The taxonomy of anadromous Ponto-Caspian shads remains in question, with molecular studies revealing low genetic divergence between species inhabiting the Black, Caspian and Aegean Sea basins (Faria et al. 2006; Vernygora et al. 2018).

In the absence of a definitive taxonomic revision, the Red List continues to follow the nomenclature provided by Fricke et al. (2023).

The Pontic Shad has experienced a sharp reduction in the extent of suitable spawning habitat since the mid-20^th century, and it is now estimated to enter c. 2,000 km of river stretches. The global population, quality of suitable habitat and number of mature individuals are estimated to be declining, but the species cannot currently be placed into any threat category based on Red List criteria. It is therefore assessed as Least Concern.

This species is native to the Black Sea and Sea of Azov basins, including the lower-to-middle reaches of larger inflowing rivers to which it migrates during spring and summer (see 'Habitats and Ecology').

Since the mid-20^th century its breeding range has been significantly reduced due to dam construction (see 'Threats'). For example, historic records indicate that it formerly ascended the Danube River for c. 1,600 km to the vicinity of Mohács (Hungary) and the Dnieper for c. 950 km to Kiev (Ukraine). It is now restricted to the lower portions of these rivers, i.e., below the Iron Gates Dam in the Danube (c. 860 km upstream, although the majority of spawning takes place between 180-500 km) and the Kakhovka Dam in the Dnieper (c. 120 km upstream).

In the Don River it continues to occur upstream to Serafimovich (c. 900 km), albeit in much smaller numbers since construction of the Tsimlyansk Dam (see 'Conservation'). It is still able to migrate c. 350 km upstream in the Dniester River, as far as the Dubăsari Dam in Moldova.

Elsewhere, the other known spawning subpopulations enter the lower reaches of the Southern Bug River in Ukraine, the Kızılırmak and Sakarya river systems in northern Türkiye, and the Rioni River in Georgia.

The Pontic Shad has since the early 1990s colonised the lower Kuban River in Russia, where it has been reported upstream to the Krasnodar Dam. The dam was constructed in the mid-1970s and has greatly reduced turbidity in the lower Kuban, which probably created suitable conditions for the shad to enter.

Records from the Sea of Marmara probably represent vagrant foraging individuals, and it is not believed to be resident in the basin.

There is little doubt that the Pontic Shad's global population contracted significantly during the latter half of the 20th century (see 'Distribution' and 'Threats'), but the extent of the decline has not been quantified. More than 50% of its former breeding range has been lost since the 1950s, and there is evidence that it has been extirpated from some river systems, e.g., the Khobi River, Georgia.

Although the largest subpopulation, which migrates to the Danube River, is increasingly well-studied, a lack of data from elsewhere hampers accurate evaluation of its population status and trend. Moreover, the conservation status of the Danube subpopulation has been described as favourable in some reports, while others have concluded that it is over-exploited (see 'Use and Trade').

Population estimates are further complicated because this species appears to undergo a cyclical pattern of abundance. This has been exemplified by fluctuating commercial landings in the Danube delta region, which varied between 200-2,400 tonnes annually during the period 1960-1998, and between 174.6-634.5 tonnes from 2010-2021. Some researchers have linked these events to increased flood-pulse runoff from the river driving short-term eutrophication events and temporary increases in productivity along the western coast of the Black Sea. Others have argued that heavy flooding could negatively affect recruitment due to increased turbidity, meaning generations spawned in years of low flow lead to greater numbers of migrating adults 2-3 years later. In either scenario, the annual recruitment of Pontic Shad is evidently affiliated to water level fluctuations, at least in the Danube River.

In the absence of a precise overview, the Pontic Shad's global population trend is estimated to be slowly declining when the ongoing threats (see 'Threats') are taken into account.

This species is euryhaline, anadromous and iteroparous, and enters larger rivers in order to spawn. Individual subpopulations are believed to exhibit a high degree of fidelity to particular foraging and spawning sites, implying that the overall population is spatially-structured.

Outside the reproductive season adult individuals are pelagic, and many winter at depths of 30-40 metres or more in specific foraging areas, e.g., the Danube subpopulation is known to overwinter in the southwestern Black Sea.

Migratory subpopulations begin to move towards their spawning grounds when water temperatures reach 5-6°C, normally in late March. Migration peaks from April to May at water temperatures of 9-13°C and usually ends by early June, but may extend to August. Males tend to migrate before females, and spawning itself takes place between May and August when the water temperature exceeds 15°C. This species is a fractional spawner, with females releasing several thousand eggs in batches several times per week. The pelagic eggs are mostly released at depths of 2-3 metres in fast-flowing stretches of large river channels, and migratory post-spawning adults return to offshore foraging areas in the Black Sea. Newly-hatched larvae drift passively downriver in the upper water column, sometimes settling in floodplains before juveniles arrive to river deltas and estuaries during their first summer. They migrate to the sea during autumn and remain there until they reach sexual maturity.

Both males and females mature at 2-3 years of age, with the majority spawning for the first time at 3 years. They are reproductively active for 2-5 years with each individual spawning up to 4 times during its lifetime, although once or twice is the norm. Some older individuals are thought to die post-spawning, since the adults do not feed while migrating. Maximum age in both sexes is 8-9 years, and maximum recorded size is 37.0 cm standard length.

At sea this species feeds primarily on smaller fishes such as European anchovy (Engraulis encrasicolus) and zooplankton. Foraging intensifies during the post-spawning summer period, and less food is taken during the winter.

