This report explains in simple terms how the fish and water control requirements can be reconciled and proposes design criteria to enable fish to negotiate structures such as sluice gates, weirs and fish passes. It also explains the Ministry's legal position with regard to obstructions in migratory fish rivers and gives examples of the procedures necessary to obtain approval for satisfactory structures. The information on fish swimming speeds and endurance and the relation of three parameters to water control structures and fish passes is essential to the effective management of migratory fish in our rivers.