Biohut® is an ecological tool developed by Ecocean and scientifically validated as a rehabilitation measure in Mediterranean ports. A Biohut reproduces the two main functions of fish nursery ecosystems : invertebrates and algae grow among the substrate and provide food resource to fish, and the empty cages create a shelter against predators. Biohut can help enhancing the survival rate of fish in damaged ecosystems such as ports and they are currently installed in several locations in Europe. The wide range of substrates depends on the ecological context and needs. BESE-elements are used for substrate in both marine and freshwater ecosystems.