The taxonomy of roaches inhabiting northern Italy, the Western Balkans and southern Greece has not been definitively resolved.

At the generic level, they were prior to the mid-2010s included in the genus Rutilus, before being transferred to the resurrected genus Leucos based on a series of molecular and morphological characters (Bianco and Ketmaier 2014). However, a number of authors have opted against support of this split (Barbieri et al. 2015, Tutman et al. 2018, Ćaleta et al. 2019, Freyhof et al. 2020).

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

The North Italian Roach 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 both globally and for the EU 27 member states.

This species is native to the northern Adriatic Sea basin, where the bulk of its range extends from the Esino River in the Marche region of Italy to the Raša River in Istria County, Croatia. Further south in Croatia, a few isolated subpopulations are present in Zadar County, including Lake Veliko on the island of Pag, at least two short coastal streams in Ravni Kotari near the city of Zadar, and possibly the Lake Vrana basin.

In Italy, it has been introduced outside of this range since the mid-20^th century, particularly in rivers draining the Ligurian/Tyrrhenian slope where it is considered invasive (see 'Habitat and Ecology'). It is also established in at least one artificial accumulation lake on the island of Sardinia.

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 reductions in abundance have been reported in Italy, Switzerland and Slovenia since the mid-to-late 20^th century, and this pattern is suspected to be ongoing based on field observations, declining habitat quality and the effects of introduced taxa (see 'Threats').

For example, in Italy it may have been completely extirpated from right-bank tributaries of the Po River, while in Switzerland only very few individuals have been recorded from lakes Lugano and Maggiore during surveys carried out post-2010. In Slovenia, it is no longer present in the majority of the Soča (it. Isonzo) River, where it may currently be restricted to middle and lower reaches of the Vipava River tributary system.

This gregarious, somewhat lentic, species typically inhabits sluggish river stretches, backwaters, oxbows, side channels and floodplain or fluvial lakes. Although mostly confined to lowland environments, it is present in perialpine lakes of the Po River system in Italy and Switzerland. It is often associated with submerged vegetation, and frequently colonises artificial accumulation lakes and drainage channels (but see 'Threats').

In rivers draining to the Adriatic Sea south of the Po River, some of its fluvial habitats comprise relatively small, shallow channels characterised by seasonal variations in discharge. Such reaches can be significantly dewatered during summer, leading to fluctuations in the abundance of resident fish species. Some individuals survive these drought periods in remnant pools which function as refugia.

Outside of its native range, this species has reportedly contributed to declines in lacustrine subpopulations of the Appenine Roach (Sarmarutilus rubilio) in central and southern Italy as a result of competitive interactions.

The maximum reported lifespan is 7 years, with male individuals reaching sexual maturity at age 1+ or 2+ and females at 2+. This species is a fractional, polygamous spawner, and the annual reproductive period extends from April to August with a peak in May and June.

This species is plausibly threatened by river regulation and other forms of anthropogenic habitat modification, although it is reportedly adaptable to moderately degraded conditions. Nevertheless, the construction of large dams plus smaller weirs and other barriers throughout its range has severely altered natural flow and sedimentation regimes, fragmented subpopulations, and reduced the extent of suitable habitat for all life stages.

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 is likely to threaten sites located in temporal rivers, some of which may also have been damaged by the removal of riparian vegetation or industrial extraction of gravel and other sediments for urban development.

This species is also exposed to 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').

Evidence from Switzerland indicates that genetic introgression with the invasive non-native Common Roach (Rutilus rutilus), which has been introduced throughout the majority of its range, is likely to represent a signicant and potentially irreversible threat at some locations. In Lake Maggiore, Italy and Switzerland, there is also evidence of hybridisation with the native congener Rutilus pigus, and the breakdown of reproductive isolation between these taxa may have been mediated by the introduction of Common Roach.

Other non-native fish taxa established within this species' range include Pumpkinseed (Lepomis gibbosus), Largemouth Bass (Micropterus salmoides), Eurasian Perch (Perca fluviatilis), Common Bream (Abramis brama), Goldfish (Carassius auratus), Crucian Carp (Carassius carassius), Common Carp (Cyprinus domestic strain), Grass Carp (Ctenopharyngodon idella), Topmouth Gudgeon (Pseudorasbora parva), Black Bullhead (Ameiurus melas) and Wels Catfish (Silurus glanis), all of which are considered invasive and can exert detrimental pressures on native freshwater fauna through increased competition, predation, habitat degradation or parasite transmission. Native fish species have been completely displaced by non-native communities in some parts of the Po River system.

The negative impact of some threats could plausibly be exacerbated by increasingly rapid climate change in the Mediterranean region.

This species is not used or traded.

This species is included in Appendix III of the Bern Convention (as Rutilus rubilio) and Annex II of the European Union Habitats Directive. It is nationally-protected in Slovenia and Croatia.

It was assessed as Near Threatened for the most recent Red List of Italian Vertebrates (2022), Critically Endangered for the Swiss Red List of Fishes and Cyclostomes (2022), and Near Threatened for the National Red List of Croatia.

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

A deeper understanding of its demographics (population size and trend), current distribution and life history, particularly the identification of sites where no hybridisation with other Rutilus species has occurred, would likely prove useful in the development of future management efforts. Given the extent of its range, such efforts may be best coordinated at local or regional scales.