Successful fisheries management requires accurate information on where the fish live, how quickly they grow, what they eat and what eats them. The present book contains introduction to aquatic ecosystem, fish disorder and diseases, developmental plasticity in the circulatory system in Fish, distribution and ecology of some important river fishes and the riverine system, distribution in time and migration, adaptations to extreme environment conditions, fisheries farming system: planning, operations and other Factors, biotechnology and Its applications in aquaculture and fisheries. The purpose of this book is to introduce the ecology of fishes by describing the inter-relationships between fishes and the aquatic habitats they ocupy.