Marine fauna: better understand sharks
Shark is all the rage lately. Especially since the shredded body of a fisherman was found on Flamingo Island last December. Should we be afraid?
Who hasn’t seen Jaws? A franchise that certainly contributes to the bad press given to the Sharks. Considered to be giant predators of the oceans, they spread fear.
A fear that has gripped some Mauritians since a fisherman’s lifeless body was torn apart by sharks on Flamingo Island last December. Since then, several videos have been circulating on social media where you can see sharks in several areas of the island (see box). Why are they walking around? Explanations with environmental engineer and oceanographer Vassen Kauppaymuthoo.
He states from the beginning that sharks are part of the marine ecosystem and play an important role in the ecological balance of the oceans. “Sharks have existed in oceans and lagoons for over 420 million years. There are over 500 species of sharks grouped into 35 families,” he says.
However, Vassen Kauppaymuthoo says their population has been declining rapidly over the past few decades. “Especially because of shark fins destined for Asian countries that kill over 100 million sharks every year. »
The collapse of fish stocks around the world has also affected the shark population. Collapse related to overfishing and industrial fishing (one-third of fish stocks have been depleted, one-third will be depleted soon, and the final third is estimated to be depleted by 2050), as well as climate change in large non-toxic zones.
The result: sharks now have to find new territories with an imbalance at the species level, says Vassen Kauppaymuthoo. “While opportunistic species such as bulldog sharks and tiger sharks are increasing, reef sharks (white tip, black tip) and oceanic blue sharks are also disappearing. »
What about white sharks? “I only saw it once while diving off the coast of Flic-en-Flac. Prefers cold waters like Capo in South Africa. »
Why do they walk around us?
The presence of sharks near our shores and even in lagoons represents a change in behavior and territory. Oceanographer says this can be attributed to the presence of fish farms and marinas/fishing ports where fishermen gut the fish and throw them back into the sea.
Vassen Kauppaymuthoo cites the example of what happened on Reunion Island. “The ‘shark crisis’ began in 2011, with the establishment of the Saint Paul Marine Farm. Between 2000 and 2011, the number of attacks increased from 3 in 10 years to 25 in 2011-2021, 11 of which even swimmers died in one meter of water! »
The species involved in unprovoked attacks are mainly bulldog and tiger sharks, he continues. Therefore, he believes that the presence of sharks in our waters can be attributed to the presence and development of aquaculture farms that attract territorial bulldog sharks and slowly destroy other reef shark species.
According to Vassen Kauppaymuthoo, the shark is looking for prey to feed on. However, hunting wild prey requires a lot of energy and fishing performance is often mediocre. “Sometimes we come across schools of dolphins being followed by sharks – I’ve personally seen some in the west – because they’re part of their prey. This is one of the reasons why swimming with dolphins in the open ocean is dangerous. »
He points out that fish farms have high concentrations of fish that are easy to catch in murky waters by ripping the nets with their sharp teeth. Moreover, he says, additional nets or shark hunting by aquaculture farms will not change the situation.
“This situation is particularly worrying after more than 42 years without a fatal attack. This could indicate an increase in attacks in Mauritius. This would be disastrous for the people of Mauritius as well as tourism and maritime activities. However, for over 15 years I have reported on the risk of sharks associated with aquaculture activities. »
The oceanographer advocates a scientific study to determine the number and species of sharks present in the island’s lagoons, including in the east, where most of the aquaculture activity takes place. This will clarify the situation and take necessary action. “I can’t imagine what would happen if we went through a ‘shark crisis’ like Reunion. This is a risk that should be taken very seriously. »
Reef sharks are sometimes seen during the day. Before Mauritius’ coastal areas were developed, they occupied the ecological niche of our lagoons. They are found in the lakes of St. Brandon. Vassen Kauppaymuthoo recalls that a bulldog shark about two meters long was caught in a channel dug for fishermen in the lagoon at La Preneuse. In general, sharks are quite shy and do not like noise and disturbance caused by human activity. “They have a very powerful electromagnetic field sensor system, Lorenzini lamps. »
Pay attention to the videos in circulation
Vassen Kauppaymuthoo asks to be careful with pictures and videos found on social networks from other parts of the world. He recommends checking the source before posting a photo or video to avoid spreading false information.