Based on twenty years of research experience, this unique, large format volume presents an up-to-date treatment of the biology, relation to the host, taxonomy and diagnostic features of protozoan parasites infecting fishes. By presenting definitions of all 151 genera, keys for the determination of all main groups of fish protozoa, copious illustrations and half-tone plates, and details on the technique of investigation, the book makes it possible to determine all protozoan parasites of fishes down to generic level. In each genus, all important pathogenic species are dealt with, special attention being paid to their pathogenic action, and these are well documented by photomicrographs. A wide range of information is given on host-parasite relations, including data on pathogenicity of separate groups and species; and a host-parasite checklist enables a quick orientation on protozoa that may be encountered in one hundred economically important fish species. In addition to the to the true protozoan phyla, an appendix lists a few organisms of uncertain position with alleged or possible relation to protozoa; altogether, 561 species are described. This book is the first of its kind and should be invaluable reading for all fish parasitologists, fisheries biologists, aquaculturists and all others interested in protozoan parasites of fishes.