Piscivore

Fish were the diet of early tetrapod evolution (via water-bound amphibians during the Devonian period); insectivory came next; then in time, the more terrestrially adapted reptiles and synapsids evolved herbivory.

Some non-piscine aquatic animals, such as whales, sea lions, and crocodilians, are not completely piscivorous; often also preying on invertebrates, marine mammals, waterbirds and even wading land animals in addition to fish, while others, such as the bulldog bat and gharial, are strictly dependent on fish for food.

Some creatures, including cnidarians, octopuses, squid, cetaceans, spiders, grizzly bears, jaguars, wolves, snakes, turtles and sea gulls, may have fish as significant if not dominant portions of their diets.

It is hypothesized that the secondary piscivores' diet change is due to an adaptation to maintain efficiency in their use of energy while growing.

This list includes specialist piscivores, such as Laganosuchus, as well as generalist predators, such as Baryonyx and Spinosaurus, found to have or assumed to have eaten fish.