Re-Establishing Naturally Reproducing Sturgeon Populations in the Caspian Basin: A Wicked Problem in the Ural River

Abstract

Although Eurasia’s Caspian basin once supported the world’s richest and most diverse complex of sturgeon species, recent human activities have decimated populations of these ecologically and economically important fish. All five anadromous Caspian sturgeon species are critically endangered, and the potamodromous sterlet is also threatened. The precipitous decline of these species is due to a combination of factors that includes illegal, unreported, and unregulated (IUU) fishing; destruction of feeding and spawning habitat; water pollution; and the environmental consequences of climate change. International efforts are currently underway to re-establish sustained naturally reproducing sturgeon populations in the basin. Here, we update and review the status of sturgeon in the Caspian Sea with emphasis on the northern basin and the inflowing Volga and Ural rivers. We then focus on efforts to restore sturgeon in the Ural, which originates in Russia and flows through Kazakhstan before entering the Caspian Sea. With nearly ideal hydrological conditions for sturgeon, the Ural is the basin’s sole remaining river that allows migrating sturgeon unimpeded access to potentially productive spawning grounds. The challenge of re-establishing sturgeon in the Ural River exhibits the classical characteristics of wicked problems: ambiguous definitions, changing assumptions and unanticipated consequences, tradeoffs and economic dependencies, an incomplete and contradictory knowledge base, and no straightforward pathway toward a final solution. This challenge is examined here for the first time from the perspective of its wicked dynamics, with consideration given to approaches that have proven effective elsewhere in resolving wicked environmental problems.

1. Introduction

Sturgeons are representative of a relict group of large, late-maturing, and long-lived fish of the family Acipenseridae. All 27 species are native to areas above the thirtieth parallel in the northern hemisphere [1], and due to their longevity, position in the food chain, and preferential bottom feeding characteristics, they are highly sensitive to changes in habitat [2]. Extremely valuable and sought primarily for their roe, sturgeons are easy to capture and have been harvested to near-extinction [3]. Habitat fragmentation is a prime factor in the catastrophic decline of these species [4], but unsustainable harvests in response to economic incentives, weak fishing regulations, and lax regulatory enforcement are also important [5,6,7]. Thousands of large and smaller dams have also changed the flow regimes of the world’s rivers, disrupting natural patterns of sediment transport and nutrient availability and blocking the movement of migratory fish such as sturgeon [8,9,10]. These detrimental effects are exacerbated by the extraction of sand and gravel, channelization, isolation of side channels and backwaters, and other anthropogenic disturbances [11].

Most sturgeon populations in Europe, Asia, and North America have declined to the extent that they have little chance of surviving unless conservation measures are introduced [4]. Their status is precarious, even in environmentally conscious Europe, where habitat destruction and overfishing led to the severe depletion of most sturgeon species during the Middle Ages [12]. The Atlantic sturgeon (Acipenser sturio) is extinct in the Black Sea basin, and although reintroduction efforts are underway in the Elbe and Rhine rivers, only one population continues to exist [13]. Moreover, all six sturgeon species of the Danube River are also classified as vulnerable, endangered, or already extinct. There is political will to save the European sturgeon, but transboundary conflicts and the lack of large natural populations impede their preservation [12,14]. The destruction of habitat, changes in water quality, and overfishing led to a familiar pattern of the decline of the lake sturgeon (A. fulvescens) in most of its North American range more than a century ago [14,15]. On the other hand, there is reason for restrained optimism about populations of the shortnose sturgeon (A. brevirostrum) and the Atlantic sturgeon (A. oxyrinchus oxyrinchus), both of which are protected in the United States under the Endangered Species Act [16]. The status of sturgeon is also promising in China, where stocking has restored endangered populations of Yangtze sturgeon (A. dabryanus) and the Chinese sturgeon (A. sinensis) [17,18].

Nowhere is the future of sturgeon more uncertain than in Eurasia’s Caspian basin [19,20]. According to the International Union for Conservation of Nature [21], 6 of the 20 sturgeon species that still exist in the wild are native to the Caspian basin, which is renowned for its rich but imperiled sturgeon resources that once provided most of the world’s caviar [5,22]. Anadromous Caspian species, all critically endangered, include the Russian sturgeon (A. gueldenstaedtii), Persian sturgeon (A. persicus), beluga (Huso huso), stellate sturgeon (A. stellatus), and ship sturgeon (A. nudiventris). These species feed in the sea and spawn in the Ural, Volga, and other inflowing rivers. The sixth species, sterlet (A. ruthenus), is potamodromous but also at risk. Three of these species—Russian sturgeon, stellate sturgeon, and beluga—are of the greatest commercial importance in the basin [23].

