This species has a complex taxonomic history. With the exception of the morphologically distinct ciscoes, its scientific name has at some point been applied to virtually all Eurasian whitefish subpopulations, often alongside the vernacular English names "Common Whitefish" or "European Whitefish". This extremely broad concept of the species continues to appear in published literature (see below).

In addition, most of the synonyms currently associated with this species relate to taxa described from outside its native range and are therefore likely to be reassigned in the future.

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 Bourget Whitefish is natively endemic to to Lake Bourget, France. It has a restricted range (extent of occurrence (EOO) c. 49 km²), which meets the threshold for the Critically Endangered category under Criterion B1 (EOO < 100 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, threatened by habitat modification 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 Lake Bourget (fr. Lac du Bourget) in the upper Rhône River system, France. A subpopulation inhabiting nearby Lake Aiguebelette (fr. Lac d'Aiguebelette) is considered to be non-native, although a fish referred to as "lavaret" was apparently recorded there in the 17^th century.

During the early 20^th century this species was, alongside whitefish species from the Swiss lakes Constance, Zug and Neuchâtel, utilised for restocking Lake Geneva (fr. Lac Léman) after the collapse of its native stock. The current Lake Geneva whitefish population is understood to consist of hybrids between some or all of these taxa.

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.

Overall abundance declined significantly during the mid-20^th century (see 'Threats'), but has generally increased since the 1990s (see 'Conservation').

Recent fisheries data show a period of high abundance between 2009-2011, after which landings markedly decreased. These swings appear to be dependant on food availability during early life stages (see 'Habitats and Ecology'), and indicate that the population size is to some extent unstable.

Lake Bourget is a perialpine, monomictic, naturally oligotrophic lake formed after the last glacial period. It has a maximum depth of 147 metres, and in summer is the largest freshwater lake in France.

The Bourget Whitefish inhabits the pelagic zone, where it feeds predominantly on zooplankton. In particular, the relative abundance of the cladoceran genus Daphnia appears to be a significant driver of whitefish biomass and recruitment in the lake. Fluctuations in Daphnia availability may be related to the re-oligotrophication process (see 'Conservation'), shifts in phytoplankton community structure, changes in the abundance/quality of prey, or top-down control by planktivorous fishes.

The annual reproductive period occurs in December when spawning takes place in shallow water on shoreline gravel beds.

From the 1920s, Lake Bourget experienced phosphorous enrichment due to discharge of untreated domestic wastewater and agricultural runoff. This process intensified during the 1940s and the lake was considered to be eutrophic by the 1970s.

The concurrent decline in the Bourget Whitefish population is likely to have been driven by a combination of factors, including shifts in zooplankton community structure, clogging of spawning sites due to increased sedimentation, and increased resource competition from fish species which benefitted from the eutrophication process.

Eutrophication also resulted in the development of hypoxic conditions in deeper areas of the lake, which led to extinction of the sympatric Savoy Whitefish (Coregonus bezola) through the loss of its profundal foraging and spawning habitats.

The Rhône River flows into Lake Bourget through the modified Canal de Savières waterway during flood periods, and these inputs of oxygen-rich river water favour the mixing of the lake's water column. It is therefore likely that the construction of multiple dams on the Rhône upstream of the Canal de Savières since the late 19^th century has contributed to deoxygenation of the profundal zone by reducing the intensity of flood episodes. The Rhône is also likely to have transported additional nutrients to the lake after the river became polluted during the mid-20^th century.

Although water quality in Lake Bourget has improved since the 1980s (see 'Conservation'), the profundal zone remains largely hypoxic and there is a risk of a delayed release of phosphorous stored in sediments.

The supplementary stocking of hatchery-reared native whitefishes, whereby gametes are stripped from wild individuals and larvae reared under hatchery conditions before being released as fingerlings, is a common practice in the alpine region. However, the artificial influx of juvenile individuals can impair natural recruitment, impose artificial sexual selection and drive hybridisation due to the inadvertent crossing of similar-looking taxa in hatcheries. In the case of Lake Bourget, natural recruitment has reportedly increased since the scheme began in the late 1980s, and in 2008 stocked individuals were found to account for only c. 15% of commercial landings. Moreover, stocking was initiated using larve derived only from the native population in recognition of its genetic distinctiveness, and it is unclear whether non-native genetic material has ever been introduced.

A handful of non-native fish species are established in the lake, among which the Wels Catfish (Silurus glanis) is of particular concern. Research has demonstrated that this benthic predator feeds upon whitefish of all age classes, but that young-of-the-year are most actively consumed, especially in summer.

The filamentous cyanobacterium Planktothrix rubescens, which produces toxins that can induce fish mortality if concentrated in certain tissues, has formed major blooms comprising 20-50+% of algae biomass in Lake Bourget since the mid-1990s. It was not observed between 2010-2015, but reappeared in 2016.

The warming of Lake Bourget due to climate change constitutes a plausible ongoing and future threat.

This species is harvested on a commercial basis, but the number of professional fishers operating on Lake Bourget has fallen from around 120 in 1970 to fewer than ten today. During the 1950s, annual landings were c. 90 tonnes, but fell to < 1 tonne by the 1970s. Between 2000-2020 they ranged from 6.2-78.4 tonnes. Recreational angling is permitted, with landings representing 7% of the overall total between 2000-2020.

This species is included (as Coregonus spp.) in Appendix III of the Bern Convention and Annex V of the European Union Habitats Directive. It is listed as a non-native species and was not assessed in the most recent (2019) iteration of the French National Red List, but this may be a result of taxonomic confusion (see 'Taxonomic Notes'). Lake Bourget is included in the European Union's Natura 2000 network of protected areas (site FR8202010), and is a Ramsar site under the Convention on Wetlands of International Importance (site no. 1268).

Investment in a system to redirect treated urban wastewater directly to the Rhône River plus other measures introduced since the 1980s have driven an improvement in water quality, and the lake is currently classified as oligomesotrophic. In particular, the level of phosphorus declined rapidly after 2008, and limnological data reveal a pattern of nutrient regression consistent with re-oligotrophication. The return of more favourable habitat conditions is likely to have driven the observed increase in whitefish recruitment since mitigation measures began.

Supplementary stocking continues with up to 19 million hatchery-reared larvae released annually over the period 2000-2020.

This species' life history is not well-studied, and identification of its preferred spawning sites may aid in the development of future management measures.