Status: Vulnerable
Known as: Dusky Shark, Dusky whaler, brown whaler, bay-shark, dusky ground shark, shovelnose, bronze whaler and brown shark
Estimated numbers left in wild: 20% of levels in the 1970s.
Table of Contents
Description of Dusky Shark
The dusky shark is a fairly large shark included in the requiem shark group. Requiem sharks are those that are most likely to be involved in attacks on humans, although the dusky shark has instituted few of these.
However, because the dusky shark inhabits waters often used by humans recreationally, the possibility of attack is still present.
The female dusky shark is larger than the male, and is between 320 centimetres and 420 centimetres in length, and can weigh up to 180 kilograms.
Males usually top out at around 150 kilograms. These sharks are bronze/grey to slate or dark-slate on their dorsal surfaces, and white beneath. They have a rounded shark snout with an impressively toothed mouth opening below.
Distribution and habitat
Dusky sharks prefer warm waters and will migrate from more temperate regions when colder weather arrives. They have been known to migrate for great distances, up to 3,200 kilometres.
These sharks are very sensitive to the salinity of the water and will avoid estuaries where fresh water may be mixing with salt. Although these sharks are most common on the continental shelves adjacent to landmasses, they will venture into deeper water near the drop off point of the shelves.
Feeding
Dusky sharks take a wide variety of prey including bluefish, octopuses, squid, groupers, skates, mullet, sharks, and herring. They will also eat refuse that has been dumped into the ocean.
Breeding
Springtime is when dusky sharks mate and the gestation period is about 8 months. The embryo sharks initially receive nourishment from a yolk sac, but when this has been used up, a placental attachment with the mother’s body is made. The newborn dusky shark is approximately 1 meter at birth, and it takes the female a year to recover from the ‘pregnancy’ before she is ready to mate once again. A litter will consist of between 6 and 14 young. These sharks can live up to 50 years.
Location
The dusky shark has a worldwide distribution along continental shelves. They are found along the Atlantic coast from Maine down to Argentina. On the Pacific side, dusky sharks live along the California coast. They surround Australia and live around the coastal regions of most of Africa.
Conservation
Threats
The trade in shark fins has resulted in significant losses in dusky sharks. It is estimated that about ¾ million of these sharks are killed for their fins every year. Besides this direct predation, dusky sharks can become entangled in fishing nets or beach mesh, especially the younger, smaller individuals.
The dusky shark is also taken for its oil and the skin is made into leather. Because of the ‘fight’ the dusky shark gives when hooked, it is prized in sport fishing.
Conservation efforts
Due to the declining numbers of dusky sharks off the United States coast, commercial fishing of this species is forbidden on the US coasts. Sport fishing, however, is allowed. The dusky shark as yet receives no protection in other parts of the world.
Organisations
Oceana
Oceana is the largest international organization focused only on ocean conservation, protecting marine ecosystems and endangered species such as the Dusky Shark.
