Beavers do not eat fish. They are vegetarians and eat plant food found near rivers, streams, marshes and lakes. They eat the leaves, twigs and bark from trees. Aspen, birch and willow trees are favorite foods for beavers.
Beavers also eat aquatic plants, grasses, shrubs and some crops. Their sharp front teeth allow them to cut the bark and branches, and they have microorganisms in their digestive tract that ferment the food and allow them to digest some of the cellulose found in the plant matter. Beavers living in cold climates store a cache of food underwater that they can access when the water ices over and other food is scarce.