Dogfish is a true fish, amongst Jellyfish, Starfish, Dogfish and Silverfish. Jellyfish can not be listed as a fish because it does not meet the requirements of being a fish. A fish must have gills, fins and a vertebra which is all lacking in a jellyfish. Also, starfish falls within the same criteria as a jellyfish. It is a star-shaped aquatic animal that leaves stuck to a surface. Silverfish are also more like aquatic insects rather than fishes. Thus the only dogfish can be counted as a fish among the four.