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Carcharhinus plumbeusBrown shark(Also: Shark)

By Tom Lesinski

Geographic Range

Sandbar sharks are found worldwide in tropical and warm temperate waters. These sharks can be found in the western Atlantic, the eastern Atlantic, the western Pacific, the western Indian, and the eastern Indian oceans. They may also be found in the Caribbean, Gulf of Mexico, and the Mediterranean Sea. Important areas for juveniles in United States include Cape Cod, Massachusetts; Cape Canaveral, Florida; Bulls Bay, South Carolina; Delaware Bay, New Jersey; the Chesapeake Bay, and the Eastern Shore of Virginia. ("International Union for Conservation of Nature and Natural Resources", 2009; Carlson, 1999; Compagno, et al., 2005)

Habitat

Sandbar sharks tend to be coastal, typically found on muddy or sandy flats in bays, harbors, estuaries and river mouths. They may also be found offshore, on banks near islands or flat reefs. Sandbar sharks may live in depths ranging from 1 m (inter tidal waters) to 280 m in water with salinities of ~20 parts per thousand (ppt). Juveniles inhabit coastal nursery areas of temperate waters to eat and avoid predation. Adults are migratory and prefer tropical waters. ("International Union for Conservation of Nature and Natural Resources", 2009; Carlson, 1999; Compagno, et al., 2005)

  • Range depth
    1 to 280 m
    3.28 to 918.64 ft
  • Average depth
    20-55 m
    ft

Physical Description

Sandbar sharks are generally a grey-brown color or “bronzy,” as Compagno, et al. (2005) described. They have white undersides and dusky posterior edges to their fins. They also have an “inconspicuous” white band on their flank. Compagno et al. (2005) described them as having a “moderately long rounded snout” and “high triangular saw-edged upper teeth.” Their first dorsal fins are especially large compared to other sharks. As newborns, these sharks are about 56 to 75 cm total length (TL). At maturity they reach 140 to 180 cm total length and as adults they reach 240 to 300 cm total length. These sizes may vary depending on location. (Compagno, et al., 2005)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    45 to 90 kg
    99.12 to 198.24 lb
  • Range length
    240 to 300 cm
    94.49 to 118.11 in

Development

Sandbar sharks have internal fertilization and are viviparous, meaning they give birth to live young. The embryos remain in the uterus for 9 to 12 months until they are fully developed, during which time they receive nutrients from the placenta. When the pups are born they have the same physical features as adults, but they are smaller. It takes about 8 years for sandbar sharks to mature. (Carrier, et al., 2004)

Reproduction

Male and female sandbar sharks only interact during mating; otherwise the sexes swim in separate schools. To initiate mating, male sandbar sharks follow and bite the dorsal fins of females until they flip over. Once flipped over, the male inserts one clasper into the cloaca. Sandbar sharks are considered polygynandrous, meaning females will reproduce with multiple males. ("International Union for Conservation of Nature and Natural Resources", 2009; Compagno, et al., 2005; Joung and Chen, 1995; Portnoy, et al., 2007)

Sandbar sharks mate in the warm months of the year and females only give birth every 2 to 3 years. The gestation period for sandbar sharks ranges between 9 and 12 months and they may give birth to litters ranging from 1 to 14 pups. The gestation period, litter size, and time of the year when pups are born vary depending on geographic location. Males reach sexual maturity at 160 to 165 cm total length or when claspers are fully developed and have reached the proper hardness. Female sharks reach sexual maturity at 165 to 170 cm total length. Sex differentiation research has shown that levels of steroid hormones may be responsible for development of gonads and secondary sex organs. When near birth, females will enter nursery grounds. At birth, pups range in length from 56 to 75 cm, but some sources have found pups as small as 40 cm. Pup size may be related to mother size, environment, and litter size. Sandbar sharks are the slowest growing and latest maturing of all sharks. ("International Union for Conservation of Nature and Natural Resources", 2009; Compagno, et al., 2005; Joung and Chen, 1995; Joung, et al., 2004)

  • Breeding interval
    Sandbar sharks breed every 2 to 3 years, usually in the warmer months.
  • Breeding season
    Mating occurs in warm months; months vary due to geographic location.
  • Range number of offspring
    1 to 14
  • Average number of offspring
    5-12
  • Range gestation period
    9 to 12 months
  • Average time to independence
    0 minutes
  • Average age at sexual or reproductive maturity (female)
    7.5 - 8.2 years
  • Average age at sexual or reproductive maturity (male)
    8.2 years

There is little information regarding any parental investment of sandbar sharks after birth. However, females invest heavily in protecting the young during their development before birth. (Compagno, et al., 2005)

  • Parental Investment
  • no parental involvement
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Sandbar sharks are considered long-lived. However, few sources reveal information on the lifespan and longevity of sandbar sharks. In one study, Joung et al. (2004) found the oldest male to be 19.8 years old and the oldest female to be 20.8 years old. While, Sminkey et al. (1996) mention that sandbar sharks can live to be over 30 years old. According to Joung et al. (2004), “lack of accurate age information on sharks has been a major stumbling block to fisheries research.” Sandbar sharks can be found in captivity in aquariums, but captive lifespan is unknown. (Joung, et al., 2004; Sminkey and Musick, 1996)

