Predation All fish species are subject to predation by other fish, by avian predators such as herons, dippers and kingfishers and by mammals such as otters. These predators have existed in the Wye and Usk catchments for millennia and are an important part of the natural environment. However, the impacts of predation are more significant when the population of a prey species is already depleted. Such impacts may be even more adverse when a new predator species arrives on the scene. Read more about predation in the Wye and Usk and what the Foundation has done to mitigate the effects on already-depleted fish species.