Operational noiseLess intensive than construction noise but longer lasting are the sounds from wind turbines in operation136. The operational noise stems from vibrations in the tower caused by the gearbox mesh in addition to the generator, causing underwater noise137. While this is not thought to be deadly for fish it has raised concern that it may be masking biologically important sounds, causing hearing loss and raising stresslevels leading to reduced immune system functions138. The distance from which fish can detect wind turbine noise depends on a number of factors including the number and size of the turbines, the hearing capabilities of the fish species, other forms of background noise, wind speed, water depth and type of sea bottom139