This book is dedicated for ecological studies of the Maithon reservoir covering its morphometric, climatic, limno-chemical and biological parameters, which altogether govern the fish productivity, would help in better management and development of fishery of this reservoir.It is apparent that the physico-chemical condition of the Maithon was in general conducive for aquatic habitat. Temperature, dissolved oxygen, water reaction, alkalinity, sp. conductivity, calcium and magnesium contents were conductive for fish growth.