Do sharks sleep?

Sharks do not sleep. Instead they have active and restful periods, where they lower their movement. It was once believed that all sharks need to swim constantly in order to breathe since they extract oxygen from the water flowing through the gills during movement. While some species of sharks do need to swim constantly, this is not true for all sharks. Some sharks such as the ragged-tooth shark have spiracles that force water across their gills allowing for stationary rest.

How do sharks mate?

Male sharks have paired reproductive organs called a claspers, and female sharks have an opening called a cloaca. Fertilization occurs when a clasper is inserted into the cloaca and sperm is injected into the female. When mating begins, a male shark will bite onto the female to hold themselves during mating. This can be a difficult process with both sharks often ending up with wounds. Once mounted, the male inserts the clasper which hold inside the cloaca with a hook until the sperm is released.

What is the difference between sharks and rays?

Sharks have gills on the side of their heads while rays have flattened bodies and their gills slits are located on their under-side.

Are humans part of a shark’s diet?

No. Humans are not part of a shark’s diet. Sharks evolved millions of years before humans evolved. Their diet consists of marine organisms, although some sharks are opportunistic feeders and will eat anything they can find.

What is the biggest shark in the world?

The whale shark is the biggest shark in the world. The largest recorded whale shark measured 12.65 metres and is recorded in the Guinness Book of Records.

Do sharks have bones?

No, sharks don’t have bones. Instead they have skeletons made up of cartilage, a connective tissue strong enough to give support but softer than bone. Cartilage is found in the human ear and nose. Because cartilage is softer than bone, it is very rare to find complete fossil remains of sharks.

Which sharks are now extinct?

There are several sharks that have gone extinct over time, but perhaps the most famous of them all is the megalodon. The megalodon could was the largest shark, growing up to 18 metres and weighing up to 70 tons. Other extinct sharks include Otodus, Ptychodus, Helicoprion, Edestus and Stethacanthus, just to name a few.

How many sharks are killed each year?

Approximately 100 million sharks are killed globally each year, and one of the major incentives for this is the shark fin trade. Some estimates suggest that this is a conservative estimate and as many as 273 million sharks are killed each year.

What should I do when I encounter a shark?

The ocean is beautiful, and a place many of us want to access for fun, relaxation, sport or inspiration. But, if you are not fully aware of all the risks of bathing in the ocean, or are not prepared to take these risks, do not go into the ocean. The ocean is a shark’s home after all – we are just visitors.


Big sharks are predators in their ecosystem (just like lions are in theirs, and we have to be respectful of them in a wilderness area) and are more likely to identify a solitary individual as potential prey, so stay in a group. This also just makes for smart bather behaviour, and sharks are seldom your biggest risk: you should always swim with friends, and know about local rip currents, tides and swell. Identify where your local lifeguards are stationed on duty and familiarise yourself with the National Sea Rescue Institute (NSRI) safety app ( ).


“Big sharks are also primarily visual hunters which allows them to correctly distinguish you from their preferred prey species. Therefore, avoid entering the ocean when it is murky, during darkness or twilight hours when sharks rely on senses other than their vision to locate potential prey. Remember, most sharks also have bad eyesight.


If you encounter a shark, remain as calm as you can and assess the situation without panicking. Panicked, erratic movements are likely to increase the shark’s curiosity, draw it closer to you and possibly send signals similar to those of injured or distressed prey. Use any equipment (camera, surfboard, etc.) you may be carrying to create a barrier between yourself and the shark.


If you see a shark, calmly alert other ocean users around you. Remain in or create a group, and leave the water in a calm and swift, but smooth, manner” (

Do sharks lay eggs or give birth to live young?

Sharks have various modes of reproduction. There are oviparous (egg-laying) species and viviparous (live-bearing) species. Oviparous species lay eggs that develop and hatch outside the mother’s body with no parental care after the eggs are laid. The egg capsules have a yolk-sac that nourishes the developing
embryo. Viviparous species can be separated into two categories: placental (having a placenta, or true connection between maternal and embryonic tissue), or aplacental (lacking a placenta). Among the aplacental species, there are those whose embryos rely primarily on a yolk-sac for nutrition during gestation and those that consume yolk-filled, unfertilized egg capsules (oophagy).

What are your thoughts on catch and release?

Catch-and-release angling can be valuable, with low consequences for the long-term survival of a population, when done responsibly according to best practices. Catch-and-release can equally still be detrimental when these considerations aren’t applied, or when particularly vulnerable animals are caught and don’t survive handling and release. The impacts of catch and release angling can vary from species to species, with very different considerations and consequences for all different sharks, rays and bony fishes (we call these teleosts) – both for their individual stress and responses, and for the survival of their population. For that reason, it’s most useful to assess each species on a case-by-case basis. It’s difficult to give a blanket statement that applies in all cases.


Just so that we know we’re all talking about the same thing: in catch-and-release fishing, fish are unhooked after capture and released back into the water. This is often after a quick measurement and weighing of the fish, followed by photography. We get two different kinds of catch-and-release fishing: for recreation (sport, competition or fun), by anglers in the public and for science.

Scientific catch-and-release is usually to tag, weigh, measure and identify different species, and from this we get valuable information necessary for management and protection. For example, it’s thanks to a scientific catch-and-release programme that we got some of the first evidence that MPAs (Marine Protected Areas) work in SA. Scientists showed that the galjoen, as well as zebra seabreams, white steenbras, Cape stumpnose, white musselcracker and blacktail seabream recovered after the proclamation of the De Hoop MPA. That kind of information is vital to help motivate for other protected areas, or to keep track of the health of populations.


Recreational catch-and-release fishers need a permit, and often adopt voluntary actions (such as barbless hooks) to minimise negative impacts on fish. When done using the best fishing practices and handling procedures, catch-and-release has little negative impact on some fish, but many others (such as silver kob) can suffer barotrauma (stress caused by decreased pressure, often from ascending too rapidly to the surface). Effects include organ rupture and skin haemorrhage, and some animals die post-release – or their behaviour is so altered, their ability to hunt and move is impaired. Some people also wrongly assume that all sharks and rays are stronger and more resilient to catch-and-release, but they too can die a slow death when, for example, they are left on the jetty or shore for too long, or become stressed and exhausted when they fight on a fishing line for too long.


If catch-and-release is happening, how can we be more responsible, informed and minimise harm? There is a lot of work happening along the South African coast to help educate anglers so that they can apply best-practice: check out WWF and Fish For Life’s Responsible Angler guide (, the Fish for Life programme, ORI’s TAG programme ( and this article that uncovers a little of why scientific catch-and-release for tagging can be helpful: Arm yourself with the right knowledge for whichever species you’re handling, and avoid those which scientists point out as too vulnerable.