The desperate plight of the world-renowned Caspian sturgeons has triggered widespread concern from environmental, governmental, and economic perspectives [24,25,26]. Efforts to increase and stabilize the basin’s sturgeon populations have been ongoing for decades, but there is a new sense of urgency as sturgeon numbers in the basin approach thresholds below which recovery will not be possible. Stocking; preventing illegal, unreported, and unregulated (IUU) fishing; and preserving the key remaining sturgeon habitats in riverine and lacustrine areas of the basin are all receiving attention [7,27,28]. There is also growing interest in relieving pressure on natural sturgeon populations by shifting commercial production to aquaculture [29].

Here, we update and review the status of sturgeon in the northern Caspian basin, with emphasis on the Ural River and to a lesser extent the Volga River. Although endowed with a nearly ideal sturgeon habitat and a long history of prolific sturgeon fisheries, the Ural is vulnerable to all of the threats that are decimating sturgeon numbers throughout the Caspian basin [28]. But unlike the Volga and other dammed rivers in the basin, the reaches of the Ural that are indispensable for sturgeon migration and spawning remain uninterrupted. The challenge of restoring natural sturgeon populations to the Ural River is consequently of immense significance and warrants a high prioritization. It also exhibits the dynamics of wicked environmental problems and is considered here from this perspective.

2. The Caspian Basin as an Environment for Sturgeon

The Caspian basin encompasses an area of about 3.5 million km² [30]. The Caspian Sea, which covers nearly 10% of the basin, lies below sea level and is the largest closed body of saline water in the world [31], with a 6500 km coastline that borders five littoral countries—Russia, Kazakhstan, Turkmenistan, Azerbaijan, and Iran (Figure 1). The sea has an average depth of 180 m and a nominal volume of about 78,000 km³ and is fed by more than 130 rivers, which deliver an average annual flow of about 290 km³. One river, the Volga, accounts for more than 80% of total inflows [31]. The water balance and level of salinity in the Caspian Sea depend on precipitation, river flow, groundwater, and evaporation, all of which fluctuate substantially over short and lengthy periods of time. The sea consequently undergoes significant recurring temporal changes in volume and surface area. The resulting variations in depth, salinity, and water temperature allow the sea to support a wide variety of biota, including sturgeon, which are well adapted to its varying hydrological conditions. The massive Volga and smaller Ural were historically dominant in providing key riverine spawning habitats, allowing sturgeon to flourish in the basin for millennia prior to human intervention [28].

Although Caspian fisheries existed prior to the 13th century [32,33], human impacts on sturgeon populations were negligible during the Middle Ages, when the basin was inhabited by nomadic pastoralists. Sturgeon was prized at the time of the Volga–Ural Region’s incorporation into the Russian Empire during the second half of the 15th century. They were still abundant in the Caspian Sea and inflowing rivers and harvested primarily for meat [34]. Rising demand driven by changing tastes and religious practices gradually increased the fishing pressure on Caspian sturgeon [3], elevating catches to about 50,000 tons per year by the end of the 17th century [35]. The Ural and Volga soon became prime sources of sturgeon, which were harvested from the Ural and marketed by Cossack settlers and monasteries that controlled the local fishing industry [33,36,37]. The fish habitat was stringently protected by both custom and strict fishing regulations [36,38].

The Caspian basin became the world’s leading source of sturgeon stocks, harvests, and caviar production during the 19th and 20th centuries [39]. Annual landings were 34,000–38,600 tons from 1901 to 1915 [40], but the October Revolution of 1917 and subsequent events reduced harvest to 4000–10,000 tons and prompted a brief recovery of sturgeon stocks, which had been declining for some time [41]. Intensive sea fishing with hook and line gear, which had been banned in 1914 but then reintroduced in the 1930s, briefly elevated sturgeon catches to between 20,500 and 22,130 tons [42]. World War II reduced landings to 3890–7610 tons [23,43], but they increased again after 1946 [41,44]. Black caviar was widely available in the USSR after the war (Figure 2), and its price was comparable to that of butter as recently as the 1950s and early 1960s (3, Nurtazin, unpublished observations).

