The Northern Iberian Chub 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, and hence does not approach the thresholds for Criteria C or D. There exists no quantitative analysis which would permit application of Criterion E.

Although no explicit 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 12 years = 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 Atlantic river systems draining the northwestern Iberian Peninsula. Its range extends northward from the Mondego River in Portugal to the Lérez River in Spain, including the Douro (es. Duero) and Minho (es. Miño) river systems.

Isolated subpopulations inhabit the Alcoa River in Portugal and the Alberche River in the Tagus (es. Tajo, pt. Tejo) River catchment, of which the latter formerly belonged to the Douro system but was captured by the Tagus following a vicariant event. A third subpopulation inhabiting the Zêzere River in the lower Tagus basin, Portugal, has also been treated as conspecific in the past, but is omitted from this assessment since its taxonomic identity remains in question.

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.

There exists documented evidence of decline since the mid-20^th century. This pattern is suspected to be ongoing in some parts of its range, particularly Spain, based on field observations, declining habitat quality and the effects of introduced taxa. For example, the Alberche River subpopulation is understood to be on the verge of extirpation.

This species tends to be absent from large and deep lowland rivers, but is otherwise considered to be a habitat generalist since it occurs in rivers and streams at different altitudes and with a diverse range of flow regimes.

Many of its habitats are characterised by seasonal variations in discharge, and can be significantly dewatered during summer. Some individuals survive these drought periods in remnant pools which function as refugia. It has also colonised some artificial accumulation lakes at locations where there is access to suitable spawning habitat (but see 'Threats').

It feeds largely on invertebrates, but also consumes organic detritus and smaller fishes.

Male individuals become sexually mature at age 1+ and females at 2+. The annual reproductive period extends from April to June, and is characterised by mature adults moving short distances to preferred spawning sites comprising beds of gravel or other coarse substrata in shallow, fast-flowing water.

At some locations this species hybridises extensively with the congener Squalius alburnoides, which comprises an allopolyploid complex reliant on sympatric bisexual Squalius species for the production of diploid individuals.

This species is threatened by river regulation and other forms of anthropogenic habitat degradation. 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 dams 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 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 or other sediments for urban development.

This species is also threatened by diffuse and point source agricultural, domestic and industrial pollution, which has reduced the extent and quality of habitat at some locations 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').

Non-native fish species established within the Northern Iberian Chub's range include Common Carp (Cyprinus domestic strain), Largemouth Bass (Micropterus salmoides), Pumpkinseed (Lepomis gibbosus), Northern Pike (Esox lucius) and Eurasian Pikeperch (Sander lucioperca) all of which are considered invasive and can exert detrimental pressures on native freshwater fauna through increased competition, predation, habitat degradation or transmission of pathogens.

The ongoing spread of non-native Common Bleak (Alburnus alburnus) throughout much of this species' range is understood to represent a particular threat since it is able to hybridise with the Northern Iberian Chub and other native Squalius species.

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

This species is not used or traded.

This species is included in Appendix III of the Bern Convention (as Leuciscus pyrenaicus).

It was assessed as Vulnerable in the Atlas and Red Book of the Freshwater Fishes of Spain (2002) and Least Concern in the Portugese Red Book of Freshwater and Diadromous Fishes (2023).

It occurs within the boundaries of various protected areas throughout its range, including a number of national parks and sites included in the European Union's Natura 2000 network.

It has been included in a series of studies investigating the efficiency of fishways in both Portugal and Spain, and some subpopulations may have benefitted from an increasing tendency to install or improve such structures on existing barriers within its range. For example, the European Union co-funded LIFE project 'Cipríber' (LIFE13 NAT/ES/000772), took place from 2014-2019 in Salamanca Province, Spain. During this project, a series of management activities aimed towards improving fluvial connectivity for native fishes included construction of 40 fish passes and partial or complete demolition of 15 dams and other man-made barriers in tributaries of the Douro River.

A deeper understanding of this species' population trend, current distribution and life history, particularly the identification of key spawning sites, would likely prove useful in the development of future management actions. Given the extent of its range, such efforts may be best coordinated at local or regional scales.