Lake Constance Whitefish: An example of species loss in alpine lakes

Species or just a form?

The Lake Constance whitefish or kilch belongs to the genus Coregonus—a group of salmonids found in cool, oxygen-rich waters across the Northern Hemisphere. In Europe, they are known as Felchen, Maränen, Reinanken or Renken (whitefish). Hardly any other fish group is considered as taxonomically difficult: many forms have arisen only since the last Ice Age and differ little in outward appearance, while being highly specialized ecologically.

After the retreat of the glaciers around 10,000 to 15,000 years ago, coregonids colonized numerous European lakes. From originally anadromous ancestors, different forms adapted to specific habitats developed within a short time—for example to different water depths or food sources (Ford, 2024). This process of adaptive radiation led to individual lakes harboring several, sometimes very similar but ecologically clearly distinct whitefish forms.

This is precisely where the problem lies: are these forms independent species or merely variants of a widespread species? In the case of the Lake Constance whitefish, this question remains unresolved to this day. While some researchers regard it as a valid species, others assign it to the so-called Coregonus lavaretus complex—a broadly defined species group with numerous locally differentiated forms.

The classification depends strongly on regional research traditions. In Northern Europe (for example Scandinavia and Great Britain), many whitefish forms are lumped into a few species, above all Coregonus albula and C. lavaretus (Ford, 2024). In Central Europe (for example Germany, Switzerland, Austria), by contrast, a much finer subdivision is common. More than 60 species have been described here, including the Lake Constance whitefish as well as the species that disappeared in the 1950s, fera (C. fera) and Gravenche (C. hiemalis) from Lake Geneva.

These different approaches reflect a fundamental problem: coregonids are evolutionarily young forms whose delimitation is based less on clear genetic differences than on ecological and morphological traits—such as habitat depth, diet, or gill raker structure.

Regardless of its exact taxonomic status, one thing is certain: the Lake Constance whitefish was part of a specialized fish fauna of the alpine lakes that arose in the course of postglacial adaptation. Its distinctiveness lay less in striking external features than in its specific ecological niche.

For lack of a uniform taxonomic consensus, the IUCN Red List follows the systematics of Fricke et al. (2024) and lists the Lake Constance whitefish as an independent species that is now extinct.

Lake Constance whitefish – fact sheet

alternative names	kilch, Bodensee kilch, strumose whitefish
scientific names	Coregonus gutturosus, Salmo gutturosus, Coregonus acronius, Coregonus acronius var. bavarica, Coregonus acronius  var. acronius, Salmo maraena gutturosa, Salmo maraena media
original range	Lake Constance (Germany, Austria, and Switzerland)
time of extinction	in the 1970s
causes of extinction	eutrophication, oxygen depletion, hybridization
IUCN status	extinct

From subspecies to species

The Lake Constance whitefish was first scientifically described in 1818 by the physician and naturalist Carl Christian Gmelin—though initially not as an independent species, but as a subform of the common whitefish under the name Salmo maraena gutturosa. This classification reflected the practice of the time, which treated locally distinct whitefish forms as variants of a few collective species.

Yet in the same year a more differentiated view gained ground: the form was recognized as a distinct species and transferred to the genus Coregonus (Coregonus gutturosus). No single first description can be identified with certainty; rather, species status emerged in the context of the developing whitefish systematics of the early 19th century, when ecological and morphological differences were increasingly taken into account.

Thereafter, the taxonomic classification remained controversial for a long time. Thus Wilhelm Ludwig von Rapp (1854) grouped several similar whitefish forms from different alpine lakes—including Lake Constance, Lake Geneva, and Lake Attersee—under the name Coregonus acronius. This unification reflects a phase in which whitefish diversity was more often merged than differentiated.

Only toward the end of the 20th century did a more strongly differentiating view gain acceptance again. In European Freshwater Fishes (1997), the Swiss ichthyologist Maurice Kottelat returned to the designation Coregonus gutturosus. In doing so, he deliberately restricted species status to the ecologically specialized, deepwater form of Lake Constance and separated it from other whitefish populations.

Where did the kilch live?

The Lake Constance whitefish was an endemic inhabitant of Lake Constance, a large pre-alpine lake in the Rhine catchment bordering Germany, Switzerland, and Austria. The lake formed after the last Ice Age and belongs to the so-called peri-alpine lakes.

