This taxon was formerly regarded to be conspecific with the Cactus Roach (Rutilus virgo), which is native to the Danube River system. However, a series of molecular analyses published since the late 2000s have demonstrated that the two species are distinct (Ketmaier et al. 2008, Perea et al. 2010, Geiger et al. 2014, Levin et al. 2017).

Global and European regional assessment: Vulnerable (VU)
EU 27 regional assessment: Vulnerable (VU)

The 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 suspected that an ongoing reduction based on field observations, declining habitat quality and the effects of introduced taxa may approach or meet the thresholds for Vulnerable or Endangered under Criterion A (≥ 30% or ≥ 50% over the past 15 years = three generations). As a result of this data uncertainty, Near Threatened and Endangered are equally plausible Red List categories for the present assessment, and this species is assessed as Vulnerable for both Europe and the EU 27 member states.

This species is native to the northern Adriatic Sea basin, where its range extends eastwards from the Po River to the Livenza River.

The majority of available records pertain to fluvial lakes in the Po catchment, including Maggiore, Lugano, Como, Iseo and Garda, all of which are associated with left-bank tributaries of the river. The precise limits of its current distribution are somewhat unclear, especially in fluvial environments, since some areas have not been exhaustively sampled.

It has reportedly been introduced to the Arno River system, which drains to the Ligurian Sea in northwestern Italy, plus some lakes in the Tuscan-Emilian Apennines National Park and Lazio region. The precise locations and present status of these translocated subpopulations have not been clearly confirmed.

This species' population size is unknown, but it is understood to exceed the minimum threshold for Red List criteria (< 10,000 mature individuals). The current population trend has not been quantified, but an ongoing reduction which may have exceeded 30% within the past three generations is suspected as a result of a continued decline in habitat quality. The number of subpopulations is unclear.

Its abundance and range are understood to have declined significantly after the mid-20^th century, with a notably sharp reduction since the 1990s. This is particularly evident in the Po River system, where a number of lacustrine subpopulations have been extirpated and it may no longer be present in some major tributaries or the lower reaches of the main stem. The results of recent field surveys indicate that it might today be restricted to the Mergozzo, Maggiore, Lugano, Como, and Mezzola lake basins and their outflowing rivers, plus the upper Po catchment in the Piedmont region of Italy. Lakes Como and Mezzola are understood to contain the largest remaining stocks, but an accurate appraisal is likely to be hampered by the ubiquitous presence of hybrid individuals (see 'Threats').

This pattern is suspected to be ongoing throughout most of its range, albeit its status in rivers located east of the Po system, e.g., the Adige, Brenta and Livenza, is uncertain.

This gregarious species inhabits deep, naturally oligotrophic perialpine lakes and slow-moving reaches of large perennial river channels. It has colonised some artificial lakes created by gravel extraction alongside the main stem of the upper Po River.

There is little information available regarding its habitat use, but it is believed to be relatively sedentary outside of the reproductive period (see below), when it tends to aggregate in the vicinity of macrophyte or algae beds. Lacustrine individuals are most often observed in the littoral zone, but there is evidence to suggest that they move to deeper water during the winter.

Its diet is understood to comprise algae, aquatic macroinvertebrates, organic detritus and periphyton.

The maximum recorded age is 10 years. Male individuals mature at age 2+ and females at age 2-3+. It is potamodromous, and the annual reproductive period extends from April to May. Its spawning behaviour is characterised by mature adults migrating short distances to specific fluvial sites, which usually comprise well-washed gravel beds in riffles. It is a fractional, polygamous spawner, and nuptial male individuals develop conspicuous epidermal breeding tubercles on the head and body. Adult females produce 35,000-60,000 eggs per kilogramme of body weight.

This species is primarily threatened by introgressive hybridisation and resource competition with the congeneric, non-native Common Roach (Rutilus rutilus), which has been widely introduced to northern Italy since the 1980s and today comprises a principal component of the ichthyofauna in most perialpine lakes of the Po River system. At some locations, e.g., Lake Maggiore, it is now among the most abundant fish species.

