Shark Fishing Has Negative Effects On Coral Reefs

As the apex predators are removed from the reefs, mid-level predators flourish and diminish other species that reefs rely on.

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The United Nations estimates 23 million sharks are harvested each year to quench the demand for shark fin soup. Hammerhead shark. Photo credit: Thinkstock
John Virata

Canadian and Australian scientists have determined that shark fishing has a detrimental effect on coral reefs. They found that when sharks near coral reefs decline, the number of herbivorous fish also declines as the population of mid-level predators, such as snappers, rises. Herbivorous fish are important to reef ecosystems because they eat algae that can oftentimes overwhelm young corals.

The scientists studied reefs about 300 kilometers off the coast of Australia in an area where Indonesians have been fishing for sharks for several centuries and continue to do so under an Australian-Indonesian agreement.

“The reefs provided us with a unique opportunity to isolate the impact of over-fishing of sharks on reef resilience, and assess that impact in the broader context of climate change pressures threatening coral reefs,” said Jonathan Ruppert, a University of Toronto Ph.D graduate who was part of the team that conducted long term monitoring of the reefs of Australia’s northwest coast. Ruppert was also lead author of the study.

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“Shark fishing appears to have quite dramatic effects on coral reef ecosystems. Given that sharks are in decline on reefs worldwide, largely due to the shark fin trade, this information may prove integral to restoration and conservation efforts,” Ruppert said.

The study says that reef sharks are closely tied to certain coral reefs and that even small Marine Protected Areas can be effective in protecting sharks and allowing coral reefs to recover from such maladies as coral bleaching or destructions from cyclones or hurricanes. The study will appear in the September 28 issue of the PLoS One Journal.

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Article Categories:
Fish · Lifestyle