With an area of around 536 km², Lake Constance is divided into two main sections: the distinctly deeper Upper Lake (max. over 250 m) and the much shallower Lower Lake (average approx. 13 m, max. 45 m). As a species adapted to great depths, the kilch was confined to the Upper Lake. There it primarily inhabited the profundal—the lake’s cold, low-light deep zones.

Early sources are misleading in this respect: Gmelin (1818) wrote that the kilch occurred “mainly in the Lower Lake near Konstanz.” This statement contradicts later findings and can probably be explained by the fact that Gmelin described fishing and trading locations, not the actual habitat. Konstanz lies at the transition between the Upper and Lower Lake and was a central transshipment point for fishery yields.

More recent accounts show that the kilch stayed mainly at depths of around 100 meters and over the course of the year even reached depths of up to about 140 meters (Kottelat & Freyhof, 2007; Ford, 2024). In these areas it fed mainly on bottom-dwelling invertebrates such as mussels and snails—an indication of its adaptation to life on the lake bed.

For reproduction, it temporarily left these deep zones. Egg laying took place at intermediate depths between about 10 and 60 meters, mainly from summer into autumn (Kottelat & Freyhof, 2007; Ford, 2024). It then returned to greater depths.

The Lake Constance whitefish was part of an ecologically differentiated system of several whitefish forms that partitioned the lake along depth and food gradients. While the kilch inhabited the deep areas, other species lived in other zones: the Blaufelchen or Wartmann’s whitefish (Coregonus wartmanni) in open water, the Gangfisch (C. macrophthalmus) closer to shore, and the Sandfelchen or sand whitefish (C. arenicolus) on the lake bed in shallower areas. This spatial partitioning illustrates that the different whitefish forms divided up the Lake Constance habitat among themselves and were each adapted to different environmental conditions.

What distinguishes the Lake Constance whitefish from other whitefish?

At first glance, the whitefish of Lake Constance look very similar. Individual variation and overlapping traits make it difficult to identify individual forms with certainty. Even so, the species differ in central aspects of their biology—especially morphology, diet, habitat, and reproductive behavior (Rey et al., 2023).

Within this system, the Lake Constance whitefish occupies a special position: it is characterized less by individual striking traits than by the combination of several features that mark it out as a specialized inhabitant of the deep zone.

Morphology and diet

The morphological differences between the whitefish forms are usually subtle and can generally be recognized reliably only by combining several traits. An analysis by Christian Ruhlé and Theodor Kindle (1992) shows that these differences are closely linked to the respective way of life.

A fundamental comparison can be made between river-spawning whitefish of the Alpine Rhine and the forms of Lake Constance: river spawners tend to be slimmer and more streamlined—an adaptation to life in flowing water. The whitefish of Lake Constance, by contrast, show greater variability in body shape. Bottom- and deepwater-dwelling species such as the kilch are often more compactly built.

The head and mouth structure is closely connected with diet. While river-spawning forms are adapted to taking food from the current, the whitefish of Lake Constance show stronger specialization on different food sources: pelagic species feed on plankton in open water, benthic forms seek their food on the lake bed, and deepwater-dwelling species specialize in zoobenthos

Mouth position—superior, terminal, or inferior—directly reflects these strategies. In the kilch, the inferior mouth points to feeding close to the bottom. In addition to benthic invertebrates, the kilch apparently also ate fish eggs, especially those of the Blaufelchen (Walter, 1913). This behavior additionally places it as an opportunistic predator within the food web.

Gill rakers as a key trait

A central distinguishing feature of whitefish is the number of gill rakers, which serve as a filtering system when food is taken in. Their number also provides clues to diet: while species with many fine gill rakers filter plankton from the water, lower numbers point to a diet of larger prey such as zoobenthos.

For the Lake Constance whitefish, a medium number of about 14 to 25 gill rakers is given (Kottelat & Freyhof, 2007). Together with its blunt snout and inferior mouth, this points to a specialization in bottom-associated food.

Victor Fatio (1890), however, already pointed out that the number of gill rakers alone is not a reliable species characteristic. What matters is rather the combination of several properties. For the kilch he gives values from about 17 gill rakers upward, which supports its classification as a benthically oriented form.

Ecological niche and habitat partitioning

All Lake Constance whitefish are schooling fish, but they use different areas of the lake and each occupy their own ecological niches. While the Blaufelchen lives pelagically in open water, the Gangfisch, Sandfelchen, and kilch occupy different depth zones and are more strongly bottom-oriented (Rey et al., 2023; Steinmann, 1950).

