This species' distribution in the northern Aegean Sea, Sea of Marmara and southwestern Black Sea basins requires further research.

In particular, molecular analyses have demonstrated that individuals from the Struma (el. Στρυμόνας/Strymon; mk. Струма) River system and Lake Volvi (el. Βόλβη) in the Mygdonia drainage basin are conspecific with the Ponto-Caspian taxon Rutilus lacustris (Levin et al. 2017). However, the relationship between these subpopulations and those inhabiting adjacent river systems in The Republic of North Macedonia, Greece, Bulgaria and the Republic of Türkiye have not been fully-investigated (Tsoumani et al. 2014, Barbieri et al. 2015). These latter subpopulations are currently retained within Rutilus rutilus for Red List purposes, pending confirmation of their taxonomic status.

Global and European regional assessment: Least Concern (LC)
EU 27 regional assessment: Least Concern (LC)

This species 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. There is no evidence that any population size reduction approaches the threshold for Vulnerable under Criterion A (≥ 30% over the past ten years or three generations). 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.

Therefore, the Common Roach does not currently meet the thresholds for any Red List criteria, and it is assessed as Least Concern.

This species is native to the majority of Western Eurasia north of the Pyrenees and Alps, where its range extends eastwards from Great Britain, southeastern Norway and France to the Russian Federation. It occupies most river systems draining to the North, Baltic, and White seas, plus the Rhône River and rivers of the northern Aegean Sea and Sea of Marmara in the Mediterranean basin, most watersheds from the Dnieper River southward to the Filyos River in the western Black Sea basin, and the Volga River catchment in the Caspian Sea basin.

The Volga and Northern Dvina rivers represent the eastern limit of its distribution. It is present throughout the Volga watershed, but is less abundant in the lower and middle reaches of the system, which are dominated by the congeneric Pontic Roach (Rutilus lacustris).

It is naturally absent from northern Great Britain, the majority of Fennoscandian rivers draining to the Norwegian and Barents seas, and a portion of the northern Aegean Sea basin comprising the Struma River and Mygdonia drainage basin (see 'Taxonomic Notes').

It has been widely introduced outside of this range in central Norway (Trøndelag County), the British Isles (northern Scotland, the English Lake District, Isle of Man and Ireland), France (Brittany, Corsica and rivers south of the Loire and west of the Rhône), the Iberian and Apennine peninsulas, Croatia, North Africa (Morocco, Algeria and Tunisia), Cyprus and the Republic of Türkiye.

It was introduced to southeastern Australia during the mid-19^th century, and is currently present in rivers draining to Port Phillip Bay and parts of the Goulburn River (Murray-Darling River system) in the state of Victoria.

This species' population size is unknown, but it far exceeds 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.

Some site-scale declines have occurred since the mid-20^th century, particulary in Fennoscandia, while significant reductions in abundance and biomass have recently been observed in the Meuse River, Belgium, and Loire River, France (see 'Threats').

Elsewhere, its abundance has generally been favoured by cultural eutrophication processes, widespread translocations to novel locations, and its tendency to colonise artificial environments such as accumulation lakes and canals (see 'Habitat and Ecology'). Its non-native range has increased significantly over the past few decades, and this pattern is understood to be ongoing in Ireland and the Mediterranean basin.

The native subpopulations inhabiting lakes Brienz and Walen, Switzerland, are genetically distinct from those inhabiting other pre-alpine lakes (see 'Conservation').

This gregarious, eurytopic species is present in a wide variety of freshwater habitats, although it demonstrates a general preference for lentic water bodies in lowland areas. It occupies river and stream channels, backwaters, oxbows, lakes, ponds, and coastal wetlands, plus littoral or supratidal brackish environments where it is able to withstand salinities of 10-14 ‰. It can be particularly abundant in productive lake systems, and readily colonises artificial canals and fluvial accumulation lakes. It is able to tolerate and even thrive in eutrophic conditions, and can withstand a water temperature range of four to over 30° C, although growth is largely restricted below 12° C.

It often exhibits spatial and temporal variations in foraging behaviour depending on resource availability, undertaking periodic, e.g., daily or seasonal movements between the littoral and pelagic zones of lakes, or from river channels to backwaters and side-arms. At some locations, the majority of individuals move to deeper water during the winter.

