Dusky Shark

Threat Level: Medium

The Dusky Shark is also known as bay-shark, black whaler,
bronze whaler, brown dusky shark, brown shark,
common whaler, dusky ground shark , dusky shark,
and shoveln.

DUSKY SHARK

Scientific Name.... Carcharhinus Obscurus
Family Name...... Carcharhinidae

General Information: The dusky shark has a long, streamlined body with a broad, rounded short snout. The first dorsal fin is much larger than the second with a dermal ridge found between the two dorsal fins. The upper lobe of the caudal fin is larger than the lower. The pectoral fins are long and curved on the trailing edge.

Size: The average length of dusk sharks are about 10 feet, and the maximum around 13.6 feet.

Teeth: The upper teeth of the dusky shark are triangular and slightly oblique with serrated edges, while the front teeth are virtually erect. Lower teeth differ since they have narrow, erect cusps with more finely serrated edges than the upper teeth. Both sets of teeth become increasingly concave as they move distally in the jaw.

Color: The dusky shark is a brown-gray to gray above and white below. A faint pale stripe extends along the side of the body to the pelvic fins. In juveniles, the tip of the lower caudal fin and the undersides of the pectoral fins are notably dark or dusky, but this is indistinct in adults.

Feeding Habits: There primary diet consists of bony fishes, including( catfishes, eels, groupers, lizard fishes, jacks, tunas, flatfishes, mackerel spade fishes and goatfishes) and elasmobranchs. They are also a predator of angel sharks, saw sharks, catsharks, smoothhounds, skates and butterfly rays. Although less important in the diet, they also eat some crustaceans (including crabs and lobsters), also cephalopods (including cuttlefishes and octopuses ) sea stars, snails, and sea snakes. It seems to have a particular preference for bottom-dwelling prey items and schooling species including squid, anchovies, sardines, and tuna.

Social Behaviour: This species segregate to some degree by sex. They are known to feed actively during the day.

Habitat | Migration | Distribution: This shark is found in western and eastern North Atlantic, western Indian Ocean, western and eastern Pacific. This species occurs primarily above coastal shelves in offshore waters adjacent to the open ocean. It is widely distributed in warm temperate and tropical waters. It can be found from the surface to depth of 1240 feet. Like many other large requiem sharks, it migrates into higher latitudes during warm months and more central latitudes during winter.

Reproduction: They are viviparous and females give birth to a litter of 6-10 young that are up to 3 feet long. They mate in spring, and give birth after a 16-month gestation period. Females move into shallow water to drop their young and mate every two years. Reports on studies of mature females showed signs of mating wounds on the caudal peduncle and first dorsal fin. They reported observing three mature females with tooth rake marks over the eyes or on top of the head.

Swimming: Because the upper lobe of the caudal fin is well developed, indicates that the dusky shark is a strong swimmer.

Population Report: Numbers are dwindling in many areas. Numbers of this species in the western Atlantic have fallen because of overfishing.