Different Types of Fish Species In the World and Their Facts. Fish is a member of the paraphyletic group of organisms. This consists of gill-bearing aquatic craniates animals with limbs and digits. Most of the fishes are hagfish, cartilaginous, bony fish, and lampreys. Fishes are ectothermic, which means cold-blooded. Fish are abundant in most the bodies of water. Fishes are an important resource for humans worldwide, especially as food because it consists of a lot of minerals, vitamins, and proteins as it stays in water bodies. These are served as religious symbols. https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcT_hanYYtIcCCQAHPzTwtq1Ksp5nuFeGQjilzE9ArZaXA&s