This taxon is currently regarded as valid for global Red List purposes, but was treated as a subpopulation of the Arctic charr, Salvelinus alpinus (Linnaeus 1758), for the most recent national assessment (Nunn et al. 2023).

The taxonomic status of Salvelinus subpopulations inhabiting the British Isles has not been definitively resolved since a series of endemic species were described between the mid-19^th and early 20^th centuries (Adams & Maitland 2007).

In the United Kingdom and Ireland, all of these taxa are treated as junior synonyms of the Arctic Charr, the name of which has been routinely applied to a widespread complex of polymorphic charr populations occurring throughout the Holarctic region (Jonsson & Jonsson 2001). However, there remains considerable uncertainty regarding the systematics of the genus across the majority of this range (Reist et al. 2013; Taylor 2016; Whiteley et al. 2019).

Members of this "Arctic Charr complex" exhibit bewildering subpopulation-scale ecological and morphological variability. When such divergence occurs within a single lake system, the different sympatric forms are often referred to as “morphs”, “morphotypes”, "ecomorphs" or "ecotypes" (Snorrason et al. 1994; Adams et al. 1998; Knudsen et al. 2006; Klemetsen 2010; Muir et al. 2016).

Some of these subpopulations and sympatric forms have over time been described as nominal species, including at least 15 from North America, around 30 from Europe and 12 from Siberia and the Far East. However, these taxa encompass only a small fraction of charr distribution and diversity, and there exist significant differences in opinion regarding which of them should be considered valid (Savvaitova 1995; Adams & Maitland 2007; Kottelat & Freyhof 2007; Klemetsen 2010; Whiteley et al. 2019).

With the above in mind, there is an emerging consensus that the striking genetic and phenotypic diversity exhibited by members of this genus cannot be adequately represented by a single accepted taxonomic system (Whiteley et al. 2019).

The Red List currently follows the nomenclature provided by Fricke et al. (2024), albeit a species-oriented conservation management approach is unlikely to prove appropriate for members of this genus (Barthelemy et al. 2023; also see 'Conservation').

Global and European regional assessment: Vulnerable (VU)
EU 27 regional assessment: Not Recorded

The Welsh Charr has a restricted range (extent of occurrence (EOO) c. 373 km², area of occupancy (AOO) c. 24 km²), which meets the thresholds for the Endangered category under Criterion B1 (EOO < 5,000 km²) and Criterion B2 (AOO < 500 km²), and the extent and quality of habitat are estimated to be declining. However, it occurs at seven locations which does not meet the threshold for the Endangered category. Therefore, this species is assessed as Vulnerable under Criterion B (B1ab(iii)+2ab(iii)).

This species is endemic to northwestern Wales, United Kingdom, where its native range comprises Llyn (lake) Peris and Llyn Padarn in the Afon (river) Seiont system, Llyn Cwellyn in the Afon Gwyrfai system and Llyn Bodlyn in the Afon Ysgethin system.

Introduced subpopulations resulting from cases of benign introduction are established in lakes Ffynnon Llugwy, Llyn Dulyn and Llyn Cowlyd, all of which are located in the upper Conwy River catchment. These subpopulations are included in the present assessment, since the known intent of the introductions was to reduce the extinction risk of the taxon, the occupied sites are geographically close to the natural range, viable offspring have been produced, and at least five years have passed since the translocations took place.

An additional translocated charr subpopulation inhabiting Llynnau Diwaunydd in the Conwy system is not considered to represent a case of benign introduction since the individuals used to stock the lake may have been of Scottish origin. Elsewhere in the Conwy, presumably transient individuals have occasionally been reported from Llyn Eigiau and Coedty Reservoir, which are connected to Llyn Dulyn via an artificial tunnel (see 'Conservation').

The small size of these lakes precludes their accurate depiction on the range map accompanying this assessment.

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.

