This book provides a comprehensive guide to the taxonomy, morphology, biology, and identification of parasitic crustaceans across marine, brackish, and freshwater environments. It presents practical methodologies for studying these organisms, including contemporary approaches such as DNA-based analyses and digital imaging, alongside established taxonomic techniques. The volume examines host-parasite interactions, life-history strategies, reproductive biology, and moulting processes, offering valuable insights into the diversity and ecology of major parasitic crustacean groups. It also covers emerging issues relevant to fisheries and aquaculture, including the effects of climate change, species introductions, and the expansion of global aquaculture systems. Designed as both a reference and teaching resource, the book supports students, researchers, taxonomists, parasitologists, fisheries scientists, and aquaculture professionals by providing an authoritative and up-to-date synthesis of current knowledge. By integrating foundational concepts with recent advances and methodological developments, it delivers a practical framework for the study, identification, and management of parasitic crustaceans and their interactions with aquatic hosts.

Dr. Panakkool Thamban Aneesh, M.Sc., B.Ed., Ph.D. was formerly Assistant Professor at the Graduate School of Integrated Sciences for Life, Hiroshima University, Japan. Over the past 16 years, his research has focused on the taxonomy and ecology of marine fauna, particularly parasitic crustaceans of marine fishes and invertebrates, deep-sea fish parasites, and marine crustaceans. He received his Ph.D. from Kannur University, India, in 2014. Following doctoral studies, he held research positions at Sree Narayana College, the ICAR-Central Institute of Brackishwater Aquaculture, the Zoological Survey of India, the University of Kerala, the National University of Singapore, and Northwest University, South Africa. Dr. Aneesh has made significant contributions to biodiversity, taxonomy, moulting biology, reproductive physiology, and life history of fish parasitic crustaceans. He has described one new family, six new genera, and more than 35 new species. The cymothoid isopod Ichthyoxenos aneeshi Mitra & Chowdhury, 2024, was named in his honour.

Dr. Ameri Kottarathil Helna, M.Sc., B.Ed., Ph.D. is a Scientific Officer at the Regional Forensic Science Laboratory, Kerala, India. For over a decade, she has conducted research on the taxonomy, growth, and reproductive biology of parasitic crustaceans infesting marine fishes. She earned her Ph.D. from Kannur University in 2017, with a focus on the reproductive biology of parasitic crustaceans. She subsequently continued her research at Sree Narayana College, Kannur, and the University of Kerala. Dr. Helna has co-authored the description of one new family, five new genera, and more than 18 new species of parasitic crustaceans.

Dr. Balu Alagar Venmathi Maran, M.Sc., M.Phil., Ph.D., D.Agr. is Associate Professor at the Organisation for Marine Science and Technology, Nagasaki University, Japan. He previously served as Associate Professor at Universiti Malaysia Sabah and has held research positions in South Korea at KIOST, Kyungpook National University, and Chonnam National University. With more than 30 years of teaching and research experience, his expertise includes marine fish parasite taxonomy, aquaculture health management, fish immune responses, jellyfish biodiversity and toxins, and marine natural products. His current research integrates artificial intelligence into biological imaging and marine biodiversity studies. Dr. Maran has described one new family, three new genera, and more than 50 new species of parasitic copepods, and has led numerous nationally and internationally funded projects. Listed among the world’s top 5% scientists in the Global Scientist index, SciRank Global Registry (2025), he is a member of the IUCN Commission on Education and Communication. He serves as Editor for PeerJ and Frontiers in Marine Science and has received several awards for scientific innovation and research excellence.

Dr. Appukuttannair Biju Kumar (Kumar A.B.), M.Sc., M.Phil., Ph.D. is Vice Chancellor of the Kerala University of Fisheries and Ocean Studies (KUFOS), India. Previously, he was Professor and Head of the Department of Aquatic Biology and Fisheries at the University of Kerala. Trained in fish parasitology at the Czech Academy of Sciences, his doctoral work focused on metazoan parasites of flatfishes from southwest India. His research interests encompass aquatic biodiversity, taxonomy, ecology, conservation biology, invasive species, and fisheries management. Over more than three decades, he has mentored numerous researchers and organised national and international taxonomy training programmes towards capacity development in Taxonomy. Together with his collaborators, he has described 11 new genera and over 60 new species of aquatic organisms, including fish parasites. Listed among the world’s top 2% scientists in Zoology and Marine Biology in the Stanford-Elsevier Rankings (2024), he is a member of the IUCN Species Survival Commission and serves as Editor-in-Chief of the Journal of Aquatic Biology & Fisheries.