Requiem shark
Requiem sharks are sharks of the family Carcharhinidae in the order Carcharhiniformes. They are migratory, live-bearing sharks of warm seas (sometimes of brackish or fresh water) and includes such species as the tiger shark, bull shark, spinner shark, blacknose shark, blacktip shark, grey reef shark, blacktip reef shark, silky shark, dusky shark, blue shark, copper shark, oceanic whitetip shark, and whitetip reef shark. Family members have the usual carcharhiniform characteristics. Their eyes are round, and one or two gill slits fall over the pectoral fin base. Most species are ovoviviparous, the young being born fully developed. They  vary widely in size, from as small as adult length in the Australian sharpnose shark, up to adult length in the tiger shark. Scientists assume that size and shape of their pectoral fins have the right dimensions to minimize transport cost. Requiem sharks tend to live in more tropical areas, but tend to migrate. Females release a chemical in the ocean in order to let the males know they are ready to mate. Typical mating time for these sharks are around spring to autumn. Requiem sharks are involved in a large proportion of attacks on humans, among the top five  species; however, due to the difficulty in identifying individual species, a degree of inaccuracy exists in attack records. Etymology. The common name requiem shark may be related to the French word for shark, "requin", which is itself of disputed etymology. One derivation of the latter is from Latin "requiem" ("rest"), which would thereby create a cyclic etymology ("requiem-requin-requiem"), but other sources derive it from the Old French verb "reschignier" ("to grimace while baring teeth"). The scientific name Carcharhinidae was first proposed in 1896 by D.S. Jordan and B.W. Evermann as a subfamily of Galeidae (now replaced by "Carcharhinidae ). The term is derived from Greek karcharos" (sharp or jagged); and "rhine" (rasp), both elements describe the jagged, rasp-like skin. Rasp-like skin is typical of shark skin in general, and is not diagnostic to Carcharhinidae. Hunting strategies. Requiem sharks are extraordinarily fast and effective hunters. Their elongated, torpedo-shaped bodies make them quick and agile swimmers, so they can easily attack any prey. They have a range of food sources depending on their location and species that includes bony fish, squids, octopuses, lobsters, turtles, marine mammals, seabird, other sharks and rays. They are often considered the "garbage cans