TRANSACTIONS MAPPING THE DISTRIBUTION OF FRESHWATER FISH IN THE BRITISH ISLES PETER S . M A I T L A N D
The Nature Conservancv,
Edinburgh
Introduction THE recent discovery of the burbot (Lota Iota) has emphasised our ignorance of the actual distribution of freshwater fish in the British Isles. T h i s species, formerly not uncommon in rivers in eastern England, was thought to have become extinct in this country as a result of dredging and severe pollution in many major rivers. No specimens had been seen for many years, but in 1969 one was caught in the Great Ouse area near Aldreth and it is hoped that a viable population, albeit a small one, still exists in this area. It is vital that the status of this and other native species be ascertained as soon as possible so that conservation measures may be introduced to aid their survival. T h e numbers of some quite common species are also declining and it is important that information is available on those too. A project to map the distribution of all species of freshwater fish in the British Isles was started by the author in 1966 and is continuing. T h e first phase of the scheme has been completed and preliminary maps for some species are available (Maitland, 1969). T h e second phase is still under way and help is invited from anyone interested in fish to assist in completing our knowledge of their present status and distribution in this country.
The Scheme T h e aim of the present survey is to collect as much detailed information as possible on the occurrence and distribution of freshwater fish over the whole of the British Isles. T h e basis of presenting the results of the scheme is to indicate by means of a Symbol the presence of each species in every 10-kilometre Square of the Ordnance Survey National Grid in which it occurs, thus producing a distribution map of each. Basically what is required for the production of these maps is a list for each 10-kilometre Square in the British Isles of the fish species occurring there.