The largest sharks, including species such as tiger sharks and great whites, play a pivotal role in maintaining the health of marine ecosystems. Despite their importance, these apex predators are significantly impacted by fishing activities. Their feeding habits help maintain ecological balance, and their presence alone can deter prey from over-consuming essential plant life. However, various shark species that are essential for ocean health are under increasing threat from overfishing, climate change, energy extraction, and shipping activities.
A recent study led by Florida International University (FIU) highlights the vital role sharks play in ocean health and emphasizes the need to consider shark size in conservation strategies.
Mike Heithaus is a co-author of the study and executive dean of FIU’s College of Arts, Sciences & Education. Heithaus said, “When we look around the world, we see that sharks can play lots of different roles in ecosystems – and some of them are really important. That means we need to maintain a diversity of sharks in our oceans as well as a wide range of sizes of sharks. It also means we need to be rebuilding heavily depleted populations and managing for how sharks will function in oceans that are changing due to human uses and climate change.”
Heithaus' research in Shark Bay, Australia, spanning over two decades, represents the most comprehensive study globally on sharks' ecological roles. The findings document how sharks control prey populations and contribute to the overall health of marine ecosystems.
"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, FIU marine scientist and co-lead author.
Sharks contribute to ocean health by feeding in offshore waters and transporting nutrients back to reefs. Some sharks move nutrients essential for the base of the food chain, while others serve as a food source themselves or even as scratching posts for fish to remove parasites. However, the abundance of oceanic sharks has decreased by 71% over the past 50 years, and populations of the top five reef shark species have declined by 63%.
"This study verifies what we've 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 alike need to recognize that sharks are keystone species that have a now-proven significant effect on marine environments."
As global temperatures rise, predator conservation - on both land and seas - becomes increasingly critical. Warming waters cause some shark species to migrate, potentially increasing human-shark encounters as the blue economy grows. Ensuring the protection of sharks vital for healthy oceans is at a critical juncture. The scientists recommend policies to expand Marine Protected Areas and implement fisheries management measures, such as catch/size limits and gear restrictions.