The Soviet Union implemented a grandiose plan between the two world wars to industrialize the Volga region. The construction of the world’s largest cascade of hydroelectric plants on the Volga River and its tributaries was initiated in the mid-1930s and reached its peak in the 1950s. The prioritization of cheap energy and shipping imposed a heavy burden on the hydrological system as the Volga was gradually altered from a free-flowing, 3250 km river into a system of reservoirs with extremely low flows and depressed oxygen concentrations. The dams reduced the distance available for sturgeon migrations to just 550 km and prevented spawners from reaching most of their traditional, high-quality spawning grounds. A single obstruction, the Volgograd dam, blocked sturgeon from reaching 187 spawning sites in the upper reaches of the Volga and its tributaries—roughly 80% of the total along this historically productive river [44,45].

Several steps were taken to mitigate the damage caused by dams obstructing the Volga River. The remaining spawning grounds below the Volgograd dam were enlarged artificially, but their area totaled just 372 ha, about 10% of what was available previously [45,46]. Expensive infrastructure that enables fish to bypass dams was also constructed, and live spawners were even transported to upstream spawning sites [47]. The results of these efforts have nevertheless been disappointing [48]. Fewer than 1% of sturgeon attempting to maneuver past the Volgograd dam, for example, were successful [49], and it was evident as early as 1967 that the natural reproduction of sturgeon along the Upper Volga was effectively zero [44,50,51].

To make matters worse, hydrological conditions in the remaining sturgeon spawning habitat of the Volga are often unfavorable [52]. Under regulated conditions, the Volga’s runoff volume during the April–July period of high water is 30% lower than that under natural conditions, but runoff during the December–March period surges to 65 km³—more than twice that measured prior to dam construction [53,54,55]. These flow dynamics are doubly detrimental to the small sturgeon populations remaining in the river. Reduced fluxes of spring floodwater reduce the availability and quality of spawning grounds, and sharply higher fluxes during the colder months disturb sturgeon overwintering in deep pools. Water flow in the spawning grounds downstream of the Volgograd dam was consequently favorable in only 13 of the first 40 years after regulation of the Lower Volga [56]. In addition, the water availability in these reaches was sufficient for sturgeon spawning in just 8 of 34 years spanning 1959 to 1993 [57].

The Volga basin is now home to 40% of Russia’s population; demands on its water resources are eight times the Russian average [58,59,60], and up to 20% of Russia’s wastewater is discharged into the basin each year [61]. Most municipal and industrial water treatment facilities are physically worn out, outdated, and inefficient, and high levels of pollution consequently enter the river and its tributaries, where they increase the mortality of sturgeon, especially growing larvae [62,63]. In spite of all of these factors, significant catches of anadromous sturgeon species—from 25,000 to 30,000 tons annually—persisted into the late 1970s due to the natural spawning of residual fish generations that had been present before the flow of the lower Volga was regulated [30,41,64]. Landings nevertheless soon plummeted [65]. Similar unfavorable dynamics reduced spawning in Azerbaijan’s Kura River, which was dammed in 1960 [28].

3. Preservation of Naturally Reproducing Sturgeon in the Caspian Basin: The Ural River

There are many reasons to be pessimistic about the future of natural populations of Caspian sturgeon, and indeed, some experts have concluded that rescue efforts are futile [28]. Although the status of sturgeon in the Volga, Kura, Telek, Sulak, and other smaller rivers is dire, sustained natural reproduction of sturgeon may still be feasible in the nearly free-flowing lower and middle reaches of the Ural River (Figure 3). The unfavorable factors described above have caused numbers of Ural sturgeon to decline, but small residual populations continue to exist in the basin and could provide the basis for recovery operations. This possibility began to receive serious attention in the late 1990s when the Caspian Environment Programme was inaugurated as an umbrella organization to stem the environmental deterioration of the Caspian Sea [66]. This was followed by the Ural Basin Project, which during the early years of this century sought to focus international efforts on the potential to restore sturgeon to the Ural and its tributaries. The Ural Basin Project developed an aggressive and very detailed sturgeon rescue plan that included the establishment of an International Ural Sturgeon Park [67]. Although the park has not yet materialized, 111,500 ha of the Akzhaiyk State Nature Reserve at the mouth of the Ural River has received protection as a Ramsar wetland site of international importance [27].

