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Thursday, Aug. 1, 2024 (Halifax) _ Shark conservation must go beyond simply protecting shark populations -- it must prioritize protecting the ecological roles of sharks, according to new research that found the largest of many of the biggest shark species play an oversized role in healthy oceans but are often the most affected by human activity.

Sharks help shape and maintain balance in an ecosystem from the bottom-up. That means a variety of sharks in a variety of sizes are needed, yet their contributions are under threat from overfishing, climate change, habitat loss, energy mining, shipping activities and more.

The study, led by Florida International University (FIU) and Dalhousie University, was published today in Science and sheds new light on the role sharks play in healthy oceans and why size should be a factor in conservation decisions.

"Sharks are important in many ways – from helping to protect seagrass beds from overgrazing to keeping seal populations in check, sharks are key players in oceans globally," said co-author Aaron MacNeil, a professor of Biology at Dalhousie and CRC Chair in Fisheries Ecology.

"This study lays out the various roles that sharks play in marine ecosystems and makes the case that healthy shark populations correspond to healthy oceans. Understanding how sharks contribute to ecosystem health is critical for deciding what steps to take in restoring them to full function."

Besides helping to maintain balance within the food web, reef sharks feed in offshore waters and bring nutrients back to the reef. Others move nutrients around that are used at the base of the food chain. Sharks can also serve as food for other species and even as scratching posts for fish to remove parasites. Shark abundance has, however, plummeted by 71 per cent for oceanic species in the past 50 years. Populations of the top five reef shark species have been decreased by 63 per cent.

As their numbers plummet, so too does their important role in ocean health.

"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, a researcher at Florida International University and lead author of the study.

The issue of shark conservation becomes all the more critical as global temperatures increase, leading some sharks to head to new areas to find temperatures they can thrive in.

"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."

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Media contact:

Alison Auld
Senior Research Reporter
Communications, Marketing and Creative Services
Dalhousie University
Cell: 1-902-220-0491
Email: alison.auld@dal.ca