Migratory fish can be defined as fish that follow predictable movements and migration patterns throughout their life cycle. A classic example of a migratory fish would be salmon, which leave their native rivers and springs towards the ocean as juveniles, but return to spawn in their native rivers. While these fish are not present during all times of operation, they can appear in great numbers. Resident fish can be defined as those saltwater fish that do not migrate. It is important to note that while these fish do not undergo long distance migrations, they do have daily, tidal, and seasonal movements. Examples of resident fish can be sharks and rays, rockfish or flatfish.
The risk posed by offshore wind and marine renewable energy stressors on migratory fish depends on various factors such as the affected species, life stage, population level of affected species, and scale of project. The most important issues pertaining to fish typically encompass noise, electromagnetic fields, and habitat change. While they can be affected by the same stressors as migratory fish, resident fish may be more susceptible to exposure which can potentially increase their risks.