Scientists studied what baby blacktip sharks eat in different parts of the Galapagos Islands by collecting samples from 107 sharks without harming them. They found that baby sharks in different areas eat different types of fish based on what’s available in their local waters. The sharks’ diet also changed depending on ocean conditions—they ate more variety during cooler years than warmer years. This research helps us understand how sharks survive and what might happen to them if ocean conditions or food sources change due to climate change or overfishing.

The Quick Take

  • What they studied: What different baby blacktip sharks eat in various locations across the Galapagos Islands and how their diet changes with ocean conditions
  • Who participated: 107 juvenile blacktip sharks caught and released alive from 14 different bays across four islands in the Galapagos Archipelago, spanning an area of about 240 kilometers
  • Key finding: Baby sharks’ diets vary significantly by location and ocean conditions. The most common prey were mullet fish (20% of diet), sergeant-major fish (13%), and damselfish (12-11%). Sharks in the eastern islands ate more variety, and sharks sampled during cooler ocean years ate more diverse diets than those sampled during warmer years.
  • What it means for you: Understanding what sharks eat helps scientists predict how climate change and overfishing might affect shark populations. If the fish sharks depend on disappear, sharks could struggle to survive. This research supports better ocean conservation strategies that protect both sharks and their food sources.

The Research Details

Scientists collected samples from 107 baby blacktip sharks living in mangrove bays throughout the Galapagos Islands. Instead of harming the sharks, they used a non-invasive method—gently swabbing the sharks’ cloacas (a single opening used for reproduction and waste) to collect fecal matter. They then used advanced DNA technology called metabarcoding to identify exactly what fish species were in each sample. This method is like reading a genetic barcode on each piece of food to identify what the shark ate. The researchers collected samples from sharks across 14 different bays on four islands, covering an area of about 240 kilometers, and released every shark alive after sampling.

This research approach is important because it allows scientists to study what wild sharks eat without killing them or keeping them in captivity. The non-invasive sampling method means researchers can study many sharks over time and track how their diets change. By comparing sharks from different locations and different years, scientists can see how environmental factors like temperature and food availability influence what sharks eat, which helps predict how they’ll respond to future changes.

This study is reliable because it used a large sample size (107 sharks) across multiple locations and time periods. The DNA metabarcoding method is scientifically rigorous and can identify prey species with high accuracy. The researchers released all sharks alive, making this an ethical study. However, the study only looked at two different time periods (2021 and 2023), so longer-term patterns would require more years of data. The study was published in Scientific Reports, a well-respected peer-reviewed journal.

What the Results Show

The research revealed that baby blacktip sharks in the Galapagos eat a variety of fish species, with the most common being Thoburn’s mullet (found in 20% of sharks’ stomachs), followed by sergeant-major fish at 13.4%, Galapagos ringtail damselfish at 12.7%, scalloped hammerhead shark at 11.7%, and yellowtail damselfish at 10.7%. Importantly, the variety of prey species differed depending on where the sharks lived. Sharks sampled in the bays around San Cristobal Island had the most diverse diets, eating more different types of fish compared to sharks in other areas. This suggests that different parts of the Galapagos have different amounts and types of fish available for sharks to eat.

The study also discovered that ocean conditions significantly affect what sharks eat. During 2021, when cooler ocean conditions called ‘La Niña’ occurred, baby sharks ate a wider variety of prey species. In contrast, during 2023, when warmer ocean conditions called ‘El Niño’ occurred, sharks ate less variety. Scientists believe this happens because El Niño conditions reduce the overall number of fish species and their populations in the ocean, leaving sharks with fewer food choices. This finding is important because it shows that climate patterns directly influence shark nutrition.

This research builds on previous studies showing that predators’ diets usually match what prey is available in their environment. The finding that sharks in the eastern Galapagos (where more fish species live) eat more diverse diets confirms this pattern. The discovery that El Niño conditions reduce prey diversity for sharks aligns with other research showing that El Niño harms many ocean ecosystems. This study provides new specific evidence about how these climate events affect sharks.

The study only collected samples during two different years (2021 and 2023), so we can’t be certain whether the differences between those years represent a true pattern or just variation between those specific years. The research focused only on baby sharks in mangrove bays, so the results may not apply to adult sharks or sharks in other habitats. Additionally, the DNA method can identify what fish were eaten, but it cannot tell us exactly how much of each fish type the shark consumed—only whether it was present in the stomach. Finally, the study doesn’t explain all the reasons why sharks in different locations eat different foods, as factors beyond just prey availability could play a role.

The Bottom Line

Based on this research, ocean conservation efforts should focus on protecting the fish species that baby sharks depend on, particularly mullet and damselfish. Reducing overfishing in shark nursery areas and protecting mangrove habitats is important. Monitoring how climate change affects fish populations in the Galapagos can help predict future impacts on sharks. These recommendations have moderate-to-strong support from this research, though longer-term studies would provide even stronger evidence. (Confidence level: Moderate)

Ocean conservation organizations, fisheries managers, and policymakers in the Galapagos should use this information to make decisions about protecting shark habitats and managing fishing. Climate scientists studying ocean ecosystems will find this relevant. General ocean lovers should care because healthy shark populations indicate healthy ocean ecosystems. This research is less directly relevant to people who don’t live near or work with sharks, though it contributes to our understanding of global ocean health.

Changes from conservation efforts based on this research would take years to show results. Protecting fish populations and shark habitats might take 3-5 years to show measurable improvements in shark diet diversity. Climate-related changes to shark food sources are already happening and will likely continue over the next 10-20 years, making this research increasingly important for future planning.

Want to Apply This Research?

  • Users interested in ocean conservation could track ‘shark habitat protection actions’ by logging conservation efforts in their area, such as supporting marine protected areas, reducing plastic use, or participating in beach cleanups. Set a monthly goal to learn about one local ocean conservation initiative.
  • Users can reduce their impact on shark ecosystems by choosing sustainable seafood options (checking seafood sustainability guides), reducing plastic consumption, and supporting ocean conservation organizations. The app could provide weekly tips about sustainable fishing practices and ocean-friendly choices.
  • Track long-term engagement with ocean conservation by monitoring: (1) number of sustainable seafood choices made per month, (2) plastic reduction milestones, (3) conservation articles read or shared, and (4) donations or volunteer hours contributed to ocean protection organizations. Create quarterly reports showing personal impact on ocean health.

This research describes what baby sharks eat in the Galapagos Islands and should not be interpreted as advice for interacting with sharks. Sharks are wild animals and should be observed only from a safe distance or through professional guided experiences. This study does not provide information about shark behavior, safety, or how to avoid shark encounters. If you have specific questions about shark conservation or ocean health, consult with marine biologists or conservation organizations. This summary is for educational purposes and does not replace professional scientific or medical advice.