Abstract: The past years, improvement of fish survival at hydropower dams has shifted from development of fish guidance systems towards the development of ‘fish-friendly’ turbines. A variety of technical features of turbines is altered in order to reduce mortality of fish passing the turbine. Data on mortality rates at traditional, currently applied turbine types, shows a great variation for fish species and life stages. ‘Improvements’ applied in novel turbine types must thus be tested thoroughly, both in small-scale (laboratory) flume test as well as under real-time field condition, before any conclusion can be drawn for long term application. The current question is, how to test the fish-friendliness of a turbine, such that water authorities, regulators, permitting authorities, etc, will accept a ‘minimum’ (?) of fish mortality. A variety of new turbine types as well as turbine test facilities are under development. Any statement on improvement of fish survival requires certification on this matter. For this, there is a strong need of a protocol to test the ‘fish friendliness’ independently. As it will take many years before new turbine types have long-term data on fish mortality, test protocols must be designed to provide the best possible representativeness.