Sharks are to the oceans as tigers are to the jungles, as the presence of both apex predators not only signifies the health of their respective environments, but also helps to maintain it. A new study, published on Thursday in the journal Science, suggests shark conservation must go beyond merely protecting them and must prioritize protecting their ecological roles.
The largest sharks of many of the biggest species, such as tiger sharks and great whites, play an oversized role in maintaining the health of oceans, the study, led by Florida International University, found, but these are also the species affected the most by fishing.
These predators help to maintain balance in the marine ecology through their eating habits, the research says. Sometimes their mere presence is enough to scare away prey that would over-consume much-needed plant life in the oceans.
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A variety of sharks are needed for healthy oceans, yet they are under increasing threat from overfishing, climate change, energy mining, and shipping. The study sheds light on the role these fish play in regulating the health of oceans, and why size should be a factor in conservation decisions.
“Some of these roles are really important,” said Mike Heithaus, study co-author and executive dean of Florida International University’s College of Arts, Sciences & Education. “We need to maintain a diversity of sharks in our oceans as well as a wide range of sizes of sharks. We need to rebuild heavily depleted populations and manage for how sharks will function amid climate change.”
Heithaus’s work in Shark Bay, Australia, is the most detailed study yet on the ecological roles of sharks. There, he documented the top-down roles like keeping prey in check. “It’s time to have a conversation about everything sharks are doing to maintain ocean health so we can better prioritize conservation efforts and have the biggest impact,” said Simon Dedman, marine scientist at the university and co-lead author of the study report.
Sharks feed in offshore waters and bring nutrients back to the reef. Others move nutrients that are used at the base of the food chain. They also serve as food themselves and even as scratching posts for fish to remove parasites. But the shark population has plummeted by 71% for oceanic species in the past 50 years. Populations of the top five reef shark species have been depleted by 63%.
“This study verifies what we have long suspected—sharks are critical to ocean health,” said Lee Crockett, executive director of the Shark Conservation Fund, which funded the study. “This landmark study serves as confirmation that marine conservationists, philanthropists, policymakers, and the public need to recognize that sharks are keystone species that have a now-proven significant effect on marine environments.”
Shark conservation becomes all the more critical as global temperatures rise, leading some sharks to move away from the warming waters. As the blue economy expands, people’s encounters with sharks are likely to increase. Finding a balance that protects the sharks most needed for healthy oceans is hitting a critical point. The scientists have recommended policy to increase spatial measures like marine protected areas and fisheries management measures like catch/size limits and gear limitations.
SOURCE: PR Newswire
