The Caspian Vimba does not approach the range size thresholds for Vulnerable under Criterion B1 (extent of occurrence (EOO) < 20,000 km²) or D2, and Criterion B2 is precluded by its uncertain area of occupancy (AOO). The population size is believed to exceed mature 10,000 individuals, hence it does not approach the thresholds for Criteria C or D. There exists no quantitative analysis which would permit application of Criterion E.

Although no range-wide population trend data exists, significant site-scale declines have occurred within the last 20-30 years, and a suspected ongoing reduction based on declining fisheries data, AOO and habitat quality might meet the threshold for Vulnerable under Criterion A2 (≥ 30% over the past 15 years = 3 generations).

As a result of this data uncertainty, Least Concern and Vulnerable are equally plausible Red List categories for the present assessment, and this species is assessed as Near Threatened.

This species is endemic to the Caspian Sea basin, where the majority of records pertain to the southern and western coastlines, comprising the Republic of Dagestan (Russian federation), Azerbaijan and the Islamic Republic of Iran.

It is understood to be a vagrant in the lower Volga River and its delta, where there only exist sporadic reports of single individuals and no evidence of reproduction. It has never been reported from the Ural River system, and may be entirely absent from the eastern side of the Caspian watershed.

This species' population size is unknown, but is likely to exceed the minimum threshold for Red List criteria (< 10,000 mature individuals). The current population trend has not been quantified, and the number of subpopulations is unclear.

The results of recent field studies suggest that it remains extant throughout its range, but that abundance has reduced markedly since the 1990s. This pattern is suspected to be ongoing, based on declines in fisheries landings, habitat quality, and an as yet undetermined contraction in area of occupancy (AOO).

Putative subpopulations inhabiting different river systems in Iran exhibit notable genetic and morphological variation, and may represent divergent genetic lineages (see 'Conservation').

Outside of the annual reproductive period this benthopelagic, semianadromous species inhabits brackish environments including coastal lagoons, estuaries and the littoral zone of the Caspian Sea itself.

It mostly feeds on aquatic invertebrates, supplemented by organic detritus, plant material and smaller fishes.

Maximum recorded lifespan is 15 years, although there exist very few reports of individuals older than age 7+. Adult individuals mature at age 2-4+, and current understanding suggests that the generation length is 4-5 years.

The spawning season extends from April to July, and is characterised by the upstream migration of mature adults to specific sites comprising beds of gravel or other coarse substrata in shallow, flowing water. In Iran these tend to be located 25-75 kilometres upstream. Spawning may also occur in the vicinity of artificial structures, sandy shorelines or among the roots and stems of aquatic plants, provided there is sufficient water movement.

Reproductive males develop a conspicuous epigamic colour pattern, with the upper part of the body becoming darker and reddish pigmentation appearing on the belly and fins. Minute epidermal breeding tubercles are visible on the body in both sexes, but are more prominent in males. Adult females are reportedly larger than males of the same age, and fecundity increases with age and body size, reaching up to 89,000+ eggs per individual.

Post-spawning adults return to their downstream foraging sites, and juveniles drift to nursery zones near the mouths of their natal rivers within the first few months of life.

This species is primarily threatened by river regulation and other forms of anthropogenic habitat degradation, which have resulted in widespread loss of the heterogenous, interconnected fluvial habitats required to complete its life-cycle. The construction of large dams plus smaller weirs and other barriers throughout its range has severely altered natural flow and sedimentation regimes, blocked migration routes, and reduced the extent of suitable habitat for all life stages. Hydroelectric dams also create unnatural fluctuations in discharge and water temperature (hydropeaking) which bring about artificial dewatering of downstream river stretches and loss of stable nursery habitat for juveniles. Furthermore, the combined effect of hydropeaking, dam flushing operations, changes in land use, and the removal of riparian vegetation has increased accumulation of fine sediments at some spawning sites, plausibly impairing the hatching and survival rates of eggs and larvae.

