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)

Global and European regional assessment: Vulnerable (VU)
EU 27 regional assessment: Not Recorded

The Dwarf Limmat Whitefish is endemic to Europe, where it occurs in the lakes Zurich and Walen, Switzerland. The species has a restricted range (extent of occurrence (EOO) c. 464 km², area of occupancy (AOO) c. 112 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 two locations, 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 two locations with plausible future threats of climate change and the introduction of non-native species which 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.

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 remains relatively abundant and stable in Lake Walen, whereas the Lake Zurich subpopulation is currently believed to be small following a significant decline after the mid-20^th century (see 'Threats').

The two subpopulations existing today are genetically indistinguishable, and it may have been extirpated from Lake Zurich which was subsequently recolonised by individuals from Lake Walen.

Zurich and Walen are monomictic, perialpine, naturally oligotrophic lakes formed after the last glacial period. They were originally connected as a larger single basin named Lake Limmat, but were later 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 19th 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 form a monophyletic lineage alongside extirpated populations from nearby lakes Greifen and Pfäffikon. Current knowledge suggests that the Dwarf Limmat Whitefish occupies the profundal zone, where it is believed to feed predominantly on zooplankton plus some benthic prey, e.g., chironomid larvae and gastropods. There may be two annual reproductive periods which take place during summer and winter, respectively, when spawning occurs at depths of c. 20-80 metres.

During the 20^th century, Lakes Zurich and Walen became increasingly eutrophic due to nutrient inputs from agriculture and insufficiently-treated domestic wastewater. This process peaked during the 1970s, since when water quality has markedly improved (see 'Conservation').

While Lake Walen experienced relatively moderate eutrophication and remained oxygenated even at its greatest depths, Lake Zurich was significantly more degraded and the profundal zone became anoxic. These changes exerted an acute effect on whitefish population structure and selection.

For example, microsatellite analyses have demonstrated considerable genetic admixture between the three endemic whitefishes in Lake Zurich, which has been attributed to increased hybridisation and reduced foraging opportunities for the deepwater species 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.

Recent evidence suggests that climate change-induced warming of the lakes is leading to increasing stratification and profundal anoxia during the summer, which might be reducing the extent of suitable habitat for individuals which spawn during this period.

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

Whitefishes are exploited on a commercial basis in lakes Zurich and Walen, 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 in Lake Zurich and six in Lake Walen, therefore overfishing is not considered to be a threat to whitefish stocks.

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.

However, the Dwarf Limmat Whitefish is not targeted, nor is it reared artificially or otherwise stocked into the lakes.

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 lakes Zurich and Walen, which are currently classified as mesotrophic and oligotrophic, respectively.

The translocation of whitefishes between lakes in Switzerland has been illegal since 1991.

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