A systematic description of this partitioning was provided by Paul Steinmann (1950), who understood the whitefish as a structure of ecologically differentiated forms within a single lake. The decisive factor here is the separation along habitat and feeding mode.

The kilch occupied the deepest parts of the lake and thus clearly differed from near-shore or pelagic species. Although Steinmann recognized that transitions can exist between individual whitefish forms, he emphasized—like Fatio (1890)—that the kilch is ecologically clearly delimitable and should not be equated with superficially similar species such as the Gravenche.

Reproduction: river spawners and lake spawners

Another central difference lies in reproductive behavior. While Alpine Rhine whitefish ascend into flowing waters to lay eggs, the Lake Constance whitefish spawn in the lake itself (Ruhlé & Kindle, 1992).

For reproduction, the kilch, which otherwise stayed at great depths, sought out intermediate depth zones. Historical sources mention about 10 to 20 meters (Walter, 1913), while newer accounts give a range of up to about 60 meters.

This separation shows that even within a connected water system, different reproductive strategies can exist. The kilch was fully adapted to life in the lake.

Throat swelling—trait or artifact?

Gmelin already adopted in his 1818 first description of the Lake Constance whitefish regional names already in use such as Kropfmaräne, Kropffelchen, and Sandfelchen. While “Sandfelchen” probably refers to its bottom-associated way of life, he related the term “Kropf-” to a conspicuous feature that he linked with the spawning season:

“In the spawning season, which falls in September and October, its throat is swollen like a bladder, at which time they are called Kropffelchen.”

He interpreted this appearance as a biological trait—presumably a swelling in the throat or gill region during the breeding season. It must be taken into account that he most likely made his observations on captured animals and could not examine living fish in their natural habitat. Because the kilch rose from great depths into more accessible areas for reproduction and there occurred at higher density, it was caught much more frequently at that time. The connection between “swollen throat” and spawning season therefore seemed obvious to Gmelin.

Fatio (1890) provides another explanation: according to him, the supposed “swollen throat” arises only when the fish is caught. When a kilch is brought to the surface from greater depth, the swim bladder expands greatly as a result of the rapid drop in pressure. This can cause the abdomen to balloon and create the impression of swelling in the neck or throat area. The swim bladder “may even burst with a bang,” according to Emil Walter (1913). In many cases the animals were thereby severely deformed or damaged.

The eponymous “Kropf-” was therefore probably not a permanent or species-specific trait, but an artifact of the capture conditions.

Why did the Lake Constance whitefish become extinct?

A global meta-analysis by Leonidas Vardakas et al. (2025) shows that almost one third of all freshwater fish species alive today are threatened with extinction. Although freshwater fish make up more than half of global fish diversity, they are among the most threatened vertebrate groups. Particularly affected, besides carps (Cyprinidae) and minnows (Leuciscidae), are also the salmonids (Salmonidae), to which whitefish of the genus Coregonus belong. Of these, at least 13 species are already regarded as extinct.

Since the middle of the 20th century, extinction rates have accelerated significantly. Vardakas et al. identify above all changes to natural ecosystems, pollution, and invasive species as the main causes—factors that often act together and reinforce one another.

In European lakes, eutrophication in particular plays an important role. Nutrient inputs lead to profound changes in lake ecology and are considered the main cause of the collapse of many specialized whitefish forms. Species with narrow habitat ranges and high ecological specialization are regarded as especially vulnerable.

How great the original diversity of this fish group was is shown by a study by Oliver M. Selz et al. (2020): historically, around 50 whitefish species in about 30 lakes existed in the pre-alpine lakes of Central Europe. In Switzerland alone, around 35 endemic species were still known about a century ago, of which a third had already disappeared by the middle of the 20th century.

The Lake Constance whitefish is part of this broader pattern. Its disappearance cannot be traced back to a single cause, but is the result of several interacting processes.

Eutrophication as the central cause of extinction

The German limnologist Wilhelm Nümann showed in 1972 that increasing eutrophication of Lake Constance in the 1960s and 1970s triggered profound changes in the fish community. The deeper water layers were primarily affected: there was oxygen depletion in the benthic zone and fundamental shifts in the food web. These developments hit the Lake Constance whitefish particularly hard as a deepwater form.

