People in various parts of the world eat the flesh of many species of sharks. In England, for example, dogfish sharks are often used in preparing fish and chips, which consists of fried fish and French fried potatoes. The liver oil of certain species of sharks contains large amounts of vitamin A. Until the late 1940's, when scientists discovered an inexpensive way to manufacture vitamin A, shark liver oil ranked as a main source of this vitamin. Since the late 1950's, sharks have been used increasingly in scientific research. Medical researchers are particularly interested in the fact that few sharks have ever been found with a cancerous tumor.
Scientists hope to discover what protects sharks from disease.
Commercial shark fishing increased during the 1980's, partly because shark fins brought high prices in Asian markets. Fishing crews caught so many sharks that populations dwindled worldwide. Conservationists feared that many shark species would become extinct. During the 1990's, some countries began to protect sharks. South Africa, for example, declared great white sharks a protected species and banned fishing for great whites or selling their jaws or other body parts.