It is characterised by a broad dietary niche, and utilises a range of resources from organic detritus and cyanobacteria to zooplankton, periphyton, macrophytes and benthic macroinvertebrates. This generalist trophic ecology facilitates the exploitation of novel habitats, an opportunistic use of resources, and fluctuations in food availability. In general, juveniles are largely planktivorous whereas older individuals tend to favour benthic resources. However, adults often demonstrate a shift towards pelagic resources in the presence of other benthivorous fish taxa. At some locations, the diet of larger individuals mostly comprises non-native molluscs such as the Quagga Mussel (Dreissena bugensis) and Zebra Mussel (Dreissena polymorpha).

In a number of post-glacial lakes, high Common Roach abundance and subsequent intraspecific competition have driven the emergence of resource polymorphism along the benthic-pelagic axis. Benthic individuals tend to inhabit the littoral zone and possess a comparatively robust body shape, whereas pelagic individuals are more slender. Research indicates that although such polymorphic subpopulations demonstrate some evidence of assortative mating, the extent of divergence is primarily driven by phenotypic plasticity. The native subpopulations inhabiting lakes Brienz and Walen, Switzerland, are genetically distinct from those inhabiting other pre-alpine lakes and are considered to be of high conservation value. Some subpopulations are distinguished by stunted growth, and this is understood to be dependant on intraspecific density and/or ecological factors, particularly resource limitation.

In nutrient-enriched lakes, this species demonstrates a marked foraging efficiency and can rapidly come to dominate resident fish assemblages. It may thus influence the energy flow, nutrient cycling and community structure of entire aquatic ecosystems by accentuating or amplifying the effects of eutrophication through elevated algal productivity. In particular, high densities of Common Roach tend to result in significantly depleted zooplankton communities, the loss of which can drive increased phytoplankton abundance, turbidity, oxygen consumption, nutrient recycling by excretion and internal loading as the fish switch to benthic resources.

A high biomass of Common Roach can thus prolong the recovery of lake systems that suffered from cultural eutrophication during the 20^th century, even in the wake of measures designed to mitigate external nutrient loading such as improved domestic water treatment. Since the late 1980s, its physical removal from numerous central and northern European lakes has thus been applied as a biomanipulation technique to improve water quality. In Norway, fears over its negative impact on the quality of urban drinking water outside of its native range have led to eradication efforts such as the experimental draining of watercourses or application of the broad-scale piscicide rotenone.

This species is also regularly linked to reduced abundance or site-scale extirpation of sympatric fish taxa such as Common Bream (Abramis brama), Eurasian Perch (Perca fluviatilis) and Eurasian Ruffe (Gymnocephalus cernua) through dietary overlap and interspecific competition. In the littoral zone of the Baltic Sea, an increase in Common Roach biomass is understood to be driving declines in the abundance of Blue Mussel (Mytilus edulis). In the Mediterranean basin and some naturally oligotrophic lakes outside of its native range, it has negatively impacted species of conservation concern, including European Eel (Anguilla anguilla) and salmonids such as charr (Salvelinus spp.), trout (Salmo spp.) and whitefish (Coregonus spp.).

The maximum recorded age is 18 years, and individuals mature at age 1-5+ (usually 1-2+) depending on subpopulation. Males tend to reach maturity one year prior to females. The annual reproductive period extends from spring to summer and is initiated by rising water temperatures (usually 12-16°C), with the precise timing dependant on latitude and prevailing environmental conditions (e.g., April to June in the Baltic Sea basin, but extending to August in some parts of France). Nuptial individuals of both sexes develop breeding tubercles on the head and body, which are more prominent in males.

Many subpopulations migrate short distances to favoured spawning sites in affluent rivers, floodplains, backwaters or lakes. In the Baltic Sea basin, some subpopulations inhabiting brackish coastal waters are anadromous, although in areas that are strongly-influenced by freshwater runoff during the spring, e.g., the northwestern Gulf of Finland, spawning takes place in low-salinity bays, inlets, lagoons or littoral areas following the break-up of winter surface ice. Under all of these scenarios, older individuals tend to migrate earlier in the season.

It is a fractional, polygamous spawner, and individual females can produce up to 300,000 eggs per kg of body weight. Spawning sites tend to comprise shallow littoral habitats or riffles with dense submerged vegetation or coarse, stony substrata. The eggs are adhesive and hatch after 4-12 days, depending on water temperature. The larvae drift for approximately four weeks, before juveniles move into shallow, sheltered nursery zones where they remain for several months.