Other non-native fish taxa established within this species' range include Pumpkinseed (Lepomis gibbosus), Largemouth Bass (Micropterus salmoides), Eurasian Perch (Perca fluviatilis), Eurasian Pikeperch (Sander lucioperca), Eurasian Ruffe (Gymnocephalus cernua), Common Bream (Abramis brama), Common Barbel (Barbus barbus), Goldfish (Carassius auratus), Crucian Carp (Carassius carassius), Common Carp (Cyprinus domestic strain), Grass Carp (Ctenopharyngodon idella), Topmouth Gudgeon (Pseudorasbora parva), Black Bullhead (Ameiurus melas), Wels Catfish (Silurus glanis), Brown Trout (Salmo trutta) and Rainbow Trout (Onchorhyncus mykiss), all of which are considered invasive and can exert detrimental pressures on native freshwater fauna through increased competition, predation, habitat degradation or parasite transmission. Since the 1990s, native fish communities have been increasingly displaced by non-native species in some parts of the Po River system.

This species is also threatened by lake and river regulation and other forms of habitat degradation, which have resulted in widespread loss of the heterogeneous, interconnected fluvial habitats required to complete its life-cycle. The construction of dams, sills, 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. The water level of some lakes is controlled for domestic water supply, irrigation and hydropower generation, leading to marked fluctuations and interfering with the extent of available littoral habitat. The availability of appropriate spawning sites is thus likely to have decreased significantly throughout this species' range.

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 probably increased the accumulation of fine sediments at some spawning sites, which may impair 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, which has reduced the extent and quality of spawning sites through a loss of the shallow gravel banks required for egg deposition. Some sites may also have been damaged by the industrial extraction of riverine gravel and other sediments for urban development.

This species is also likely to have declined due to widespread agricultural, domestic and industrial pollution during the 20^th century, some of which persists today. In particular, all large perialpine lakes in the Po River system suffered from anthropogenic eutrophication driven by the development of industry and agriculture, which led to increased loading of nutrients and other contaminants from domestic wastewater and runoff. These events not only resulted in declining water quality, but are likely to have interfered with food availability due to changes in the structure of planktonic and zoobenthic communities. In Lake Orta, the discharge of pollutants from a textile factory resulted in severe acidification and the extirpation of all native fish species between 1926 and the 1980s. The Lake Maggiore commercial fishery was temporarily closed around the turn of the 21^st century due to the levels of contaminants (principally the organochloride DDT) detected in the flesh of some fish species.

Additional threats include the degradation of littoral habitats for urban development, plus ongoing shifts in the temperature and mixing regimes of the perialpine lakes due to climate change. Overharvesting also represents a plausible threat, but further research is required (see 'Conservation').

Commercial and recreational fisheries operate on perialpine lakes of the Po River system, although the number of professional fishers has declined considerably since the late 20^th century. The Italian Roach is harvested and typically sold dried, salted or smoked, but the current level of offtake is unclear.

In some lakes, non-native fish species introduced intentionally to supplement commercial or recreational fisheries or unintentionally (e.g., as bait fish or escapees from put and take fisheries) today comprise the majority of landings, e.g., > 75% in Lake Maggiore (also see 'Threats').

This Italian Roach is included in Appendix III of the Bern Convention and Annex II of the European Union Habitats Directive.

It was assessed as Endangered for the 2022 Red List of Italian Vertebrates, and Critically Endangered for the 2022 Swiss Red List of Freshwater Fishes.

It is present within the boundaries of various protected areas, some of which are included in the Ramsar Convention on Wetlands of International Importance and/or the European Union's Natura 2000 network.

From 2016-2020 it was included as a target species within the framework of the European Union co-funded project IdroLIFE (LIFE15 NAT/IT/000823). Actions included the construction of nature-like fishways, removal of barriers, non-native species control and release of hatchery-reared juveniles in Lake Mergozzo and a 45 kilometre stretch of the Toce River, both of which drain to Lake Maggiore.

Investment in wastewater treatment facilities and other policy-led measures since the 1980s has driven water quality improvements in most of the perialpine lakes, some of which have returned to their natural oligotrophic state while others remain mesotrophic.

Commercial harvesting of this species is currently prohibited in some areas, e.g., Lake Maggiore and the Veneto region of Italy.

A deeper understanding of this species' demographics (population size and trend), current distribution and life history, with a particular focus on the identification of key spawning sites, would likely prove useful in the development of future management efforts. The effects of harvesting in perialpine lakes should also be evaluated, since basin-scale management plans may be required.