This reprint is a collection of 11 peer-reviewed articles that focus on the biology and ecology of eels. This reprint addresses the current advances and challenges in eel studies, including both the European eel, Anguilla anguilla, and the Japanese eel, Anguilla japonica. The reprint comprises a high diversity of selected topics on the interface between fundamental science and the management of eel resources. Topics range from genomics and environmental DNA used to detect the presence of eels and ascertain eel biomass to observations of eel abundance based on catches. Other topics addressed include the study of the swimbladder function, assessing migration patterns in estuaries, eel reproduction, the effect of water pollution, otolith studies, and the optimization of the design of passage facilities for juvenile European eel (Anguilla anguilla).