The researchers documented the most extensive migration of silky sharks ever recorded.Japanese Greenfinch).
This study reveals important insights into the behaviour of this overfished species and highlights the urgent need for internationally coordinated management measures to prevent further population declines.
Genie's epic migration
An adult female silky shark, nicknamed “Genie” after the late Dr. Eugenie Clark, was tagged with a satellite transmitter attached to its fin in July 2021 near Wolf Island in the Northern Galapagos Marine Protected Area.
Genie set out on a 546-day, more than 27,666-kilometer journey. This epic voyage was the equivalent of crossing the United States from east to west nearly four times, including two extensive westward migrations on the way to Hawaii, and traveled 4,755 kilometers from the tagging site into international waters where fishing pressure is high and regulations are minimal.
Genie smashed previous migration records by almost six times, demonstrating the widespread use of this shark in the open ocean, far beyond national jurisdictions. This discovery highlights the urgent need to establish regulations to protect marine biodiversity beyond national jurisdictions.
Understanding Silky Shark Migration
Lead study author Dr. Pelayo Salinas de Leon is co-principal investigator of the Charles Darwin Foundation's (CDF) Shark Ecology Project.
“Understanding the migration routes of silky sharks and other threatened pelagic sharks is crucial to developing effective management strategies to reverse the ongoing global population decline,” Dr. Salinas de Leon said.
“Sharks have been roaming the world's oceans for hundreds of millions of years and the boundaries of maps drawn by humans mean nothing to them. Their extended migration through international, heavily fished waters puts them at great risk and highlights the need for a coordinated global response to ensure the survival of this critically endangered species.”
Silky Shark Vulnerability
Silky sharks are particularly vulnerable to overfishing due to their slow growth, late maturity and high demand in the global shark fin trade. They are classified as “Vulnerable” on the IUCN Red List of Threatened Species and are frequently caught in both artisanal and industrial fisheries, making them a conservation priority for CDF and other organizations.
Remarkably, more than 99 percent of the time Genie was tracked occurred within international waters far west and south outside the Ecuador-controlled exclusive economic zone around the Galapagos Islands, highlighting the vital importance of international cooperation in conserving marine sharks that migrate long distances.
Protecting this iconic species
“Getting shark tracks with high location resolution for longer than a year is difficult at best. In this case, we were able to track Genie for a year and a half, revealing unexpectedly consistent and repeated migration routes over long distances, far offshore, far beyond national management zones and current marine protected areas,” said Mahmoud Shivji, co-author of the study.
“This discovery serves as a call to all stakeholders in marine conservation and fisheries management to work together to protect these iconic species and the marine ecosystems they inhabit.”
Published in Journal of Fish BiologyThis study is an important reminder of the interconnectedness of the global marine environment and the collective action needed to protect marine biodiversity.
About the Silky Shark
The Silky Shark, named for its smooth skin texture, is a pelagic shark commonly found in tropical and subtropical waters around the world.
These sharks are medium-sized and can be recognized by their streamlined bodies and elongated, rounded snouts. They are usually dark grey in colour with a lighter underside, allowing them to blend into the ocean depths whether viewed from above or below.
As Ginny proved, Silky Sharks are highly mobile and use their keen sense of smell and hearing to find prey, feeding primarily on fish and squid. Silky Sharks are considered to be one of the most aggressive sharks, especially when food is available.
The study was conducted by researchers from the Charles Darwin Foundation (CDF), the Guy Harvey Research Institute (GHRI), the Save Our Seas Foundation Shark Research Center (SOSF-SRC) at Nova Southeastern University in Florida, and the Galapagos National Park Service (GNPD).
Image courtesy of Pelayo Salinas de Leon
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