A groundbreaking study has, for the first time, mapped the population structure of silky sharks (Carcharhinus falciformis) across the Eastern Pacific Ocean—offering valuable data that could significantly enhance the conservation and management strategies for this vulnerable oceanic species.
Silky Sharks: One of the Most Caught Oceanic Sharks Worldwide
Silky sharks are the second most commonly caught oceanic shark species globally, just behind blue sharks. They inhabit tropical waters and are frequently caught as bycatch in pelagic fisheries using longline and purse-seine gears, as well as small-scale coastal fishing operations.
Despite concerns over overfishing, effective conservation has been hindered due to a lack of comprehensive data—especially regarding how silky shark populations are distributed throughout the Pacific region.
30 Years of Data Combined for the Most Extensive Silky Shark Study to Date
In a major collaborative effort, researchers from UC San Diego’s Scripps Institution of Oceanography, The Nature Conservancy, and the Inter-American Tropical Tuna Commission (IATTC) compiled over three decades of silky shark data.
Led by marine ecologist Brendan Talwar, the team analyzed:
- Population genetics
- Tagging and movement patterns
- Life history traits
- Fisheries data from nearshore and offshore sources
This resulted in the most complete scientific dataset on silky sharks ever assembled.
“This study takes us a huge step forward in creating more accurate population models for silky sharks,” said lead author Brendan Talwar, postdoctoral scholar at the Semmens Lab, Scripps Oceanography.
Surprising Findings: Distinct Silky Shark Stocks in the Eastern Pacific
Published in the journal Reviews in Fish Biology and Fisheries, the study reveals a three-stock population model for silky sharks in the Eastern Pacific:
- Northern stock
- Central stock
- Southern stock
Each of these appears genetically and behaviorally distinct from populations in the Central and Western Pacific Ocean, challenging previous assumptions that silky shark populations were well-mixed across the ocean.
This model could revolutionize shark conservation policies, influencing how the species is managed across nearly 50 million square kilometers of marine ecosystems.
Juvenile Silky Shark Habitats: More Complex Than Expected
The study also uncovered critical insights into juvenile silky shark habitats. While juveniles were known to inhabit areas near the continental shelf, researchers found evidence of offshore nursery grounds, where larger pelagic fleets often catch young sharks.
Bycatch Data Highlights Urgent Conservation Needs
By analyzing bycatch data, researchers discovered:
- 81% of silky sharks caught by purse seine fisheries (using fish aggregating devices or FADs) are juveniles.
- 45% of those caught by longline fisheries are also juveniles.
“Juvenile sharks may be drawn to floating objects in open oceans because they provide shelter, food, and safety,” explained Talwar.
These findings stress the urgent need for bycatch reduction strategies to protect immature sharks that are critical for population recovery.
A Model for Global Shark Conservation Efforts
Study co-author Lyall Bellquist, an independent fisheries scientist, emphasized the success of multi-institutional collaboration.
“This project shows the power of bringing together data and expertise from across the globe to inform science-based conservation of vulnerable shark species,” said Bellquist.
Following this success, the IATTC Ecosystem and Bycatch Working Group has recommended similar research initiatives for critically endangered hammerhead sharks in 2024.
Key Takeaways:
- Silky sharks face significant threats from overfishing and bycatch.
- New three-stock population model redefines management zones across the Eastern Pacific.
- Juvenile shark bycatch is alarmingly high, especially in FAD-associated purse seine fisheries.
- Collaborative research is essential for effective shark conservation strategies.
📚 Reference:
Talwar, B. S., et al. (2025). Informing the spatial management of Silky Shark (Carcharhinus falciformis) in the Eastern Pacific Ocean. Reviews in Fish Biology and Fisheries. DOI: 10.1007/s11160-025-09948-5
📌 Provided by: University of California – San Diego