Fishes migrate on different spatial and temporal scales, utilising the best suited habitat during different stages of the life cycle to increase individual fitness. The diadromous migrations of salmonids and eels between spawning and feeding habitats are well known examples. Humans have exploited fishes during their migrations for several thousand years, and many migrating species have a high economic value. During this course, insights will be given in ecological causes and evolutionary consequences of fish migrations, migration patterns, orientation, navigation, anthropogenic impacts, and with examples from a range of fish species in northern marine and freshwater systems. The course will also introduce the students to biotelemetry and other tag and tracking methods, with emphasis on use of radio and acoustic transmitters, manual tracking and use of automatic data logging stations, use of sensors measuring physiological and environmental factors, data storage tags, satellite pop-up archival tags, sampling design, tagging techniques, and ethics and animal welfare issues related to fish tagging.