products;
• promoting the adoption of CITES labelling as mandatory in the domestic market;
• establishing a state laboratory for the genetic control of sturgeon to support effective enforcement;
• creating a live gene bank for sturgeon;
• restoring the artificial reproduction of local populations;
• resume full-scale monitoring of natural sturgeon populations in natural waters;
• strengthen the enforcement of existing legislation on illegal, unregistered and unregulated fishing, including bycatch;
• restore historical migration corridors;
• raise public awareness of the importance of protecting and preserving sturgeon in the wild; and
• the need for legislative changes aimed at reducing the bureaucratic procedures involved in obtaining permits for the study of sturgeon, as set out in Ukraine’s Red List Act.

Correction note

A correction has been made to this article. Details can be found at: 10.3389/frish.2026.1980300.

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Footnotes

Edited by: Michele Luca Geraci, Istituto per le Risorse biologiche e le Biotecnologie marine, Italy

Reviewed by: Roman Novitskyi, Dnipropetrovsk State Agrarian and Economic University, Ukraine

Mladen Avramović, Karlstad University, Sweden