This species hybridises extensively with Pontic Roach in the Volga River system. Throughout Europe, it produces fertile hybrids with Common Bream (Abramis brama) which are able backcross with the parent taxa, although there is little evidence that second generation individuals occur in natural systems. The primary mechanism is understood to be hybridisation between male Common Roach and female Common Bream, and in some lakes the abundance of hybrid individuals may exceed that of the parent species. Natural hybridisation with Common Nase (Chondrostoma nasus), Eurasian Rudd (Scardinius erythrophthalmus), European Chub (Squalius cephalus), Ide (Leuciscus idus) and White Bream (Blicca bjoerkna) has also been reported.

Outside of its native range, introgressive hybridisation with Common Roach has been highlighted as a causal factor in the dramatic declines of locally-endemic taxa, e.g., North Italian Roach (Leucos aula), Italian Roach (Rutilus pigus) and Apennine Roach (Sarmarutilius rubilio) in Italy.

At some locations this species is a major vector of parasites, including the tapeworm Ligula intestinalis and bucephalid trematode flatworms.

Warming water temperatures driven by climate change are predicted to drive a further expansion in its range at northern latitudes, with potentially disruptive consequences for aquatic biodiversity, fisheries management and water quality.

This species is generally viewed as tolerant to the majority of ubiquitous threats impacting freshwater habitats within its range (see 'Habitat and Ecology').

Nonetheless, its natural genetic diversity is likely to have been significantly reduced due to widespread environmental degradation, artificial translocations and unregulated stocking with hatchery-reared individuals of unverified origin.

Mature Common Roach individuals often suffer from disrupted gonadal development due to the presence of estrogens or estrogen-mimicking chemicals in discharges of domestic sewage effluent, and this has been linked to site-scale recruitment deficits in several countries, e.g., Denmark, France, Sweden, United Kingdom.

In Fennoscandia, the extensive acidification of post-glacial lakes due to anthropogenic sulphur emissions has caused thousands of individual stocks to go extinct since the mid-20^th century.

Evidence from France indicates that some fluvial subpopulations have been negatively-affected by river regulation and other forms of habitat degradation, which may have blocked migration routes and reduced access to suitable spawning habitat.

In the Meuse River, Belgium, a sharp decline in abundance since around the turn of the century has been linked to a significant (c. 70%) decrease in primary production caused by rapid expansion of invasive Asian clams (Corbicula spp.).

In Ukraine, there is evidence that intensive commercial harvesting has caused a reduction in the abundance of larger individuals in some artificial lakes, although it is unclear whether there has been any negative impact on the structure of affected subpopulations.

This species is harvested commercially for human consumption in some parts of its native range, especially in Eastern Europe where it is typically salt-cured and dried. The industrial production of Common Roach patties has been trialled in Finland, but concerns have been raised over the prevalence of zoonotic parasites in wild individuals.
Its use in the production of agricultural fertilizer, animal feed and bioenergy production has also been investigated.

It is reared in commercial hatcheries for stocking to supplement wild subpopulations in a number of countries, and is extensively produced for stocking as a forage fish or use as live bait in recreational fisheries targeting predatory species, e.g., 1,500-2,000 tonnes per year in France. It is often reared in polyculture ponds alongside Common Carp (Cyprinus domestic strain).

It is widely utilised in recreational fisheries throughout Europe, e.g., around 800 tonnes are landed annually by recreational anglers in coastal Finland alone.

Both the commercial and recreational fisheries sectors are the primary vectors for translocation of this species outside of its native range.

This species is frequently restocked in order to reinforce wild subpopulations for fisheries purposes throughout its native range, although the conservation value of these activities has been widely debated.

It is present within the boundaries of numerous protected areas, including national parks and sites listed in the Ramsar Convention on Wetlands of International Importance. In the EU 27 member states, some of these are included in the European Union's Natura 2000 network.

Some subpopulations may have benefitted from improvements in habitat and/or water quality associated with implementation of the European Union Water Framework Directive 2000/60/EC, such as efforts to restore fluvial connectivity through barrier removal or the creation of fishways.

Abundance has increased in some previously acidified Fennoscandian lakes as a result of reduced pollutant emissions and extensive treatment with limestone since the 1980s.

Subpopulations inhabiting some Swiss lakes exhibit notable genetic divergence and are considered to be of high conservation value (see 'Population'). It is plausible that other such subpopulations exist, and once identified these should be carefully managed to prevent the introduction of non-native lineages.