This is a new concept of the species that excludes Coregonus sarnensis, Coregonus muelleri and Coregonus supersum, all former components of C. zugensis that are now recognised as valid species.

This species has been referred to as Coregonus sp. "Albeli", C. sp. "Albeli-Albock", C. sp. "Zugeralbeli" and C. sp. "Zugerseealbeli" in some published literature.

It has also been 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).

It was formerly believed to occur in Lake Lucerne (fr. Lac des Quatre-Cantons; de. Vierwaldstättersee) and possibly lakes Alpnach (fr. Lac d’Alpnach; de. Alpnachersee) and Sarnen (fr. Lac de Sarnen; de. Sarnersee), but these subpopulations have now been assigned to congeneric taxa (Selz and Seehausen 2023).

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).

Global and European regional assessment: Extinct (EX)
EU 27 regional assessment: Not Recorded

The Zug Whitefish has not been observed in the wild since the early 20^th century, and no ex situ subpopulations exist. This species is therefore assessed as Extinct.

This species was endemic to Lake Zug (fr. Lac de Zug; de. Zugersee) in the upper Rhine River system, Switzerland.

Fisheries records suggest that this species was declining by the 1870s, and became extinct prior to 1950.

Lake Zug is a meromictic, perialpine, naturally oligotrophic lake formed after the last glacial period. It has a maximum depth of 197 metres, and is subdivided by a peninsula into a deep southern basin with steep slopes and a shallower northern basin.

Three whitefish species which differed in traits related to feeding and reproductive ecology along depth gradients were formerly endemic to the lake, two of which are now extinct.

The Zug Whitefish is understood to have occupied pelagic habitats in the profundal zone, where it fed predominantly on zooplankton.

The annual reproductive period probably extended from mid-October to late December, and spawning took place in the deeper parts of the lake.

Discharge of urban waste water and agricultural runoff into its tributary rivers caused Lake Zug to become increasingly eutrophic from the early 19^th century onwards, and by the early 1980s it was among the most polluted lakes in Switzerland.

These conditions are believed to have driven the extinction of the Zug Whitefish and Obliterated Whitefish (Coregonus obliterus) due to depletion of oxygen in the water column below c. 100 metres depth, leading to their profundal spawning sites becoming inaccessible.

The Enduring Whitefish (Coregonus supersum) is the only endemic congener that remains extant in the lake, and is likely to have survived because it is able to complete its life cycle in comparatively shallow water.

A secondary outcome of such changes in the available range of spawning depths is the potential for overlap and increased gene flow between different whitefish species that were formerly segregated along depth gradients. This raises the possibility of speciation reversal and extinction events due to hybridisation and introgression, which have been observed in some other Swiss lakes but not yet studied in Lake Zug.

This species was formerly harvested on a commercial basis.