We’ve all heard the famous phrase “you are what you eat”, but how true is it? From a biological-chemical point of view, this is a very useful truth. Thanks to the fact that all living things take the chemical elements of food into the body, we can study different tissues and identify the sources of the food consumed. The chemical imprint of food is stored in muscles, skin, bones, blood, teeth, vertebrae, whiskers, etc.

I study the feeding ecology of sharks. I have been doing it for over 5 years now and I really enjoy it. One way to study this behavior is to open their stomachs and sort through the prey you find. This is a traditional technique that currently has alternatives, fortunately, because it is very invasive. Personally, I prefer to see sharks happily swimming in the sea than in the harbor. How to study the feeding behavior of sharks without harming them? Excellent question! One option is to take a biopsy of your muscles. This requires swimming past them carrying a Hawaiian spear like a slingshot with a small arrow on the tip of the spear. When you are very close to the shark, aim the spear at the base of the dorsal fin (I recommend looking at pictures of shark anatomy) and release the spear. The dart will remove a small sample of muscle, and the shark will swim away without much stress.

The movie Shark (Jaws, English), by Steven Spielberg, made us see sharks as hunters of people…

The next stage of our experiment is to take the pieces of muscle to the laboratory where, after using various chemicals and grinding the samples, you end up with a powder. This powder is encapsulated and inserted into a machine called a mass spectrometer. The machine reads the ratios of different elements in shark samples. In my case, I’m interested in the ratio of carbon to nitrogen: carbon tells me if sharks feed in coastal ecosystems or in the open sea, while nitrogen tells me their position in the food chain. Usually, when we think of sharks, we think of top predators that rule the food pyramid from the top levels. But sharks come in all sizes and colors, and there are those that occupy the lower levels of the food web, for example, the leopard shark, the basking shark, and the nurse shark.

At the end of our experiment, we will be able to define which ecosystems are most used by the sharks in our study, and this allows us to protect those areas to ensure that their populations remain abundant. Sharks are the white blood cells of the ocean, responsible for maintaining balance. When we snorkel or dive in a healthy ecosystem, it is normal to see many sharks. Movie Shark (Jaws, in English), by Steven Spielberg, has made us think of sharks as hunters for humans, however, these powerful and intelligent creatures work to keep the fish populations we consume healthy and abundant. Let’s learn more about sharks and learn to respect and love them. (OR)