‘I was terrified. The metal of the cage hit the boat with a loud thud, and the waves rose high. I had just gotten my diving license the week before and couldn’t swim properly. The first shark swam towards the bait. I started to feel warm and cozy. Would I really do this? But when it became clear that the animal had little interest in meat, she became calmer. As soon as I entered the cage, my fear turned into fascination. Sharks have lived on this earth longer than trees, but we barely know anything about them.
PhD candidate Gibbs Kogoro now works at Wageningen University. After advice from a study advisor, he ended up on a boat in South Africa that allows tourists to dive with white sharks. This practical training was closer to his childhood dream than studying medicine in America, which he briefly fled. “At seven o’clock on a Saturday morning, when I was eight years old, I wasn’t in bed, but I was watching nature documentaries about lions, rhinos and wild animals. I thought it was strange that people from all over the world would come to my country to see things.” I rarely saw it. The main nature parks were just a few hours drive from our home in Nairobi, but we rarely went there because I had eight brothers and sisters. My dream was over Wildlife– A biologist, but I did not recognize myself in the people I saw in the documentaries. That’s why it doesn’t seem like an option to me.”
After six years on a dive boat, you ended up studying biology and researched the genetic diversity of hammerhead sharks in South Africa for a master’s degree in genetics. What came out of that?
“Hammerhead sharks are an endangered species worldwide. They occur in South Africa but we didn’t know much about the local population. My research showed that there is little diversity in the population. With the predatory species producing only a few young per year, which takes Long time to grow, you want more diversity I discussed these findings at conferences, and after a year the species was granted protected status in South Africa and then I realized: if I wanted to make a difference, I had to do more research.
Research itself does not always immediately lead to new policy. Often more is needed.
“Right. That’s why I think science communication is important and I know all the fisheries policy makers in the countries where I conduct research and give workshops and talks to local fishermen. In a few years there may be no more sharks. It’s not enough to publish a scientific paper. You have to To be more creative.”
Another way Kogoro disseminates his research is through documentaries. This is what he and other biologists suggest National Geographic documentary film On color change in white sharks. To do this, they cleverly used the behavior of predators, which jump out of the water during an attack on a seal and thus can be seen in full. Animals only do this in South Africa. It is not known why. The researchers lured the sharks with a fake seal. For the stamp, they mounted a panel colored in shades of gray on a floating scaffold. The moment the shark jumped out of the water, filmed from the boat. This allowed scientists to correctly compare the shark’s color with the grayscale palette.
You mentioned in the documentary that sharks seem to turn pale when attacked. How can a shark change its color?
“We think this is driven by adrenaline that is released during an attack. We have done tests in the laboratory on white shark skin tissue in which we exposed it to adrenaline. This caused the melanocytes, the melanocytes, to shrink and become lighter. Under the influence of melanocyte-stimulating hormone, they produced The cells have more pigment and become darker.
And because it becomes lighter it is less noticeable?
“This is our hypothesis. This could explain why white sharks always appear out of nowhere. This pale color gives them an advantage in the 10-15 meter depth where they hunt. There is still sunlight there, but much less. Everything there is pale in color.” .
“Unfortunately we have only been able to photograph a few sharks. I would like to continue my studies, but first I must find new funding. This is difficult. Shark fanatics like me love solving such mysteries, but they have no direct applications to humans.” While this may make people view these animals more positively.
For his doctoral research, Kogoro is also looking at skin color changes in blacktip reef sharks in the Maldives. They increasingly have white spots.
Is it a genetic defect that often occurs due to inbreeding?
“This is our hypothesis. There is inbreeding due to severe overfishing. The colouration, known as leucism, is occurring in more and more animal species. People know it as vitiligo. Leucism may be associated with other abnormalities such as infertility and deafness. We do not yet know what the consequences will be for fish Shark, but I’m not sure and let’s say you do this with, for example Gene drives [een toepassing van genetische modificatie om snel en efficiënt een genetische eigenschap door een populatie te verspreiden] If you can solve it, it will always be temporary because you are not doing anything about the underlying problem: human consumption.
Shown in your presentations are graphs from the WWF Shark and Ray Meat Network report from 2021. What is striking is that Spain dominates the global trade in shark meat as an exporter, both in terms of value and volume. Italy is the largest importer by value.
“Shocking, isn’t it? Everyone always looks to China when it comes to the shark meat trade, but Europe is responsible for 22 percent of the trade. Often people don’t even know they’re eating shark or ray because it’s disguised as something on the menu, though… for example. Calpsifish In Germany, Calderada de Pata Roca In Portugal or as Rock salmon in England. It is time to look at ourselves instead of pointing the finger at the East.
Do you see yourself more as a researcher or an environmentalist?
“Deep in my heart I’m a researcher, and I always have been. Someone who loves discovering new things and talking about them. But if we’re not careful, there won’t be any more sharks to tell good stories about soon, and that definitely makes me a conservationist as well.”
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