Dwindling shark population threatening overall ocean health

Dwindling shark population threatening overall ocean health
A whale shark in Indonesia

One of the world’s most feared predators is under attack. Experts say only about 10% of the world’s sharks remain due to overfishing that could upset the balance of sea life and threaten a variety of local jobs and the global food supply.

Every year sharks are captured by the millions and their fins are removed and sold as the main ingredient in shark fin soup. Their wounded bodies are often dumped back into the sea to die. It’s a cruel harvest that is so widespread it threatens to damage the delicate balance of life in the ocean.

“You take out the sharks, which eat some mid-class predator in the ocean, if you take out those the mid-class predator group expands dramatically,” said Randall Brummett, senior aquaculture specialist for the World Bank. “They eat a lot more of the fish lower on the food chain which in turn eats less phytoplankton or zooplankton, which in turn can create massive algae blooms.”

In other words, sharks are a vital part of a healthy and vibrant food chain – in which each link relies on the others for survival – and that includes man. 

“We are sea creatures, too, as dependent on the ocean as the sharks, the turtles, the whales,” said oceanographer Sylvia Earl. “Without the ocean, none of us, ourselves included, could survive.”

The new measure of the global health of the ocean, known as the Ocean Health Index, monitors 10 vital aspects of ocean health, including biodiversity – the interconnected and inter-dependent web of species that if managed sustainably results in abundant resources both in the water and on land.

 “Biodiversity is the number and variety of species in the ocean. And what is important to remember is that it really underpins all of the ecosystem services that we rely on the oceans to provide,” said Elizabeth Selig, a marine ecologist. “So, for example, the corals that make up a coral reef are responsible for providing coastal protection, and fisheries, and the tourism that supports livelihoods around the world.”

The global 2012 Ocean Health Index score for Biodiversity is 83 out of 100, an indication that overall man is managing biodiversity well. And there’s evidence that when it comes to sharks, he may be improving. Some countries are changing policies in an attempt to reduce shark finning, while others are turning to sharks as a living resource.

Gentle giants known as whale sharks, once overfished as food, are now being considered as a main attraction for a growing tourism industry around the world. “People are beginning to care about sharks, not just as creatures that they once feared, but now, creatures that have a charisma,” said Earle. 

In fact, sharks are far from the menace some believe them to be.  Shark attacks killed 12 people worldwide in 2011, while people kill more than 30 million sharks every year – a very real threat to biodiversity and life on Earth.

“The ocean has an amazing capacity to rebuild itself. However, we have exploited so many species so much that it seems very, very difficult for them to come back,” said oceanographer Enric Sala. “For example, some sharks in the Mediterranean have been reduced by 99%.”

You can learn more about shark finning, shark conservation efforts and the overall health of the ocean and what it means to you by visiting http://www.OceanHealthIndex.org.