This book summarizes the latest understanding of the impact of xenobiotics on the developmental and reproductive processes of aquatic animals, particularly nektonic forms, which comprise an important group of aquatic ecosystems. Aquaculture is quickly becoming the largest contributor of fish protein for human consumption. As the aquaculture business expands, farmed fish will be exposed to more environmental toxins, necessitating the use of chemical therapeutic drugs for fish. This book brings together experts on the regulation of environmental toxins and food chemicals from around the world, as well as researchers looking into the metabolism and disposal of foreign chemicals (xenobiotics) in fish species. The impact of xenobiotics on reproductive and developmental biology of all living forms has become of prime importance at the current time. As the effect of these xenobiotics on aquatic animals is an emerging area for research and development, several groups across the world are working on these aspects, targeting different groups of fishes in both marine and freshwater ecosystems. This collective work highlights several key and updated recent aspects of different types of xenobiotics entering aquatic ecosystems, impacts of these agents on reproductive physiology, developmental biology, breeding biology, hormonal imbalance, aquatic ecology, and pollution on the aquatic ecosystem. The unique aggregation of different types of stressors to aquatic animals under a single volume will be a useful reference for readers, including scientists, teachers, students, researchers and policymakers and those involved in aquaculture and environment conservation.