In the 20th century, strong population growth in the catchment area led to intensification of industry and agriculture. As a result, nutrient inputs from wastewater and agricultural runoff steadily increased. After the Second World War, pronounced eutrophication set in, leading to increased algal growth, water turbidity, and finally—with a peak around 1979—stable stratification of the water body and oxygen depletion in deep water (Ford, 2024).

Catch statistics from commercial fisheries show that all whitefish species suffered under these changes: yields fluctuated strongly and stabilized again only when phosphorus levels declined (Rey et al., 2023).

For deepwater-dwelling species, this had serious consequences. In the oxygen-poor zones, many organisms could no longer survive, and reproduction was also impaired: the eggs of many whitefish no longer developed in the oxygen-poor sediments.

For a stenotopic species like the Lake Constance whitefish, this meant the loss of its entire ecological niche. Peter Rey et al. put it succinctly in 2023:

“The kilch is probably extinct because its lifestyle, food preference, and reproduction were so adapted to deepwater conditions that it could not evade the consequences of nutrient loading during the eutrophic phase of the lake.”

General limnological studies support these relationships. In a long-term study (2005), the Danish researcher Martin Søndergaard showed that lakes react extremely sensitively to changes in nutrient balance: with increasing eutrophication, phytoplankton biomass rises sharply, accompanied by algal blooms and increasing turbidity. At the same time, the fish community shifts—species of nutrient-poor systems such as salmonids and coregonids decline, while perch and carp-like fish dominate.

At the same time, food webs change. An increase in plankton-feeding fish reduces larger zooplankton, intensifies algal development, and increases the sedimentation of organic matter. This in turn leads to increased oxygen consumption in the deep zones—where the kilch lived and spawned. The decline of the Lake Constance whitefish is thus part of a comprehensive ecological system change.

Lake Constance today: new threats—similar effects

Only through comprehensive water protection measures did Lake Constance recover. Today the Upper Lake is considered largely oligotrophic and the Lower Lake mesotrophic (Ford, 2024)—but for the kilch, this development came too late.

Current developments show, however, that the ecological problems of Lake Constance have not been overcome. The new Red List of fishes and crayfish of Baden-Württemberg (2025) identifies Lake Constance as the water system with the most pronounced deteriorations in the state. Several species had to be moved into higher threat categories, including coregonids such as Blaufelchen and Gangfisch.

The causes are considered to be a combination of climate change, altered food webs, and invasive species such as the three-spined stickleback (Gasterosteus aculeatus), which eats whitefish eggs and larvae. At the same time, rising water temperatures worsen oxygen conditions in deeper water layers.

Whereas in the past it was mainly eutrophication and pollution that caused oxygen depletion in deep water, today it is altered temperature and mixing processes as a consequence of climate change. The effect is the same, however: the loss of oxygen-rich deep zones—and with it the habitat of specialized species.

Species fusion as a hidden cause of extinction

Besides direct environmental changes, a less obvious mechanism probably also played a role: so-called “speciation reversal,” that is, the collapse of previously separate species through hybridization.

Selz et al. (2020) show that many alpine whitefish species arose through ecological specialization within individual lakes. Different depth ranges, food sources, and spawning grounds led to the formation of clearly distinct forms. This diversity is considered a classic example of adaptive radiation (Selz & Seehausen, 2023).

With increasing eutrophication, however, these differences were lost. Habitats became more homogeneous, ecological boundaries blurred, and reproductive barriers broke down. Anthropogenic eutrophication not only changed habitats, but also removed the underlying selection regimes that had previously kept the species separate. As a result, not only population declines occurred, but also genetic mixing.

This means: even if individual animals still existed, the species as an independent evolutionary lineage may already have been lost. In this case, the extinction of the kilch would have been not only a demographic process, but also a genetic one. The Lake Constance whitefish thus exemplifies a mechanism by which biodiversity is lost not only through the disappearance of individuals, but also through the dissolution of species.

Fisheries as a possible influencing factor

For centuries, whitefish have made up a considerable part of the fish yield in Lake Constance, which is why commercial fishers referred to them as “Brotfisch” (bread fish). The Lake Constance whitefish, too, was a popular food fish. Gmelin reported in 1818:

“[Er] has extremely tasty and esteemed flesh, so that each one is sold for 6 to 16 groschen. In August, especially in calm rainy weather, they are often caught so frequently that the fishers of Konstanz have obtained more than 40,000 in a single trip.”

