Shark dandruff aiding in preservation of coral reefs: Insights on its impact.
In a groundbreaking study, researchers have found evidence of a significant decline in shark populations over the past 7,000 years, with the steepest decline occurring in the late 20th century. The study, published in the Proceedings of the National Academy of Sciences, was made possible through the generous support of various organisations, including Panama's Secretariat for Science and Technology (SENACYT), the Smithsonian Tropical Research Institute (STRI), and the Save Our Seas Foundation, among others.
Erin Dillon, a researcher, spent two years in Panama studying shark denticles from a fossil reef in Bocas del Toro and modern reefs. Shark scales, known as dermal denticles, reduce drag and protect sharks from abrasion and ectoparasites. Dillon's research shows that denticle assemblages can be used to help reconstruct past shark communities.
The oldest samples contained a higher proportion of denticles from fast swimming, pelagic sharks like hammerheads and requiem sharks. However, all denticle types declined over time, but those from commercially valuable, fished species declined the most. This decline coincided with the development of a shark fishery in Panama, which selectively targeted pelagic sharks.
Today, nurse shark denticles are relatively more common than they were in the past. The decline in denticles belonging to nurse sharks, which are infrequently harvested, suggests indirect factors like the loss of coral reef habitat or prey items were also to blame.
The study further sheds light on the importance of sharks in ocean health and the great diversity and functioning of coral reefs. Sharks play crucial roles in maintaining balance within these ecosystems. The Smithsonian Tropical Research Institute, headquartered in Panama City, Panama, was instrumental in this study. The Institute furthers the understanding of tropical biodiversity and its importance to human welfare, trains students to conduct research in the tropics, and promotes conservation by increasing public awareness of the beauty and importance of tropical ecosystems.
It's important to note that placoderms and marine reptiles, larger predators, ruled the oceans for millions of years before sharks, but extinction events allowed sharks to survive and become top predators. Aaron O'Dea, a STRI paleobiologist, studies ecological and evolutionary processes across time using fossil and modern coral reefs.
The oldest known denticles are approximately 455 million years old. This research was published with the DOI 10.1073/pnas.2017735118. The findings underscore the need for continued research and conservation efforts to protect these vital marine species and their habitats.
