A generalist apex predator, the dusky shark can be found from the coast to the outer continental shelf and adjacent pelagic waters, and has been recorded from a depth of 400 m (1,300 ft).

This species is viviparous with a three-year reproductive cycle; females bear litters of 3–14 young after a gestation period of 22–24 months, after which there is a year of rest before they become pregnant again.

Females are capable of storing sperm for long periods, as their encounters with suitable mates may be few and far between due to their nomadic lifestyle and low overall abundance.

The International Union for Conservation of Nature (IUCN) has assessed this species as Endangered worldwide and Vulnerable off the eastern United States, where populations have dropped to 15–20% of 1970s levels.

French naturalist Charles Alexandre Lesueur published the first scientific description of the dusky shark in an 1818 issue of Journal of the Academy of Natural Sciences of Philadelphia.

[5] Many early sources gave the scientific name of the dusky shark as Carcharias (later Carcharhinus) lamiella, which originated from an 1882 account by David Starr Jordan and Charles Henry Gilbert.

In the western Atlantic Ocean, it is found from Massachusetts and the Georges Bank to southern Brazil, including the Bahamas and Cuba.

In the eastern Atlantic Ocean, it has been reported from the western and central Mediterranean Sea, the Canary Islands, Cape Verde, Senegal, Sierra Leone, and possibly elsewhere including Portugal, Spain, Morocco, and Madeira.

[4][18] The dusky shark is nomadic and strongly migratory, undertaking recorded movements of up to 3,800 km (2,400 mi); adults generally move longer distances than juveniles.

Sharks along both coasts of North America shift northward with warmer summer temperatures, and retreat back towards the equator in winter.

[1] Off South Africa, young males and females over 0.9 m (3.0 ft) long disperse southward and northward respectively (with some overlap) from the nursery area off KwaZulu-Natal; they join the adults several years later by a yet-unidentified route.

[1][5][19] Off Western Australia, adult and juvenile dusky sharks migrate towards the coast in summer and fall, though not to the inshore nurseries occupied by newborns.

[19] A tracking study off the mouth of the Cape Fear River in North Carolina reported an average swimming speed of 0.8 km/h (0.50 mph).

[27] Known parasites of this species include the tapeworms Anthobothrium laciniatum,[28] Dasyrhynchus pacificus,[29] Platybothrium kirstenae,[30] Floriceps saccatus,[31] Tentacularia coryphaenae,[32] and Triloculatum triloculatum,[33] the monogeneans Dermophthirius carcharhini[34] and Loimos salpinggoides,[35] the leech Stibarobdella macrothela,[36] the copepods Alebion sp., Pandarus cranchii,[37] P. sinuatus,[20] and P. smithii, the praniza larvae of gnathiid isopods,[37] and the sea lamprey (Petromyzon marinus).

In turn, the juvenile sharks have decimated populations of small bony fishes, with negative consequences for the biodiversity of the local ecosystem.

[5][39] The dusky shark is a generalist that takes a wide variety of prey from all levels of the water column, though it favors hunting near the bottom.

[41] The bite force exerted by a 2 m (6.6 ft) long dusky shark has been measured at 60 kg (130 lb) over the 2 mm2 (0.0031 in2) area at the tip of a tooth.

Very rarely, the largest dusky sharks may also consume sea turtles, marine mammals (mainly as carrion), and human refuse.

[4][5][40][43][44] In the northwestern Atlantic, around 60% of the dusky shark's diet consists of bony fishes, from over ten families with bluefish (Pomatomus saltatrix) and summer flounder (Paralichthys dentatus) being especially important.

Cartilaginous fishes, mainly skates and their egg cases, are the second-most important dietary component, while the lady crab (Ovalipes ocellatus) is also a relatively significant food source.

[45][46] The run of the southern African pilchard (Sardinops sagax), occurring off the eastern coast of South Africa every winter, is attended by medium and large-sized dusky sharks.

Pregnant and post-partum females do not join, possibly because the energy cost of gestation leaves them unable to pursue such swift prey.

[4][5] Females are capable of storing masses of sperm, possibly from multiple males, for months to years within their nidamental glands (an organ that secretes egg cases).

[5][25] Females move into shallow inshore habitats such as lagoons to give birth, as such areas offer their pups rich food supplies and shelter from predation (including from their own species), and leave immediately afterward.

[4][46] These nursery areas are known along the coasts of KwaZulu-Natal, southwestern Australia, western Baja California, and the eastern United States from New Jersey to North Carolina.

Females also provision their young with energy reserves, stored in a liver that comprises one-fifth of the pup's weight, which sustains the newborn until it learns to hunt for itself.

[54] In addition, the meat is sold fresh, frozen, dried and salted, or smoked, the skin is made into leather, and the liver oil is processed for vitamins.

[57] Commercial and recreational retention of dusky sharks was prohibited in 1998, but this has been of limited effectiveness due to high bycatch mortality on multi-species gear.