Constructed water structures and hydropower plants almost certainly create a barrier for the ichthyofauna migration. This is the reason for decrease of fish population downstream as well as upstream the river. Fish passes are designed to enable fish migration. This book proposes a methodology for design of fish passes. The design begins with obtaining and analyzing of background materials, water management inputs, situation, ichthyologist data, etc. The next step is design of longitudinal section and cross section according to maximal discharge, fish numbers and space possibilities, boulder elements design (single stones, boulder sills) for achievement of required water level and velocity regimes. Each fish pass design requires multidisciplinary cooperation, therefore this book should be especially useful to hydraulic engineers, ichthyologists, ecologists, specialists in channel improvement and aquatic habitat modelling, operators of water structures and hydropower plants, as well as fishery association.