Galápagos, Ecuador
Galapagos Silky Shark Project
Tracking silky sharks between the offshore islands of the Eastern Tropical Pacific to assess how well the region's marine protected areas protect them.
Led by Universidad San Francisco de Quito, with MMF
Silky sharks (Carcharhinus falciformis) aggregate around the remote volcanic islands of the Eastern Tropical Pacific, yet they are also among the sharks most often caught in tropical tuna fisheries.
This collaborative study is led by Dr. Alex Hearn of the Universidad San Francisco de Quito, with research partners across the region. It combines tracking data from across the Eastern Tropical Pacific to show how the sharks use these islands and how far they travel between them. MMF is one of the partners, and MMF’s Dr. Chris Rohner leads our part of the analysis.
Silky sharks occur in warm waters worldwide and are listed as Vulnerable on the IUCN Red List. In the Eastern Tropical Pacific, they aggregate seasonally over seamounts and steep reef slopes at offshore islands from Mexico to the Galapagos.
Objectives
- Estimate how long individual sharks remain at each island, and whether some are resident while others pass through.
- Determine whether the sharks’ presence varies by season or time of day, and how ocean conditions such as water temperature affect it.
- Measure how often sharks move between island groups, and how far offshore they range.
What's next
- Publish the study. A paper is in preparation, and results will be added here once it is published.
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About the study
Acoustic and satellite tracking
Between 2009 and 2016, research teams fitted 44 silky sharks with acoustic tags at four island groups: the Galapagos (Ecuador), the Revillagigedo Islands (Mexico), Cocos Island (Costa Rica), and Malpelo Island (Colombia). Underwater receivers at 33 sites, including Clipperton Atoll (France), log each pass of a tagged shark, while satellite tags on a further 35 sharks track their movements across the open ocean between the islands.
Implications for protection
Whether individual silky sharks remain at one island or move widely between them is still poorly understood, yet the answer bears directly on how well the region’s marine protected areas can protect them. The results will show how much protection silky sharks receive from these protected areas, and where they are exposed to fishing outside them.
Dr. Chris Rohner
Dr. Simon Pierce
Galapagos Whale Shark Project
Galápagos Yellowfin Tuna Project