The validity of this taxon has been considered questionable in the past, but is unambiguously supported by a range of genetic and morphological evidence (Gigliarelli et al. 2013, Tancioni et al. 2013, Lucentini et al. 2014).

The Etruscan Chub is suspected to have undergone a population size reduction of at least 80% within the past 15 years (= three generations), based on field observations, declining habitat quality and the effects of introduced taxa.

Therefore, this species is assessed as Critically Endangered under Criterion A (A2ace).

This species is endemic to western Italy, where it is present in the Magra, Serchio, Arno, Ombrone, and Tiber (it. Tevere) river systems.

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

Field observations indicate that it has experienced a significant and continued population size reduction since the late 20^th century, and it has been completely extirpated from the Ombrone, lower Arno and lower Tiber river catchments (see 'Threats'). This pattern is suspected to be ongoing throughout most of its range, and it is increasingly restricted to short reaches of minor rivers and streams in upland areas. The results of surveys carried out between 2018-2023 indicate that the reduction is especially severe in the upper Tiber watershed (A. Carosi and M. Lorenzoni, pers. comm.). A suspected population size reduction of at least 80% has occurred within the past three generations (15 years).

In contrast, the only published report from the Magra River, where a relatively large subpopulation was discovered during the early 2010s, states that it is widespread in the system.

This species is most abundant in the middle and upper reaches of tributary rivers and streams with clear water, well-developed riparian vegetation and rocky to stony substrata, e.g., mixed bedrock, gravel and pebbles. It is absent from larger, lowland river channels, but has occasionally been reported to inhabit adjacent watercourses with dense aquatic vegetation.

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, and site-scale abundance may fluctuate considerably as a result of this cycle.

It feeds largely on invertebrates, but also consumes organic detritus and plant material, while larger individuals also prey on smaller fishes and amphibian larvae.

The maximum reported lifespan is 6+ years, and the annual reproductive period extends from April to June. Nuptial individuals are understood to form polygamous spawning aggregations at spawning sites comprising beds of gravel or other coarse substrata in shallow, flowing water. Females probably produce two batches of c. 3,000 eggs each over the course of the season.

The construction of dams, sills, weirs and other barriers has altered natural flow and sedimentation regimes, fragmented subpopulations, and reduced the extent of suitable habitat for all life stages throughout this species' range.

The extent of dry season refugia available to subpopulations inhabiting temporal rivers (see 'Habitat and Ecology') is reportedly declining through a combination of increasingly prolonged drought periods, unregulated water abstraction and removal of riparian vegetation.

This species is further 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. These impacts can be particularly severe when discharge is reduced during the summer.

Some spawning and nursery sites may have been damaged by the extraction of riverine gravel for urban development, or increased sedimentation caused by dam flushing operations and detrimental land use practices.

A number of non-native fish species that are documented to exert negative effects on native ichthyofauna through predation, resource competition, habitat degradation or transmission of pathogens are established within this species' range, including Pumpkinseed (Lepomis gibbosus), Largemouth Bass (Micropterus salmoides), Eurasian Perch (Perca fluviatilis), Goldfish (Carassius auratus), Common Carp (Cyprinus domestic strain), Topmouth Gudgeon (Pseudorasbora parva), Black Bullhead (Ameiurus melas), Brown Trout (Salmo trutta) and Rainbow Trout (Oncorhynchus mykiss). The South European Nase (Protochondrostoma genei), which is native to Italy but does not naturally occur within the Etruscan Chub's range, is understood to represent a particular issue since it exhibits comparable habitat preferences.

In the Tiber River system, there is evidence that this species' distribution is gradually shifting to higher altitude reaches, and this phenomenon has been linked to climate change, deteriorating habitat quality and the presence of non-native taxa in downstream reaches.

This species is not used or traded.

This species is included in Appendix III of the Bern Convention (as Leuciscus lucumotis) and Annex II of the European Union Habitats Directive (originally as Leuciscus lucumonis).

It was assessed as Critically Endangered for both of the most recent (2013 and 2022) iterations of the Red List of Italian Vertebrates.

Its range overlaps the boundaries of various protected areas, including several national parks and a number of sites included in the European Union's Natura 2000 network.

An experimental captive rearing attempt was carried out in 2015, with several hundred juveniles raised by artificially stripping gametes from ripe adult individuals. It is unclear whether the technique has yet been applied at a larger scale.

A pilot scheme to remove non-native species from two streams in the Tiber River system took place from 2020-2022, leading to an increase in the number of Etruscan Chub individuals at both sites. Depending on the results of molecular analyses (see below), these putatively depleted subpopulations could later be supplemented with individuals translocated from other locations.

Significant genetic divergence has been detected between subpopulations inhabiting different river systems, and even among individual locations within the Tiber catchment. It is recommended that subpopulations should be managed on an independent basis in order to preserve these unique lineages, meaning any translocation of individuals between locations must be carefully managed.

A deeper understanding of this species' population trend, current distribution and life history, including the identification of key spawning and summer refuge sites, would likely prove useful in the development of future management efforts.