Sandbar Sharks, Carcharhinus plumbeus
Taxonomy Animalia Chordata Elasmobranchii Carcharhiniformes Carcharhinidae Carcharhinus plumbeus
Description & Behavior
Sandbar sharks, Carcharhinus plumbeus (Nardo, 1827), aka brown shark, queriman sharks, sandbar sharks, sharks, and thickskin sharks, are moderately large sharks that measure up to 2.5 m in length, 2 m on average, and weigh a maximum of 118 kg. Sandbar sharks can weigh anywhere between 45-90 kg as adults. The average is 50 kg for males and 68 kg for females. Sandbar sharks are stout sharks with moderately long, round snouts, and high, triangular, saw-edged upper teeth. This species has an interdorsal ridge and a distinctively large first dorsal fin. Sandbar sharks are blue-gray or brown to bronze in color on the dorsal side and flanks, and white on the ventral side. The tips and outer margins of their fins are sometimes darker than the rest of their body.
World Range & Habitat
Sandbar sharks, Carcharhinus plumbeus, can be found in subtropical waters ranging from 23-27°C in temperature between 44°N-36°S in the western Atlantic from southern Massachusetts, USA to southern Brazil; in the Gulf of Mexico, Bahamas, Cuba and south and west Caribbean. In the eastern Atlantic, sandbar sharks are found from Portugal to Democratic Republic of the Congo, and the Mediterranean. The Indo-Pacific range of this species includes scattered records from the Red Sea, Persian Gulf and East Africa to the Hawaiian Islands, and in the eastern Pacific in the Revillagigedo and Galápagos islands.
Sandbar sharks are found in inshore and offshore waters, on continental and insular shelves, as well as in deep water. This species is also common in bays, river mouths, and harbors; however it avoids the surf zone and beach areas. It spends most of the time in water from 20-65 m deep but undoubtedly moves into deeper water to undergo migration.
Feeding Behavior (Ecology)
Sandbar sharks, Carcharhinus plumbeus, are opportunistic bottom-feeders that prey on bony fishes, smaller sharks, rays, cephalopods, gastropods, crabs, and shrimps. Sandbar sharks feed throughout the day but becomes more active at night.
Sandbar sharks, Carcharhinus plumbeus, are viviparous, meaning the embryo develops and receives nourishment via a placental sac in the mother who bears the young live rather than in eggs. Males reach maturity between 1.30-1.80 m while females mature at 1.45-1.80 m. Pups range from 55-70 cm long at birth.
In the northern hemisphere, mating occurs in the spring or early summer (May-June). Sharks in the southern hemisphere mate during the warmer summer months between late October to January. The mating process begins when the male follows a female, occasionally biting her between the dorsal fins until she gives him access to insert one clasper into the cloaca. As with other shark species, females are often seen with permanent scars as a result of this mating ritual.
Once fertilization occurs, the gestation period ranges 8-9 months in the western Atlantic population where pups are born between June-August, 12 months for females inhabiting the coast of southeastern Africa where pups are born between December to February. Litter size varies by region, but is typically between 6-13 pups depending on the size of the mother. Females give birth in shallow water nursing grounds where they are protected from predation by larger sharks such as bull sharks, known to prey on juvenile sandbar sharks. Bays and estuaries between Delaware and North Carolina off the US coast are common sandbar shark nurseries. Juveniles remain in or near the nursing grounds until late fall after which they form schools and migrate to deeper waters. They return to the nursing grounds during warmer months. They repeat this migratory pattern until they are about 5 years of age when they begin to follow the wider migrations of adults.
Conservation Status & Comments
Sandbar sharks, Carcharhinus plumbeus, are considered harmless to humans. This species is slow to mature and has a low reproductive rate and is therefore particularly vulnerable to threats such as commercial hunting and subsequent overfishing. To prevent this from happening, a management plan was implemented in US waters in 1993.
The sandbar shark is listed as a Vulnerable A2bd+4bd (VU) on the IUCN Red List of Threatened Species:
VULNERABLE (VU) - A taxon is Vulnerable when the best available evidence indicates that it meets any of the criteria A to E for Vulnerable (see Section V), and it is therefore considered to be facing a high risk of extinction in the wild.
References & Further Research
Research Carcharhinus plumbeus » Barcode of Life ~ BioOne ~ Biodiversity Heritage Library ~ CITES ~ Cornell Macaulay Library [audio / video] ~ Encyclopedia of Life (EOL) ~ ESA Online Journals ~ FishBase ~ Florida Museum of Natural History Ichthyology Department ~ GBIF ~ Google Scholar ~ ITIS ~ IUCN RedList (Threatened Status) ~ Marine Species Identification Portal ~ NCBI (PubMed, GenBank, etc.) ~ Ocean Biogeographic Information System ~ PLOS ~ SIRIS ~ Tree of Life Web Project ~ UNEP-WCMC Species Database ~ WoRMS
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