In some published literature, this species is referred to as a subpopulation or subspecies of the Least Cisco (Coregonus albula).

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 Breiter Luzin Cisco is now restricted to Lake Breiter Luzin, northern Germany. The species has a restricted range (extent of occurrence (EOO) c. 16 km², which meets the thresholds for the Critically Endangered category under Criterion B1 (EOO < 100 km²). The area of occupancy (AOO) is uncertain, but if the species occurs throughout the lake, the AOO probably exceeds the threshold for the Critically Endangered category under Criterion B2 (AOO < 10 km²). It is present at one location where the quality of habitat is estimated to be declining.

Therefore, this species is assessed as Critically Endangered under Criterion B (B1ab(iii)).

This species is currently restricted to Lake Breiter Luzin in the state of Mecklenburg-Vorpommern, northern Germany. It is understood to have been extirpated from some nearby lakes.

This species' current population size and trend have not been quantified.

It occurs sympatrically with a subpopulation of the more widespread European Cisco (Coregonus albula), which is believed to comprise c. 95% of the overall cisco stock. Microsatellite analyses have demonstrated that there may be an ongoing loss of genetic differentiation between these two species, which may be indicative of speciation reversal (see 'Threats').

Dimictic and naturally oligotrophic Lake Breiter Luzin has a maximum depth of 58.5 metres and was formed during the last glacial period.

The Breiter Luzin Cisco occupies relatively deep habitats in the pelagic zone, where it feeds on zooplankton such as copepods and cladocerans, supplemented by the relict mysid crustacean Mysis relicta. Maximum lifespan is c. six years and adult individuals become sexually mature at age 2+. The annual reproductive period extends from April to July, peaking in May and June, and spawning is believed to occur in the littoral zone.

In contrast, the sympatric European Cisco subpopulation forages at shallower depths and reproduces in autumn.

Anthropogenic pressure in the Breiter Luzin basin is considered to be relatively low, but an accelerating trend towards eutrophication due to discharge of domestic wastewater was observed after the mid-20^th century.

Water quality has improved since the 1980s (see 'Conservation'), but the lake ecosystem has not completely recovered and is currently classified as mesotrophic.

The impact of these environmental changes on the Breiter Luzin Cisco has not been investigated in depth, but signals of increasing hybridisation with the European Cisco have been detected and may be driving the observed erosion in genetic structure, while raising the possibility of speciation reversal (see 'Population').

Furthermore, anthropogenic eutrophication has repeatedly resulted in the decline of one or more endemic Coregonus species in other post-glacial European lakes due to increased gene flow between ecologically-segregated species.

Several non-native fish species, including European Eel (Anguilla anguilla), Common Carp (Cyprinus domestic strain) and Wels Catfish (Silurus glanis), have been introduced to Lake Breiter Luzin to supplement the recreational fishery, and plausibly threaten native fish stocks through habitat degradation, resource competition or predation.

Warming of the lake due to climate change represents a plausible future threat.

A small commercial fishery mostly exploiting the European Cisco (referred to locally as "Feldberger Maräne") operates on Lake Breiter Luzin.

Recreational angling is also permitted, but the Breiter Luzin Cisco is not targeted.

This species is included (as Coregonus spp.) in Appendix III of the Bern Convention and Annex V of the European Union Habitats Directive. Lake Breiter Luzin lies entirely within the boundaries of the Feldberg Lake District Nature Park (de. Naturpark Feldberger Seenlandschaft) protected area, and is included in the European Union's Natura 2000 network (site DE2646305).

Investment in wastewater treatment facilities since the mid-1980s has driven an improvement in the water quality of the lake.

This species is not well-studied, and a deeper understanding of its demographics (population size and trend), life history and response to the identified threats would likely prove useful in the development of future management actions.