In some published literature, this species is treated as a subpopulation of the Bourget Whitefish (Coregonus lavaretus) or a member of the "Coregonus lavaretus species complex", and referred to by the English vernacular names "Common Whitefish" or "European Whitefish" (see below).

At the regional scale, the systematics of European ciscoes and whitefishes (Coregonus spp.) has been the subject of considerable debate since the turn of the 21^st century, with little indication of a definitive outcome.

It is widely accepted that non-anadromous members of this group have repeatedly undergone adaptive radiations in boreal, subarctic and perialpine lakes (Douglas et al. 1999, Østbye et al. 2005, Kahilainen and Østbye 2006, Harrod et al. 2010, Hudson et al. 2011).

Subpopulations inhabiting these systems largely diversified in the wake of the most recent glacial period 10,000-15,000 years ago. They are typified by parallel patterns of divergence in traits associated with foraging (i.e., gill raker counts, benthic vs. pelagic feeding ecology), physiology (i.e., growth rate, habitat depth partitioning) and reproductive ecology (i.e., reproductive timing and spawning habitat).

Up to six different sympatric forms sometimes referred to as “morphs”, "ecomorphs" or "ecotypes" have been recorded in perialpine lakes, and these radiations might be even more diverse in some large systems of northeastern Europe (Præbel et al. 2013, Doenz et al. 2018, Bitz‐Thorsen et al. 2020, Öhlund et al. 2020).

However, there exist significant differences in opinion regarding the taxonomic status of these forms.

In Northern Europe, including the United Kingdom, all except a handful of Irish subpopulations are usually regarded as belonging to two widely-distributed species; Coregonus albula (ciscoes) and C. lavaretus (whitefishes), with the latter also frequently referred to as the "Coregonus lavaretus species complex” (Etheridge et al. 2012, Wanke et al. 2017, Häkli et al. 2018, Crotti et al. 2020). Within this comparatively uniform taxonomic concept, the catch-all English vernacular name “Vendace” is typically used for C. albula while "Common Whitefish" or "European Whitefish" are applied to C. lavaretus.

Conversely, researchers and fisheries authorities based in Central Europe have tended to treat the different forms as distinct taxa, leading to the recognition of more than 60 species across the European region (Kottelat and Freyhof 2007, Selz et al. 2020, De-Kayne et al. 2022, Selz and Seehausen 2023). Under this diverse taxonomic concept, the name “Vendace” is restricted to its original usage for the United Kingdom endemic Coregonus vandesius and the native range of C. lavaretus is limited to its type locality of Lake Bourget in France.

In the absence of a region-wide consensus, the Red List continues to follow the taxonomy provided by Fricke et al. (2024).

The Ammer Whitefish is endemic to Europe, where it is endemic to Lake Ammer, southern Germany. The species has a restricted range, with an extent of occurrence (EOO) of c. 59 km²), which meets the threshold for the Critically Endangered category under Criterion B1 (EOO < 100 km²). It occurs in a single location where the number of mature individuals is inferred to be undergoing continuing decline. Therefore, this species is assessed as Critically Endangered under Criterion B (B1ab(v)). The species has not been seen in the wild since 2010, and is considered to be Possibly Extinct.

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

This species' current population size and trend have not been quantified. However it has declined significantly since the mid-20^th century (see 'Threats'), and this pattern is suspected to be ongoing with no confirmed observations since 2010.

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 'Threats' and 'Conservation'). The Ammer Whitefish is understood to occupy the profundal zone at depths of 30-80 metres. Little is known of its life history, but the annual reproductive period is believed to peak from mid-June to mid-July, when spawning occurs at depths of 40-50 metres.

Other endemic fish species inhabiting the lake include the Ammer Ruffe (Gymnocephalus ambriaelacus) and Ammer Char (Salvelinus evasus).

The Ammer Whitefish commercial fishery collapsed around the mid-20^th century, prior to which overharvesting may have comprised a threat.

The lake was regarded to be eutrophic from the 1950s until the 1990s as a result of agricultural and domestic pollution during the 19^th and 20^th centuries, and this is believed to have driven a significant decline in abundance due to deoxygenation of the profundal zone. Although subsequent management actions have led to re-oligotrophication and a marked improvement in water quality (see 'Conservation'), the lake remains in a mesotrophic condition and the extent of suitable habitat may be very small or even nonexistent.

Toxic cyanobacterial blooms have been recorded annually in the lake since around 1990, and are believed to be responsible for irregularities subsequently observed in the growth and development of stocked whitefish strains. The appearance of these blooms has been linked to the re-oligotrophication process.

The stocking of non-native congeners may also have accelerated the decline of the Ammer Whitefish through introgressive hybridisation, but this requires clarification.

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

This species was harvested commercially until at least the 1940s, but is no longer used or traded. Both its local vernacular and scientific names are today often misapplied to stocked whitefish strains in recreational angling and tourism literature.

This species is included (as Coregonus spp.) in Appendix III of the Bern Convention and Annex V of the European Union Habitats Directive. 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). At the national scale, it has been assessed as Threatened with Extinction for the German National Red List (2023).

t 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 stabilised 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').

Field surveys designed to assess the current abundance and population trend of the Ammer Whitefish are urgently required.

Should it prove to remain extant, investigation of its life history and the design of an appropriate conservation management plan are strongly recommended.