“The researchers have documented the longest migration of any silky shark, highlighting its widespread movements in international waters and highlighting the need for global cooperation in shark conservation. The study demonstrates the urgency of establishing regulations to protect marine biodiversity and manage the threats faced by long-distance migrating sharks.”
Researchers documented the longest silky shark migration on record and revealed serious conservation gaps that require immediate attention.
In a recent study, scientists documented the most extensive migration of silky sharks ever recorded (Japanese Greenfinch) traveled 27,666 kilometers in 546 days. Their study reveals important insights into the behavior of this overfished fish. seed It stresses the urgent need for internationally coordinated management measures to prevent further population declines.
This study Journal of Fish Biology, The study was conducted by researchers from the Charles Darwin Foundation (CDF), the Guy Harvey Research Institute (GHRI) at Nova Southeastern University in Florida, the Save Our Seas Foundation Shark Research Center (SOSF-SRC), and the Galapagos National Park Service (GNPD).
A close-up look at silky sharks. Credit: Pelayo Salinas de Leon
Genie's epic journey
Named after the late Dr. Eugenie Clark, the adult female silky shark was tagged with a satellite transmitter attached to her fin near Wolf Island in the Galapagos Marine Protected Area in July 2021. Jeanie embarked on an epic journey that covered 27,666 km over 546 days. Her journey was equivalent to crossing the continental United States from east to west four times, and included two epic migrations westward 4,755 km (halfway to Hawaii) from her tag site into international waters where fishing pressure is high and regulations are few.
Time is of the essence: Researchers attach satellite tags to the silky sharks' fins to track their movements in near real time, a procedure that takes about five minutes. Credit: Pelayo Salinas de Leon
Record-breaking migration proves need for international regulation
The study exceeds previous recorded movements by a factor of almost six and reveals that sharks are extensively using the open ocean beyond national jurisdiction, highlighting the urgent need for regulations to protect marine biodiversity across borders.
Dr Pelayo Salinas de Leon, lead author of the study and co-principal investigator of the Charles Darwin Foundation's Shark Ecology Project, said: “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. Sharks have been roaming the world's oceans for hundreds of millions of years and the boundaries of maps that humans have drawn on paper mean nothing to them. Their long migrations through heavily fished international waters put them at great risk, highlighting the need for a coordinated global response to ensure the survival of this critically endangered species.”
Ocean Voyager. Genie's location estimated from her tag location on Wolf Island, Galapagos Marine Reserve. She was tracked for 546 days with a SPOT tag attached to her fin. Courtesy of Save Our Seas Foundation.
Silky Shark Vulnerability
Silky sharks are particularly vulnerable to overfishing due to their slow growth, late maturity and high demand for the global shark fin trade. Listed as Threatened on the IUCN Red List, silky sharks are one of the most frequently caught sharks in both artisanal and industrial fisheries, making them a conservation priority for CDF and other organizations.
An endangered species, silky sharks tend to coexist with schools of tuna and floating objects, making them especially vulnerable to attack by industrial tuna fishing boats that fish around drifting fish-aggregating devices. Photo by Pelayo Salinas de Leon
International cooperation is important
Remarkably, more than 99 percent of the time Genie was tracked occurred in international waters far west and south of the Ecuador-controlled exclusive economic zone around the Galapagos Islands, highlighting the vital importance of international cooperation in conserving long-distance migrating marine sharks.
Pelagic sharks are under serious threat. Large schools of Silky Sharks, once common around tropical oceanic islands in the eastern Pacific, are becoming increasingly rare due to a global decline in populations, mainly due to overfishing. Photo by Pelayo Salinas de Leon
“Obtaining shark tracks with high location resolution for more than a year is challenging 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 and far offshore, far beyond national management zones and current marine protected areas. This discovery serves as a call to all stakeholders involved in marine conservation and fisheries management to work together to protect these iconic species and the marine ecosystems they live in,” added co-author Dr Mahmoud Shivji from SOSF-SRC and GHRI.
Reference: “The longest recorded migration of silky sharks (Japanese Greenfinch) Reveals Extensive Use of International Waters in the Tropical Eastern Pacific, by Pelayo Salinas de Leon, Jeremy Vaud, Ryan Logan, Jennifer Suarez Moncada, and Mahmoud Shivji, May 17, 2024 Journal of Fish Biology.
Posted on: 2015/01/11
