This is a histopathological description and atlas of normal and diseased tissues in common species of fish that are found in a range of environments, both freshwater and marine, and from farmed, aquarium and wild situations. It is a veterinary text of pathology in fish. This set of notes was originally intended as an aid to graduate students coming from a comparative pathology background, and who therefore already had a fairly good grasp of the basic principles and jargon appropriate to the subject. They were meant to illustrate some of the ways in which teleost fish respond in a range of disease situations, and to compare and contrast these responses to mammals. They were never intended to be an exhaustive list of aetiologies, but were aimed primarily at the diagnostic pathologist faced with a section of fish tissues, possibly for the first time. The first edition seemed to appeal to a far wider audience than was originally intended, and it sold out rapidly, as did the second printing. The publishers were understandably keen to see a second edition, but after only five years I did not feel that our understanding of disease processes had progressed significantly to justify the effort. However, it is now seventeen years after the first printing, and the book is long overdue for a rewrite, even though I still question whether my own level of understanding has advanced markedly! Despite virtual stagnation in most forms of traditional animal production, aquaculture has continued to grow substantially in the intervening years, as have our interest in and awareness of the importance of the aquatic environment. Mirroring this, private and public aquaria have flourished, enabling the study of disease in individual animals, as opposed to the more usual group approach. Fish have also become one of the major tools for genetic research, and in some countries their use in laboratories has outpaced the more conventional rodents to become numerically the most important species. Inevitably these factors have conspired to produce a parallel increase in the numbers of samples requiring diagnosis. There is no denying that conventional morphological pathology takes a lot of effort to achieve a decent degree of competency, and that many students seem reluctant to put in the work required, turning instead to other newer and "sexier" areas of endeavour. During this time of expanded and sometimes pressing diagnostic need, we have seen a parallel growth in the exciting field of molecular biology, and many of the newer techniques now in routine use in most diagnostic laboratories are based in this discipline. Finding a way of harnessing the power intrinsic to molecular approaches and applying them to conventional pathology remains a worthy goal, especially considering the extremely valuable archives of paraffin wax blocks found in most diagnostic laboratories. By their very nature, however, many molecular techniques in the fish world are aetiologically driven. Understanding disease processes, and the impact that pathogens have upon their hosts have regrettably taken a back seat, and even finding money for training students in the discipline of pathology has become extremely hard to find. How can we possibly hope to control disease in a rational manner if we do not properly understand its sequential pathology and pathophysiology? One of the major attractions for prospective students contemplating entering the field of fish pathology is the chance to work with a brand new disease entity. In few other areas would this be possible. When constantly faced with new diseases and new pathogens, in a wonderful but sometimes bewildering variety of different species of fish, there is no substitute for morphological pathology as the initial approach. As last time, therefore, I have attempted to set out each chapter in a similar fashion. An overview of normal is followed by the general response of each tissue to disease, and then a few specific diseases. Inevitably the diseases chosen to illustrate these processes are in large part a reflection of the interests of the writer(s) as well as of the commercially important fish species. Mostly they are taken from routine diagnostic material. I have tried hard to integrate the text into a readable whole, cross-referencing chapters to each other, and leaving as few gaps as possible. Once again, the text assumes a reasonable working knowledge of pathology and the jargon appropriate to the subject.

Table of Contents:
Preface; Acknowledgements; 1 Introduction, 10; 2 Gills and Pseudobranchs, 24; 3 Skin, 64; 4 Kidney, 90; 5 Spleen, Thymus, Reticulo-Endothelial System, Blood, 120; 6 Cardiovascular System, 140; 7 Gastrointestinal Tract, Swimbladder, Pancreas and Peritoneum, 168; 8 Liver, 200; 9 Nervous System, 218; 10 The Eye, 244; 11 Endocrine and Reproductive Systems, 266; 12 Musculoskeletal System, 288; 13 Neoplasia, 321; 14 Physiological and Clinical Pathology, 336; Index, 356.