This definitive environmental history of medieval fish and fisheries provides a comprehensive examination of European engagement with aquatic systems between c. 500 and 1500 CE. Using textual, zooarchaeological, and natural records, Richard C. Hoffmann's unique study spans marine and freshwater fisheries across western Christendom, discusses effects of human-nature relations and presents a deeper understanding of evolving European aquatic ecosystems. Changing climates, landscapes, and fishing pressures affected local stocks enough to shift values of fish, fishing rights, and dietary expectations. Readers learn what the abbess Waldetrudis in seventh-century Hainault, King Ramiro II (d.1157) of Aragon, and thirteenth-century physician Aldebrandin of Siena shared with English antiquarian William Worcester (d. 1482), and the young Martin Luther growing up in Germany soon thereafter. Sturgeon and herring, carp, cod, and tuna played distinctive roles. Hoffmann highlights how encounters between medieval Europeans and fish had consequences for society and the environment - then and now.