In this book, the authors present current research in the study of fish ecology and marine ecosystems. Topics discussed include the metabolic rate of marine fish in early life and its relationship to their ecological status; antioxidant defence in marine fish; teleostean fish and the genomic content; the genetic structure of the masu salmon; the catadromous freshwater eel and the taxonomic representations of marine fish from archaeological assemblages in the Beagle Channel, Argentina.