Answer:
The areas of animal grazing such as horse, cattle are highly rich in the nutrients such as nitrogen (N), potassium (K) and phosphorus (P), which are mostly accumulated in the manures as well as in the fertilizers. These nutrients when washed away by the surface runoff and adds to the nearby rivers. It then releases these essential nutrients to the soil. This enhances the amount of total nutrients in the water, as a result of which eutrophication condition occurs. This directly affects the aquatic ecosystem, thereby leading to the reduction of aquatic species such as fishes.
