Dusky Shark Facts

Dusky Shark Profile

Requiem sharks are a big family of agile predators, some, like the whitetip reef shark, are highly specialised hunters, filling in niches nothing else can. Others, like the bull shark, are much less picky and will gobble down more or less anything they bump into.

Dusky sharks are in the latter category, but while generalist predation is usually a lot more resilient to extinction than specialisation, their reproductive strategy is proving to be their Achilles’ heel, as the species is now listed as endangered. 

Dusky Shark Facts Overview

Dusky sharks are, as the name suggests, part of the sexiest family of sharks, known for maintaining an athletic figure that balances power and grace to kill with great efficiency and generally swim around looking gorgeous. 

Unlike more specialist species in the family, these will eat most things, organic or not, and can chomp with great force into whatever’s put in front of them. This makes them potentially dangerous, but our threat to them is substantially more urgent than theirs is to us.

This is a sensitive shark with a lot of threats, and it’s in great trouble. 

Interesting Dusky Shark Facts

1. They’re requiem sharks

The requiem shark family, Carcharhinidae, is a large group of mostly tropical sharks, known for their sleek appearance and long pectoral fins. There are 60 or so species in the family, and all have such great figures, that it’s hard to pick a favourite. 

They do have a characteristic expression, though, fixed on their faces as a result of a very round eye, that makes them look perpetually surprised. Possibly as a result of wolf-whistling shrimp, we don’t know. 

Dusky sharks have a lot of competition in the looks department from such catwalk classics as the sandbar shark, blue shark and oceanic whitetip. They’re known for being generally slow-moving but rapidly igniting into a powerful, high-speed charge when hunting. 

This family contains sharks that are known as the “garbage cans of the sea”, and the Dusky is one of them. ¹

2. They’ll eat anything

Of all the requiem sharks, the dusky has perhaps the least athletic body. Its relatively chunky build reflects its indiscriminate diet, and it’s definitely got the look of a generalist species.

Dusky sharks will eat fish, birds, bats, licence plates, planes, trains and automobiles; and sometimes, people. 

Requiem sharks are the top five groups of sharks involved in attacks on humans, though this is still a very low number, and while the species is hard to establish in most cases, the Dusky has one confirmed kill to its name.  

3. They can bite very hard

Since most researchers are just big kids with doctorates, one of the most common questions they ask about sharks is, “Which one bites the hardest?”

This isn’t as easy a question to answer objectively (you could probably compare four sharks subjectively before you run out of limbs), but one way to try is to get a shark to bite a piece of soft metal and then measure the depth of the holes. 

One such test came out with the Dusky on top, measuring a frightening 60kg of pressure over the 2mm tooth point area. That’s not dissimilar to having someone stand on a sharp nail while you hold it over your hand. 

But these experiments don’t tell the full story. First, it’s hard to know whether a shark is giving its all, both in and out of the bite experiment – they’re notoriously aloof. 

Second, that was one tooth among many, and it’s impossible to infer how the force would be spread out across all gazillion in the mouth (they have about 60 rows of teeth). Still, it bites well and it bites hard. ²

4. They get sharksuckers

From biting to sucking, this predator is commonly surrounded by groupies that dock onto its skin for a free ride. 

Remoras are the well-known freeloaders of the ocean and Duskies prove very attractive to one particular species, the live sharksucker, Echeneis-naucrates.

These cool-looking fish have special docking attachments on the top of their head which act like a Velcro sucker and latch onto the shark. 

They get towed around by their host and get to feed on the parasites they carry, as well as the scraps they leave after a big meal. ³

5. They get stressed 

Remoras can be overwhelming on occasion, but as a general rule, they’re not all that much bother. 

What upsets a dusky shark far more is being pulled out of the water. Researchers occasionally have to do this as part of tracking experiments and fisheries continually do it as part of the pure and comprehensive devastation of ocean life. 

Duskies are difficult to put back into the water safely, on account of how stressful the experience of leaving it is. This is not unique to the species, or even the class of fish, and many, many species have a low survival rate even when they’re thrown back in. 

The measurable stress levels in this shark species, however, have been a matter of conversation relating to the refinement of research processes to make the experience less painful. ⁴

6. They have a three-year reproductive cycle

While no species enjoy being routinely killed by stress and gillnets, duskies are particularly vulnerable to losses on account of their slow rate of reproduction. 

Usually, a generalist is more resilient to extinction than a specialist, but in this species, the benefits of a flexible diet are offset simply by how long it takes for an individual killed to be replaced. 

Gestation alone takes up to two years, but to get there, a dusky shark needs to survive for up to 20 years old to reach sexual maturity. After giving birth, females take a year off, and all of these factors combine to make this species the slowest breeder of all sharks. 

This is one of the most significant factors in the decline of the species. ⁵

7. Dusky sharks have an incredible range of threats

There are so many problems for this poor shark, that it’s hard to know where to start.

Aside from the threats it shares with all ocean inhabitants – being dragged up by mistake in gillnets and trawls – it has a 67% mortality rate when it’s thrown back in. 

And that’s if it survives onto the boat in the first place, which it often doesn’t. In the US pelagic longlines 34% of the time, they’re brought in dead. In the bottom longlines in the Northwest Atlantic, 81% of these sharks don’t survive the trip onto the boat. 

International fishing industries always seem like small fish in a big pond, and their exploits go unnoticed by almost all of us so far away on land, but their damage to the ocean, and by extension, to the rest of the world’s ecosystems, is reaching a tipping point. 

Millions of species like this Dusky shark are about to disappear from under our noses, never to return.

Dusky Shark Fact-File Summary

Scientific Classification

1. “Species Implicated in Attacks”, Florida Museum.
2. “The Power of Shark Bites”, Biology of Shark and Rays.
3. “Sharksucker”, Florida Museum.
4. G. CLIFF (1983), “PATHOLOGICAL AND PHYSIOLOGICAL EFFECTS OF STRESS DURING CAPTURE AND TRANSPORT IN THE JUVENILE DUSKY SHARK, CARCHARHINUS OBSCURUS”, SEDAR.
5. Colin A. Simpfendorfer (2002), “Validated age and growth of the dusky shark, Carcharhinus obscurus, from Western Australian waters”, Sci Hub.