Dam construction has also negatively impacted a number of coastal wetlands associated with the lower reaches of rivers draining to the Caspian Sea. For example, the surface area of Agrakhan Bay, a large wetland located in the delta of the Terek River, Dagestan (Russian Federation), has decreased from c. 340 km² to c. 258 km² over the past century due to the river's discharge being reduced by accumulation dams. Water depth has decreased considerably, and the northern part of the bay today comprises a series of small, shallow and increasingly isolated waterbodies where it was previously a single much deeper lagoon. Abundance of the Caspian Vimba and other semianadromous fish species has declined significantly, and there was a tenfold decline in the local commercial fishery between the early 20^th century and 2018.

Elsewhere, the quality of fluvial habitat has been further diminished by bank stabilisation, channelisation and other efforts to enhance flood protection or exploit water resources for irrigated agriculture. Some spawning sites may also have been damaged by the industrial extraction of riverine gravel and other sediments for urban development.

This species is also threatened by diffuse and point source agricultural, domestic and industrial pollution, which has at some locations reduced the extent and quality of habitat due to eutrophication or discharge of toxic substances. In Gilan Province, Iran, the Anzali Wetland comprises a coastal lagoon located close to the mouth of the Sefid-Rud River. Its surface area has decreased by more than 75% since the 1930s, and it is further impacted by sedimentation, eutrophication, agricultural and industrial contaminants, and the introduction of non-native aquatic species including invasive macrophytes. The commercial fishery collapsed during the 1960s, and the wetland has been listed on the Montreux Record since 1993.

Overharvesting may also represent a threat, but no reliable range-wide overview is available (see 'Use and Trade').

Non-native fish species established within the Caspian Vimba's range include the Goldfish (Carassius auratus), Prussian Carp (Carassius gibelio), Grass Carp (Ctenopharyngodon idella), Silver Carp (Hypophthalmichthys molitrix), Bighead Carp (H. nobilis), Rainbow Trout (Oncorhynchus mykiss) and Topmouth Gudgeon (Pseudorasbora parva), all of which are considered invasive and can exert detrimental pressures on native freshwater fauna through increased competition, predation or habitat degradation.

The ongoing expansion of the congeneric Vimba Bream (Vimba vimba) in the northern Caspian basin represents a plausible threat due to the potential for introgressive hybridisation between the two species. The Vimba Bream was introduced to the Volgograd Reservoir during the late 1980s, and has since spread throughout the lower Volga River and into the adjacent Ural River catchment.

Introduction of the invasive Warty Comb Jelly (Mnemiopsis leidyi) to the Caspian Sea during the late 1990s has driven drastic declines in pelagic, zooplanktivorous fish species and altered food web dynamics throughout the Caspian Vimba's non-breeding range, but it is unclear whether there has been any direct negative impact.

Ongoing and future climate change in the Caspian Sea basin could plausibly exacerbate most of the above issues.

This species is targeted by commercial and subsistence fisheries throughout its range, particularly during its annual spawning migration when large numbers are caught as they aggregate in rivers (see 'Habitat and Ecology'). In Azerbaijan, annual landings are anecdotally < 150 tonnes and in Iran < 500 tonnes, but the actual level of offtake is uncertain due to inconsistent data availability and widespread unauthorised harvesting.

It appears to be produced or reared in aquaculture facilities in both Azerbaijan and Iran, but few details are available.

This species is not covered by any specific national or international legislation or management plan(s). It is present within the boundaries of various protected areas, some of which are also listed under international treaties such as the Ramsar Convention on Wetlands of International Importance (e.g., sítes 36, 40, 46, 47, 111, 1076 and 1109) or UNESCO World Network of Biosphere Reserves (e.g., the Volga Delta, Russian Federation, and Miankaleh Biosphere Reserve, Iran).

All five littoral states bordering the Caspian Sea are signatories of the Framework Convention for the Protection of the Marine Environment of the Caspian Sea (aka the Tehran Convention), which has been in force since 2006. The objective of this convention is “the protection of the Caspian environment from all sources of pollution including the protection, preservation, restoration and sustainable and rational use of the biological resources of the Caspian Sea”, but progress towards meeting this target has thus far been limited by protracted negotiations regarding the legal status of the basin.

A deeper understanding of this species' demographics (population size and trend), current distribution, and life history, particularly the identification of key spawning sites, would likely prove useful in the development of future management efforts. The potential existence of multiple genetic lineages also warrants further research, since these may need to be considered independently for conservation purposes. Given the extent of its range, such efforts may be best coordinated at local or regional scales.