Global and European regional assessment: Near Threatened (NT)
EU 27 regional assessment: Near Threatened (NT)

The Italian Barbel (Barbus plebejus) 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 does not approach the thresholds for Vulnerable under Criterion C (< 10,000 mature individuals) or D1, and there exists no quantitative analysis of extinction probability which would permit application of Criterion E.

However, a suspected population size reduction, based on a continuing decline in habitat quality and the effects of introduced taxa and pollution, might meet the threshold for Vulnerable under Criterion A (≥ 30% over the past 18 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 (A2ce) both globally and for the EU 27 member states.

This species is native to rivers of the northern Adriatic Sea basin. Its range extends eastward from the Tronto River in Italy to the Krka River in Croatia, and thus includes the Po and other north Italian river systems (just reaching to Switzerland), the Soča River (it. Isonzo) in Italy and Slovenia, the Reka River in Slovenia, rivers of the Istrian Peninsula, and the Zrmanja River in Croatia.

It has been introduced to a number of rivers elsewhere in Italy, particularly those draining to the northern slope of the Tyrrhenian Sea, e.g., the Arno and Ombrone systems, where it is hybridising with the native Horse Barbel (Barbus tyberinus).

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, but is suspected to be declining. The number of subpopulations is unclear.

In Italy, its area of occupancy (AOO) has contracted significantly since the late 20^th century. Overall, up to 60% of identified subpopulations in the Po River and smaller systems draining to the Adriatic Sea south of its delta are believed to have been extirpated and are unlikely to be recovered (see 'Threats' and 'Conservation'). This pattern is suspected to be ongoing at an undetermined number of localities.

No significant declines have yet been reported in rivers located east of the Po in Italy, Slovenia or Croatia, although in the latter country it is considered to be severely fragmented.

This relatively large-bodied, benthic species inhabits deeper stretches of the upper and middle courses of flowing, well-oxygenated rivers with substrata of gravel or sand. Males become sexually mature at age 2-3+, and females at 4-5+. Reproduction takes place in upstream riffles from April to August, peaking in May and June. The diet comprises aquatic invertebrates, detritus and occasionally smaller fishes.

The quality of habitat is estimated to be undergoing continuing decline based on field observations and the identified threats (see 'Threats').

This species' decline in northern Italy has been largely driven by the expansion of non-native fishes ostensibly introduced for sports fishing purposes, particularly the Common Barbel (Barbus barbus) and Wels Catfish (Silurus glanis).

While the Wels Catfish predates on native fishes, the Common Barbel exhibits strong niche overlap and is able to both out-compete and hybridise with the Italian Barbel.

In the Po River system, the Common Barbel has rapidly expanded its range since it was first detected during the mid-1990s, leading to a near-complete loss of Italian Barbel in the Po main stem and the lower reaches of major tributaries, and widespread introgressive hybridisation between the two species in upstream reaches. The latter scenario also includes a number of subpopulations isolated above dams and other barriers, indicating that unregulated anthropogenic translocations continue to play a major role in the dispersal of hybrid individuals.

The Common Barbel has more recently been recorded in rivers south of the Po, e.g., the Metauro River, where hybridisation is also known to have occurred. In some of these systems, barriers have thus far prevented upstream dispersal of hybrid lineages.

Additional threats identified throughout the Italian Barbel's range include construction of dams and weirs, which interfere with flow and sedimentation regimes and block access to its upstream spawning grounds, water abstraction leading to reduced flows, extraction of gravel and sand from riverbeds, removal of riparian vegetation, pollution from agricultural, industrial and urban sources and canalisation of natural channels. This species is targeted by recreational fishers.

A combination of these factors is believed to have driven an initial decline in native barbel subpopulations, which may have partially facilitated the colonisation of non-native species.

This species is targeted by recreational fishers but is not otherwise used or traded.

This species is included in Appendix III of the Bern Convention, plus Annexes II and V of the European Union Habitats Directive. It is assessed as Vulnerable in the latest (2022) Red List of Italian Vertebrates, and is currently assessed as Vulnerable for the National Red List of Croatia. It is nationally-protected in Croatia. It occurs within the boundaries of numerous protected areas, some of which are included in the European Union's Natura 2000 network.

The European Union co-funded LIFE project LIFE13 NAT/IT/001129 BARBIE ran from 2014 to 2018, and was designed to preserve and restore the native populations of this species and the congeneric Brook Barbel (Barbus caninus) within 14 protected areas in the Emilia-Romagna region of northern Italy (Po River system).

The project included plans to eradicate non-native fish species alongside ex situ breeding and stocking efforts in locations from where the two species had previously been extirpated, and monitoring was due to continue post-project. The results had not been published at the time of this assessment.

The results of studies carried out in the Po River suggest that habitat restoration is unlikely to be effective for this species' conservation and rehabilitation, because its decline has been driven by non-native specie, the removal of which constitutes a practically impossible task in such a large river system.

Future conservation and research efforts should therefore prioritise a revision of stocking and translocation practices for non-native species, alongside management measures aimed towards identifying and preserving the remaining non-introgressed Italian Barbel subpopulations.