In the past, the primary threats were impoundment and floodplain drainage in large river systems, which have significantly restricted access to adult spawning grounds and juvenile nursery zones throughout its range (see 'Distribution' and 'Population').

Pollution and degradation of coastal wetlands is also widespread in the Black Sea and Sea of Azov, further reducing the extent and quality of suitable nursery habitat for first-summer juveniles prior to their offshore migration.

The Black Sea and Sea of Azov ecosystems have also suffered extensive anthropogenic degradation, leading to radical declines in the abundance of native fish species. After the 1960s, increased discharge of agricultural, domestic and industrial wastes from their inflowing rivers resulted in intensive eutrophication of the Black Sea's shallow northwestern shelf and the Sea of Azov. This led to increased primary production and a shift towards mesotrophy in the eastern and southern portions of the Black Sea basin. Dam construction during the mid-20th century vastly reduced solid loads reaching the seas, hindering siliceous phytoplankton and favouring flagellate blooms. Further ecological disruptions have been driven by overfishing of pelagic predators and planktivorous fishes since the advent of industrial-scale fishing during the 1970s, and the unintentional introduction with ship ballast water of the invasive warty comb jelly (Mnemiopsis leidyi).

The combined effect of these pressures on the structure and functioning of the Black Sea and Sea of Azov pelagic food webs has been drastic. A series of environmental crises included the 1989-1991 collapse in populations of small pelagic fishes, which comprise the major diet component for adult Pontic Shad. Pelagic fish stocks have since recovered to a limited extent (see 'Conservation'), but remain far below their pre-1989 levels. Moreover, recent estimates suggest that 75-85% of available Black Sea fisheries resources are over-exploited, and more than 40% fully collapsed.

There exists strong evidence that the Danubian Pontic Shad subpopulation has been over-exploited. Annual commercial landings in the Danube delta region over the 11 years between 2010-2021 failed to even approach the recommended quota on all but three occasions. Furthermore, it has been demonstrated that the fishing mortality rate exceeds the natural mortality rate in the lower Danube River. Illegal and unreported landings are also believed to be widespread in the area. Studies have also revealed evidence of overfishing in the subpopulation inhabiting the southeastern Black sea off the coast of northern Türkiye.

Pollution from agricultural, domestic and industrial sources may also be negatively impacting Pontic Shad subpopulations. For example, research conducted on migrating individuals collected downstream of the Iron Gates dam complex on the Danube River revealed an accumulation of heavy metals (particularly arsenic and cadmium) in their muscle tissue that exceeded the maximum concentration deemed acceptable for human consumption.

This species is fished commercially throughout its range using gillnets, pound nets, beach seines, and trawl nets, and is marketed fresh, salted, smoked and canned for human consumption. It is most heavily-exploited during the annual spawning migration, e.g., in the Danube Delta region c. 90% of all commercial landings in the entire river system occur during this period.

In Romania the annual catch varies from 200-500 tonnes, with a market value of c. €1.5 million. From 1996-2016 annual landings in the Dniester River and its estuary varied from 1.3-62.0 tonnes, with an average of 24.6 tonnes. Data for landings elsewhere is limited.

Landing totals are widely assumed to be underestimated throughout the species' range due to illegal and unreported fishing.

This species is listed (as Alosa pontica) under appendix III of the Bern Convention and Annexes II and V of the EU Habitats Directive. It is also protected at the national level in some countries, e.g., Serbia, Romania, Bulgaria.

No species-specific conservation actions are in place, but a specialised fish lift intended to ease the passage of migratory fish species was installed at the Tsimlyansk Dam on the lower Don River during the 1950s. Small numbers of Pontic Shad are reportedly able to utilise both the lift and nearby ship navigation locks to access the river upstream of the dam, where the species continues to spawn.

In the Danube River system, a handful of individuals are caught annually by fishers above the Iron Gates complex, which presumably bypass the dams through ship navigation locks. As of 2019 the European Union is funding a project to investigate the feasibility of restoring fish migration pathways at the Iron Gates.

The breakdown of former Soviet Union economies in Eastern Europe during the 1990s, plus the introduction of several national and international programs focused on improving the environmental status of the Black Sea has driven a partial recovery of the ecosystem. The warty comb jelly population has also decreased markedly following the 1997 Black Sea invasion by its natural predator, the comb jelly Beroe sp. It is unclear whether these improvements have positively impacted the Pontian Shad population, however.

There exist more than 20 coastal nature reserves of varying regional, national and international status in the Black Sea basin, plus eight in the Sea of Azov. Four of these are UNESCO Biosphere Reserves, including the Danube delta. All Black Sea border nations have also ratified the Ramsar Convention on Wetlands, and in Ukraine alone 22 wetlands have been designated Ramsar status. Many reserves throughout the Pontic Shad's range still lack effective infrastructure and management plans, however.

A stated priority of the Bucharest Convention on the Protection of the Black Sea Against Pollution, signed by all Black Sea bordering nations in 1992, is “sustainable use of commercial fish stocks and other marine living resources". However, long-term efforts to establish a legally binding document covering fisheries and the protection of living marine resources have not proven successful, and fisheries management remains inadequate throughout the Black Sea. European Union fishing quotas are in place for the waters of member states Romania and Bulgaria, but they do not cover Pontic Shad.

Recommended priority areas for research include detailed assessments of population dynamics, status and trends at global and subpopulation levels, harvest and trade trends, and ecology of the juvenile and marine phases. Long-term population monitoring should ideally be implemented throughout the Pontic Shad's range.

Resolution of anadromous Ponto-Caspian shad taxonomy would also be highly beneficial in terms of accurately identifying populations of particular conservation interest throughout the region.