There are four interrelated requirements for recovery of sturgeon in the Ural River. The first is the availability of abundant, high-quality sturgeon habitat, especially spawning and feeding sites, as well as favorable hydrological conditions to sustain these areas. The elimination of premature mortality due to overfishing is the second requirement, which if not addressed would preclude the recovery of sturgeon populations even if the habitat is restored. The destruction of the habitat and overfishing are the two critical factors most responsible for the decline of sturgeon globally and in the Caspian basin [68]. The third requirement, an effective stocking program, is necessary to replenish Ural sturgeon populations that have been depleted below the threshold necessary to permit natural recovery. And fourth, transboundary cooperation between Russia and Kazakhstan is essential to ensure that all of the preceding steps are coordinated along the length of the Ural River.

3.1. Habitat

The snow-fed Ural River originates in Russia and flows for a total length of 2428 km, 1084 km of which is in Kazakhstan [31]. It has traditionally ranked second after the Volga in terms of Caspian sturgeon reproduction potential and catches, yielding roughly 45% of the number of fish produced by its much larger neighbor; indeed, the Ural’s specific productivity, as measured by the number of sturgeon individuals per unit volume of water, is 10 times that of the Volga [28,69,70]. Historical productivity, as measured by the large number of spawners entering the Ural and by the corresponding sturgeon harvests, has consequently been substantial. The river’s high-quality habitat, including its hydrographic and hydrological properties, is ideal for sturgeon migration and reproduction [28]. The interannual variability of flow, which averaged 8.1 km³ per year between 1961 and 2020, is among the highest of the large rivers of the world [71,72]. In the lower reaches of the river, it can vary 13-fold, from 0.1 m/sec during low water to 13 m/sec during high water [73]. Pools are replaced with riffles at almost every turn of the stream, and bars of gravel and pebbles provide preferred spawning sites for sturgeon [74,75]. Moreover, spring floods are common, with 60 to 90% of the annual flow occurring in April–June, precisely the period when sturgeons are spawning. Flooding ensures that oxygen concentrations are favorable [73], and it creates turbidity, which protects eggs and larvae from predators [48,76,77].

Although substantial natural variability in the hydrological regime of the Ural River has always existed and never prevented high natural spawning activity, sturgeon reproduction has collapsed in recent years [1,44]. The migration of juvenile ship sturgeon was last detected in 2007, and that of Russian sturgeon and beluga were last detected in 2010. The migration of juvenile stellate sturgeon, previously the river’s most abundant species, was not even detected in 2010 and 2015, and just 156 and 64 specimens were observed in 2014 and 2016, respectively [78,79]. Indeed, the situation has deteriorated to the extent that the mere discovery of a school of sterlet by echo sounding made recent headlines [80].

Ural’s spawning sites are in a constant state of flux due to natural hydrological variability, but there are now unmistakable signs of trouble [28,81,82]. Although information about the current condition of spawning areas in Russia is scarce, the sites spanning nearly 800 km of the river’s lower reaches in Kazakhstan were recently surveyed [83]. The number of these sites has fluctuated only slightly over the past half century—from 63 sites in 1968 to 70 in 1986, 63 in 2004, and 68 in 2016. The diminished area and degradation in the quality of these sites is the greater concern. All but two that had been examined in 2004 had contracted in area by 2016, often substantially, and preferred gravel-pebble spawning substrates, which are often mined for construction materials, were identified at only four sites in 2016. Other sites had become silted and sandy or dominated by vegetation. These detrimental changes are associated with declining annual flows and shifts in peak seasonal flows from spring to winter; both are conditioned by warming temperatures, which accelerate the rate of early season snow melt and increase evaporation during the warmer months [72,84,85,86,87,88].

The problem of water availability is exacerbated by withdrawals to meet municipal, industrial, and agricultural needs [89,90] and is compounded by the pollution that accompanies petroleum extraction, industrial development, and irrigated crop production [72,81,88,90,91,92]. Domestic water treatment systems in the Ural basin are outdated, and even when available, they are sometimes not used [93,94,95]. Most of the catchment is polluted with heavy metals from mining and metallurgy, and concentrations of toxic nitrites, oxides, and organic compounds are often above allowable limits [74,96]. Moreover, pollutants from the Ural River are eventually swept into the Caspian Sea, adding to the already significant contaminant load and further degrading sturgeon habitat [97,98,99,100]. Contaminated water subjects Caspian sturgeon to serious disorders, including tumor formation, muscle atrophy, gonadal dysfunction, and abnormal morphogenesis [44,101,102]. Moreover, low water levels force spawners to utilize less productive habitats in the lower reaches of the river and sometimes even block access to these areas [96]. This reduces the migration distance to the sea, resulting in juveniles that are undersized and ill-prepared to adapt to saline conditions [87].

