This week’s featured species is well known for its strikingly tall dorsal fin that can be more than 1/10th of the shark’s body length. The Sandbar Shark (Carcharhinus plumbeus) is a large fusiform bodied shark with a gray or brown dorsal side with a stark white belly (Tricas et al., 1997). Its famous first dorsal fin is very tall, triangular, and broad, resembling the pectoral fins. Its caudal fin has a well developed upper lobe for strong swimming. Its striking appearance and ability to adapt to living under human care makes it a very popular species in zoos and aquariums.
The sandbar shark can be found in tropical and warm temperate waters around the world. During the winter months, the sandbar shark spends its time in warm, tropical waters. In the summer, these sharks migrate into seasonally warm temperate waters. It is during the summer months that pregnant females give birth to their pups in shallow, protected nursery habitats. In the United States, female sandbar sharks are known to utilize the Delaware and Chesapeake Bays to pup. The pups then spend the summer in the safety of the bay while they learn to hunt and grow. In the winter, they migrate further south to tropical waters (Klimley, 2013). These nursery habitats are critical for the survival of the sandbar pup. If these nursery habitats begin to degrade, whether it be from pollution, habitat loss, construction, runoff, or other influences, it may have a major impact on the survival rates of the pups and thus impact the overall species (Skomal, 2016).
The sandbar shark has a wide variety of prey items in its diet. They typically feed on small bottom fishes, mollusks, crustaceans, other elasmobranchs, and even invertebrates (Musick et al., 2009). Unlike some other large sharks in the Carcharhinidae family, they are not known to consume mammalian carrion or garbage as a general rule (Musick et al., 2009). Their teeth are specially designed to handle a varying diet. Their upper jaw has triangular, serrated teeth that are ideal for cutting and sawing; while the lower jaw is made of narrow, gripping teeth to help hold slippery prey items (Klimley, 2013).
The sandbar shark is under threat of coastal shark fisheries around the world (McAuley, Leary, & Sarginson, 2008). They are often targets of longliners, hook and line, fixed bottom nets, and even hook and reel fisheries. They are also highly prized for their fins. Their fins fetch a high value on the Asian markets, and it is estimated that 2 – 3% of all fins in Hong Kong belong to the sandbar shark (Musick et al., 2009). Sandbar sharks are incredibly vulnerable to over fishing. They are a k-selected species, which means that they have slow growth rates, mature late in life, and have a relatively low fecundity (Klimley, 2013; Musick et al., 2009). It takes roughly 23 years for a population of sandbar sharks to double in size (Sminkey & Musick, 1996). Fishing pressures on the sandbar shark have led to regional population declines in the Northwest and Central Atlantic, the Mediterranean, Southern Brazil, Western Australia, and most likely the Northeastern Pacific (Musik et al., 2009). According to the longest continuous survey of shark populations in North Carolina, the sandbar shark has seen declines as much as 87% since the 1970’s (Klimley, 2003).
In the United States and Canada, the sandbar shark is protected under the Shark Management Plans. They are considered a prohibited species in the Western Atlantic off the eastern coast of the United States. This means that if they are caught, they must be released immediately, with minimal injury, and without ever leaving the water (Musick et al., 2009). Careful populations management is required for this vulnerable species.
Authority: Nardo, 1827
Family: Carcharhinidae; 59+ species
Length: Maximum 7.5 feet (2.3 m)
Weight: Typically 100 lbs (45.3 kg) but can reach over 200 lbs (90.7 kg)
Habitat: Inland waters of harbors, bays, estuaries, and river mouths; adjacent offshore waters; shelves
Depth: Surface to 919 feet (280 m) but typically found in waters less than 328 feet (100 m)
Reproduction: Placental Viviparous
Gestation: 8 – 12 months
Litter Range: 1 – 14 pups
Home Range: Worldwide tropical and warm temperate waters
Diet: Bottom fishes and invertebrates
IUCN Status: Vulnerable
(Tricas at al., 1997; Musick et al., 2009; Skomal, 2016)
Thanks so much for checking out the Sandbar Shark! If you missed last week’s featured species, don’t miss the brilliant Bronze Whaler Shark. If there is a species of shark you’d love to know more about, leave me a comment or send me a message! I would love to do a feature on your favorite species.
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Featured Image Source
National Aquarium (Photographer). (n.d.). Sandbar Shark [Digital Image]. Retrieved from https://www.aqua.org/Experience/Animal-Index/sandbar-shark
Klimley, A. P. (2013). The biology of sharks and rays. University of Chicago Press.
McAuley, R., Leary, T., & Sarginson, N. (2008). Demersal gillnet and longline fisheries status report. State of the fisheries report, 9, 225-229.
Musick, J.A., Stevens, J.D., Baum, J.K., Bradai, M., Clò, S., Fergusson, I., Grubbs, R.D., Soldo, A., Vacchi, M. & Vooren, C.M. (2009). Carcharhinus plumbeus. The IUCN Red List of Threatened Species. Retrieved from https://www.iucnredlist.org/species/3853/10130397
Skomal, G. (2016). The Shark Handbook: The Essential Guide for Understanding the Sharks of the World. (2nd ed.). Kennebunkport, ME: Cider Mill Press.
Sminkey, T. R., & Musick, J. A. (1996). Demographic analysis of the sandbar shark, Carcharhinus plumbeus, in the western North Atlantic. Oceanographic Literature Review, 11(43), 1156.
Tricas, T. C., Deacon, K., Last, P., McCosker, J. E., Walker, T. I., & Taylor, L. (1997). The Nature Company Guides: Sharks and Rays. (L. Taylor, Ed.). Hong Kong: The Nature Company, Time Life Books.