Dusky shark

The Dusky shark (Carcharhinus obscurus) is also known as the "bronze whaler," "black whaler," "brown dusky shark," "brown shark," "common whaler," and "shovelnose."​ This cosmopolitan species is found in most tropical and temperate waters. They are highly migratory, moving between the northern and southern part of their respective oceans during the summer and winter months. Males and females tend to do separate migrations, however off of South Africa, immature dusky sharks have undergone this seasonal migration with females going north and males going south. Another example is off Western Australia (WA), but both the young/mature sharks move inshore during the summer/autumn months. Young dusky sharks tend to congregate in shallow, coastal nurseries in estuaries and bays (from New Jersey to Cape Hattaras), while adults tend to avoid said estuaries/low salinity areas.

Dusky sharks look a lot like your "typical" shark in that they are almost torpedo-shaped. Their snout is a little shorter than most others and they have a low interdorsal ridge. They are blue-grey in color which fades into its creamy white underbelly. The fins of young dusky sharks are usually darker than those older sharks. They are often confused with the sandbar shark (Carcharhinus plumbeus) but you can tell the difference between the two in that dusky sharks have smaller and more posterior first dorsal fin.

These shark tend to eat a wide variety of bony fish, as well as cartilaginous fish and invertebrates. This includes, but is not limited to herring, eels, mullet, groupers, grunts, croakers, bluefish, mackerel, tunas, various flatfish, a variety of sharks, skates and rays, crabs, octopuses, squid, and starfish. Talk about a wide palette! 

In the western Atlantic, these sharks mate in the spring only mating every second year. Their gestation period is about 8 months up to 16 months. These sharks are viviparous, and litter numbers range from 6-14 pups. Young dusky sharks may be preyed upon by larger sharks, such as bull sharks. Mature dusky sharks probably don’t have many predators. However, a copepod (Pandarus sinuatus) is parasitic and loves the dusky.
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These sharks are harvested in WA for its fins, and it’s taken on commercial longlines as bycatch in a number of fisheries around the world. Their meat is eaten, their skin is used as leather and it’s liver for oil. Due to their large size, they are also targeted by recreational fishermen as a sport fish. On a global scale, dusky shark populations are considered at-risk, and the IUCN assessing these animals as Vulnerable (VU). 

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glossary

• Commercial fishery: The activity of catching fish and other seafood for profit.
• Cosmopolitan: Worldwide distribution.
• Dorsal fin: Fin located on the back.
• Gestation: The period in which a fetus develops, beginning with fertilization and ends at birth.
• Invertebrates: Animals with no backbone (i.e. crustaceans, jellyfish, corals, sea anemones).
• IUCN: International Union for Conservation of Nature.​
• Pup: Give birth to baby sharks (pups).
• Pups: Baby sharks.
• Recreational fishery: Also called sport fishing, it is fishing for pleasure or competition.
• Temperate waters: The water between tropical seas and the Polar Regions (10-21° C, 50-69.8° F).
• ​Teleost: Bony fishes.
• Tropical waters: Waters that are between the Tropic of Cancer (23.5° N) and the Tropic of Capricorn (23.5° S).
• Viviparous: Eggs hatch inside the female's body and the babies are fed by a placenta which transfers nourishment from the mother to the babies (via an umbilical cord which is connected to the baby shark behind the between the pectoral fins).

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