Global and European regional assessment: Near Threatened (NT)
EU 27 regional assessment: Vulnerable (VU°)

The Neretva Chub has a restricted range (extent of occurrence (EOO) c. 9,250 km²), which meets the threshold for the Vulnerable category under Criterion B1 (EOO < 20,000 km²). The extent and quality of habitat are estimated to be declining, but it is not understood to be severely-fragmented, the number of locations is unknown, and there is no evidence that it demonstrates extreme fluctuations.

Therefore, this species is assessed as Near Threatened at the global and European regional scales, because it is close to qualifying for Endangered under Criterion B.

In the EU 27 member states, the EOO is c. 1,040 km², which meets the threshold for Endangered (EOO < 5,000 km²). It is present at four locations where the quality of habitat is estimated to be declining. However, these sites are linked to a transboundary river system inhabited by the largest extant stock, hence its assessment is downlisted by one category from Endangered to Vulnerable under Criterion B (B1ab(iii)).

This species is native to the Neretva and Trebišnjica river systems, which together comprise a single large catchment in the Dinaric Karst region of southern Bosnia and Herzegovina, Croatia and Montenegro.

In the lower Neretva, it is putatively absent from the Lištica and Trebižat tributary systems, which are somewhat isolated by landscape features (see 'Habitat and Ecology'). The precise limits of its upstream distribution in the river are unclear, but it is reportedly present in the artificial Jablaničko accumulation lake.

It occurs sympatrically with the congeneric Italian Chub (Squalius squalus) and a putative undescribed species in the Trebišnjica River, and hybridisation between the three has occurred (see 'Conservation'). There are some doubts as to which of them are native to the system.

A subpopulation inhabiting the Ljuta River (not to be confused with a tributary of the upper Neretva bearing the same name) system in Konavosko polje, Croatia, is genetically introgressed with the Italian Chub (Squalius squalus) as a consequence of past natural hybridisation. It is included within this assessment, since resident individuals are morphologically congruent with the Neretva Chub.

Its extent of occurrence is 9,250 km², and 1,040 km² in the EU 27 region.

This species' current population size and trend have not been quantified, and the number of subpopulations is unknown.

Field observations indicate that a significant decline in abundance is likely to have occurred since the mid-20^th century, particularly in the upper Neretva and Trebišnjica rivers (see 'Threats').

The Neretva is the largest river system in the Dinaric Karst region and mostly flows through Bosnia and Herzegovina, with only its delta located in Croatia. Its relatively pristine upper reaches occupy a sparsely-populated mountainous valley, and currently terminate in the Jablaničko accumulation lake near the town of Konjic. The middle course of the river flows through a steep-sided gorge and is punctuated by three additional large dams, which have impounded the majority of its main stem downstream to the city of Mostar. Its lower reaches are mostly canalised, and receive water from a series of tributaries, some of which are connected only via subterranean flows (e.g., the Lištica River) or partially isolated by waterfalls (e.g., the Trebižat River). It ultimately flows through a wide alluvial delta bounded by a number of seasonally-fluctuating wetlands, including lakes Desansko and Kuti in Croatia and Hutovo Blato in Bosnia and Herzegovina.

The Neretva Chub has been recorded throughout the Neretva system upstream to the Jablaničko and Ramsko reservoirs, the latter of which is constructed on the Rama River, a tributary of the Neretva which flows into Jablaničko. The majority of records between these reservoirs and the city of Mostar pertain to the series of artificial lakes which interrupt the Neretva main stem, plus the lower reaches of some affluent rivers. Downstream of Mostar, this species inhabits the river's main channel and most tributary systems. It therefore occupies a range of lotic and lentic fluvial habitats from large to small river channels with variable, often seasonally fluctuating, discharge rates, and contrasting extents of human modification. It also occurs in some man-made drainage channels, and is present in most wetlands associated with the lower Neretva.

The Trebišnjica River is located in Bosnia and Herzegovina, with a small part of its upper catchment in Montenegro. Prior to modification it was the longest karstic sinking river in Europe. It flows through a series of polje (depressed flat plains surrounded by limestone ridges), which under natural conditions would be partially inundated from late winter to early summer due to increased river discharge and rising groundwater. These temporal wetlands represent important spawning and nursery habitat for native fishes throughout the Dinaric Karst system, but in the Trebišnjica catchment their formation is currently limited by human development (see 'Threats'). The lowermost portion of the Trebišnjica flows through Popovo polje, from where it mostly discharges to subsurface conduits draining to the Ombla Spring near Dubrovnik, Croatia. However, some of its water flows underground to Čapljina Spring in the Hutovo Blato basin, and the river is therefore often regarded as belonging to the Neretva catchment. The Neretva Chub has been recorded throughout the Trebišnjica system, including the artificial Bilećko, Goričko and Vrutak accumulation lakes. Field observations indicate that some individuals inhabiting the Trebišnjica utilise estavelles and ponors to access subterranean water bodies, a phenomenon which might also occur in some tributaries of the Neretva.

Konavosko is a lowland karstic polje comprising an isolated coastal plain enclosed by hills and limestone ridges. A series of small rivers and springs rise mostly along its northern edge and drain towards the Ljuta River, which flows for a short distance before draining to the Adriatic Sea through a ponor at its southern margin. The Neretva Chub is present in the river itself, which comprises a shallow, relatively small channel with abundant submerged vegetation in places, plus a network of artificial drainage channels that have been excavated in the floor of the polje in order to control seasonal flooding and supply water for agriculture.

This species is primarily a benthic predator feeding on aquatic invertebrates, particularly insect larvae and gastropods, alongside small amounts of organic detritus and plant material. Larger (over 15 cm total length) individuals also consume small fishes.

