Global and European regional assessment: Vulnerable (VU)
EU 27 regional assessment: Endangered (EN)

The Southern Dalmatian Minnow has a restricted range (extent of occurrence (EOO) c. 6,086 km²), which meets the threshold for the Vulnerable category under Criterion B1 (EOO < 20,000 km²). It occurs at six locations where the extent and quality of habitat are estimated to be declining due to pollution and the artificial dewatering or channelisation of karstic watercourses. Therefore, this species is assessed as Vulnerable under Criterion B (B1ab(iii)) at the global and European regional scales.

In the EU 27 member states, the EOO is c. 316 km², which meets the threshold for the Endangered category (EOO < 5,000 km²), and it is assessed as Endangered under Criterion B (B1ab(iii)). No downlisting of this category is deemed appropriate due to the fragmented distribution of the extant subpopulations.

This species' native range mostly comprises rivers associated with the left bank of the lower Neretva River in Croatia, Bosnia and Herzegovina, and a small part of Montenegro.

In Bosnia and Herzegovina, it is present in Ljubomir, Dabarsko, Fatničko and Popovo poljes within the Trebišnjica River system, and in Croatia it occurs in the Ombla spring, where the lower Trebišnjica re-emerges after flowing underground for 20 kilometres, plus the isolated Konavosko polje, east of Dubrovnik. The native status of the latter subpopulation apparently requires confirmation, but it is included here since there exists no clear evidence that it has been introduced.

Elsewhere in the Neretva system, it has previously been reported from the Buna River in Bosnia and Herzegovina, but there are no recent records.

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

Field observations indicate that the quality of habitat has declined significantly across most of its range over the past half-century. It has been extirpated from a number of former sites in Bosnia and Herzegovina, including the type locality in Popovo polje, since the 2010s.

This small-bodied, gregarious species inhabits both lotic and lentic habitats in an area characterised by karstic sinkholes, sinking rivers, caves and complex underground drainage systems.

There is a strong interaction between surface and ground water, with numerous springs emerging around the margins of depressed flat plains known as polje, which are typically separated by limestone-dolomite ridges. These water sources may be perennial or ephemeral and can flow very strongly during periods of high rainfall, typically flooding the poljes to form temporary wetlands which persist from late autumn to early summer.

When the flood water eventually subsides into the porous karst, most rivers and streams are dewatered to some extent, and some dry out entirely. During such periods the Southern Dalmatian Minnow is mostly restricted to spring-fed perennial reaches and sinkhole ponds. Some individuals also utilise ponors to access subterranean water bodies, where they may remain for several months per year. A small number of subpopulations have been observed in cave systems with no nearby surface access, where they might be permanent residents.

This species' diet mostly comprises small aquatic invertebrates.

Adult male individuals are smaller and possess relatively longer pelvic fins than females.

Its life history has not been well-studied, but the annual reproductive season extends from late spring to early summer, when mature adults enter flooded poljes to spawn. Nuptial individuals develop a conspicuous epigamic colour pattern, and males develop prominent breeding tubercles on the head and pectoral fins. The eggs are deposited on gravel, pebbles and other submerged surfaces.

This species is primarily threatened by the introduction of non-native fish species, in addition to habitat loss through pollution and the artificial dewatering or channelisation of karstic watercourses.

At some locations, e.g., Popovo polje, former temporal wetlands no longer flood during its reproductive period, and the whole subpopulation is more-or-less confined to subsurface waterbodies and spring outflows in the vicinity of ponors.

The Trebišnjica River system has been heavily modified by the "Lower Horizons" hydropower scheme, with several dams and three hydroelectric power plants in operation. The artificial lakes associated with these barriers have favoured the widespread establishment of non-native fish species (see below). 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. This has caused annual discharge from the Ombla spring to decrease by almost 20%, and groundwater circulation in the area has been severely altered.

Subpopulations inhabiting Dabarsko and Fatničko poljes are increasingly threatened by the ongoing "Upper Horizons" strategy. This project aims to supplement the Lower Horizons infrastructure by artificially redirecting water from several higher altitude poljes to the Trebišnjica River via a cascading series of canals, tunnels and smaller hydroelectric stations. Two tunnels and a concrete canal connecting Dabarsko and Fatničko poljes to Bileća reservoir are already complete, and as of mid-2023 construction was underway on a tunnel that will transfer water to Dabarsko from a reservoir to be built on the Zalomka River in nearby Nevesinjsko polje. Once complete, the Upper Horizons project is expected to completely disrupt the natural cycle of flooding in Dabarsko and Fatničko poljes, and thus significantly reduce the extent of habitat for the Southern Dalmatian Minnow.

Observational evidence suggests that Delminichthys subpopulations can decline rapidly in the presence of non-native fish taxa, a number of which are established within this species' range. These include Pumpkinseed (Lepomis gibbosus), Eastern Mosquitofish (Gambusia holbrooki), Prussian Carp (Carassius gibelio), Topmouth Gudgeon (Pseudorasbora parva) and Rainbow Trout (Oncorhynchus mykiss), all of which are documented to adversely affect native fish abundance through resource competition, habitat degradation, predation of various life stages or transmission of pathogens.

This species is not used or traded.

This species is included in Appendix III of the Bern Convention (as Phoxinellus adspersus) and Annex II of the European Union Habitats Directive (originally as Phoxinellus spp.).

In Bosnia and Herzegovina, it is strictly protected in the Republic of Srpska and protected in the Federation of Bosnia and Herzegovina. In Croatia, it is nationally-protected and currently assessed as Endangered for the National Red List.

No specific conservation management plan is in place, but in Croatia it is a target species for two protected areas included in the European Union's Natura 2000 network (sites HR2000946 and HR2001010).

Dabarsko and Fatničko poljes have together been identified as an internationally significant Key Biodiversity Area and a candidate Emerald Network area of special conservation interest, but do not currently lie within the boundaries of any protected area.

It is strongly recommended that future research should prioritise the identification of potential conservation sites, in addition to confirming its population trend, life history and response to the identified threats (particularly its interaction with non-native fish species), in order to formulate an appropriate management plan.