Silky shark shatters records by swimming over 17,000 miles

Researchers have documented the most extensive migration ever recorded for a silky shark (Carcharhinus falciformis). 

The study reveals critical insights into the behavior of this severely overfished species and emphasizes the urgent need for cooperative international management measures to prevent further population declines.

Epic migration by Genie 

An adult female silky shark, nicknamed “Genie” in honor of late shark ecologist Eugenie Clark, was tagged with a fin-mount satellite transmitter near Wolf Island in the northern Galapagos Marine Reserve in July 2021. 

Genie embarked on a vast journey, covering more than 27,666 kilometers over 546 days. This epic voyage, equivalent to crossing the United States from coast to coast approximately four times, included two significant westerly migrations halfway to Hawaii, extending as far as 4,755 kilometers from the tagging site into international waters – areas of high fishing pressure and minimal regulation.

Genie shattered previous movement records almost six-fold, illustrating the shark’s extensive use of the open ocean, far beyond national jurisdictions. This discovery demonstrates the urgent need to establish regulations to conserve ocean biodiversity beyond areas of national jurisdiction.

Understanding the migration of silky sharks

Study lead author Dr. Pelayo Salinas de León is the co-principal investigator of the shark ecology project at the Charles Darwin Foundation (CDF).

“Understanding the migratory pathways of silky and other threatened pelagic sharks is crucial for developing effective management strategies to revert ongoing global population declines,” said Dr. Salinas de León.

“Sharks have been roaming the world’s oceans for hundreds of millions of years, and the map boundaries we humans have established on paper mean nothing 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 group of species.”

Vulnerability of silky sharks

Silky sharks are particularly vulnerable 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 frequently caught in both artisanal and industrial fisheries, making them a conservation priority for CDF and other organizations.

Remarkably, more than 99% of the time Genie was tracked occurred within international waters to the west and south, far outside the Ecuador-managed Exclusive Economic Zone around the Galapagos Islands. This highlights the critical need for international cooperation in the protection of these long-distance traveling oceanic sharks.

Protecting this iconic species 

“Obtaining shark tracks with good location resolution for over a year is difficult at best. In this case, we were able to track Genie for 1.5 years, revealing unexpectedly consistent, repeated travel pathways of massive distances going far offshore, well beyond national management and current marine protected areas,” said study co-author Mahmood Shivji.

“This finding is a call to action for all stakeholders involved in marine conservation and fisheries management to work together to protect these iconic species and the oceanic ecosystems they inhabit.”

Published in the Journal of Fish Biology, this study serves as a crucial reminder of the interconnectedness of our global marine environments and the collective action required to safeguard ocean biodiversity.

More about silky sharks

Silky sharks, named for their smooth skin texture, are a species of pelagic shark commonly found in tropical and subtropical waters around the globe. 

These sharks are medium-sized and can be recognized by their streamlined bodies and elongated, rounded snouts. They are typically a dark gray color with a lighter underside, which helps them blend into the ocean depths when viewed from above or below.

Silky sharks are highly mobile, as demonstrated by Genie, and primarily feed on fish and squid, using their acute sense of smell and hearing to locate prey. They are considered to be one of the more aggressive shark species, particularly when bait is present.

The research 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 Directorate (GNPD). 

Image Credit: Pelayo Salinas de León

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