The Schelly or common whitefish (Coregonus lavaretus), is a rare and endangered species of freshwater fish, in the whitefish family. It is one of only four species of freshwater fish under the protection of the Wildlife and Countryside Act 1981.
With effect from July 2002, the Environment Agency has introduced a fisheries byelaw, banning the use of all freshwater fish as live bait or as dead bait in 14 of the lakes in the Lake District. Anglers who do not comply with the new byelaw could face fines of up to £2,500.
At Haweswater, the fishery officers are now culling all of the cormorants that visit the lake, in order to protect this endangered fish. An analysis of reservoir management data over a 30 year period (1961-1991) has revealed that the decline of the schelly population is associated with increased water abstraction and reduced water levels. Entrapment during abstraction is not significant. Year class strength is probably determined by lake levels during the January-March spawning and incubation period whereas subsequent growth rate is influenced by lake levels during June-October.