In short, the complexity of restoring the remaining sturgeon habitat in the Ural River to a condition that will sustain natural populations should not be underestimated [103,104,105]. The global climatic changes that are driving up temperatures in the basin and altering flows are enormously difficult to counteract, and steps to prevent pollution from entering the river would be costly. Moreover, although spawning, early rearing, and the feeding behavior of sturgeon are reasonably well understood, lack of knowledge about other aspects of sturgeon biology adds ambiguity to the problem of habitat restoration [1,106]. The overall challenge is compounded in the Ural River, which hosts multiple sturgeon species, each with its own needs and preferences. These factors are crucial for determining the scale of habitat restoration, the steps needed to maintain the habitat, and the monitoring process necessary to evaluate the success of restoration efforts [103,107].

3.2. Overfishing

Overfishing was recognized as a threat to sturgeon populations as early as the eighteenth century, and except for a few short periods, it has remained a chronic problem [23,28]. Various methods have been employed since at least the mid-nineteenth century to constrain fishing in the Ural River and preserve its valuable sturgeon stocks [38,41]. Aware of the fragility and value of sturgeon, Russia and its predecessor and successor states issued multiple regulations governing the length of fishing seasons, the use of fishing gear, catch and size limits, the location of legal fishing areas, and eventually outright bans on fishing [19,41,83]. Although sturgeon fishing was legal across the Caspian basin during the Soviet era, restrictions were gradually tightened beginning in the early 1950s. Stringent enforcement by an authoritarian state ensured that IUU fishing, although practiced, was a minor issue [28,40], but the widespread use of hooks and nylon nets led to the deaths of millions of immature specimens, often as bycatch [23,30]. The 1962 ban on net fishing in the sea shifted fishing to the mouths of the Ural and other rivers, inadvertently increasing fishing pressure on spawners and migratory populations. Legal fishing and harvests for scientific purposes continued after the collapse of the Soviet Union in 1991, but relaxed enforcement allowed IUU fishing to skyrocket [7,44]. Simultaneously, the privatization of caviar trade created a lucrative black market and generated additional incentives for poaching [108].

Commercial fishing for beluga in the Caspian Sea was prohibited in 2000, and that of Russian and stellate sturgeon followed in 2005 [109]. Although Russia banned all sturgeon fishing in 2007 [45] and Kazakhstan enacted a basin-wide moratorium on the commercial harvest of sturgeon in 2010 [78], IUU fishing continues to deplete the Caspian basin’s alarmingly low sturgeon stocks [98,109,110]. Many poachers are local residents who use small boats to fish illegally and sometimes catch sturgeon [111], but others belong to bands of organized criminals that are willing to bribe officials and use weapons to defend their illegal activities [28,108]. Criminals in speedboats often set hundreds of meters of sturgeon lines and hooks in the sea, indiscriminately killing mature and immature specimens; others enter the Ural River and harvest migrating spawners and juveniles [112,113].

Reliable statistics are for obvious reasons not available, but recent seizures from the Ural and adjacent areas of the Caspian Sea provide evidence of the damage done by criminal activities (Figure 4,

Table 1. Recent reports of IUU fishing and trade of sturgeon in the Ural River and nearby areas of the Caspian Sea.

Date and Location	Seizure/Action	Reference
2018, Qaraqiya	Arrest at the border and seizure of sturgeon	[115]
2018, Mangistau	Sturgeon weighing 223 kg	[116]
2020, Atyrau	345 sturgeon weighing > 1 ton	[117]
2021, Various	4.6 tons of sturgeon	[118]
2021, Mangistau	3 tons of sturgeon in industrial freezers	[119]
2022, Atyrau	0.5 tons of sturgeon	[120]
2022, Aktau	76 sturgeon weighing 300 kg	[121]
2023, Atyrau	93 people convicted of IUU fishing and trade	[114]

). Kazakhstan governmental agencies intensify the enforcement of fishing regulations during the spawning season, which lasts from 1 April to 31 May, with annual “Bekire” campaigns. More than 150,000 m of nets, 6650 m of gear with hooks, and 348 individual sturgeon with a total weight of 2175 kg were confiscated during the most recent campaign in 2023 [114].

