In the clear waters of Sental, Nusa Penida, something exciting is happening beneath the waves.

For the first time in years, juvenile whitetip reef sharks (Triaenodon obesus) are being seen regularly at our coral restoration site — a powerful sign that the reef isn’t just growing back, but coming back stronger and healthier than ever.

Our team began noticing the return of juvenile whitetip reef sharks at the start of 2025. Since then, sightings have become consistent, with sharks frequently spotted resting in the same area of reef structure we’ve been restoring.

Here’s what we’ve recorded so far:

January 2: Two juvenile sharks observed under the same coral overhang
April 2: Four juveniles seen in the same location
April 9: Three sharks remain, one spotted with a fishing hook in its mouth
April 12 & 13: Biologists from Blue Corner removed fishing hook from the mouth of the injured shark
May 1: Five sharks observed: 2 at the main spot, 3 nearby
May–July: Between 2 to 5 sharks consistently present on every visit

Notably, some individuals have grown by nearly a meter in length since January — a clear sign they’re staying and thriving.
This consistent presence of the juvenile sharks is a remarkable pattern — one we’ve never seen around the Nusa Islands before.

Whitetip reef sharks are key predators in coral reef ecosystems. When they’re around, it usually means the ecosystem is functioning well. They help maintain the balance by controlling fish populations, which in turn helps coral grow.

In Nusa Penida, these sharks have been rare due to overfishing and a lack of enforcement in the past. So the fact that young sharks are returning — and sticking around — is more than just cool. It may mean the reef is finally strong enough to support apex predators again.

At Blue Corner Conservation, we’ve spent years rebuilding damaged reef structures through coral restoration efforts. Now, we're seeing signs that it's not just the coral coming back — but also the entire food web. These juvenile sharks may be using the restored reef as a nursery — a safe space with plenty of food and shelter. That’s exactly what a healthy reef should provide.

What’s Next: Tracking the Sharks

To deepen our understanding of this encouraging shark return, we are currently developing a scientific study on whitetip reef shark movement, residency, and habitat use in the Sental restoration site. Using acoustic telemetry, we aim to track these juvenile sharks over time — learning how long they stay, where they go, and how they interact with the recovering reef.

This research will help answer critical questions:
Are restored coral reefs becoming reliable shark habitats?
Do these sharks show long-term site fidelity?
What role do they play in the ecosystem’s recovery?

We are actively seeking funding and research support to launch this project. Once underway, the findings will be shared with local stakeholders, marine park authorities, and the public, contributing to science-based conservation planning for Nusa Penida and beyond. By linking predator return to coral recovery, we hope to learn more about how restored reefs can support entire ecosystems — not just corals, but the species that depend on them.

The return of sharks to Sental is more than just a win for marine science — it’s a symbol of hope. It shows that with the right care, protection, and persistence, nature can bounce back.

We’ll keep monitoring the site and sharing what we learn. Until then, keep following along — the reef has more stories to tell.

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Aulia Zeintrinanda - Blue Corner Marine Research