This description shows that the kilch could at least at times be caught in large quantities. By contrast, Fatio (1890) describes the kilch as difficult to access. As a species living mostly at great depths, it could usually be caught only with bottom nets; there was hardly any targeted fishery, and it appeared only rarely on markets. In addition, the animals generally did not survive capture, which further limited their use.

The apparent contradiction can be plausibly explained: the mass catches described by Gmelin probably reflect exceptional situations in which the kilch temporarily rose to more accessible depths, for example during calm rain. Under normal conditions, its way of life in great depths largely shielded it from regular fishing. The time gap of around 70 years between the two sources (1818 and 1890) also suggests that stocks and fishing practices may have changed.

At the beginning of the 20th century, Emil Walter also points out that in its preferred summer habitats at depths of 50 to 80 meters, the kilch was difficult for the fishery of the time to reach, so that large catches remained confined to exceptional situations.

More recent assessments confirm this picture. Matthew Ford (2024) states that the kilch was commercially exploited until the 1960s, but that catching it was technically demanding. Because of the rapid pressure difference during hauling up from great depths, the animals were often badly deformed or destroyed. Walter describes them as “unsightly because of a greatly swollen or burst abdomen and of inferior quality for sale.”

Another aspect is the kilch’s role in the food web. Historical observations suggest that it acted as an egg predator and among other things ate the eggs of the commercially important Blaufelchen. From a fisheries perspective, this may have contributed to the kilch not being regarded as worthy of protection. Walter puts it clearly:

“Here [In der Tiefe] it feeds mainly on the eggs of the Blaufelchen and thus, like the burbot, which also consumes considerable quantities of spawn, hampers an extensive increase of the important kilch. Therefore it is only advantageous for the fishers that it does not occur in particularly large numbers.”

Since Blaufelchen were and are the most important target species of the fishery (Rey et al., 2023), strong egg predation by the kilch is likely to have been assessed as disadvantageous.

In addition, its economic importance was comparatively low: at about 29 centimeters in length and around 125 grams in weight, Walter says the kilch was “by far not as popular as the Blaufelchen,” which can reach up to 60 centimeters and four kilograms; it was also less attractive than Sandfelchen or Gangfisch.

Catch statistics for commercial fisheries are available for Lake Constance from 1911 onward and show that whitefish long accounted for the overwhelming share of catches—sometimes several hundred to more than a thousand tons per year (Rey et al., 2023). Since the individual whitefish forms were not recorded separately, however, direct statements about the kilch are not possible. The data nevertheless illustrate the considerable exploitation pressure on the system as a whole.

Overall, much suggests that the Lake Constance whitefish was indeed used, but was not subjected to a constantly high fishing pressure. Its ecological specialization and hard-to-reach way of life are more likely to have protected it from intensive exploitation. Commercial fishing alone therefore seems unlikely to have been the main cause of its extinction.

Use of fish scales as an indirect influencing factor

Already in his first description, Gmelin provided evidence that the Lake Constance whitefish was used not only as a food fish, but also served as a raw material of economic significance:

“From their shining scales the smallest are sent to France in order to produce from them the pearl essence (Essence Orientale) with which imitation pearls are coated.”

This so-called pearl essence—also known as fish silver, silver gloss, or Essence d’Orient—is a shimmering substance from fish scales, especially of herrings and whitefish. Its visual effect is based on microscopic guanine crystals that strongly reflect light and thereby produce the characteristic mother-of-pearl sheen. Since the 17th century, it has been used in the production of artificial pearls. Gmelin’s mention shows that the kilch, too, was integrated into this supraregional trade context. Its scales were apparently collected and exported.

For population development, however, this use is likely to have played only a subordinate role. The scales generally arose as a by-product of fishing, since the animals were primarily caught for their flesh. Although the additional use increased the species’ overall economic value and may indirectly have increased fishing pressure, there is no indication that scale use was an independent driver of population decline.

Moreover, over the course of the 20th century the production of pearl essence from fish scales increasingly lost importance with the development of synthetic materials. The disappearance of the Lake Constance whitefish can therefore hardly be attributed to this use, but must rather be seen in the context of comprehensive ecological changes.

When did the kilch go extinct—or is it still alive?