3.3. Stocking

Although small numbers of hatchery-produced sturgeon were released into the waters of the Caspian basin in the late nineteenth century, stocking did not become widespread until the 1950s when the Soviets constructed hatcheries to supplement natural reproduction and ensure that commercial fisheries production goals were met [19,45]. Most of these hatcheries, which captured spawning females annually for use as broodstock, were in the Volga, and they were operated on the basis of scientific principles to maximize recruitment [19,122]. Although juveniles were released after they had reached a size and weight calculated to yield a 3% survival rate as mature specimens [123], the mortality of juvenile fish was high [44,99,109], and the actual rate of survival to maturity was less than 1% [124,125]. Total sturgeon numbers continued to drop [28], and wild broodstock eventually became so rare that Volga hatcheries were forced to drastically curtail their activities [45,126].

Kazakhstan opened the first two hatcheries on the Ural River in 1998. They are located in the delta, just 30 km from the seacoast and far from traditional spawning sites [81,127]. These hatcheries were designed to utilize captured broodstock and operate on principles similar to those employed by the Volga hatcheries [28]. In recent decades, their combined average annual production has been about 7 million fry [128]. There was initial optimism that stable Ural sturgeon populations could be restored by rearing juveniles to a larger, more viable size prior to release [129,130,131], and this led to proposals to construct additional hatcheries and raise the annual production of juvenile fish to as much as 150 million [132]. The mortality of juveniles released from the existing hatcheries was nevertheless high, natural spawning populations could not be maintained, and as was the case in the Volga, an acute shortage of broodstock soon constrained the activities of the Ural hatcheries [133].

A total of 24 sturgeon hatcheries have now been built in the lower reaches of the Volga, Ural, and several other rivers: 10 in Russia, 4 in Azerbaijan, 2 in Kazakhstan, and 7 in Iran, where more than 100 million juveniles are raised annually to replenish natural populations [134]. In addition, enterprises with various forms of ownership have been licensed by Russia and Kazakhstan to artificially produce, release, and in some cases sell juvenile sturgeon. By the end of the 1990s, more than 3 billion juvenile sturgeon had been released into the Caspian Sea, and although this has significantly increased the share of fish originating from released juveniles, natural populations have not recovered [66]. Stocking nevertheless remains an important tool to restore natural populations of migrating sturgeon to the Ural River, but hatcheries must be restructured to meet international standards for preservation of the diversity of the sturgeon gene pool and to raise young fish that are adapted to natural habitat conditions. This will require access to technologies to ensure that biological characteristics such as homing and spawning behavior are retained, that juveniles are of a viable weight before they are released [135,136], and that the production of juvenile sturgeon is balanced by species composition [137].

The Ural-Atyrau Sturgeon Fish Hatchery has already begun domesticating wild spawners to establish lines of broodstock to sustain future stocking programs [138], but this process carries several long-term risks [139,140]. Reliance on a narrow gene pool from captive broodstock increases the likelihood of loss of fitness and introduction of undesirable characteristics into the population [139,141]. Moreover, the routes and timing of natural sturgeon migrations in the Caspian basin are not yet fully understood; new methods to monitor fish movements are available, but the scarcity of residual Caspian sturgeon populations has made it difficult to exploit them to increase our understanding of sturgeon biology and behavior [30,106,142,143]. The release of juveniles into wild populations characterized by depleted gene pools may also lead to undesirable interspecific hybridization [19,144,145]. Thus, on the one hand, stocking measures based on domesticated spawners hold great promise for future re-establishment of naturally reproducing sturgeon populations in the Ural River [110,135,146,147], but on the other, these measures are characterized by uncertainty and can be challenging to implement [148].

3.4. Transboundary Cooperation

Although both Russia and Kazakhstan contribute habitat to Ural River sturgeon (Figure 3), downstream access to these sites and feeding areas in the Caspian Sea is controlled by Kazakhstan [28]. The upper reaches of the river, as well as most of the Ural’s tributaries, lie in Russia, which generates and regulates most of the flows into the river [31]. Naturally reproducing populations of sturgeon thus depend on environmental services provided by both countries and are subject to environmental threats generated in both countries. Each assigns priority to the protection of the Ural River and surrounding basin, but although there is agreement on basic principles and the need for joint action, the implementation has proceeded slowly. In the words of Alexander Chibilev, an expert on the Ural River: “Both states spend huge amounts of money on the restoration of the Ural. But a cursory review of what it is being spent on is enough to understand that this money will not have an effect. We spend a lot on conferences, round tables, and forums, but very little on concrete action”. [149].

