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 Biel Whitefish is endemic to Europe, where it occurs in Lake Biel, Switzerland. The species has a restricted range (extent of occurrence (EOO) c. 44 km², area of occupancy (AOO) c. 40 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 a single location threatened by 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 Lake Biel (fr. Lac de Bienne; de. Bielersee) in the upper Rhine River system, Switzerland.

Contrary to some published reports, it is not native to nearby lakes Morat (fr. Lac de Morat; de. Murtensee) or Neuchâtel (fr. Lac de Neuchâtel; de. Neuenburgersee).

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, but fisheries data indicate that it was relatively stable during the period 1984-2018.

Lake Biel is a monomictic, perialpine, naturally oligotrophic lake formed after the last glacial period. It has a maximum depth of 74 metres and is connected to adjacent Lake Neuchâtel (fr. Lac de Neuchâtel; de. Neuenburgersee) via a canalised stretch of the Thielle River. In 1878, it was artificially linked to the Aare River through the manmade Aare-Hagneck Canal in order to control seasonal flooding. This engineering scheme significantly increased the size of the Lake Biel catchment as well as the delivery of sediment into the lake itself.

Prior to the 1970s, the lake was inhabited by a second, now extinct, whitefish species which occupied the profundal zone and is referred to as Coregonus cf. restrictus, C. sp. "Bräter" or C. sp. "Balch-Pfärrit" in some published literature (see 'Threats'). A non-native subpopulation of the congeneric Bernese Whitefish (Coregonus albellus) is understood to be established in Lake Biel, having probably arrived from nearby Lake Thun (de. Thunersee) via the Aare-Hagneck Canal.

The Biel Whitefish primarily inhabits the pelagic zone of the lake at depths of 10-35 metres. It feeds predominantly on zooplankton, but may also target benthic prey during colder months of the year. The annual reproductive period extends from December to January when spawning takes place on sloping shorelines at depths of 2-20 metres.

This species is possibly threatened by resource competition with the non-native Bernese Whitefish (see 'Habitat and Ecology'). Introgressive hybridisation is not considered to be a threat, since the two species are somewhat segregated by their reproductive ecology.

It is also plausible that the extent of suitable spawning habitat has been progressively reduced since the late 19^th century, due to increased sedimentation from the diverted Aare River and accumulation of dumped waste materials from river modification projects.

The non-native Three-Spined Stickleback (Gasterosteus aculeatus) is present in Lake Biel, and has been associated with recent whitefish declines in Lake Constance (fr. Lac de Constance; de. Bodensee) through competition for zooplankton resources and predation of early life stages. Although its abundance in Lake Biel is not currently considered to be problematic, it may represent a plausible future threat.

The invasive Quagga Mussel (Dreissena bugensis) was first recorded in Lake Biel during 2019. Once established, this filter-feeding mollusc can drive driving significant food web alterations, including energy sources and pathways for pelagic fishes, due to its propensity to alter zooplankton abundance, community structure and composition.

A rising human population in the lake's catchment after the turn of the 20^th century drove the development of industry and agriculture, which led to increasing pollution from domestic wastewater and runoff. The lake subsequently entered a phase of eutrophication which peaked during the 1970s and led to the development of periodic anoxia in the hypolimnion. These events are likely to have driven the extinction of the sympatric profundal whitefish subpopulation (see 'Habitat and Ecology') by significantly reducing the extent of habitat and the abundance of zoobenthos which comprised the main component of its diet. The trophic status of the lake has today improved to an extent, as a result of management activities (see 'Conservation').

Warming of the lake due to climate change constitutes a plausible ongoing and future threat.

This species is harvested commercially.

This species is harvested commercially, although both annual landings and the number of professional fishers operating on Lake Biel have declined significantly since the late 1980s. A total of eight professional fishing licenses were issued in 2022.

These outcomes have been partially attributed to the lake's improved trophic status (see 'Conservation'), which is likely to have driven a natural reduction in productivity and a concurrent reduction in the size of adult whitefish.

This species is included (as Coregonus spp.) in Appendix III of the Bern Convention. Several protected areas are established around Lake Biel. Investment in wastewater treatment facilities and other policy-led measures since the 1980s has driven an improvement in water quality, and the lake is currently considered to be meso-oligotrophic.

An annual species-specific closed fishing season extends from July to January. Translocation of non-native whitefishes has been prohibited throughout Switzerland since 1991.

It is recommended that future research should focus on confirming this species' current population trend and response to the ongoing threats.