Why are sharks so important

Hammerhead shark school
Hammerhead sharks school. Pic by Alexander Safonov 

After more than 400 million years of existence in the oceans and seas of our planet sharks are now in serious danger of extinction what would put at serious risk the balance of marine ecosystem. Every year more than 100 million all types of sharks specimens are killed by humans, the most part of them for shark fin soup. This dish, one of the most expensive in Asian cuisine, is enjoying great popularity due to the growing Chinese middle class just because this meal shows the economic position among Chinese society… and today more and more people can afford it. The infamous shark finning, along with shark fishing for its meat or oil, is filling the seabed with mutilated shark and fish markets have thousands of bodies that cannot do its necessary work balancing between sea species. 

shark fin market
Asian fish market with sharks fins

Our insensitivity towards sharks is largely due to the simplistic idea that we have of sharks because of the movie «Jaws» by Spielberg. Since then we associate sharks as a human-killing machines. From this perspective it is much more difficult to realize the importance of shark species to humans. In the past 50 years the population of of large sharks (white shark, bull shark, tiger shark, hammerhead shark and mako shark)has been reduced up to 90% and they are now in the top of the IUCN Red as one of the most endangered species. Who then is the insatiable murderer?

Oceans, to be healthy and balanced, need to have a sufficient population of sharks. As top predators, they have a very important role in the regulation of the food chain and provide a balance absolutely necessary. Their diet is varied thereby to help maintain the oceanic food chain: feed on the most abundant species populations helping to balance between different species. Thus, sharks avoid the formation of «invasions» that monopolize an area, helping to create more diversity on a reef, for example. In fact, there are areas where invasions have occurred in the case of the Caribbean, the lionfish (of Indian Ocean origin) and today are teaching sharks to feed on this species to maintain population balance.

tiburón comiendo pez león
Sharks are being trained in Roatan, Honduras, to help hold off the invasion of lionfish

Another of the tasks that sharks do to maintain healthy oceans is hunting the weaker and sick specimens as are easier to hunt and, as they do not swallow the whole animal, helps ocean scavengers to obtain their food. That behavior helps to create healthier and stronger species that sharks prey improving the species. 

But shark finning is not the only activity that is decimating its population. Bycatch is also doing enormous damage to the existence of sharks. Over the errors caused by this fishing technique many sharks are thrown overboard after being captured… but most are dead or seriously injured. 

Why sharks are so important for our oceans?

Necessary for the existence of the local fishing industry

The loss of these predators in some areas of the planet has shown the effect it produces, called cascade effect. In the North Atlantic the populations of white sharks, hammerhead sharks or thresher sharks fell by 75% in the last 15 years, which has caused populations of different species of rays and small sharks have multiplied. Indirectly, the disappearance of large sharks has sunk a century old industry harvesting scallops. ¿How can this happened? Those rays and small sharks have few natural predators so without big sharks their populations multiply exponentially and increasingly need more food.

When these animals end up in the scallops will have to start eating more of other species, like oysters, again damaging both the seabed and the economy of local collectors. So when these bivalves disappear the seafloor with increase the population of the algae that will grow in an uncontrolled manner, in turn affecting the ecosystem of other fish and crustaceans that will see their environment modified.

The existence of large sharks ensuring balance in the area and their disappearance has sunk an industry that probably did not even know about the importance of sharks to keep their business up and damaged an ecosystem will recover only when sharks return .

Gray shark over reef
The disappearance of the reef sharks fosters the decline in reef fish populations that feed on algae. Image PacificKlaus

In the struggle for Caribbean reef occupation not only occurs among fish, also between algae and corals. The disappearance of sharks in these areas is benefiting the increasing population of species like groupers, reef species that sharks prey. These little fish have a key role in reef health because they feed on algae and other plant species balancing the battle for space between corals and algae. Thus, the disappearance of sharks is helping to defeat the coral algae and coral disappears if you lose a space that ensures biodiversity haven for thousands of species … including some large ocean as whales between feeding include corals expel eggs per billion and in unison.

We should begin to ask if we could live in a world without sharks. The sea absorbs a third of CO2 from the atmosphere, provides food and oxygen and we need to survive as a species healthy. The disappearance of sharks would seriously damage the balance of the oceans affect us directly.

Source Oceana

Deja un comentario

Tu dirección de correo electrónico no será publicada.

Ir arriba