Russia and Kazakhstan have signed numerous water management agreements since 1992, but most have been developed without local input and have been poorly implemented with insufficient cross-border sharing of information [150,151]. Although the two countries have cordial relationships and strong economic and cultural ties [26,152], environmental assessment, monitoring, and restoration activities are too often scaled to the sub-basin level as defined by the transboundary. The lack of basin-wide approaches creates obvious barriers to the re-establishment of sturgeon in the Ural River. Notwithstanding good intentions, the benefits of habitat restoration, reducing pollution, combatting IUU fishing, and stocking efforts will be severely limited if they apply to only portions of the river and its surrounding ecosystem. There are nevertheless reasons for guarded optimism. Joint patrols to combat poaching were initiated in 2007 [28], and the two countries signed an “Agreement between the Government of the Russian Federation and the Government of the Republic of Kazakhstan on the Conservation of the Ecosystem of the Basin of the Transboundary River Ural” in 2016 [26]. Very recent joint discussions have also led to coordinated, science-based proposals to improve water quality in the river [26].

4. The Wicked Nature of Re-Establishing Sturgeon in the Ural River

The challenge of returning naturally reproducing populations of sturgeon to the Ural River adds to the growing list of Central Asia’s wicked problems [153,154,155]. These problems are especially common in natural systems, where the issues are complex and often contentious, the dynamics non-linear, and the political stakes high [156,157,158]. They are stubborn and extremely difficult to resolve because steps can be taken to make the problem better or worse, but they rarely lead to a final solution. The problem consequently persists, evolving over time and frustrating those seeking to resolve it. There is no debate about the need to preserve Ural sturgeon populations and the river’s spawning grounds, yet the wicked nature of the problem (

Table 2. Wicked characteristics of the problem of re-establishing naturally reproducing populations of sturgeon in the Ural River.

Wicked Problem Characteristic	Examples	Ural Sturgeon References
Difficult to define with multiple solutions	Shifting paradigms of fundamental issue; lack of regional cooperation; no consensus on preventing IUU fishing	[28,150,159]
Assumptions changing	Centralized Soviet control suddenly relaxed in 1991; climate change emerges as an issue	[88,154]
Tradeoffs	Hydroelectric power vs. sturgeon; stocking to support fishing vs. stocking to re-establish natural populations	[100,132]
Dynamic with strong economic drivers	Fishing regulations change over time; powerful incentives to produce caviar	[3,41,160]
Incomplete and contradictory knowledge	Lack of basin-wide data; knowledge gaps in sturgeon life histories; inability to quantify effects of poaching	[106,150,161]
Interconnected with other wicked problems	Water–energy–food; overall management of the Caspian basin; geopolitical conflicts	[162,163,164]

) has stymied decades of efforts to return naturally reproducing sturgeon to the river.

Unanticipated consequences are another hallmark of wicked problems. The twentieth century experienced just two periods when landings of Caspian sturgeon plunged to near zero, allowing populations to recover (Figure 5). Both correspond to periods of conflict that disrupted economic activities—the First World War from 1914 to 1919 and World War II from 1939 to 1945. These conflicts, which were unrelated to efforts to stabilize populations of Caspian sturgeon, achieved this goal by temporarily refocusing national interests and interrupting the caviar trade [3,44]. Figure 5 also illustrates an unexpected and undesirable consequence of the 1962 ban on sturgeon fishing in the Caspian Sea, which was intended to preserve sturgeon populations. Instead, it exacerbated the problem by displacing fishing activities to the basin’s rivers, where harvests increased [28,41,44].

Wicked problems defy efforts to identify simple solutions, and as past experience makes clear [28], attempts to re-establish naturally breeding sturgeon populations in the Caspian basin’s last remaining major free-flowing river have not yet been successful. Several strategies that may not provide a final solution to the problem but can help achieve progress toward a solution are nevertheless available. Three are especially relevant to sturgeon and the Ural River. The first is to focus on the long rather than the short term [165]. Efforts to resolve the Ural sturgeon problem have traditionally been tactical and characterized by centralized control and management, shifting priorities, and programs that are in effect for limited time periods, often on just one side of the transboundary [28,45,150,151]. A concerted attempt was made in 2007–2008 to strategically focus international attention on a basin-wide strategy to rescue sturgeon in the Ural River [166]. The final resolution adopted during the planning process urged Russia, Kazakhstan, and the broader international community to undertake 26 steps that, although not framed in terms of a wicked problem, reveal wicked dynamics [28,158]. Although the attempt failed to achieve its primary goal of establishing an International Ural Sturgeon Park, the need to adopt a long-term perspective was clearly articulated and remains a priority today. It is noteworthy that this perspective has now been incorporated into a recent agreement between Kazakhstan and Russia [26].

