Shark (fish)

s are fish that constitute more than 500 known species and belong to the. Sharks occur in all of the world's seas, and the vast majority of species live exclusively in saltwater. The two shark species with the most documented cases of attacks on humans are the and the. The two physically largest shark species are the and the.

Quotes

 * The life span of sharks can be determined by keeping them in captivity, by tagging, or, more commonly, by counting growth rings in their vertebrae or spines and estimating the age. Only a few species of sharks have been kept in captivity for long periods of time. When sharks have been captured young and have lived in captivity for prolonged periods, a rough idea of their potential life span can be obtained. Although keeping sharks in captivity for many years is a difficult feat, some sharks have lived for decades in captivity, indicating that they have long life spans. Unfortunately, most aquaria do not keep accurate records of the life span of their captive sharks, and valuable data on the longevity of sharks is lost.
 * José I. Castro,


 * I have heard from Dr. Allan of Forres, that he has frequently found a Didion, floating alive and distended, in the stomach of the shark; and that on several occasions he has known it eat its way, not only through the coats of the stomach, but through the sides of the monster, which has thus been killed. Who would ever have imagined that a little soft fish could have destroyed the great and savage shark?
 * Charles Darwin, (1st edition 1839; Didion antennatus is a synonym for .)


 * When the young is completely formed, the yolk remains attached to the belly by a long chord, consisting of blood vessels, and the fish swims about in the surrounding jelly with this attached to it. If the bag is torn, and the fish is taken out and put into the water, it swims about, but if the vessels going to the yolk are wounded, the fish immediately dies.
 * , (quote from p. 209)


 * ... While sharks kill an average of four humans a year, humans kill 100 million sharks each year. ... While recreational fishing is doing considerable harm to the shark population around the world, commercial fishing is decimating it. Sharks are harvested throughout the world for their meat, skin, fins, liver, and cartilage. ... Specifically sharks are killed as a by-product of the $40 billion tuna industry, which provides the United States with enough tuna to feed every American 2.6 pounds per year.
 * William McKeever,