The sandbar shark, Carcharhinus plumbeus, comes from the Carcharhinidae family of sharks, also called requiem sharks.
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 weighs as much as 18% of the shark’s whole body. Sandbar sharks usually have heavy-set bodies and rounded snouts that are shorter than the average shark’s snout. Their upper teeth have broadly uneven cusps with sharp edges. Its second dorsal fin and anal fin are close to the same height. Females can grow to 7 or 8 feet, males up to 6 feet. 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. They are most active at night, at dawn, and at dusk.
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, which is probably one of the most important nursery grounds on the United States east coast for this species.
The sandbar shark’s main predator is man. Natural predators are the tiger sharks, and rarely by great white sharks. The sandbar sharks, and other requiem sharks, prey on finfish rays, bottom dwelling animals, seabirds and turtles.
Sandbar sharks are viviparous. The embryos are supported in placental yolk sac inside the mother. The female reproduces every two years. They give birth to 8 to 10 young. They carry the young for 1 year before birth.
Illustration: © Diane Rome Peebles