The Llyn Peris subpopulation was extirpated during the late 1970s (see 'Threats'), prior to which a number of individuals were translocated to Ffynnon Llugwy and Llyn Dulyn (see ‘Conservation’).

Recreational fisheries records suggest that the Llyn Padarn subpopulation declined significantly between 1997-2007, and no individuals have been caught by anglers since 2008. A particularly sharp contraction is likely to have occurred in 2009, although subsequent management efforts may have increased the effective subpopulation size (see 'Threats' and 'Conservation').

The Llyn Cwellyn subpopulation is currently considered to be stable, whereas the status of the Llyn Bodlyn subpopulation is unclear and may be precarious (see 'Threats').

The translocated subpopulations inhabiting Ffynnon Llugwy, Llyn Dulyn and Llyn Cowlyd are understood to remain extant but are not currently monitored. The results of environmental DNA surveys carried out at Ffynnon Llugwy and Llyn Cowlyd during 2019 indicate that charr biomass is relatively high compared to Llyn Padarn and Llyn Cwellyn.

All of the lake basins to which this species is native comprise naturally cool oligotrophic systems formed after the last glacial period.

Llyn Peris has been significantly modified to create the lower reservoir of the Dinorwig pumped-storage hydroelectric scheme, and has a maximum depth of 34 metres. The previously inflowing Afon Nant Peris has been diverted, and now empties into the adjacent Llyn Padarn via an artificial tunnel. A dam has been constructed at its outlet and the water level fluctuates by at least 15 metres on a daily basis, depending on electricity demand. These alterations resulted in extirpation of the species from this location (see 'Threats' and ‘Conservation’).

Llyn Padarn is currently threatened by eutrophication (see 'Threats') and has a maximum depth of 27 metres, but is mostly shallower with a mean depth of 15.9 metres. It is located immediately downstream of Llyn Peris, to which it was formerly connected by the very short Afon-y-Bala.

Llyn Cwellyn has a maximum depth of 40 metres and has not been extensively modified, although the lake is exploited for domestic water supply and in 1976 a small dam was constructed at its outlet. Fluctuations in water level are not considered to constitute a threat at this location (see 'Conservation').

Llyn Bodlyn is located at a higher altitude than the other lakes and has a maximum depth of 22 metres. In 1894, its outlet was dammed to provide water for domestic supply, and the level of the lake can fluctuate significantly during drought periods (see 'Threats').

The three lakes occupied by translocated subpopulations have been modified by construction of dams, leats, pipelines and tunnels to increase their capacities for domestic water supply and hydropower generation. All are located at higher altitudes and are deeper (> 40 metres) than those occupied by the natural subpopulations, but little is known of the charr inhabiting these lakes.

The Welsh Charr occupies the pelagic zone, where it feeds on zooplankton and emerging insects such as chironomid pupae. It probably undertakes diel vertical migrations related to foraging during warmer months of the year, when the lakes stratify and it spends most of the day in profundal refuge habitats. It is therefore critical that oxygen levels in the profundal zone remain sufficient for survival during this period. Oxygen levels can become depleted by decomposition of dead algae and other organic matter from the surface, such as can occur during and shortly after an algal bloom.

No evidence of trophic polymorphism has been detected in any of the three native subpopulations, but as a result of greater productivity linked to eutrophication the maximum recorded size increased from 25.0 cm TL during the 1970s to 42.0 cm TL by 1997. Recent field surveys suggest that it may now be decreasing, presumably as a result of management actions designed to improve water quality (see 'Conservation').

Sexual maturity is reached at age 3-4+, and the annual reproductive period extends from November to December. Nuptial individuals develop an intense epigamic colour pattern at this time. Fecundity is generally low, with individual adult females producing 100-800 eggs depending on body size.

