University of Hawai‘i Study Links Cookiecutter Shark Activity to Night and Moon

Researchers with the University of Hawai‘i published a multidisciplinary study on Dec. 29, 2025 that clarifies when and why Cookiecutter sharks produce the distinctive circular wounds seen on larger animals and fish. The paper used a large dataset from longline fisheries together with ecological analyses and a review of ʻōlelo Hawaiʻi records and nūpepa to place the species in cultural context and to test patterns suggested by Indigenous knowledge.

The study’s core finding was clear: bite events occurred predominantly during nighttime hours and were strongly tied to lunar cycles. Attack frequency rose during low-illumination periods of the lunar month, suggesting Cookiecutter sharks are most active under darker conditions. These patterns were identified by matching fisheries reports of bite incidents to time-of-night and moon phase, then examining ecological drivers alongside Hawaiian-language accounts and historic observations.

That blending of datasets is consequential for Kaua‘i. Longline fisheries reporting provided practical, contemporary records of interactions between gear, catch and marine wildlife. Historic ʻōlelo Hawaiʻi sources and nūpepa added temporal depth and local ecological knowledge, helping researchers interpret the behavior in ways that are meaningful to Hawaiian communities. By treating those records as scientific evidence rather than anecdote, the study foregrounded kūpuna knowledge and the potential for Indigenous perspectives to refine modern marine science.

Local impacts include improved capacity for fisheries managers and conservation agencies to anticipate periods of higher Cookiecutter activity and to design monitoring or mitigation measures that reduce damage to gear and non-target species. For marine mammal and fisheries observers on Kaua‘i, the results offer a clearer seasonal and nightly framework for interpreting circular bite wounds and for prioritizing response efforts. The research also strengthens arguments for collaborative management models that compensate for historical marginalization of Native Hawaiian knowledge in resource decisions.

Public health and community resilience are connected to these findings through livelihoods and cultural practices tied to the ocean. Reducing unexpected interactions between people, gear and marine wildlife can protect economic stability for small-scale fishers and support cultural continuity for communities that rely on ocean resources.

The study demonstrates a practical pathway for integrating Indigenous knowledge systems with modern datasets, offering a model for other island communities navigating the scientific and social dimensions of coastal resource management.