Based on Peter Maitland's earlier Key to British Freshwater Fishes, published by the FBA in 1972, this new edition has been extensively enlarged and updated. Fifty-seven species are recognised in a checklist for Britain and Ireland, including several new species such as Black Bullhead, False Harlequin and Sunbleak, which have recently become established in Britain. Additionally, Sterlet, Siberian Sturgeon, Grass Carp, Channel Catfish and Brown Bullhead are also included in the keys to species (though not illustrated) because they may be encountered in fresh and estuarine waters within the British Isles. All species in the checklist are illustrated by line drawings accompanying the relevant key couplets, and most of them are depicted in 48 colour photographs - where possible these have been taken from live specimens. Accurate identification is assisted by additional text in a new section summarising important external features of each species, their general body size, habitat, reproduction, food, distribution, and use for angling and commercial fishing. In addition to the keys for identifying 23 families and 62 species of adult fish, keys to family level are also provided for identifying the eggs and small (post-larval) stages, and the scales of adult fish; the scales are illustrated with photographs and line drawings emphasising the most important diagnostic features.