The sandbar shark (''Carcharhinus plumbeus''), also known as the brown shark or thickskin shark, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of requiem shark, and part of the family Carcharhinidae, native to the

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

and the

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

. It is distinguishable by its very high first

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

and interdorsal ridge. It is not to be confused with the similarly named sand tiger shark, or ''Carcharias taurus.''

Description and growth

The sandbar shark is one of the largest coastal sharks in the world, and is closely related to the dusky shark, the bignose shark, and the bull shark. Its

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 Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

are close to the same height. Females can grow to 2–2.5 m (6.6–8.2 ft), males up to 1.8 m (5.9 ft). The maximum recorded weight is 240 kg (530 lb). Female sandbar sharks have an average fork-length (tip of the nose to fork in the tail) of 154.9 cm with the males' average fork-length being 151.6 cm.Baremore, Ivy E.; Loraine F. Hale (1 June 2012). "Reproduction of the Sandbar Shark in the Western North Atlantic Ocean and Gulf of Mexico". ''Marine and Coastal Fisheries: Dynamics, Management, and Ecosystem Science''. American Fisheries Society. 4: 560–572. doi:10.1080/19425120.2012.700904. Its body color can vary from a blue-ish brown, grey or 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 An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environm ...

, 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 The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

they range from

Massachusetts Massachusetts ( ; ), officially the Commonwealth of Massachusetts, is a U.S. state, state in the New England region of the Northeastern United States. It borders the Atlantic Ocean and the Gulf of Maine to its east, Connecticut and Rhode ...

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

. Juveniles are common to abundant in the lower

Chesapeake Bay The Chesapeake Bay ( ) is the largest estuary in the United States. The bay is located in the Mid-Atlantic (United States), Mid-Atlantic region and is primarily separated from the Atlantic Ocean by the Delmarva Peninsula, including parts of the Ea ...

, and nursery grounds are found from

Delaware Bay Delaware Bay is the estuary outlet of the Delaware River on the northeast seaboard of the United States, lying between the states of Delaware and New Jersey. It is approximately in area, the bay's freshwater mixes for many miles with the saltw ...

South Carolina South Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders North Carolina to the north and northeast, the Atlantic Ocean to the southeast, and Georgia (U.S. state), Georg ...

. Other nursery grounds include Bonjuk Bay in

Marmaris Marmaris () is a municipality and Districts of Turkey, district of Muğla Province, Turkey. Its area is 906 km2, and its population is 97,818 (2022). It is a port city and tourist resort on the Aegean Sea, Mediterranean coast, along the shorel ...

Muğla Muğla () is a city in southwestern Turkey. The city is the center of the district of Menteşe, Muğla, Menteşe and Muğla Province, which stretches along Turkey's Aegean Sea, Aegean coast. Muğla's center is situated inland at an altitude of ...

Turkey Turkey, officially the Republic of Türkiye, is a country mainly located in Anatolia in West Asia, with a relatively small part called East Thrace in Southeast Europe. It borders the Black Sea to the north; Georgia (country), Georgia, Armen ...

and the

Florida Keys The Florida Keys are a coral island, coral cay archipelago off the southern coast of Florida, forming the southernmost part of the continental United States. They begin at the southeastern coast of the Florida peninsula, about south of Miami a ...

Predators and diet

Natural predators of the sandbar shark include the

tiger shark The tiger shark (''Galeocerdo cuvier'') is a species of ground shark, and the only extant member of the genus '' Galeocerdo'' and family Galeocerdonidae. It is a large apex predator, with females capable of attaining a length of over . Popula ...

and, rarely, great white sharks. The sandbar shark itself preys on

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

, rays,

crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

s, and

mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

s. They have also been found to primarily consume

osteichthyes Osteichthyes ( ; ), also known as osteichthyans or commonly referred to as the bony fish, is a Biodiversity, diverse clade of vertebrate animals that have endoskeletons primarily composed of bone tissue. They can be contrasted with the Chondricht ...

, or bony fish,

octopuses An octopus (: octopuses or octopodes) is a soft-bodied, eight-limbed Mollusca, mollusc of the order (biology), order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, ...

, european squid, and

cuttlefish Cuttlefish, or cuttles, are Marine (ocean), marine Mollusca, molluscs of the order (biology), suborder Sepiina. They belong to the class (biology), class Cephalopoda which also includes squid, octopuses, and nautiluses. Cuttlefish have a unique ...

when in areas such as the Mediterranean or the Gulf of Gabés. Sandbar sharks have been described as being a top predator in their ecosystem's food chain. Sandbar shark seaworld

Maturity and reproduction

There are disagreements about when exactly sandbar sharks reach sexual maturity, but most studies conclude that females reach sexual maturity around 13 years of age, while males tend to reach maturity around age 12 years old. Sandbar sharks are viviparous, with the embryos supported in placental yolk sac inside the mother. Females have been found to exhibit bot
biennial
consistently reproducing every two years and returning to the same place to have deliver the pup, and triennial, reproducing every three years and returning to the same place for delivery, migration and

gestation period In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation. It begins when a fertilized zygote implants in the female's uterus, and ends once i ...

s. They also 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

Fishing restrictions

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, sandbar sharks are not considered to be dangerous to people. Very few attacks are attributed to sandbar sharks. As a result, they are considered one of the safest sharks to swim with and are popular sharks for aquaria. However, on August 2, 2021, a 12-year-old girl was bitten on her leg by a sandbar shark in Ocean City, Maryland, United States. This was confirmed by Ocean City authorities on August 5, 2021. The victim required 42 stitches.

Immune system studies

Immune system genes, specifically MHC genes, are under study to understand the

adaptive immune system The adaptive immune system (AIS), also known as the acquired immune system, or specific immune system is a subsystem of the immune system that is composed of specialized cells, organs, and processes that eliminate pathogens specifically. The ac ...

in sharks such as the sandbar. Sandbars contain MHC class I, MHC class IIα, and class IIβ genes. Shark MHC genes are known to be similar to

tetrapod A tetrapod (; from Ancient Greek :wiktionary:τετρα-#Ancient Greek, τετρα- ''(tetra-)'' 'four' and :wiktionary:πούς#Ancient Greek, πούς ''(poús)'' 'foot') is any four-Limb (anatomy), limbed vertebrate animal of the clade Tetr ...

rather than

. Similarities include the lack of

cysteine Cysteine (; symbol Cys or C) is a semiessential proteinogenic amino acid with the chemical formula, formula . The thiol side chain in cysteine enables the formation of Disulfide, disulfide bonds, and often participates in enzymatic reactions as ...

s in class IIα1 domains in tetrapods and carcharhinids. Also, there are a fewer number of classical loci in sharks and tetrapods, when compared to other animals.

Conservation status

The New Zealand Department of Conservation has classified the sandbar shark as "Data Deficient" under the

New Zealand Threat Classification System The New Zealand Threat Classification System is used by the Department of Conservation to assess conservation priorities of species in New Zealand. The system was developed because the IUCN Red List, a similar conservation status system, had s ...

References

{{DEFAULTSORT:Sandbar Shark Carcharhinus Fish of the Atlantic Ocean Viviparous fish Fish of Hawaii Fish of Israel Fish of the Dominican Republic Fish described in 1827 Taxa named by Giovanni Domenico Nardo