European beavers have a positive effect on coarse fish populations and a neutral relationship with game fish. It has been suggested that beaver dams in the head waters of Scottish salmon rivers would destroy spawning beds. Although this is a debateable contention, it is true that beavers can build dams from rocks. Experience from Norway where a healthy, wild salmon population exists demonstrates that they can readily leap beaver dams to spawn in the waters above. 

Beavers typically have a positive impact on fish populations by maintaining river levels and water flow as well as creating new spawning pools. In times of drought beaver pools act as significant fish refugia. Beaver felled timber in water courses can afford fish fry protection from predatory birds such as Cormorants (Phalacrocorax carbo) and Goosanders (Mergus merganser). The significantly higher populations of aquatic invertebrates generated by the submerged timber provide a larger prey base for fish. Beavers generally prefer slow-flowing rivers rather than the fast-flowing streams used by salmon and evidence from Norway suggests that there are few if any adverse impacts to salmon fisheries caused by beaver dams. Dams do not impede the passage of fish, and they do offer protection to fry.