Sandbar shark - Carcharhinus plumbeus

The sandbar shark Carcharhinus plumbeus is a sturdy requiem shark with a plain grey-brown back, pale underside and no bold fin markings. Its most useful field mark is the tall, upright first dorsal fin, which begins over or slightly in front of the pectoral-fin base.

NOAA Fisheries also describes the short rounded snout, large pectoral fins and the dermal ridge between the first and second dorsal fins. This combination separates it from similar coastal sharks such as bull sharks and dusky sharks.

Head, teeth and body shape

The head is broad and blunt, with a snout shorter than the width of the mouth. The upper teeth are triangular and serrated, suited to gripping fishes and other active prey. The body is powerful rather than extremely slender, fitting a shark that often hunts close to the bottom.

Adults are often around two metres long, and large animals may approach 2.4 metres. Newborns already show the typical sandbar-shark outline with a high dorsal fin and broad pectoral fins.

The sandbar shark is widespread in warm-temperate and tropical seas. In the western Atlantic it occurs from the U.S. east coast through the Gulf of Mexico and the Caribbean to South America, and it also lives in the eastern Atlantic, Mediterranean, Indo-Pacific, around Australia and parts of the central and eastern Pacific.

FishBase treats the species as coastal-pelagic but usually close to the bottom, on continental and island shelves and adjacent deeper areas. Records range from shallow coastal water to about 280 metres.

Bays, sand flats and nurseries

The name does not mean that this is simply a beach shark. Sandbar sharks use sandy or muddy bottoms, smooth shelf areas, bays, harbour mouths and estuaries, while very rough ground, heavy surf and coral reefs are less typical habitats.

Young sandbar sharks grow up in shallow protected coastal areas where food is available and large predators are less frequent. In parts of the range the species also migrates seasonally, moving north in warmer months and south or deeper when temperatures fall.

Sandbar sharks are opportunistic predators of the seafloor and the water just above it. They eat bony fishes, smaller sharks, rays and invertebrates such as crabs, shrimp, octopuses and squid.

Reproductive data from the western North Atlantic show why this species is sensitive to heavy fishing pressure: Baremore & Hale (2012) found maturity at roughly 12 to 13 years, with maternal females often older, and an average litter of about eight pups.

Live birth and young

The species is placental viviparous. Embryos develop inside the mother and, after the early yolk phase, are supplied through a yolk-sac placenta. After roughly eight to twelve months of gestation, pups are born in shallow coastal nurseries.

Birth often falls in the warm season. Newborns are about 55 to 65 centimetres long, and slow growth plus late maturity mean that depleted populations recover only gradually.

The sandbar shark is listed globally as Endangered by the IUCN Red List. The species is widespread, but its coastal habits make it exposed to commercial fisheries, bycatch, recreational fishing and trade in meat, hide, liver oil and fins.

Why the species is vulnerable

• Late maturity: many animals do not reproduce until more than a decade old.
• Small litters: litter size is limited, often only a few to a little more than a dozen pups.
• Long reproductive pauses: females do not reproduce every year.
• Coastal fisheries: longlines, nets and other gears can catch adults, juveniles and migrants.
• Nursery dependence: bays and estuaries are productive but heavily used coastal habitats.

Effective protection therefore needs low or prohibited landings, reliable species-level catch reporting, nursery protection and international rules for fisheries and trade.

Sandbar sharks are normally not aggressive toward people. They live mostly near the bottom, feed on smaller prey and are less associated with surf zones than some other coastal sharks.

Florida Museum nevertheless describes the species as potentially dangerous because large animals are strong enough to cause serious injury. Sensible handling matters: do not touch or corner the shark, and treat hooked animals with respect.

Fisheries and diving

The main contact between people and sandbar sharks is fisheries. In several regions the species has been valued for its size, flesh and fins, which contributed to declines in some stocks.

For divers the sandbar shark is less a classic reef shark than a shark of open coastal and shelf waters. Where encounters occur, the animals often look calm, powerful and broad-finned.