The Channel Minnow (Phoxinus phoxinus), formerly Common or Eurasian Minnow, was for a considerable period of time treated as the only European member of the genus Phoxinus. However, at least 23 distinct mitochondrial lineages and 14 valid species have been identified in the region since the mid-2000s. This diversity is likely to increase further, as comprehensive information for all major European river systems has not yet been compiled. Moreover, additional sampling plus morphological analyses are required to corroborate some putative species divisions which are currently supported only by inconclusive nuclear data (Denys et al. 2020, Palandačić et al. 2017, 2020, 2022, Bogutskaya et al. 2023).

Taxonomic determination has been further hampered by natural phenotypic variability within the different lineages, plus their disparate geographic distributions which do not generally reflect patterns observed in related European fish genera. Furthermore, anthropogenic translocations linked to recreational fisheries have in some cases led to uncertainty regarding native range boundaries and driven introgressive hybridisation between congeners (Museth et al. 2007, Knebelsberger et al. 2015, Miró and Ventura 2015, Ramler et al. 2017, Vucić et al. 2018, Corral-Lou et al. 2019, Palandačić et al. 2020, 2022; De Santis et al. 2021).

As a result of the increasing species diversity, much of the published literature referring to Phoxinus phoxinus in fact pertains to other taxa and should therefore be reviewed with due care.

Global and European regional assessment: Least Concern (LC)
EU 27 regional assessment: Least Concern (LC)

Although this species' population trend may be decreasing due to habitat degradation, there is no evidence that the rate of decline approaches the minimum threshold for Vulnerable under Criterion A (≥ 30% over the longer of 10 years or 3 generations). It does not approach the range thresholds for Vulnerable under Criterion B (extent of occurrence (EOO) < 20,000 km², area of occupancy (AOO) < 2,000 km²) or D2. The population size significantly exceeds 10,000 mature 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.

Therefore, the Danube Minnow does not currently meet the thresholds for any Red List criteria, and it is assessed as Least Concern.

This species has a disjointed native range, the precise limits of which remain unclear. Two major geographic clusters have been identified, the first of which inhabits right-bank tributaries of the Danube River in the northern Balkan region, from the Great Morava River downstream to the Vit River, with a somewhat isolated subpopulation in the Lepenac River (upper Vardar River, Republic of Kosovo and probably Republic of North Macedonia). The second cluster comprises the upper Danube basin from its headwaters downstream to the Ybbs tributary system (with the exception of the upper Enns River, where it is possibly absent), and parts of the upper Rhine River in Germany (Main River) and Switzerland (High Rhine, Alpine Rhine, lakes and tributaries including the Aare River).

The native status of subpopulations inhabiting tributaries of Lake Geneva in the upper Rhône River catchment is currently uncertain, and it may also inhabit additional tributaries of the Danube in Bulgaria, e.g., the Osam and Yantra rivers.

Putatively introduced subpopulations are present in the Meuse River (Netherlands and Belgium), the upper Moselle River (middle Rhine River, France), the Ruhr and Sieg rivers (lower Rhine River, Germany), and a series of small alpine lakes in the upper Po River (Italy).

This species' population size is unknown, but far exceeds 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.

Field observations indicate that it remains abundant where favourable habitat conditions exist, although declines in Phoxinus subpopulations have been documented throughout its range since at least the mid-20^th century (see 'Threats').

This small-bodied, gregarious species occurs at a range of altitudes, but is most frequently-encountered in upland rivers, streams and oligotrophic lakes.

It is somewhat eurytopic, but demonstrates a preference for relatively shallow lake shorelines or fluvial pools and glides with well-oxygenated, clear water and slow to moderate water movement. At some locations it may switch to deeper areas during cold periods.

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

Adult individuals reach sexual maturity at age 1-2+. The annual reproductive period extends from April to June, but may commence several weeks later and continue until July or August at higher altitudes. This species is a fractional, polygamous spawner, and older individuals tend to spawn earlier in the season. Spawning behaviour is characterised by mature adults migrating short distances to specific sites, usually comprising beds of aquatic vegetation or well-washed gravel. Reproductive males develop a conspicuous epigamic colour pattern, and often aggregate in the vicinity of spawning sites prior to the arrival of females. Epidermal breeding tubercles appear on the head in both sexes, but are more prominent in males.

Construction of dams, sills, weirs and other barriers throughout this species' range has altered natural flow and sedimentation regimes, fragmented subpopulations and plausibly reduced the extent of suitable habitat for all life stages. Hydroelectric schemes have created unnatural discharge and water temperature (hydropeaking and thermopeaking) regimes which bring about artificial dewatering of downstream river stretches and the 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 the accumulation of fine sediments at some spawning sites, plausibly impairing the hatching and survival rates of eggs and larvae.

Habitat quality has been further diminished by the industrial extraction of gravel and other sediments for urban development, plus flood mitigation or water abstraction schemes such as bank stabilisation and channelisation.

This species is plausibly impacted by diffuse and point-source agricultural, domestic or industrial pollution at some locations. In the future, some effects of climate change such as increased water temperature or longer periods of low discharge during summer could exacerbate water quality issues, e.g., eutrophication.

Some subpopulations may be threatened by introgressive hybridisation with introduced congeners through their use as live bait in the recreational fishing sector, or from predation by non-native fish species such as Rainbow Trout (Oncorhynchus mykiss). At some locations, restocking with hatchery-reared Brown Trout (Salmo trutta) may represent a threat due to the risk of over-predation or the transmission of non-native diseases or parasites.

This species is sometimes utilised as live bait by recreational anglers or as feed in salmonid production facilities, but is not otherwise used or traded.

This species is present within the boundaries of various protected areas, including several national parks. In the EU 27 member states, some of these are included in the Natura 2000 network.

Some subpopulations may have benefitted from improvements in habitat and water quality associated with implementation of the European Union Water Framework Directive 2000/60/EC, such as efforts to restore fluvial connectivity through barrier removal or the creation of fishways.

A deeper understanding of its native distribution in addition to its population trend and life history, e.g., the identification of key spawning sites, would likely prove useful should dedicated management efforts be deemed necessary in the future. Given the nature of its range, such efforts may be best coordinated at separate local or national scales.