British whitefishes
The taxonomic status of Coregonus subpopulations inhabiting the British Isles has not been definitively resolved since a series of endemic species were described between the early 19^th and early 20^th centuries.

Among these, C. stigmaticus is most closely related to C. clupeoides Lacépède 1803 from central Scotland and C. pennantii Valenciennes, 1848 from northwestern Wales. A number of recent studies have demonstrated that there is little morphological or genetic support for considering these as distinct species when they are compared with one another (Etheridge et al. 2012, Crotti et al. 2020).

In the United Kingdom, all three of these taxa are treated as junior synonyms of the congener Coregonus lavaretus (Linnaeus 1758), the name of which has since the mid-20^th century been applied to a widespread complex of polymorphic whitefish populations occurring across northwestern Eurasia (Crotti et al. 2021). However, the systematics of this putative assemblage and the native range of C. lavaretus remain questionable (see further discussion below).

C. stigmaticus is currently regarded as valid for global Red List purposes following Fricke et al. (2024), and the present global assessment should be considered equivalent to the most recent English national assessment for C. lavaretus (Nunn et al. 2023).

European ciscoes and whitefishes
At the regional scale, the systematics of European ciscoes and whitefishes (Coregonus spp.) has also 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 evolved in some perialpine lakes, and these radiations might be even more diverse in a few 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.

With the above in mind, it appears unlikely that the striking phenotypic diversity exhibited by members of this genus will ever be adequately represented by a single accepted taxonomic system. The Red List currently follows the nomenclature provided by Fricke et al. (2024).

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

The Schelly is endemic to a small number of lakes, including some lakes where the species was introduced for conservation reasons, in northwestern England, United Kingdom

The species has an extremely restricted range (extent of occurrence (EOO) c. 91 km²), which meets the threshold for the Critically Endangered category under Criterion B1 (EOO < 100 km²) and the quality of habitat is observed to be declining. However it is present at six locations which does not meet the threshold for the Critically Endangered category. Therefore, this species is assessed as Vulnerable under Criterion B (B1ab(iii)).

This species is endemic to the county of Cumbria in northwestern England, United Kingdom, where it inhabits lakes Haweswater, Ullswater, Brothers Water and Red Tarn in the Eden River system.

Introduced subpopulations are established in Blea Water and Small Water, both of which are minor lakes in the upper Haweswater catchment (see 'Conservation'). These subpopulations are included in the present assessment, since the known intent of the introductions was to reduce the extinction risk of the taxon, the occupied sites are geographically close to the natural range, viable offspring have been produced, and at least five years have passed since the translocations took place.

Brothers Water, Red Tarn, Blea Water and Small Water could not be included on the range map accompanying this assessment due to their small size.

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.

The Haweswater subpopulation declined significantly between the 1980s-1990s, but is currently understood to be stable albeit with low overall abundance.

There is no evidence that the Ullswater subpopulation is declining, and this lake is likely to harbour the largest subpopulation. The overall trend was estimated to be stable in 2011, although a series of plausible threats have been identified (see 'Threats').

The Brothers Water subpopulation reported to be stable and comprise a range of age classes in 2015.

The current status of the Red Tarn subpopulation is unclear, but it was estimated to be stable based on older sampling data according to a report published in 2011.

The translocated subpopulations inhabiting Blea Water and Small Water are believed to be stable.

All of the lake basins in which this species occurs were formed after the last glacial period.

Haweswater is an oligotrophic artificial reservoir that formerly comprised two smaller lakes, the outflow of which was dammed in 1939 to provide domestic water supply. The maximum water level is c. 29 metres higher than before these engineering works were completed.

Ullswater is oligomesotrophic and retains a well-oxygenated water column. It has a maximum depth of 63 metres and three main basins comprising a shallower (maximum depth c. 30 metres) northern basin, and deeper mid- and southern basins. The water level in the lake is maintained by a weir on the outflowing Eamont River, and water is artificially pumped to Haweswater during periods of high flow.

Oligotrophic Red Tarn occupies a cirque at a relatively high (c. 718 metres asl) altitude, and has a maximum depth of 26 metres. Although it is located within the Ullswater catchment, there is no means by which fish can move between the two lakes. It is replenished only via runoff from the surrounding mountain slopes and discharges towards Ullswater via a small, steeply-orientated stream. During the 1860s, the lake's outflow was dammed to provide water for a nearby lead mine (see 'Threats'), but this barrier was partially dismantled in the 1930s.

Oligomesotrophic Brothers Water has a maximum depth of 18 metres and its bathymetry is dominated by a flat central basin. A stream discharges towards Ullswater from its northwestern corner.

Blea Water and Small Water occupy remote cirques at relatively high altitudes. Blea Water has a maximum depth of 63 metres, and Small Water 16 metres.

