It is generally accepted that all outbreaks of a communicable disease are the result of interaction between the host, the pathogen, and the environment. This is particularly true in regard to fishes, which are coldblooded and utilize oxygen dissolved in water. The environment of the open sea is very stable, but in the inland waters and in fish farms extreme water temperatures, low dissolved oxygen contents, presence of fish catabolic products, and general pollution often produce stresses which contribute to outbreaks of infectious diseases. Fish suffer ill health from a variety of reasons. The best way to prevent the disease is to maintain a healthy environment in the aquarium for all times to avoid the stress which is one of the most important factor for many fish diseases. Stress may be associated with the temperature variation, deterioration of water quality, stocking density, insufficient or excess supply of food and poor environmental conditions. In some chronic diseases, such as corynebacterial kidney disease, timely use of chemoprophylaxis with sulfonamides may prevent, or reduce, losses very significantly. Fungal infections are among the most common diseases seen in temperate fish. Because fungal spores are found in all fish ponds and create problems in stressed fish. Poor water quality can also lead to an increase in fungal infections in an otherwise healthy fish population. Most fungal infections only attack the external tissues and only few fungal infections that will infect the internal organs of fish. The treatment of aquatic fish diseases has assumed major importance in this last decade especially in view of the boom in aquatic fish farming.

This book focuses on fish diseases and disorders, which is an outcome of a tremendous volume of research conducted on parasites, especially those that cause morbidity and mortality in fish. It covers theoretical and practical information to identify, treat and cure the disease. The aim of this book is to help students, researchers, and aquarists to recognize signs of illness so they can identify and resolve problems.