Spawning takes place in shallow littoral or sublittoral habitats. In Llyn Padarn, the principal spawning sites are currently gravel beds located in the Afon-y-Bala (below the Llyn Peris outlet dam) and at or near the outflow from the lake to the Afon Rhythallt (see 'Threats'). In contrast, spawning sites in Llyn Cwellyn comprise rocky ledges at the northwestern end of the lake. The location and structure of spawning sites in Llyn Bodlyn is unknown.

This species occurs sympatrically with Brown Trout (Salmo trutta) throughout its native and non-native ranges, and with juvenile Atlantic Salmon (Salmo salar) in Llyn Padarn and Llyn Cwellyn.

This species was extirpated from Llyn Peris in the mid-1970s, after the lake was drained and dammed during construction of the Dinorwig hydroelectric scheme. This project may also have contributed to the decline of the Llyn Padarn subpopulation, a significant proportion of which formerly spawned in Llyn Peris. Moreover, the Afon-y-Bala spawning site is of small size and poor ecological condition due to its proximity to a sewage outfall, plus continual warm water discharges from the hydroelectric scheme that may affect egg development.

Domestic pollution from the village of Llanberis is understood to have driven a gradual upward shift in the trophic status of Llyn Padarn since the late 19^th century. A pronounced phase of nutrient enrichment took place from the 1950s-1970s following construction of a sewage treatment plant which discharges effluent directly into the Afon-y-Bala. Llanberis is also a popular tourist destination, leading to seasonal increases in domestic waste output.

During the 2000s, it became clear that nutrient enrichment is escalating summer stratification in Llyn Padarn, resulting in deoxygenation of the hypolimnion and a reduction in the extent of profundal charr habitat. There is also evidence that the elevated trophic status has interfered with this species' growth regime. A series of potentially toxic blue-green algae (Cyanobacteria) blooms have been reported since the early 1990s, including a particularly dramatic event in 2009 that prompted a series of conservation actions (see 'Conservation').

The invasive Nutall’s Waterweed (Elodea nuttallii) and Curly Waterweed (Lagarosiphon major) are also present in Llyn Padarn. These non-native aquatic plants have reduced the extent of suitable habitat for juvenile charr and favoured the establishment of predatory fish species, among which Eurasian Perch (Perca fluviatilis) has been illegally introduced to the lake.

A significant increase in recreational pressure has been noted at Llyn Padarn since around 2020, as a presumed outcome of the United Kingdom's withdrawal from the European Union plus the COVID-19 global pandemic.

Llyn Peris and Llyn Padarn are also recovering from pollution caused by local copper and slate mines that operated until c. 1850 and 1969, respectively.

The presence of active camping and water sport areas adjacent to Llyn Cwellyn have been hypothesised as potential threats, but the lake otherwise remains in good ecological condition.

The Llyn Bodlyn subpopulation has not been well-studied, but it is understood to be threatened by fluctuating water levels since more than 60% of the lake's volume can be drained during spells of summer drought. The extent of suitable charr habitat during such periods is likely to be considerably reduced, and may plausibly result in elevated mortality.

Ffynnon Llugwy, Llyn Dulyn and Llyn Cowlyd are all exploited as water-supply reservoirs and are subject to regular fluctuations in water level. It is currently unclear whether this represents a threat to the resident charr subpopulations.

Rising water temperatures due to climate change represents a plausible ongoing and future threat to charr subpopulations in Wales. Warmer conditions may interfere with the development of early life stages, increase the duration of summer stratification events (thus aggravating the risk of deoxygenation both alone and in combination with the effects of eutrophication), and increase habitat suitability for non-native species.

This species is occasionally targeted by recreational anglers, but is not otherwise used or traded.

The recreational fishery at Llyn Padarn is currently closed due to concerns over the status of the resident subpopulation (see 'Population' and 'Threats').

The Llyn Padarn and Llyn Cwellyn subpopulations have in the past been harvested for food by local communities.

The Welsh Charr is included (as Salvelinus alpinus) as a priority species of conservation concern in the U.K. Post-2010 Biodiversity Framework, and as a Section 7 species of principal importance in the Environment (Wales) Act 2016.