For the Lake Constance whitefish, no exact time of extinction can be given. Ford (2024) cites the 1970s as the period of its disappearance; Rey et al. (2023) date the extinction more specifically to the year 1970. The species therefore likely vanished even before the peak of eutrophication, which was reached around 1979. This suggests that oxygen deficits in deep water, already beginning early, were sufficient to make the highly specialized kilch disappear. The IUCN has listed Coregonus gutturosus as extinct since 2008.

Nevertheless, a certain uncertainty remains. The kilch lived predominantly at great depths in Lake Constance and thus largely escaped direct observation. At the same time, the lake’s whitefish species are outwardly very similar, so secure identification can be difficult. Missing records are therefore not definitive proof of extinction.

In this context, people often refer to the rediscovery in 2016 of the Lake Constance deepwater char, long thought extinct for around 40 years. It shows that even deepwater fish species can survive severe environmental changes. Genetic analyses show that Salvelinus profundus did in fact survive the eutrophic phase of Lake Constance and continues to exist today as an independent population (Baer et al., 2022).

This finding can be transferred to the Lake Constance whitefish only to a limited extent, however. While the deepwater char remained genetically clearly separated from the lake’s other char forms (Baer et al., 2022), comparable evidence is lacking for the kilch. In addition, ecological and comparative studies suggest that whitefish in particular react sensitively to habitat changes and under such conditions tend toward hybridization. It is therefore likely that several factors—above all oxygen depletion and the loss of reproductive isolation—acted together in the kilch and ultimately led to the species’ disappearance.

Whether the Lake Constance whitefish may nevertheless have persisted in small relict populations cannot be ruled out with complete certainty. According to current knowledge, however, the species is regarded as extinct.

Genetic legacy of an extinct species

The extinction of the Lake Constance whitefish does not necessarily mean the complete disappearance of its genetic traces. A study by David Frei et al. (2022) shows that genetic variants of the Lake Constance whitefish can be detected in populations of surviving whitefish species—especially the Gangfisch (Coregonus macrophthalmus).

These genetic components are apparently not merely relics, but could be functionally significant. In the populations examined, there were indications that certain gene variants derived from the kilch promote adaptation to greater water depths. Indeed, spawning individuals have now been documented at substantially greater depths (up to 90 meters) than were historically recorded.

The results can be interpreted within the framework of the so-called syngameon hypothesis. According to this, hybridization within adaptive radiations can lead not only to the mixing of species, but also to new ecological adaptations. In Lake Constance, genetic components of the kilch may thus have contributed to other whitefish species now using depth zones that were formerly occupied by it.

The Lake Constance whitefish has thus disappeared as an independent species, but its genetic trace may still live on in the Lake Constance system to this day. A back-breeding project in the sense of historical reconstruction projects (as with the aurochs, quagga, or the Floreana giant tortoise) nevertheless seems unlikely: there are no populations that have preserved a large part of the original genome; instead, the genetic components are fragmented and integrated into other species.

The Lake Constance whitefish in collections

The scientific engagement with the Lake Constance whitefish goes back to the 19th century. While early works mainly provided morphological descriptions, biological and ecological aspects increasingly came into focus in the 20th century. At the same time, changing names and taxonomic uncertainties made unambiguous assignment of the species more difficult.

Today, only a few material testimonies of the Lake Constance whitefish survive. Selz et al. (2020) write:

“The only specimens of the now extinct whitefish species Coregonus gutturosus Gmelin, 1818 still existing today are in Paul Steinmann’s collection.”

Some of these historic specimens are now preserved in the Natural History Museum Bern. According to Selz et al. (2020), these are around ten individuals, most of them collected in the 1940s and 1950s. They come from older research holdings, including the collection of the Swiss zoologist Paul Steinmann, and have body lengths of between about 17 and 29 centimeters.

However, the data situation is not unambiguous. Databases such as the Global Biodiversity Information Facility (GBIF) record additional voucher specimens in various collections. It is therefore possible that further preparations exist or that individual finds have not yet been unambiguously assigned to the Lake Constance whitefish. Selz et al.’s statement presumably refers to clearly identified and scientifically secured comparative specimens.

A holotype in the modern sense does not exist for the Lake Constance whitefish. The species was described as early as 1818, at a time when the concept of a fixed type specimen had not yet become established. The preserved preparations that exist today are therefore not types, but serve as reference material for later taxonomic and comparative studies.

These few museum pieces are of special importance: they represent the last directly examinable testimonies of a species that is now extinct and form the basis for its further scientific study.

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