July Elasmobranch of the Month: Dusky Shark
The dusky shark is a large fish, growing to lengths of 400 cm (13 ft). They have the iconic “shark body” shape. Their snout is broadly rounded. Their first dorsal fin is much larger than their second, with an interdorsal ridge present. The first dorsal originates at the posterior point of the pectoral fins, while the second dorsal is located very near the caudal fin. The caudal fin is forked, with the upper lobe much longer than the lower lobe. Their coloration is white on the underside and blueish gray to gray on their topside. The teeth in the upper jaw are triangularly shaped with serrated edges. The teeth contained in the lower jaw are more narrow and more finely serrated.
Habitat and Distribution
The dusky shark has a very wide global distribution. In the western Atlantic Ocean, it ranges from Nova Scotia to Cuba and from Nicaragua to southern Brazil. In the eastern Pacific Ocean, it ranges from southern California to the Gulf of California. Its range also includes the Indo-western Pacific Ocean and the Mediterranean Sea. It is both a coastal as well as pelagic species found between 0-500 m (0-1640 feet) in tropical and warm temperate waters.
The dusky shark’s diet consists of a wide range of animals including other sharks, starfish, rays and skates, squid, crabs, lobster, and fish.
Reproduction of the dusky shark is viviparous. The young develop inside the mother for an estimated 16-22 months and are birthed live, usually in bays and lagoons. Litter sizes range from 6-14 pups, each measuring 70-100 cm (2.4-3.4 feet).
The IUCN Red List of Threatened Species currently lists the dusky shark as Endangered, with a decreasing population trend.
The dusky shark is targeted by the commercial fishing industry for use of their fins, meat, liver oil and skin. They are also taken as bycatch. Younger, smaller dusky sharks are prey to other larger shark species.
Florida Fish and Wildlife Conservation Commission
Florida Museum of Natural History
Shark Research Institute
The IUCN Red List of Threatened Species
Rigby, C.L., Barreto, R., Carlson, J., Fernando, D., Fordham, S., Francis, M.P., Herman, K., Jabado, R.W., Liu, K.M., Marshall, A., Pacoureau, N., Romanov, E., Sherley, R.B. & Winker, H. 2019. Carcharhinus obscurus. The IUCN Red List of Threatened Species 2019: e.T3852A2872747. https://dx.doi.org/10.2305/IUCN.UK.2019-3.RLTS.T3852A2872747.en. Accessed on 10 July 2023.