Dusky shark

What it is

The dusky shark is a large requiem shark with a slender, streamlined body. It features a short, rounded snout and long, sickle-shaped pectoral fins. A distinctive low ridge runs between its two dorsal fins. The skin colour ranges from bronzy or bluish grey on top to white underneath, with faint lighter stripes on the flanks. Fin tips, especially on juveniles, appear darker. Adults commonly reach 3.2 metres in length, though specimens over 4 metres have been recorded. Females typically grow larger than males.

Where it lives

This species inhabits tropical and warm-temperate waters across the globe, though its distribution is discontinuous. It lives off continental coastlines from the surf zone to the outer shelf and adjacent open ocean. Preferred water temperatures range from 19 to 28 degrees Celsius. It avoids low-salinity areas like estuaries. Populations migrate seasonally, moving towards poles in summer and equator in winter. Recorded movements can exceed 3,800 kilometres. Distinct populations exist in regions such as Indonesia and Australia.

How it lives

As an apex predator, the dusky shark hunts a wide variety of prey near the sea floor and in the water column. Its diet includes bony fish, other sharks, rays, cephalopods, and occasionally crustaceans or carrion. Large individuals can consume significant portions of their body weight in one meal. Juveniles face predation from larger sharks like the great white and tiger shark. Adults have few natural enemies. They often follow ships and may host parasites such as tapeworms and copepods. Dense aggregations of young sharks form around feeding opportunities.

Breeding and life cycle

Reproduction is viviparous, meaning females give birth to live young. This species has one of the longest gestation periods among animals, lasting 22 to 24 months. Females rest for a year before becoming pregnant again, resulting in a three-year reproductive cycle. Litters contain between 3 and 14 pups. Newborns measure approximately 70 to 100 centimetres. Growth is slow, and sharks do not reach sexual maturity until around 20 years of age. Females can store sperm for long periods due to infrequent mating encounters.

Fish and people

Commercial fisheries value this shark for its fins, used in soup, as well as its meat, skin, and liver oil. Recreational anglers also target it. Due to its large size, it is considered potentially dangerous to humans, although few attacks are attributed to it. Overfishing has severely impacted populations, particularly off the eastern United States where numbers dropped to 15–20 per cent of 1970s levels. Conservation efforts are hindered by its slow growth and late maturity.

Status and threats

The International Union for Conservation of Nature lists the dusky shark as Endangered worldwide. It is classified as Vulnerable in specific regions like the eastern United States. Population depletion is driven by high demand for shark products and the species' inability to reproduce quickly enough to replace harvested individuals. Habitat overlap with specialized relatives and migration patterns expose them to various fishing pressures across international waters.

Questions people ask about Dusky shark

Good reading and sources

• Remains found after rare shark attack on swimmer in IsraelBBC, Article

• Dusky shark on WikipediaEncyclopedia
• More photos on Wikimedia CommonsPhotos
• Wikidata recordOpen data