  • Average lifespan
    Status: wild
    20 years

Behavior

Sandbar sharks are highly migratory. As juveniles, they often live in “mixed-sex” schools in shallow, coastal nursery grounds. In the winter they move to warmer, deeper waters. Adult sharks do not school with young sharks and are separated by sex. Males and females only interact during mating in the spring and summer months. This is when the males perform the courtship mentioned in the Reproduction section. Sandbar sharks are more active at night. ("International Union for Conservation of Nature and Natural Resources", 2009; Compagno, et al., 2005; Sminkey and Musick, 1995)

Home Range

This species is not known to have a home range nor defend a territory. (Merson and Pratt, 2001)

Communication and Perception

There is little information on communication between sandbar sharks. Although, during mating, male sandbar sharks will bite the females until they flip upside down. Sharks have excellent sensory acuity that aid in finding prey and avoiding predators. They have an exquisite sense of smell that is useful for locating food. Sharks also have an electrosensory system, which is an ampullary electroreceptor system. With this system, sharks are capable of detecting “weak extrinsic electric stimuli as low as 5 nV/cm,” according to Carrier et al. (2004) (Carrier, et al., 2004; Compagno, et al., 2005)

Food Habits

Sandbar sharks mainly feed opportunistically on small bottom fish, mollusks, and crustaceans. Research suggests that their diet is related to their size. Juveniles and smaller sharks mainly feed on crustaceans, such as blue crabs (Callinectes sapidus) and mantis shrimp (Lysiosquilla scabricauda). Larger sharks feed may feed on crustaceans as well, but will also consume elasmobranch prey including small sharks, skates, and rays. According to the IUCN Red List, a sandbar shark’s diet may include “sardines, shad, menhaden, anchovies, sea catfishes, moray and snake eels, pipefish, barracuda, mullets, goatfishes, hairtails, spanish mackeral, bonito, mackeral (Scomberomorus maculatus), jacks, groupers, croakers, grunts, porgies, flounders and soles, sea robins, toadfish, cusk eels, porcupine fish, sharpnose sharks (Rhizoprionodon terraenovae), spiny dogfish (Squalus acanthias), bonnethead sharks (Sphyrna tiburo), guitarfish, skates, stingrays, squid, cuttlefish, octopi, bivalves and conchs, amphipods, shrimp and crabs.” Sandbar sharks are known to feed more actively at night. ("International Union for Conservation of Nature and Natural Resources", 2009; Ellis and Musick, 2007; Stillwell and Kohler, 1993)

  • Animal Foods
  • fish
  • mollusks
  • aquatic crustaceans

Predation

Like many other types of sharks, sandbar sharks have few predators. Pups and juveniles, however, often become prey of larger members of the Chondrichthyes class. The only other predators to sandbar sharks are humans (Homo sapiens). They are very popular in shark fisheries and are the most common shark fished on the east coast of the United States. According to the IUCN Red List “sandbar sharks were found to represent at least 2 to 3% of the fins auctioned in Hong Kong, the world’s largest shark fin trading center.” Due to the high value of their fins they are overfished and therefore have experienced population declines. ("International Union for Conservation of Nature and Natural Resources", 2009; Compagno, et al., 2005; Portnoy, et al., 2007)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

According to Stillwell et al. (1993), sharks are an integral part of the flow of energy in marine ecosystems. Sandbar sharks are considered predators rather than prey, but juveniles may be preyed upon by other sharks. Sandbar sharks are a common host for a number of parasitic copepods, including those in the families Pandaridae, Caligidae, Euphoridae, and Eudactylinidae. Other parasites are isopods in the Gnathiidae family and annelids in the Hirudinidae family, which are both typically attached to the gill filaments. Copepods are often found on the body or fins of the sharks. (Newbound and Knott, 1999; Portnoy, et al., 2007; Stillwell and Kohler, 1993)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Sandbar sharks are a large part of the commercial shark fishery in the eastern United States as well as numerous other parts of the world. They are caught for their hide, meat, fins, and liver. Sandbar sharks, above other types are sharks, are more sought after because of their size and high fin-to-carcass ratio. In recent decades, demand for them has increased tremendously. Sandbar sharks make up about 60% of the catch in fisheries along the United States Atlantic coast. Recreational fishermen also catch them as a game fish. ("International Union for Conservation of Nature and Natural Resources", 2009; Carlson, 1999; Joung, et al., 2004; Sminkey and Musick, 1995; Sminkey and Musick, 1996)

  • Positive Impacts
  • food
  • body parts are source of valuable material

Economic Importance for Humans: Negative

Sandbar sharks are not considered a threat to humans, although their size could make them dangerous. They may become aggressive when provoked. (Ellis and Musick, 2007; Sminkey and Musick, 1996)

