Featured Species: Sandbar Shark (Carcharhinus plumbeus)

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.

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Tennessee Aquarium (Photographer). (n.d.). Sandbar Shark [Digital Image]. Retrieved from https://www.tnaqua.org/

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).

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Knickle, C. (Author). (2018). World distribution map for the sandbar shark [Digital Image]. Retrieved from https://www.floridamuseum.ufl.edu/

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).

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Left: Robertson, R.D. (Photographer). (2016 Nov 17). Carcharhinus plumbeus Upper Jaw [Digital Image]. Retrieved from https://en.wikipedia.org/ Right: Robertson, R.D. (Photographer). (2016 Nov 17). Carcharhinus plumbeus Lower Jaw [Digital Image]. Retrieved from https://en.wikipedia.org/

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).

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Fig. 16.3 Change in the abundance of species over time, estimated from scientific surveys and the catch of commercial fisheries, over a period of twenty-eight years for the larger sharks in the higher tropic levels (upper row), and the smaller sharks and rays in the tropic level below them (lower row), and the bay scallop (last plot on lower row). (Klimley, 2013).

 

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.

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Flannery, A. (Photographer). (2017 May 12). Sandbar Shark in Maui [Digital Image]. (Original Content).

Shark Stats

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.

The new Ocean For Sharks Shop is open! There’s handmade ocean inspired plush animals, canvas paintings, and of course my children’s book, Winifred the Wondrous Whale Shark, available in print and PDF. Be sure to stop by. Remember proceeds benefit shark research and conservation with a donation to Project AWARE!

Conservation legislation needs public support in order to become law and help protect the environment and wildlife. Tell your representatives that you care about environmental and wildlife conservation.  It only takes a moment to make a change that will last a lifetime. Until next time finatics!

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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

Literature Cited

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 report9, 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 plumbeusThe 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 Review11(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.

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Featured Species: Bronze Whaler (Carcharhinus brachyurus)

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