Okinawa’s hidden shark hotspots have a vital role as shark sanctuaries

Okinawa and its surrounding waters represent what marine biologists call a "shark and ray hotspot" in terms of both diversity and conservation significance. In this episode of the OIST podcast, Dr. Fabienne Ziadi-Künzli, a marine biologist and shark researcher at the Okinawa Institute of Science and Technology (OIST), explained that this region creates unique habitats for sharks throughout their different life stages. 

Marine predators with surprising similarities to humans

Okinawa hosts impressive species including tiger sharks, whale sharks, bull sharks, lemon sharks, and hammerhead sharks, along with numerous deep-sea shark species that remain hidden from casual observers. "This area, for some reason, probably because of the habitats and currents, creates very unique habitats for sharks," Dr. Ziadi-Künzli highlighted. "Diversity is so high in this region and it's probably even underestimated because we do not really understand the full scope of the diversity yet."

Despite their fearsome reputation, aggressive shark encounters with humans are surprisingly rare in Okinawan waters. Dr. Ziadi-Künzli attributes this to several reasons, including the protective lagoons and coral reefs that create natural barriers, along with the healthy state of local shark populations. When examining sharks during her research, she typically finds them well-fed with adequate resources for reproduction and survival. This contrasts sharply with overfished regions like the Red Sea, where more aggressive shark behavior has been observed. This suggests that maintaining healthy marine ecosystems benefits not just sharks but human safety as well.

Sharks face numerous threats to their survival, with global fishing pressure representing the most significant challenge. Dr. Ziadi-Künzli highlighted the concerning practice of shark meat being sold under misleading or generic names such as "flake," "rock," or "white fish" in many countries, preventing consumers from making informed choices. Additionally, culinary demand for shark fins persists – most notably in soups – while both shark and especially ray skin are repurposed into luxury, high-end products.

What makes sharks particularly vulnerable is their life cycle. "They have a similar life cycle like humans," Dr. Ziadi-Künzli explained. Despite their longevity, sharks mature slowly and produce few offspring with long gestation periods, making it difficult for them to rebound from intense fishing pressure.

Important Shark and Ray Areas (ISRAs)

In response to these challenges, Dr. Ziadi-Künzli and her colleagues have been working with the Important Shark and Ray Areas (ISRA) global conservation project, successfully proposing seven critical shark habitats in Okinawa Prefecture. These designated areas include bull shark nurseries in freshwater ecosystems of Iriomote Island and Naha, a nursery for juvenile lemon sharks and a congregation site for reef manta rays in the Yaeyama Islands, a scalloped hammerhead shark congregation site in Yonaguni Island, and deep-sea shark habitats near Onna-son and a remote underwater seamount."

The ISRA project enables scientists to identify and map areas crucial for shark reproduction, feeding, and survival, providing valuable information for policymakers and conservation agencies planning marine protected areas. For more information on the ISRA project and ISRAs in Okinawa, see here.

Science and communities for shark protection

Effective shark conservation requires collaboration with local communities and Dr. Ziadi-Künzli engages in outreach work to educate people about shark ecology and dispel misconceptions about these predators. One promising approach involves working with fishing communities to implement devices that emit electric pulses, deterring sharks from biting fishing hooks. This technology helps fishermen catch more of their target species while reducing accidental shark captures. 

Marine protected areas represent one of the most effective conservation strategies for sharks. Dr. Ziadi-Künzli advocates for establishing such areas in Okinawa, pointing to the ecological and economic benefits they bring. She emphasized that sharks maintain the health of marine habitats through their predatory behaviors. For example, tiger sharks control turtle populations, which in turn prevents overgrazing of seagrass meadows essential for fish reproduction and survival. Similarly, sharks influence coral reef health through predation on a variety of fish. "Sharks again have this cascading effect, not only on seagrass beds, but also on coral reefs...., we cannot just protect corals. That doesn't make sense because we need the sharks too, to protect the corals. It’s an integrated system..."

Looking ahead, Dr. Ziadi-Künzli finds hope in the next generation's knowledge about marine ecosystems. During outreach events, she observes that children often demonstrate greater understanding of sharks than adults do. This knowledge may translate into more sustainable fishing practices as they grow up.

There is also potential for developing shark tourism in Okinawa, similar to successful models in other regions. The economic value of living sharks far exceeds their short-term value as captured resources. While establishing comprehensive protection will take time, Dr. Ziadi-Künzli remains optimistic. "It takes time, but the development so far is very positive," she stated.