This book offers a comprehensive review of current systems for fish protection and downstream migration. It offers the first systematic description of the currently available technologies for fish protection at hydropower intakes, including accurate and timely data collected by the authors and other researchers. It describes how to design and test them in agreement with the guidelines established from the EU Water Framework Directive. The book includes important information about fish biology, with a special focus on swimming and migration mechanisms. It offers a robust bridge between concepts in applied ecology and civil hydraulic engineering, thus providing biologists and hydraulic engineers with an authoritative reference guide