The second strategy is to involve stakeholders in the process [167]. The concerns of local residents, who are often impoverished and whose daily activities center on the river, have received insufficient attention in the past [7,111]. Lacking knowledge of the perilous status of sturgeon and acting out of desperation, local residents often turn to poaching, which depletes the population of fish and helps enable criminal networks to trade in sturgeon and caviar [3]. There are many untapped opportunities to educate and raise awareness in Ural communities, generating trust and exploiting local insights in planning, habitat restoration, and even enforcement of regulations [111,165,168].

Removing as much uncertainty as possible from the problem is the third strategy [169]. The uncertainties associated with insufficient information about the hydrology of the Ural River, IUU fishing, and the consequences of stocking are well known, as is the bottleneck imposed by inadequate environmental monitoring data [28,83,152,170,171]. The lack of fundamental knowledge about structural changes in populations of Ural sturgeon species due to anthropogenic and other pressures [143] also generates ambiguity. These issues are compounded by a dearth of knowledge about the Ural’s hydrobiology, which includes natural predators of sturgeon eggs and larvae, as well as the more than 50 native (and 3 non-native) fish species that coexist with sturgeon in the riverine ecosystem [27,31].

Progress in addressing the wicked Ural problem will require sustained and integrated efforts to answer a myriad of scientific questions at scale [169], and it stands to benefit from the availability of sophisticated and rapidly advancing technology that includes telemetric tagging systems to monitor fish movement, microsatellite and mitochondrial DNA analyses to differentiate fish populations, and sensors and other electronic devices to combat IUU fishing [142,172,173,174,175]. Although the financial and logistical difficulties of deploying technology to study fish in the Caspian basin are well known contributors to the current shortage of information about sturgeon [106], it is encouraging to note that they are gradually coming into use [145,176,177,178].

5. Conclusions

The problem of returning naturally reproducing sturgeon in the Ural River has especially wicked dynamics, and although acknowledging this fact will not identify a pathway to a solution, it does change the perspective and lay a foundation for progress over time [179]. The challenges are well known. The basin extends over a vast area that was once centrally managed but is now bisected by a transboundary that fragments policy decisions. Basin-wide data that could be useful in defining priority areas for habitat restoration are in short supply, and sturgeon numbers have been depleted to the extent that it is difficult to find individual specimens for study [180,181]. The lives of residents living near the river are impacted by efforts to preserve sturgeon, but they have rarely been consulted about the problem and have little trust in the authorities. And against this background, there is a sense that the clock is ticking—that if something is not done soon, it will be too late [28].

If it is futile to seek a perfect answer to the wicked Ural sturgeon problem, then what are the more limited and feasible approaches that are worthy of attention? One is to seek the advice of local residents and acknowledge community norms when formulating measures to address the problem. The value of this approach, which rests on a sound conceptual foundation and is supported by a considerable amount of empirical data [182], was demonstrated during the Tsarist era, when social norms prevented overfishing in the Ural [36,38]. There is ample evidence that the current regulatory framework, which was imposed on local communities, has been only marginally beneficial and often counterproductive in preserving Caspian sturgeon; on the other hand, there is increasing evidence that policies informed by the viewpoints of stakeholders in the basin can be surprisingly effective [109,159].

Using scarce research funding to generate scientific knowledge of direct relevance to policy represents another useful approach [183]. Wisely applied, these investments can function as an important tool to remove policy-relevant knowledge gaps that are imposed by the transboundary. Obvious priority targets for such funding include management of the river, enhancing knowledge of sturgeon biology and habitat preferences, and deepening our understanding of the spatiotemporal relationships between sturgeon populations and the other organisms inhabiting the river. Finally, measures undertaken to stock juveniles in the river and combat IUU fishing should be implemented flexibly and adaptively [179]. Although these measures significantly enhance the potential to reintroduce naturally reproducing sturgeon populations to the river, it is important to understand that they are also expensive long-term scientific experiments that entail risk and offer no certainty of success. An adaptive perspective that acknowledges the unpredictability of outcomes and accommodates tactical and strategic adjustments over time as knowledge is gained and circumstances change will consequently maximize the likelihood for progress.