|Range of the sandbar shark|
The sandbar shark (Carcharhinus plumbeus) is a species of requiem shark, and part of the family Carcharhinidae, native to the Atlantic Ocean and the Indo-Pacific. It is distinguishable by its very high first dorsal fin and interdorsal ridge. It is not to be confused with the similarly named sand tiger shark, or Carcharias taurus.
The sandbar shark is also called the thickskin shark or brown shark. It is one of the biggest coastal sharks in the world, and is closely related to the dusky shark, the bignose shark, and the bull shark. Its dorsal fin is triangular and very high, and it has very long pectoral fins. Sandbar sharks usually have heavy-set bodies and rounded snouts that are shorter than the average shark's snout. Its upper teeth have broadly uneven cusps with sharp edges. Its second dorsal fin and anal fin are close to the same height. Females reach sexual maturity around the age of 13 with an average fork-length (tip of the nose to fork in the tail) of 154.9 cm, while males tend to reach maturity around age 12 with an average fork-length of 151.6 cm. Females can grow to 2–2.5 m (6.6–8.2 ft), males up to 1.8 m (5.9 ft). Its body color can vary from a bluish to a brownish grey to a bronze, with a white or pale underside. Sandbar sharks swim alone or gather in sex-segregated schools that vary in size.
Distribution and habitat
The sandbar shark, true to its nickname, is commonly found over muddy or sandy bottoms in shallow coastal waters such as bays, estuaries, harbors, or the mouths of rivers, but it also swims in deeper waters (200 m or more) as well as intertidal zones. Sandbar sharks are found in tropical to temperate waters worldwide; in the western Atlantic they range from Massachusetts to Brazil. Juveniles are common to abundant in the lower Chesapeake Bay, and nursery grounds are found from Delaware Bay to South Carolina. Other nursery grounds include Boncuk Bay in Marmaris, Muğla/Turkey and the Florida Keys.
Predators and feeding habits
Sandbar sharks are viviparous. The embryos are supported in placental yolk sac inside the mother. Females have been found to exhibit both biennial and triennial reproductive cycles, ovulate in early summer, and give birth to an average of eight pups, which they carry for 1 year before giving birth. The longevity of the sandbar shark is typically 35–41 years.
Interactions with humans
Sandbar sharks have been disproportionately targeted by the U.S. commercial shark fisheries in recent decades due to their high fin-to-body weight ratio, and U.S. fishing regulation requiring carcasses to be landed along with shark fins. In 2008, the National Marine Fisheries Service banned all commercial landings of sandbar sharks based on a 2006 stock assessment by SEDAR, and sandbar sharks were listed as vulnerable, due to overfishing. Currently, a small number of specially permitted vessels fish for sandbar sharks for the purpose of scientific research. All vessels in the research fishery are required to carry an independent researcher while targeting sandbars.
Danger to people
In spite of their large size and similar appearance to other dangerous sharks such as bull sharks, very few, if any attacks are attributed to sandbar sharks, so they are considered not to be dangerous to people. As a result, they are considered one of the safest sharks to swim with and are popular sharks for aquaria.
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