 Fish were the diet of early tetrapods (amphibians); insectivory came next, then in time, reptiles added herbivory.Some animals, such as the sea lion and alligator, are not completely piscivorous, often preying on aquatic invertebrates or land animals in addition to fish, while others, such as the bulldog bat and gharial, are strictly dependent on fish for food.Humans can live on fish-based diets as can their carnivorous domesticated pets, such as dogs and cats.