Open Menu
Get Regular Updates!

Earth

Search
|Investigating the death of a great white shark
image|Tomasz Pedlow and Oceans Campus Investigating the death of a great white shark

Investigating the death of a great white shark

The mysterious death of a great white shark provided an opportunity for scientific insight and raising public awareness. Warning: this article contains graphic images.

Investigating the death of a great white shark

On a cold morning in Mossel Bay, South Africa, researchers, interns and members of the public gathered for a unique experience. They came to witness the dissection of a 3.2 meter great white shark.

The shark had been the fourth in a spate of recent shark deaths. In the previous weeks, three other sharks washed up in Gansbaai, 300km away.

Investigations determined they were the rare victims of orca attacks. When Oceans Research scientists and interns heard of this, many assumed this latest shark had also fallen victim to orcas.

But early investigation showed this wasn’t the case.

View Larger
Image|Tomasz Pedlow and Oceans Campus

Another killer?

The victims of the orcas had visible wounds and missing organs. This new shark washed up whole.

It had fishing line trailing from its mouth, so many people suspected illegal fishing.

Dr Enrico Gennari was given permission by the government to dissect the shark. He quickly organised its removal from the beach and put together a team to conduct the dissection.

The main goal of the dissection was to advance scientific understanding of great white sharks. Additionally the dissection would help to determine the cause of death.

By conducting the dissection in a public venue, the event would help to educate the public as well.

Dr Gennari, Dr Malcolm Smale and Dr Alison Towner performed the dissection with the help of field specialists from Oceans Research.

Taking measurements

The first step is a morphometric assessment. This means taking a huge number of measurements all over the shark’s body.

Scientists rarely get the opportunity to get detailed body measurements from sharks. This is because they move fast, surface only briefly and rarely wash-up on beaches.

View Larger
Image|Tomasz Pedlow and Oceans Campus
Oceans Campus scientists taking measurements on the shark

So why do these measurements matter? Well, they help us understand the evolution of a species.

In 2010, scientists measured the variation in position teeth from great white sharks and two extinct shark species as well as their serration pattern and growth rates. Using this data, they determined that great white sharks have teeth that are more similar to an extinct group of mako sharks than to megalodon.

This evidence suggested that great whites may have evolved from this extinct group of mako sharks.

Shark measurements can be useful in other ways too. We can compare the data collected with data from other sharks of different ages and genders. This helps scientists build up a bigger, better picture of how sharks grow and mature.

Beneath the skin

The second step of the dissection is the internal examination of the shark.

The first incision is made into the shark. Credit: Tomasz Pedlow and Oceans Campus View Larger
Image|Tomasz Pedlow and Oceans…
The first incision is made into the shark
The liver is removed to be weighed. Credit: Tomasz Pedlow and Oceans Campus View Larger
Image|Tomasz Pedlow and Oceans…
The liver is removed to be weighed

To begin with, the examiners made a large cut along the shark’s abdomen. After lifting back the thick layer of skin and tissue, the shark’s liver became visible. Sharks’ huge livers are rich in nutritious squalene, which is likely why they were eaten up during the orca attacks.

The liver of a great white shark is also a good indicator of the animal’s health. If a shark is under long term stress, the condition of the liver will show it. This shark’s liver was large and unblemished, suggesting the animal was very healthy when it died.

Some hormones in the blood are a good indicator of stress. Examiners took samples to test for stress hormones. High levels of stress hormones were detected lending weight to the theory it was a victim of illegal fishing.

The examiners then moved on to the stomach contents.

The first thing removed from this shark’s stomach was the remains of a seal. This wasn’t surprising, because there was a seal colony close by.

View Larger
Image|Tomasz Pedlow and Oceans Campus

What was more damning was the fishing hook they found in the stomach. It was still connected to the line seen trailing from the shark’s mouth.

View Larger
Image|Tomasz Pedlow and Oceans Campus
The fishing hook that was pulled from the shark's stomach

Cause of death

Acheley Nortje is a marine field specialist and an experienced fisherman. He analysed the fishing gear found in shark’s stomach.

He explained to the public that some people in the fishing community don’t believe sharks are endangered and that catching them carries a certain prestige among their peers.

The type of line and hook used suggested this angler was specifically targeting great white sharks. Red marks around the shark’s nose were likely caused by the steel line scraping across its skin as it thrashed.

Acheley explained that great white sharks need water moving over their gills to breathe, and they get tired quickly. The damage to the fishing gear suggested the shark got hooked and fought until the line broke.

The shark would have broken free, but its escape left it too tired to swim. This meant it couldn’t keep water moving over its gills and couldn’t breathe.

The high levels of stress hormone detected indicated the shark’s heart would have been racing at the time it got caught. This made things worse while it was already struggling to get enough oxygen.

Cause of death? Exhaustion and stress caused by illegal fishing.

View Larger
Image|Tomasz Pedlow and Oceans Campus
The fishing line can be seen trailing from the shark's mouth

Did any good come from it?

As Enrico told me, “It is a very sad situation, but as a scientist, we try to make the most of it.”

The death of the shark was tragic, but a dissection allowed some good to come out of it.

By holding the dissection in a public area, the public were able to watch and ask researchers questions about great white sharks.

This bringing together of experts and the public was a great opportunity for community education.

And on the scientific front, researchers were able to collect a huge amount of data from the shark. This will no doubt contribute to improving our understanding of this misunderstood animal.

Particle
Puns

Postcard #9
The science story accelerator
The rotation of the earth really makes our day

Republish

Creative Commons Logo

Republishing our content

We want our stories to be shared and seen by as many people as possible.

Therefore, unless it says otherwise, copyright on the stories on Particle belongs to Scitech and they are published under a Creative Commons Attribution-NoDerivatives 4.0 International License.

This allows you to republish our articles online or in print for free. You just need to credit us and link to us, and you can’t edit our material or sell it separately.

Using the ‘republish’ button on our website is the easiest way to meet our guidelines.

Guidelines

You cannot edit the article.

When republishing, you have to credit our authors, ideally in the byline. You have to credit Particle with a link back to the original publication on Particle.

If you’re republishing online, you must use our pageview counter, link to us and include links from our story. Our page view counter is a small pixel-ping (invisible to the eye) that allows us to know when our content is republished. It’s a condition of our guidelines that you include our counter. If you use the ‘republish’ then you’ll capture our page counter.

If you’re republishing in print, please email us to let us so we know about it (we get very proud to see our work republished) and you must include the Particle logo next to the credits. Download logo here.

If you wish to republish all our stories, please contact us directly to discuss this opportunity.

Images

Most of the images used on Particle are copyright of the photographer who made them.

It is your responsibility to confirm that you’re licensed to republish images in our articles.

Video

All Particle videos can be accessed through YouTube under the Standard YouTube Licence.

The Standard YouTube licence

  1. This licence is ‘All Rights Reserved’, granting provisions for YouTube to display the content, and YouTube’s visitors to stream the content. This means that the content may be streamed from YouTube but specifically forbids downloading, adaptation, and redistribution, except where otherwise licensed. When uploading your content to YouTube it will automatically use the Standard YouTube licence. You can check this by clicking on Advanced Settings and looking at the dropdown box ‘License and rights ownership’.
  2. When a user is uploading a video he has license options that he can choose from. The first option is “standard YouTube License” which means that you grant the broadcasting rights to YouTube. This essentially means that your video can only be accessed from YouTube for watching purpose and cannot be reproduced or distributed in any other form without your consent.

Contact

For more information about using our content, email us: particle@scitech.org.au

Copy this HTML into your CMS
Press Ctrl+C to copy

We've got chemistry. Want something physical?