This is a quite enigmatic species, described in 1784, whose taxonomic status isn’t clear.
The May Trout is rather known from anecdotes about trouts that inhabited the deep parts of the lakes within the Danube basin in Austria, and which only in the month of May appeared in shallow waters to breed.
The status of this species, as said above, is far from being clarified, if it indeed was a distinct species it appears to be extinct now.
The Graveche, also known as Kilch, Kleine Fera or Lake Geneva Whitefish was endemic to Lake Geneva, where it was formerly one of the most commonly caught species.
The species reached lengths of 25 to 32 cm, it lived mainly among or near the lake’s bottom where it fed on tiny to tiniest organisms.
Despite being one of the most common species of the lake, the species was already disappearing during the 19th century, so the catching size for this species in Switzerland was officially set to above 20 cm in 1887.
This effort, however, came too late, the Graveche disappeared completely and is now globally extinct.
The Dragon Lake is a 2,25 km² resp. 225 ha large lake in British Columbia, it is a popular destination for anglers and well known for its large rainbow trouts (Oncorhynchus mykiss (Walbaum)) – however, that wasn’t always so.
The lake was once the home for two sympatric whitefish species – both species have never been described, and both species fell victim to a so called ‘lake rehabilitation’ in the year 1956.
The term ‘rehabilitaion’ disguises the pervert idea, to reshape a lake appropriate for so called game fishes by using insecticides like rotenone and toxaphene, both of which are simply deadly for fishes, to exterminate all living things, so that, later, when the poisons have vanished from the water of the now dead lake, the desired game fishes can be introduced – in the case of the Dragon Lake rainbow trouts.
The Dragon Lake Whitefish was similar to the Lake Whitefish (Coregonus clupaeformis (Mitchill)), but differed from this species in the number of its gill rakers.