The Schelly principally occupies benthopelagic habitats in deeper parts of the lakes but probably undertakes diel vertical migrations related to foraging during warmer months of the year. This species' diet has not been well-studied, but closely-related congeners feed on zoobenthos such as chironomid larvae and sphaeriid clams, with zooplankton comprising a significant proportion of the diet in summer and autumn. The maximum recorded lifespan is 13 years. In the Haweswater subpopulation, most male individuals reach sexual maturity at age 3+ and most females at age 4+, whereas in Ullswater the growth rate is faster and both sexes tend to mature a year earlier. According to the limited available data, the growth rate of individuals inhabiting Red Tarn may be slower than those from Haweswater. The annual reproductive period extends from mid-January to mid-February, when spawning takes place on clean gravel or sand banks in shallow littoral or sublittoral zones. The eggs hatch in April and appear to require consistently cold water (< 10°C) in order to complete their development.

The water level of Haweswater fluctuated significantly between the 1970s-1990s due to water abstraction for domestic supply (see 'Habitats and Ecology'). This is believed to have driven the decline of the resident Schelly subpopulation through dewatering of breeding sites during the spawning and incubation period. More recently, prolonged periods of drought have led to the water level being temporarily reduced by up to c. 60%.

Predation by a Great Cormorant (Phalacrocorax carbo) breeding colony that settled at Haweswater during the early 1990s may have prevented subpopulation recovery despite attempted measures to mitigate the water level. The birds were themselves managed for a period but these efforts were discontinued in 2008, with perceived predation pressure increasing to c. 45% of its former level by 2010 (see 'Conservation').

The Ullswater subpopulation may be locally threatened by the deposition of fine sediments contaminated with ore from a former lead mine on spawning sites in the southern part of the lake. This issue may be compounded during periods of high flow, e.g., in the wake of storms. High levels of tourism and amenity use, especially during summer, have also been proposed as a plausible threat.

Non-native fish species established in Ullswater include the Common Roach (Rutilus rutilus), which was first recorded in 2013 and is known to compete with planktivorous fishes for food resources.

Presence of the Eurasian Ruffe (Gymnocephalus cernua) in some nearby lakes is an additional cause for concern since it is an opportunistic, largely benthivorous predator that has been strongly linked to the purported decline of the Powan (Coregonus clupeoides) in Loch Lomond, Scotland. The Swamp Stonecrop (Crassula helmsii) is also established at those sites, and if translocated this invasive plant could reduce the quality of Schelly spawning habitat through encroachment, since it tends to grow densely in sublittoral zones and does not die back in winter.

At Brothers Water, the primary identified threat is decreasing oxygen in the hypolimnion leading to a reduction in profundal refuge areas. This phenomenon may be caused by nutrient enrichment and could be exacerbated by warming temperatures.

Warming of the lakes due to climate change constitutes a major ongoing and future threat for this cold-water adapted species.

This species is not used or traded.

This species is included (as Coregonus spp.) in Appendix III of the Bern Convention.

At the national scale, it is included (as Coregonus lavaretus) in Schedule 5 of the Wildlife and Countryside Act 1981 and Schedule 3 of the Conservation (Natural Habitats, &c.) Regulations 1994, and is listed as a priority species of conservation concern in the U.K. Post-2010 Biodiversity Framework.

Its range is located entirely within the Lake District National Park protected area, which is also a UNESCO World Heritage Site. Ullswater is included in the River Eden and Tributaries Site of Special Scientific Interest (SSSI) and Special Area of Conservation (SAC). Brothers Water is itself a SSSI, and Red Tarn is located within the Helvellyn and Fairfield SSSI and the Lake District High Fells SAC.

A standardised national assessment protocol is in place, with all subpopulations monitored on a semi-regular basis since the 1990s.

A number of management measures have been implemented at Haweswater since the mid-1990s. These include the development of mobile artificial spawning substrata, attempts to manage the lake's water level in order to benefit the Schelly, and the establishment of ex situ "refuge" subpopulations through the introduction of fertilised eggs to nearby Blea Water and Small Water.

The water utility company managing the lake trialled a number of bird scaring techniques between 1999-2004 in order to discourage further nesting by the Great Cormorant, among which frequent human visits to the nesting island proved to be the most successful. Between 2004-2006 a total of 29 Great Cormorants were also shot at the site, but after 2007 no further culling took place due to a reduction in numbers and an estimated c. 75% decrease in Schelly predation.

Schelly spawning sites at Haweswater and Ullswater were identified in 2011 by studying the activity and spraints of Eurasian Otter (Lutra lutra).

A deeper understanding of this species' population trends and life history at the subpopulation level would likely aid future management efforts. In Haweswater, the impact of water level fluctuations on other factors potentially affecting growth and recruitment, such as alterations to the zooplankton community structure or temperature regime in the lake, have not yet been investigated.

The taxonomic status of British Coregonus species is in need of review, but there exist a number of complications (see 'Taxonomic Notes').