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).

The subpopulations formerly inhabiting lakes Greifen and Pfäffikon may represent distinct taxa (Zaugg 2022) but are included here pending publication of a conclusive review.

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: Vulnerable (VU)
EU 27 regional assessment: Not Recorded

The Zurich Whitefish has a restricted range (extent of occurrence (EOO) c. 240 km², area of occupancy (AOO) c. 88 km²), which meets the thresholds for the Endangered category under Criterion B1 (EOO < 5,000 km²) and Criterion B2 (AOO < 500 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 which is threatened by climate change and the introduction of non-native species that could drive it to Critically Endangered or Extinct in a very short time period.

This species is endemic to lakes Zurich (fr. Lac de Zurich; de. Zürichsee) and Walen (fr. Lac de Walenstadt; de. Walensee) in the upper Rhine River system, Switzerland. However, it has been extirpated from the latter (see 'Population' and 'Threats').

Contrary to some published reports, it is not native to nearby lakes Greifen (de. Greifensee) or Pfäffikon (de. Pfäffikersee).

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.

Recent studies suggest that it might be relatively stable in Lake Zurich following an observed decline in abundance during the 20^th century. The Lake Walen subpopulation is understood to have been extirpated before 1900 (see ‘Threats’).

Zurich and Walen are monomictic, perialpine, naturally oligotrophic lakes formed after the last glacial period. They were formerly connected as a larger single basin named Lake Limmat, but became separated by rocky debris and sediment transported from the affluent Linth River. Lake Zurich currently has a maximum depth of 136 metres and Lake Walen 151 metres.

During the early 19^th century, the Linth River was diverted to flow into Lake Walen via an artificial channel, and the Linth Canal was constructed to carry overflow water from Lake Walen to Lake Zurich. These regulation activities resulted in a significantly increased flow of glacial meltwater and increased turbidity in Lake Walen.

Three whitefish species which differ in traits related to feeding and reproductive ecology along depth gradients are endemic to this system, and they form a monophyletic lineage alongside extirpated populations from nearby lakes Greifen and Pfäffikon.

Current knowledge suggests that the Zurich Whitefish occupies midwater pelagic habitats, where it is believed to feed predominantly on zooplankton. The annual reproductive period takes place during winter when spawning occurs at depths of c. 12-100 metres.

Diversion of the Linth River and construction of the Linth Canal during the 19^th century resulted in a significantly increased flow of glacial meltwater and increased turbidity in Lake Walen, which probably drove extirpation of the resident Zurich Whitefish subpopulation.

During the 20^th century, Lake Zurich became increasingly eutrophic due to nutrient inputs from agriculture and insufficiently-treated domestic wastewater. This process peaked during the 1970s, when the profundal zone became anoxic, and exerted an acute effect on whitefish population structure and selection.

For example, microsatellite analyses have demonstrated a degree of genetic admixture between the three endemic whitefishes in Lake Zurich, which has been attributed to increased hybridisation as habitat quality declined.

This scenario is comparable to that observed in a number of other European lakes inhabited by sympatric whitefish species: anthropogenic eutrophication has repeatedly resulted in the decline of one or more taxa, due to increased habitat homogeneity driving gene flow between species that were previously segregated along ecological gradients.

Plausible future threats include warming of the lakes due to climate change, and introduction of non-native aquatic species such as the Quagga Mussel (Dreissena bugensis), which is currently expanding in Switzerland and may colonise whitefish foraging and spawning sites.

Whitefishes are exploited on a commercial basis in Lake Zurich, where they comprise more than 50% of the annual catch. They are mostly landed using pelagic nets during summer and demersal nets in winter. A maximum of 12 commercial licenses are granted, hence overfishing is not considered to be a threat. Recreational angling is permitted, with daily bag and minimum size limits for whitefishes in place, plus an annual closed season which extends from November 20 to December 31.

The Zurich Whitefish is not reared artificially or otherwise stocked into the lake.

This species is included (as Coregonus spp.) in Appendix III of the Bern Convention.

Investment in wastewater treatment facilities has driven an improvement in the water quality of Lake Zurich, which is currently classified as mesotrophic. Translocation of whitefishes between lakes has been prohibited throughout Switzerland since 1991.

A deeper understanding of this species' abundance, population trend and life history would likely prove useful in the development of future management actions.