The maximum recorded age is 7+, but its life history is otherwise not well-studied. The annual reproductive period is likely to extend from spring to early summer, during which period adults may migrate to tributaries or flooded wetlands to spawn. Observations of related species suggest that nuptial individuals are likely to form polygamous aggregations, with individual females releasing several batches of eggs over the duration of the season.

This species is plausibly threatened by river regulation and other forms of anthropogenic habitat degradation.

In the Neretva system, the construction of four large hydroelectric dams along the middle section of the river and one on the Rama River since the 1950s has altered natural flow and sedimentation regimes and potentially blocked migration routes, fragmented subpopulations, and markedly reduced the extent of suitable habitat for all life stages. The scale of annual flooding in the Hutovo Blato wetland has declined significantly due to reduced discharge of the Neretva plus some affluent springs such as Čapljina, which is also exploited for hydropower generation. The southern part of the wetland was partially impounded in 1979, and a proposed plan to divert water from Hutovo Blato for domestic use may further reduce habitat quality.

Hydroelectric dams have also created unnatural fluctuations in discharge and water temperature (hydropeaking and thermopeaking) 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 and changes in land use is likely to have increased accumulation of fine sediments and negatively impacted foraging and reproductive success at some locations. The proposed construction of around 70 additional hydroelectric projects in the upper reaches of the river plus an ongoing expansion scheme in the Trebišnjica River (see below) together represent a plausible future threat to the entire Neretva ecosystem.

The extent and quality of habitat in the Neretva catchment has been further diminished by bank stabilisation, channelisation and other efforts to enhance flood protection or exploit water resources for irrigated agriculture. In the river's delta, only three of its original twelve branches remain and most former marshes and lakes have been reclaimed for agriculture since the 1960s. Diffuse and point source agricultural, domestic and industrial pollution has resulted in eutrophication or discharge of toxic substances at some locations. The industrial extraction of riverine gravel and sand for urban development has taken place since the 1970s, and resulted in artificial deepening the of river bed and hampering the transport of heavy sediments.

Non-native fish species established in the Neretva system include Common Carp (Cyprinus domestic strain), Prussian Carp (Carassius gibelio), Sunbleak (Leucaspius delineatus), Largemouth Bass (Micropterus salmoides), Pumpkinseed (Lepomis gibbosus), Eurasian Pikeperch (Sander lucioperca), Eurasian Ruffe (Gymnocephalus cernua), Brown Bullhead (Ameiurus nebulosus), Eastern Mosquitofish (Gambusia holbrooki) and Rainbow Trout (Oncorhynchus mykiss), all of which are considered invasive and can exert detrimental pressures on native freshwater fauna through increased competition, predation, transmission of pathogens or habitat degradation. They are particularly abundant in artificial reservoirs.

The Trebišnjica River system has been heavily modified by the "Lower Horizons" hydropower scheme, which was initiated during the 1960s and now comprises several dams and hydroelectric power plants. The accumulation lakes associated with these barriers have favoured the widespread establishment of non-native fish species. Since 1978 much of the main stem has been converted into a 65-kilometre canal designed to prevent loss of water into the surrounding karst, and former temporal wetlands at some locations, e.g., Popovo polje, no longer exist. This has caused annual discharge from the Ombla spring to decrease by almost 20% and reduced productivity of the lower Neretva River. Non-native fish species introduced to the Trebišnjica system include Pumpkinseed, Eastern Mosquitofish, Prussian Carp, Rainbow Trout and Topmouth Gudgeon (Pseudorasbora parva).

The Trebišnjica system is set to undergo further modification as a result of the ongoing (as of 2023) "Upper Horizons" hydropower strategy, which aims to artificially redirect water from poljes draining to the Buna and Bregava rivers in the lower Neretva watershed to the Bileća reservoir through a cascading series of canals, tunnels and smaller hydroelectric stations. Once complete, the scheme is projected to significantly reduce discharge in the lower Neretva, and drive a range of negative impacts on Hutovo Blato and the river's delta region.

The natural hydrological regime of Konavosko polje has been disrupted since the late 1950s, when a drainage tunnel was constructed in order to prevent flooding by increasing the flow of water to the Adriatic Sea. The majority of the polje was subsequently reclaimed for agriculture, leading to an existing network of drainage and irrigation channels being markedly expanded. Non-native fish species in the Ljuta River system include the predatory Rainbow Trout and Black Bullhead (Ameiurus melas), the latter of which has also colonised the drainage and irrigation network.

This species is not used or traded.

This species is included in Appendix III of the Bern Convention (as Leuciscus svallize) and Annex II of the European Union Habitats Directive.

It is strictly protected at the regional scale in the Republic of Srpska (Bosnia and Herzegovina), and currently assessed as Vulnerable for the National Red List of Croatia.

No specific conservation management plan exists, but some parts of its range lies within protected areas, of which the Neretva Delta and Hutovo Blato are included in the Ramsar Convention on Wetlands (sites 585 and 1105, respectively). A new, ostensibly more sustainable, management policy was implemented in the Hutovo Blato basin following a European Union-funded LIFE project which ran from 2000-2002.

Konavosko polje forms part of a protected area included in the European Union's Natura 2000 network (site HR2000946), and the Neretva Chub is among the target species.

The proposed hydropower developments in the Neretva and Trebišnjica rivers have been opposed by local communities and several NGOs, leading to the publication of various news articles, reports, research projects and dissemination events, e.g., Neretva Science Week (July 2022).

A deeper understanding of this species' population trend, abundance, distribution and life history would likely prove useful in the establishment of future management efforts and priority conservation sites.