  • Negative Impacts
  • injures humans
    • bites or stings

Conservation Status

Slow growth rate and late maturation make sandbar sharks extremely vulnerable to overfishing. This is a concern due to their wide popularity in coastal fisheries worldwide. In 1996, the International Union for Conservation of Nature and Natural Resources (IUCN) Red List assessed them as vulnerable, but were re-assessed and changed to Lower risk/near threatened in 2000. Then, in 2007 sandbar sharks were listed again as vulnerable. In 1993, a management plan was created for the U.S. that involves catch and size restrictions for commercial fisheries. The plan seems to have helped slow the decline in the North Atlantic population. Western Australia has also implemented a management plan with similar guidelines. Management plans for other parts of the world have been slow coming due to insufficient data on age and growth of the sharks. ("International Union for Conservation of Nature and Natural Resources", 2009; Joung, et al., 2004; Sminkey and Musick, 1995; Sminkey and Musick, 1996)

Contributors

Tom Lesinski (author), Radford University, Karen Powers (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

cosmopolitan

having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

electric

uses electric signals to communicate

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

magnetic

(as perception channel keyword). This animal has a special ability to detect the Earth's magnetic fields.

migratory

makes seasonal movements between breeding and wintering grounds

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

nomadic

generally wanders from place to place, usually within a well-defined range.

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

piscivore

an animal that mainly eats fish

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

2009. "International Union for Conservation of Nature and Natural Resources" (On-line). The IUCN Red List of Threatened Species - Carcharhinus Plumbeus. Accessed February 03, 2010 at http://www.iucnredlist.org/apps/redlist/details/3853/0.

Carlson, J. 1999. Occurrence of Neonate and Juvenile Sandbar Sharks, Carcharhinus plumbeus, in the Northeastern Gulf of Mexico. Fishery Bulletin, 97: 387-391.

Carrier, J., J. Musick, M. Heithaus. 2004. Biology of Sharks and their Relatives. Boca Raton, FL: CRC Press LLC.

Compagno, L., M. Dando, S. Fowler. 2005. Sharks of the World. Princeton: Princeton University Press.

Ellis, J., J. Musick. 2007. Ontogenetic Changes in the Diet of the Sandbar Shark, Carcharhinus plumbeus , in Lower Chesapeake Bay and Virginia (USA) Coastal Waters. Environmental Biology of Fishes, 80: 51-67.

Heist, E., J. Graves, J. Musick. 1995. Population Genetics of the Sandbar Shark (Carcharhinus plumbeus) in the Gulf of Mexico and Mid-Atlantic Bight. Copeia, 3: 555-562.

Joung, S., C. Chen. 1995. Reproduction in the Sandbar Shark, Carcharhinus plumbeus, in the Waters off Northeastern Taiwan. Copeia, 3: 659-665.

Joung, S., Y. Liao, C. Chen. 2004. Age and Growth of Sandbar Shark, Carcharhinus plumbeus, in Northeastern Taiwan Waters. Fisheries Research, 70/1: 83-96.

McAuley, R., C. Simpfendorfer, G. Hyndes, R. Allison, J. Chidlow, S. Newman, R. Lenanton. 2006. Validated Age and Growth of the Sandbar Shark, Carcharhinus plumbeus (Nardo 1827) in the Waters off Western Australia. Environmental Biology of Fishes, 77: 385-400.

Medved, R., J. Marshall. 1983. Short-Term Movements of Young Sandbar Sharks, Carcharhinus Plumbeus (Pisces, Carcharhinidae). Bulletin of Marine Science, 33: 87-93.

Merson, R., H. Pratt. 2001. Distribution, Movements and Growth of Young Sandbar Sharks, Carcharhinus Plumbeus, in the Nursery Grounds of Delaware Bay. Environmental Biology of Fishes, 61: 13-24.

Newbound, D., B. Knott. 1999. Parasitic Copepods from Pelagic Sharks in Western Australia. Bulletin of Marine Science, 65: 715-724.

Portnoy, D., J. McDowell, C. McCandless, J. Musick, J. Graves. 2009. Effective Size Closely Approximates the Census Size in the Heavily Exploited Western Atlantic Population of the Sandbar Shark, Carcharhinus plumbeus. Conservation Genetics, 10: 1697-1705.

Portnoy, D., A. Piercy, J. Musick, G. Burgess, J. Graves. 2007. Genetic polyandry and sexual conflict in the sandbar Shark, Carcharhinus plumbeus, in the western North Atlantic and Gulf of Mexico. Molecular Ecology, 16: 187-197.

Rechisky, E., B. Wetherbee. 2003. Short-term Movements of Juvenile and Neonate Sandbar Sharks, Carcharhinus plumbeus, on their Nursery Grounds in Delaware Bay. Environmental Biology of Fishes, 68: 113-128.

Sminkey, T., J. Musick. 1996. Demographic Analysis of the Sandbar Shark, Carcharhinus plumbeus, in the Western North Atlantic. Fishery Bulletin, 94: 341-347.

Sminkey, T., J. Musick. 1995. Age and Growth of the Sandbar Shark, Carcharhinus plumbeus, Before and After Population Depletion. Copeia, 4: 871-883.

Stillwell, C., N. Kohler. 1993. Food Habits of the Sandbar Shark Carcharhinus plumbeus off the U.S. Northeast Coast, with Estimates of Daily Ration. Fishery Bulletin, 91: 138-150.

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