Medieval and early modern records show certain practices were common in traditional European aquaculture. These, combined with advice in coeval treatises on agricultural management, demonstrate how European agroecosystems linked terrestrial and aquatic operations to pursue a net energy gain in their outputs. Critical reading of three distinct bodies of sources: early modern European agricultural manuals, literature on fish culture compiled in western Latin Christendom, and managerial records of fourteenth-through seventeenth-century fish culture enterprises establishes two new understandings. First, land manages took self-conscious measures to integrate their arable and pond cultures with the aim of conserving and recycling essential nutrients. Second, agricultural handbooks from this period both reflected traditional practices of illiterate peasant farmers (and hence their "traditional ecological knowledge") and informed certain managerial decisions.