This species' entire range lies within the boundaries of the Eryri (sometimes referred to as Snowdonia) National Park. In addition, Llyn Padarn is designated a Site of Special Scientific Interest (SSSI) and Llyn Cwellyn is a Special Area of Conservation (SAC) and SSSI. Llyn Bodlyn is not currently protected within any official framework.

Individuals collected from Llyn Peris prior to the lake being drained were intentionally translocated to lakes Ffynnon Llugwy and Llyn Dulyn as a compensatory measure. Individuals from the three other native subpopulations, particularly Llyn Padarn, were also introduced to Ffynnon Llugwy between 1977-1982. These lakes are regulated and connected to others in the Conwy catchment via artificial watercourses, resulting in the establishment of an additional subpopulation in Llyn Cowlyd and the appearance of transient individuals in Llyn Eigiau and Coedty Reservoir. It is therefore likely that hybridisation and/or introgression between individuals of the four native subpopulations has occurred in the Conwy River system.

A reproducing subpopulation later discovered in Llynau Diwaunydd is understood to have been stocked towards the end of the Llyn Peris translocation programme, but no clear records are available and the geographical origin of the fish is uncertain (see 'Geographic Range').

The translocated subpopulations at Llyn Cowlyd and Ffynnon Llugwy may each comprise a greater number of individuals than any of the natural subpopulations, and this could be linked to their relative isolation from human impacts. Limiting human activity, particularly in the vicinity of spawning sites, may therefore assist in this species' conservation.

In general, the current status of the translocated subpopulations is poorly understood, and additional research is strongly recommended given that they are located within the Eryri National Park but currently receive no official protection.

The 2009 algal bloom at Llyn Padarn prompted the temporary closure of recreational activities on the lake and drove an increase in management activities. Supplemental stocking with hatchery-reared charr juveniles obtained from Llyn Padarn broodstock has since taken place on an annual basis (see 'Threats'). Efforts to establish a new translocated charr population were undertaken from 2010-2012 with the transfer of 7,000 hatchery-reared Llyn Padarn fry to Llyn Crafnant in the Conwy River system, but the results of an environmental DNA survey suggest that establishment was not successful.

Mitigation measures to reduce the amount of phosphates entering Llyn Padarn were introduced at the Llanberis sewage works in 1995, and this was linked to some minor signals of ecological recovery which were probably limited by increased loading at the facility. Additional actions leading to a reduction in chlorophyll levels at the lake's outflow were carried out in the wake of the 2009 Cyanobacteria bloom, but summer dissolved oxygen levels in the hypolimnion remain low.

At Llyn Cwellyn, there exists an operational agreement between Dŵr Cymru Welsh Water and Natural Resources Wales to ensure that the water is maintained at a level that does not adversely impact the resident charr.

The Llyn Padarn and Llyn Cwellyn subpopulations have been monitored since the 1970s, but surveys at Llyn Bodlyn and the sites occupied by translocated subpopulations has been sporadic or reliant on anecdotal anglers' reports.

This species is not currently recognised by the relevant authorities in Wales or the United Kingdom, where it is treated as a subpopulation of the Arctic Charr (Salvelinus alpinus). The taxonomy of Eurasian charrs is in need of review (see 'Taxonomic Notes'), and it has been widely recommended that their conservation management must be considered independent of their systematic classification. Each subpopulation should therefore be assessed individually, taking into account its evolutionary and genetic significance coupled with the ongoing population trend and threats to result in a priority ranking permitting the effective allocation of conservation resources through the development of site-specific, catchment-scale management plans. Sympatric morphological forms should also be managed separately, depending on their respective habitat preferences, diets and life histories. The abundance trends of many subpopulations remain unknown, and their individual assessments should ideally form the basis of future research efforts in order to ensure appropriate prioritisation. In practice, such efforts should ideally be coordinated at local, national or regional scales.