A Dusky shark is a big shark with a snout that is extensively rounded. Their colour is a dusky grey overall pattern, with somewhat darker fin tips and white undersides. This species is distinguished by having a pronounced inter-dorsal ridge between the first and second dorsal fins.
Tropical and warm temperate oceans all over the world. They are primarily found in southern African waters along the eastern seaboard, from Cape Agulhas north to Mozambique. Adult females go ashore to give birth while adults are pelagic in warm seas of the outer continental shelf at depths of 200–400 m.
The Dusky Shark’s habitat is on sandy beaches throughout the KwaZulu-Natal coast and in shallow bays along the south-eastern Cape coast, juveniles can be found in the surf zone.
Adult Dusky Sharks eat rays, small sharks, and bony fish predominantly. Young fish mostly only eat bony fish, particularly sea breams, sardines, mackerel, and grunter.
They are a species that migrate. Small sharks migrate southward from their primary nursery habitat in central-southern KwaZulu-Natal to the eastern and southern Cape, however, they don’t seem to spend the winter there. Therefore, it’s probable that not all young sharks travel north. Seasonally, large sharks from the outer shelf move ashore.
Only at 210 cm precaudal length and between the ages of 17 and 20 do they reach maturity. Most of the 16-month gestation period and mating take place outside of KwaZulu-near-shore Natal’s waters. They have a lengthy breeding season, with the majority of expectant females giving birth in the fall and winter. Puppies are born in the near-shore waters between Richards Bay and Port Edward, while the Thukela Banks’ centre region may be preferable. They are viviparous and have litters of three to sixteen puppies.
Age and growth
Dusky Sharks can grow to a maximum precaudal length of 284 cm and a total length of 377 cm, weighing 450 kg. They have an extremely slow growth rate and can live up to 70 years.
It is unknown how dusky sharks are doing right now in South African waters. The catches made by the KwaZulu-Natal Sharks Board between 1978 and 2010 have significantly decreased, and they have a very low intrinsic population growth rate. On the IUCN Red List, they are classified as Vulnerable (2007).
Both recreational shore anglers and professional ski-boat fishermen take advantage of neonates and juveniles in the waters off KwaZulu-Natal and the Eastern Cape. Nowadays, the majority of sharks caught in the aggressive shore fishery are released. In KwaZulu-Natal, juvenile, adolescent, and adult dusky sharks are caught in protected shark nets and on drumlines. Additionally, occasionally, dusky sharks are caught as bycatch in the offshore pelagic long-line fishery.