Global and European regional assessment: Endangered (EN)
EU 27 regional assessment: Not Recorded

The Mostar Minnow has a restricted range (extent of occurrence (EOO) c. 419 km^2, area of occupancy (AOO) c. 40 km²), which meets the thresholds for the Endangered category under Criterion B1 (EOO < 5,000 km²) and Criterion B2 (AOO < 500 km²). It is present at one location where the extent and quality of habitat are estimated to be declining.

Therefore, this species is assessed as Endangered under Criterion B (B1ab(iii)+2ab(iii)).

This species is endemic to Mostarsko polje in the Dinaric Karst region of southern Bosnia and Herzegovina, where it inhabits the middle and lower Lištica River plus a series of associated springs, tributaries and subsurface water bodies. The Lištica is part of the larger Neretva River system, but they are connected only by subterranean karstic conduits.

This species' current population size and trend have not been explicitly quantified.

It remains present where suitable habitat persists, but is suspected to be declining based on direct observation (field researchers and local fishers' reports), declining habitat quality and the effects of introduced taxa (see 'Threats').

Mostarsko is a typical karstic polje, comprising a depressed flat plain surrounded by limestone ridges. A series of small rivers and springs rise mostly along its northern and western edges and flow for short distances before submerging into ponors on the southeastern side.

The Lištica is an intermittent sinking river which rises in mountains to the west of Mostarsko polje before flowing through its centre and draining into a ponor at its eastern border. It resurfaces more than a kilometre away and is referred to as the Jasenica River, which flows for a few kilometres before discharging into the Neretva.

The area surrounding the lower part of the Lištica naturally floods to form an extensive ephemeral wetland (Mostarsko Blato) from late winter to early summer, although this process has been significantly restricted by engineering works (see 'Threats').

The Mostar Minnow inhabits shallow, slow-moving river and spring reaches, drainage channels and permanent wetland pools, but moves into flooded areas as they become available. It also enters the lower reaches of some intermittent tributary streams, and during the summer many individuals aggregate around perennial water sources and ponors from where the majority of the population retreats to subterranean water bodies for several months per year.

It is an opportunistic omnivore feeding predominantly on aquatic insects alongside smaller quantities of gastropods and plant material. During the early summer, individuals feed intensively and develop marked fat reserves prior to their movement into underground refugia.

The maximum recorded lifespan is c. 4 years, and individuals mature at age 1+. It is a fractional spawner and the annual reproductive period extends from late January to late May, which corresponds to the period during which Mostarsko Blato is flooded.

The Herzegovinian Spined Loach (Cobitis herzegoviniensis) is also endemic to Mostarsko polje, while the Lištica River is inhabited by a subpopulation of Softmouth Trout (Salmo obtusirostris), which is native to a small number of river systems in the Western Balkans region.

In 1947, a flood-control tunnel was installed to direct water through the limestone hill beneath which the Lištica River naturally drains from Mostarsko polje towards the Neretva, and during the 1950s a network of drainage channels was excavated in the polje itself. The combined effects of these engineering works in addition to unregulated water abstraction has lowered local groundwater levels by 1.5-2.5 metres, and driven the isolation of some ponors and springs which formerly contributed water to the wetland during flood periods.

A hydroelectric power plant supplied by water from the lower Lištica became operational in 2010, and included the construction of a storage reservoir and concrete canal. A further artificial channel was added in 2016, and a second reservoir in 2018. These activities have progressively reduced the spatial and temporal extent of the wetland.

Observational evidence suggests that Phoxinellus species tend to decline rapidly in the presence of non-native fish taxa, a number of which have been introduced to the the Lištica system. These include Common Carp (Cyprinus domestic strain) and Prussian Carp (Carassius gibelio), plus the predatory Pumpkinseed (Lepomis gibbosus), Rainbow Trout (Oncorhynchus mykiss), Brook Trout (Salvelinus fontinalis) and Brown Bullhead (Ameiurus nebulosus).

Extraction of riverine gravel and sand for urban development has driven further habitat degradation in the western portion of Mostarsko Blato, where construction of a motorway linking the area to the border with Croatia represents a plausible threat. Unauthorised road building and fly-tipping during low-water periods have also resulted in the sometimes-intentional blocking or burying of ponors, which has reduced the extent of subterranean refugia available to the Mostar Minnow. The drainage channel network is periodically dredged and stripped of both aquatic and riparian vegetation, reducing the quality of habitat available to native fishes.

Some parts of the polje have been reclaimed for agriculture, and this is likely to represent a source of diffuse organic pollution. Water abstraction during the summer reduces the extent of habitat, when some drainage channels are completely dewatered. Untreated domestic sewage was for a long period of time discharged directly into local groundwater, and it is unclear whether water treatment facilities have yet been installed.

Overharvesting also constitutes a plausible threat (see 'Use and Trade').

This species is harvested, consumed and traded on a largely unregulated basis, and the level of offtake is unclear. It was traditionally an important source of protein for local communities and harvested from boats during periods when Motarsko Blato was flooded, but is today mostly served in restaurants and boats cannot be used because the wetland is too small (see 'Threats'). Declining yields have resulted in the price per kilo increasing by more than three times since 2010, but demand remains high and destructive fishing methods involving chemicals or electricity are sometimes employed.

This species currently has no legal protection and does not occur within any protected areas.

A research project aiming to ascertain its population status and develop a conservation management plan took place from 2020-2022. The results indicate that it has suffered from significant habitat loss, but remains abundant and may comprise up to 90% of the fish community where suitable environmental conditions remain. It was added to the Bosnia and Herzegovina National Red List as an upshot of the campaign, which also included public outreach activities and short-term maintenance of a few individuals in captivity. A second project was launched at the end of 2022, in order to work towards the establishment of an official protected area in Mostarsko polje.

Recommended actions within the updated plan include additional field surveys to determine the location of spawning and nursery sites, followed by fencing and/or active protection of selected locations in order to limit overharvesting, the development of new outreach materials to educate local communities, and liaising with local angling societies, town councils and other relevant stakeholders to prevent the future introduction of non-native fish species. Moreover, it is proposed to actively manage harvesting through the introduction of catch limits, closed seasons, no-fishing zones and licenses for fishers, with a traceability scheme involving local restaurants designed to determine the effectivness of the measures. Regular monitoring is planned so that the management plan can be updated on an annual basis.