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)
Communication Channels: tactile
Perception Channels: visual ; acoustic ; chemical ; electric ; magnetic
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.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: vulnerable
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.
Sandbar sharks are not considered a threat to humans, although their size could make them dangerous. They may become aggressive when provoked.
Negative Impacts: injures humans (bites or stings)
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.
Positive Impacts: food ; body parts are source of valuable material
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.
Commensal/Parasitic Species:
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 brasiliensis), 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.
Animal Foods: fish; mollusks; aquatic crustaceans
Primary Diet: carnivore (Piscivore , Eats non-insect arthropods, Molluscivore )
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.
Biogeographic Regions: indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native ); mediterranean sea (Native )
Other Geographic Terms: cosmopolitan
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.
Range depth: 1 to 280 m.
Average depth: 20-55 m.
Habitat Regions: temperate ; tropical ; saltwater or marine
Aquatic Biomes: pelagic ; coastal
Other Habitat Features: estuarine
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.
Average lifespan
Status: wild: 20 years.
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.
Range mass: 45 to 90 kg.
Range length: 240 to 300 cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes alike
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.
Known Predators:
Anti-predator Adaptations: cryptic
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.
Mating System: polygynandrous (promiscuous)
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.
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.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); viviparous
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.
Parental Investment: no parental involvement; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female)
