Genetic studies have demonstrated that this species shares haplotypes with perialpine subpopulations of the Arctic Charr (Salvelinus alpinus), but it remains unclear whether this is a natural phenomenon or the result of human-mediated introgression (Knebelsberger et al. 2015).

At the broader scale, there remains considerable uncertainty regarding the evolutionary relationships and taxonomy of the genus Salvelinus (Reist et al. 2013; Taylor 2016; Whiteley et al. 2019).

Members of this genus exhibit bewildering subpopulation-scale ecological and morphological variability throughout their global range. 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').

The Ammer Charr is endemic to Germany and is known only from Lake Ammer. It has a restricted range (extent of occurrence (EOO) c. 59 km²), which meets the threshold for the Critically Endangered category under Criterion B1 (EOO < 100 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 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, this species is assessed as Vulnerable under Criterion D2, based on its presence at one location with a plausible future threat of climate change that could drive it to Critically Endangered or Extinct in a very short time period.

This species is endemic to Lake Ammer (de. Ammersee) in the upper Danube River system, Bavaria, southern Germany.

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.

Overall abundance is understood to have declined significantly during the latter half of the 20^th century (see 'Threats'), but has increased since the 1990s (see 'Conservation').

Dimictic and naturally oligotrophic, Lake Ammer was formed during the last glacial period. It has a maximum depth of 81 metres, and is connected to the Danube River system via the outflowing Amper River. It occasionally freezes in winter, and was until recently eutrophic due to anthropogenic pollution (see 'Conservation'). Other endemic fish species inhabiting the lake include the Ammer Ruffe (Gymnocephalus ambriaelacus) and Ammer Whitefish (Coregonus bavaricus).

The Ammer Charr occupies the profundal zone at depths of 50-80 metres, and is likely to feed on benthic invertebrates and zooplankton. Little is known of its life history, but it is believed to be reproductively active throughout the year, possibly with a peak from September to October. This may be related to the relatively stable conditions in deeper areas of the lake, since most European charr species spawn on a seasonal basis.

From the 1950s until the 1990s, Lake Ammer was regarded to be eutrophic as a result of agricultural and domestic pollution during the 19^th and 20^th centuries. This phenomenon has been linked to reduced abundance of the two native whitefish species, and may also have driven a decrease in the Ammer Charr population due to de-oxygenation of the profundal zone. Subsequent management actions have led to re-oligotrophication and a marked improvement in water quality (see 'Conservation'), but the lake remains in a mesotrophic condition.

Toxic cyanobacterial blooms have been recorded annually in the lake since around 1990, the appearance of which has been linked to the re-oligotrophication process.

The warming of Lake Ammer due to climate change represents a significant ongoing and future threat.

This species is sometimes harvested commercially and sold to local restaurants, where it is typically eaten fried.

It is occasionally targeted by recreational anglers, but is considered difficult to catch due to its preference for deep water.

It is not reared in hatcheries, and no artificial stocking has ever taken place.

This species is not currently covered by any national or international wildlife legislation, but it has been assessed as Threatened with Extinction for the German National Red List (2023).

Lake Ammer is included in the Ramsar Convention on Wetlands as a Wetland of International Importance (site no. 93), and is covered by a number of protected areas, one of which is listed in the European Union's Natura 2000 network (site DE8331302).

However, the Ammer Charr is not listed as a target species and no specific conservation actions are in place.

At the broader scale, a series of actions aiming to improve water quality in Lake Ammer were implemented after eutrophication levels reached their peak during the mid-1970s. In particular, a "ring canal" drainage system was installed and wastewater treatment facilities in the vicinity of the lake were improved, leading to a significant reduction in phosphorous concentrations by the mid-1990s.

The lake has stablised in a mesotrophic state since around the turn of the 21^st century. While this re-oligotrophication process has largely been regarded a success, there have been some potentially negative side-effects (see 'Threats').

Research focused on understanding the Ammer Charr's ecology and life history would likely prove useful in terms of future management planning, and regular population monitoring is recommended due to the identified threats.

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.