Epidemiologists study outbreaks of diseases, the causes, locations, and how various communities are affected, utilizing relative information to aid in the prevention of future outbreaks. Epidemiologists help to keep the public informed of methods to maintain and improve public health.
Based on these criteria, the smallest known extant shark species appears to be Etmopterus perryi, males of which mature at 16 to 17.5 cm TL and gravid females have been found at 19 to 20 cm TL (Springer & Burgess 1985).
There are over 470 species of sharks and they have been living on Planet Earth for 420 million years. The smallest shark-the dwarf lantern shark-is only 17 centimeters (6.7 inches) in length, while the whale shark is the largest specie in the world, with approximately 12 meters (39 feet).