Fishes are eaten by a great variety of mammals, birds, reptiles, amphibians, other fishes, and even invertebrates (some insects eat small fish). In order to survive, fishes have evolved various behavior patterns. Pond fishes always try to hide when danger threatens. They can hide by swimming to deeper water or by moving behind a rock, stump, brush, or plant. In a pond, fish communities will exist without physical structure, but fish are sure to concentrate near a structure if it is present. In fishing ponds, structures benefit fishermen more than the fish since anglers know the most productive areas for angling are near areas with habitat structure. This is why the addition of fish attractors is recommended in all but catfish-only ponds.