A new study led by researchers at UH Mānoa Hawaiʻi Institute of Marine Biology (HIMB) ToBo Lab has revealed that giant clam populations in American Sāmoa are far more stable and abundant than previously thought, demonstrating the effectiveness of traditional, community-based resource management. The research, published in the journal PeerJ, analyzed multi-decadal survey data and found that marine areas managed by local villages consistently support higher clam densities and larger clam sizes compared to federally designated no-take reserves.
"Many expected that giant clam populations would be in sharp decline, especially near populated islands," shares Paolo Marra-Biggs, lead author of the study and a PhD student at HIMB. "Instead, we found that clam abundances have remained relatively stable over the past 30 years, and in some areas have maintained high abundances. The biggest surprise was that village-managed closures outperformed federally protected no-take areas, highlighting the efficacy of cultural stewardship."
The findings carry significant implications for conservation policy, particularly concerning the current federal process to list giant clams under the Endangered Species Act (ESA). The study argues that blanket federal restrictions may not be the best fit for regions where effective Indigenous management systems are already in place.
"The push for ESA listing is supposed to protect giant clams, but our data show that in areas where federal no-take protection already exists, clams populations were among the lowest," notes Robert Toonen, senior author of the study and Principal Investigator of the ToBo Lab. "Instead, areas under traditional Indigenous management had some of the highest densities of giant clams. If giant clams were listed as endangered species, these traditional practices that have maintained high clam densities in the region would become illegal."
The research team conducted a territory-wide survey from 2022–2024, adding 264 new transects to historical surveys that were initiated in 1994. The resulting data set represents the most complete, multi-decadal compilation of giant clams for American Sāmoa, assessing population stability across six islands and various management zones.
Marra-Biggs noted that working directly with local communities was a highlight of the project.
"I am grateful to be able to work alongside local agencies and resource managers who care deeply about their reefs," Marra-Biggs notes. "This study intersects science, culture, and conservation, and seeing our results highlight the value of traditional management and support community decision-making made the work especially meaningful. It is an honor to contribute to the stewardship of the absolutely stunning reefs of American Sāmoa."
The success of this study hinged on critical Pacific-to-Pacific collaboration with partners like the American Sāmoa Department of Marine and Wildlife Resources, the National Park, and the National Marine Sanctuary of American Sāmoa. This joint effort not only supports Indigenous management and strengthens food security in the territory, but the lessons learned also extend directly to Hawai'i's efforts to revive traditional stewardship and restore coastal fisheries.
