Fish have to migrate so they don't die from the cold or starvation. They swim upstream and eventually reach there destinations. If a dam is in the way it will cause the fish to have a block in there path and they will eventually die
Answer: Large dams have led to the extinction of many fish and other aquatic species, the disappearance of birds in floodplains, huge losses of forest, wetland and farmland, erosion of coastal deltas, and many other unmitigable impacts.
