Sharks play an essential rol in the health of our oceans

Information, News, Research

3 additions to Freek Vonks ‘Naar de haaien’

By Dorien Schröder, marine biologist and shark scientist

Freek Vonk speaks passionately about sharks, and generates passion for sharks in a generation of young kids, which is fantastic. In his documentary ‘Naar de haaien’, Freek talks about sharks and the threats to their existence. Here and there I missed some some more up-to-date and factual information, sometimes a certain nuance and some facts mentioned are not quite right. So please read an addition to the documentary, written by a marine biologist with years of experience in shark research.


Fishing whole sharks is now the biggest threat

  1. Shark fin soup is the biggest threat to shark populations

This statement has not been true for a number of years. Thanks to a number of organizations that have provided education and campaigns in Asian countries, something briefly mentioned in the documentary, the demand for shark fins in China has dropped by 70% and the price has halved. 85% of the Chinese population says they eat less or no shark fin soup thanks to this information, according to a 2015 article [1]. This shows that good information can be extremely effective in the protection and conservation of animal species such as the shark. But even though the threat of shark finning has become much smaller, it has become clear in recent years that overfishing is currently the biggest threat to shark populations throughout the world.

2. Shark meat is not tasty

Contrary to what is said in the documentary, shark meat is in high demand on the market. Fillet of the herring shark is regularly sold as tuna because of the same texture of the meat, and from smaller sharks the meat is sold as ‘flake’ or ‘rock salmon’ in the fish-and-chips. Even in the Netherlands, where eating bycatch is now becoming popular, you can buy dogfish at the fish market, and ray wings are on the menu in more and more restaurants. Spain, Portugal and France land large numbers of porbeagle and blue shark, which are sold on the fish markets and threaten the Atlantic populations of these species.[2].

And not only the meat is an important commodity; shark cartilage from sharks and liver oil from sharks are also popular, including for medicine and make-up. Now that the shark fins are somewhat out of fashion, there is a new trade arising: that in gill rakers. In particular, manta rays (‘flat sharks’) have large gill plates, which are now sold on the Asian market as an ingredient for medicines. His iniated a slaughter of manta rays, especially since the sharks have become less numerous[3].

Manta gill rakers: new ingredient for Chinese ‘medicine’.


  1. The ‘questionable’ cage dive industry

Attracting sharks to a cage is done as follows. Sardines are with salt water in a bucket, and is continuously being thrown overboard in small quantities. The scent trail is taken bythe current and if a shark swims through it it will follow it towards the source, the boat. The whole story of a drop of blood in a swimming pool is just nonsense: unless a shark swims through the molecules of the blood, he will not notice it. This also means that all sharks coming to the boat are already present in that area and are not lured to a tourist area, and that impression could arise from the documentary. The documentary is unclear about thatbsp;

The sharks are then kept by the boat with a piece of bait. In South Africa that piece of bait is always pulled away in time so that the shark receives no food and no reward. The shark will therefore not associate boats with food. Most sharks lose interest after a while, since it is not smart to use so much energy to try to get hold of a piece of fish in vain. Furthermore, sharks are not smart enough to see the people aboard the boat or in the cage as separate preys, so they will never associate a person in the sea with a few living creatures on a boat where they ever smoke food.

For these reasons, I do not agree that cage diving with white sharks, as happens in South Africa, is dubious. In fact, South Africa was the first country that made white sharks a protected species, and the owner of White Shark Africa was a fierce supporter of that movement [4] . This cage dive company is located in Mossel Bay, a place where an island full of seals (Seal Island) lies 600 meters off the coast[5]. Though cage diving is also just off the coast, there have never been any incidents with visitors to the beach there.

  1. The‘rogue shark’

This piece would of course not be complete without the shark bite. According to the documentary, Freek Vonk was bitten by a ‘rogue shark’, which was also said by a number of shark researchers (not specified by name). This is interesting, since the existence of rogue sharks has for years been regarded as a myth by shark researchers [6] . The term rogue shark comes mainly from the movie ‘Jaws’, the negative effects of the way people see sharks are still noticeable. 

Behavior can be multi-interpretable and scientists can disagree on this. So this is my interpretation of what happened. The behavior of the Caribbean reef sharks showed that this was a dive in which the sharks were lured with bait. There are then several sharks in search of food, because they smell it there. They are then, as it is called, in scavenger mode and can then exert a little more dominance than normal.

When you do a shark dive with bait without a cage, you learn that you have to dive down immediately. The reason? Sharks ominate each other. The shark that is highest in the water column is the most dominant. They seek this out by looking at each other’s size, body language, and pushing each other away and sometimes biting when the other way does not work [7] . So this is in my opinion why the problem with Freek Vonk arose. He lay on the surface between sharks that were clearly searching for food in scavenger conditions. Because he lies on the surface, he unconsciously shows the sharks that he is dominant and sharks also see other types of difference in dominance [8] . But he is not bigger, nor is his body language correct, because he does not make eye contact with the sharks, for example. That’s why he gets a push from a shark, he has to leave. If he then does not listen, he is indeed bitten. Not by a rogue shark, but by the shark that was dominant at the time and found that his position was challenged by Freek.

The bite


As I said before, Freek Vonk is a fantastic ambassador for biology. But I just wanted to rectify these three mistakes. I add a number of websites below as reference, but for those who want to know more, scientific articles are available on request.

  7. (31 maart)



Comments are closed.

Contact info

You can contact us at +31 (0) 6 12195593 Or per email at:

Privacy Statement

Read our privacy statement here

Partner organisations

De Dutch Shark Society is proud to be a partner of several organisations. Check out our Mission page!
Show Buttons
Share On Facebook
Share On Twitter
Share On Pinterest
Contact us
Hide Buttons