The Ebro Nase does not approach the range 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 10,000 mature individuals, therefore it does not meet the thresholds for Criteria C or D, and there exists no quantitative analysis which would permit application of Criterion E.

Although no range-wide population trend data exists, it is possible that a suspected ongoing reduction based on field observations, declining habitat quality and the effects of introduced taxa may approach or meet the threshold for Vulnerable under Criterion A2 (≥ 30% over the past three 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 native to northeastern Spain, where it inhabits rivers draining to the Cantabrian (northeast Atlantic Ocean) and Mediterranean sea basins.

In the Atlantic basin, its range extends eastward from the Pas River in the autonomous community of Cantabria to the Bidasoa River in the Basque Country.

In the Mediterranean basin, it is present from the Llobregat River in Catalonia southward to the Ebro and Cenia rivers in the Valencian Community.

A geographically isolated but putatively conspecific subpopulation inhabits the upper Tagus (es. Tajo) River system, upstream of the Entrepeñas dam and accumulation lake in Castilla-La Mancha.

This species' population size is unknown, but is understood 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.

Significant site-scale declines in abundance have occurred throughout its range since the mid-20^th century. It is suspected that this pattern is ongoing to an as yet undetermined extent, based on field observations, declining habitat quality and the effects of introduced taxa (see 'Threats').

This gregarious species predominantly inhabits fast-flowing, perennial river and stream stretches, although some of its habitats undergo significant intra- and inter-annual variations in flow. These temporal reaches are located in rivers draining to the Mediterranean Sea, and are naturally dewatered in summer, giving rise to an increase in mortality of resident fishes of which some individuals survive for several months per year in isolated, shaded pools that function as refuge habitats. It is also known to enter artificial accumulation lakes created by dams (but see 'Threats').

Its diet is believed to comprise aquatic macroinvertebrates and periphyton.

Sexual maturity is attained at age 2-3+. The annual reproductive period extends from April to June, when nuptial adults migrate to shallow upstream spawning sites with coarse substrata. It is a fractional, polygamous spawner, and individual females can produce 6,000-15,000 eggs during a single season.

This species is threatened by river regulation and other forms of anthropogenic habitat degradation, which have resulted in widespread loss of the heterogeneous, interconnected fluvial habitats required to complete its life-cycle.

In particular, 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, fragmented subpopulations, and reduced the extent of suitable habitat for all life stages. Hydroelectric schemes have 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, 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.

The quality of available habitat has been further diminished by bank stabilisation, channelisation and other efforts to enhance flood protection or exploit water resources for irrigated agriculture. Unregulated water abstraction may constitute a particular threat to this species' upstream spawning and nursery sites, some of which may also have been damaged by the industrial extraction of riverine gravel and other sediments for urban development.

It 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. Pollution can be particularly impactful when discharge is reduced during the summer, especially in temporal rivers where native fishes are often confined to small refugia (see 'Habitat and Ecology').

The presence of dams also favours the establishment of lentic non-native fish species, of which a number documented to exert negative effects on native ichthyofauna through predation, resource competition, habitat degradation or transmission of pathogens are established and continue to expand within this species' range. These include Pumpkinseed (Lepomis gibbosus), Largemouth Bass (Micropterus salmoides), Northern Pike (Esox lucius), Eurasian Perch (Perca fluviatilis), Eurasian Pikeperch (Sander lucioperca), Common Carp (Cyprinus domestic strain), Common Bleak (Alburnus alburnus), Common Roach (Rutilus rutilus), Topmouth Gudgeon (Pseudorasbora parva), Eastern Mosquitofish (Gambusia holbrooki), Black Bullhead (Ameiurus melas) and Wels Catfish (Silurus glanis).

The negative impact of some threats could plausibly be exacerbated by increasingly rapid climate change in the Iberian Peninsula, which is already driving extended periods of drought.

This species was formerly harvested for human consumption in parts of the Ebro River system, but is no longer used or traded due to declining yields.

This species is included (originally as Chondrostoma toxostoma) in Appendix III of the Bern Convention and Annex II of the European Union Habitats Directive. It is listed as Vulnerable in the Spanish Catalogue of Threatened Species.

It is not currently included in any formal conservation plan but in some river systems, e.g., the Bidasoa, it may have benefitted from management measures targetting other fish species such as Brown Trout (Salmo trutta).

It occurs within the boundaries of various protected areas, some of which are included in the European Union's Natura 2000 network.

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.