Researchers have recorded the longest migration ever documented for a silky shark (Carcharhinus falciformis).
The study provides crucial insights into the behavior of this heavily overfished species, highlighting the urgent need for international cooperation to prevent further population declines.
Epic journey of Genie
An adult female silky shark, named “Genie” in honor of the late shark ecologist Eugenie Clark, was equipped with a fin-mount satellite transmitter near Wolf Island in the northern Galapagos Marine Reserve in July 2021.
Genie undertook an extensive journey, traveling over 27,666 kilometers in 546 days. This remarkable migration, comparable to crossing the United States coast-to-coast approximately four times, included two major westward migrations halfway to Hawaii, reaching up to 4,755 kilometers from the tagging site into international waters—areas with high fishing pressure and minimal regulation.
Genie's journey broke previous movement records nearly six-fold, showcasing the shark’s extensive use of the open ocean beyond national jurisdictions. This finding underscores the urgent need for regulations to protect ocean biodiversity beyond national borders.
Silky shark migration understanding
Dr. Pelayo Salinas de León, co-principal investigator of the shark ecology project at the Charles Darwin Foundation (CDF), led the study.
“Understanding the migratory routes of silky and other threatened pelagic sharks is essential for developing effective management strategies to reverse the ongoing global population declines,” said Dr. Salinas de León.
“Sharks have been navigating the world’s oceans for hundreds of millions of years, and the boundaries we humans have drawn are irrelevant to them. Their long migrations through heavily fished international waters expose them to significant risks, highlighting the need for a coordinated global response to ensure the survival of this highly threatened species.”
Silky shark vulnerability
Silky sharks are particularly susceptible to overfishing due to their slow growth, late maturity, and high demand in the global shark fin trade. Classified as “vulnerable” on the IUCN Red List of Threatened Species, they are often caught in both artisanal and industrial fisheries, making them a conservation priority for CDF and other organizations.
Remarkably, Genie spent over 99% of her tracked time in international waters to the west and south, far outside the Ecuador-managed Exclusive Economic Zone around the Galapagos Islands. This emphasizes the critical need for international cooperation to protect these long-distance traveling oceanic sharks.
Protecting this iconic species
“Tracking sharks with good location resolution for over a year is extremely challenging. In this case, we tracked Genie for 1.5 years, revealing surprisingly consistent, repeated travel paths over vast distances far offshore, beyond national management and current marine protected areas,” said study co-author Mahmood Shivji.
“This discovery is a call to action for all stakeholders in marine conservation and fisheries management to collaborate in protecting these iconic species and the oceanic ecosystems they inhabit.”
Published in the Journal of Fish Biology, this study serves as a vital reminder of the interconnectedness of the global marine environments and the collective action needed to protect ocean biodiversity.
About silky sharks
Silky sharks, known for their smooth skin, are pelagic sharks found in tropical and subtropical waters worldwide.
These medium-sized sharks are recognized by their streamlined bodies and elongated, rounded snouts. Typically dark gray with a lighter underside, they blend into the ocean depths when viewed from above or below.
Highly mobile, as evidenced by Genie, silky sharks primarily feed on fish and squid, using their acute senses of smell and hearing to locate prey. They are considered one of the more aggressive shark species, especially when bait is present.
The research was conducted by the Charles Darwin Foundation (CDF), the Guy Harvey Research Institute (GHRI), the Save, the Seas Foundation Shark Research Center (SOSF-SRC) at Nova Southeastern University in Florida, and the Galapagos National Park Directorate (GNPD).