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 and 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 and Maitland 2007; Kottelat and 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 Shetland Charr is endemic to the Loch of Girlsta in the Shetland Islands archipelago, northern Scotland where it has an extremely restricted range (area of occupancy (AOO) c. 4 km²), which meets the threshold for the Critically Endangered category under Criterion B2 (AOO < 10 km²). It is restricted to one location, but there is no indication of continuing decline or extreme fluctuations, hence it does not qualify for a threatened category under Criterion B.

There is no evidence of any population size reduction that would approach the threshold for Vulnerable under Criterion A (≥ 30% over the past ten years or three generations). The population size is unknown, precluding the use of Criterion C or Criterion D1, and there exists no quantitative analysis of extinction probability which would permit application of Criterion E.

Therefore, this species is assessed as Vulnerable under Criterion D2, based on its presence at one location threatened by climate change and the potential of non-native species introductions that could drive it to Critically Endangered or Extinct in a very short time period.

This species is endemic to the Loch of Girlsta in the Shetland Islands archipelago, northern Scotland. The small size of this lake precludes its accurate depiction on the range map accompanying this assessment.

A putatively conspecific subpopulation inhabits Loch More in the Thurso River system on the Scottish mainland. However, its identity has never been explicitly confirmed and it is not considered for the purposes of this assessment.

This species' current population size and trend have not been quantified, but it is understood to be the most abundant fish species inhabiting the Loch of Girlsta.

Data collated during the 2000s demonstrated that abundance increased between 2003-2008, and the population status at that time was considered to be favourable.

The Loch of Girlsta was formed after the last glacial period. It is oligotrophic and has a maximum depth of c. 22.5 metres.

This species' life history has not been well-studied, but sexual maturity appears to be reached at age 3-4+. The annual reproductive period is believed to extend from October to early November, when mature individuals develop an intense epigamic colour pattern. The eggs hatch after c. 10 weeks.

Congeners inhabiting similar environments typically occupy the pelagic zone, where they feed on zoobenthos and/or zooplankton. Spawning predominantly occurs on well-washed gravel beds in shallow littoral or sublittoral habitats.

The most recent published studies indicate that the Loch of Girlsta is of unfavourable ecological status.

The water level in the lake appears to fluctuate depending on rainfall, and this might be considered a plausible threat since this species' spawning and nursery habitats could be dewatered during drought periods. The population structure of macroinvertebrates and zooplankton, which probably represent the main components of its diet, could also be affected by swings in water depth.

The introduction of non-native fish species and rising water temperatures due to climate change represent plausible future threats.

This species is occasionally caught by recreational anglers targeting Brown Trout (Salmo trutta) in the Loch of Girlsta, but it is in general not used or traded.

The Shetland Charr is included (as Salvelinus alpinus) as a priority species of conservation concern in the U.K. Post-2010 Biodiversity Framework, and is listed among the primary features of the Loch of Girlsta Site of Special Scientific Interest (SSSI).

This species is not currently recognised by the relevant authorities in Scotland 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.