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 Stechlin Cisco is endemic to Europe, where it occurs in Lake Stechlin, northeastern Germany. The species has a restricted extent of occurrence (EOO) of c.7 km², meeting the threshold 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 a single location where the quality of habitat is estimated to be undergoing continuing decline.

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

This species is endemic to Lake Stechlin (de. Großer Stechlinsee) in the State of Brandenburg, northeastern Germany.

This species' current population size and trend have not been quantified. It is suspected to have declined significantly since around 2010, based on field observations and declining habitat quality (see 'Threats').

Furthermore, microsatellite analyses have revealed an ongoing loss of genetic differentiation between the Stechlin Cisco and sympatric European Cisco (Coregonus albula), which may be indicative of speciation reversal.

Dimictic and meso-oligotrophic Lake Stechlin has a maximum depth of 69 metres, and was formed during the last glacial period. Substrata are sandy in shallow areas, becoming muddier in deeper zones. Stoneworts (Characeae) grow to depths of c. 15 metres.

The Stechlin Cisco occupies the pelagic zone at depths of 20-60 metres, but undertakes diel vertical migrations to forage on zooplankton during the night. Its diet is predominated by small crustaceans such as cladocerans and copepods. Female individuals reach sexual maturity at age 2+ and a size of 65-110 mm standard length. Mean fecundity is 1,500 eggs per individual. The annual reproductive period extends from April to June. Spawning occurs at depths greater than 25 metres, and most individuals are believed to reproduce only once during their lifetimes.

In contrast, the sympatric European Cisco subpopulation is most abundant at depths above 25 metres and reproduces in autumn.

Anthropogenic pressure in the Lake Stechlin basin is considered to be low, but an accelerating trend towards eutrophication has been observed since the mid-1990s.

The drivers of this process are believed to be a warming of the basin due to climate change, coupled with a delayed release of phosphorous accumulated during operation of a nuclear power plant which pumped cooling water into the lake from the mid-1960s until 1989.

These stresses are giving rise to a progressive loss of the cold and oxygenated deepwater habitats to which the Stechlin Cisco is adapted, and a reduction in ecological segregation from the European Cisco since the two species are naturally separated along vertical water temperature gradients.

Eutrophication may also be driving the development of an overlap in the two species' spawning seasons, insofar as increased productivity could plausibly result in higher growth rates and lead some Stechlin Cisco individuals to mature earlier.

In combination, these factors appear to be driving increased hybridisation between the two species, leading to the detected erosion in genetic structure (see 'Population') and raising the possibility of speciation reversal.

This scenario is comparable to that observed in a number of other European lakes inhabited by sympatric Coregonus species, where anthropogenic eutrophication has resulted in the extinction of one or more taxa due to increased gene flow between ecologically-differentiated species.

A small commercial fishery operates on Lake Stechlin, but this species 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 Stechlin lies entirely within the boundaries of the Stechlin-Ruppiner Land Nature Park protected area and has been protected since 1938. It is also included in the European Union's Natura 2000 network (site DE2844301).

In 2021 a dedicated working group to investigate management solutions in response to the deteriorating ecological conditions was initiated by the Brandenburg Ministry of Agriculture, Environment and Climate Protection.

The installation of aeration devices to combat hypoxia in deep areas of the lake and artificial phosphorous precipitation are among the proposed actions.