Despite their ‘excellent’ coral cover, Palau’s reefs had fewer, smaller fish communities than expected, study finds

Palau’s reefs had the highest coral cover observed on the Global Reef Expedition but they had fewer and smaller fish than expected for a healthy coral reef ecosystem, according to a newly released report from the Khaled bin Sultan Living Oceans Foundation.

Depite having the most “excellent” and thriving coral community in the region, scientists found that reef fish stocks in Palau were not exceptionally different, but rather similar to those surveyed in other nearby countries in the south and western Pacific.

“Many of the biggest fish appeared to be missing. Signs of overfishing were also observed on some of Palau’s nearshore reefs despite existing regulations, particularly on reefs near population centers,” states the report on the state of coral reefs in Palau. 

In general, fish populations were less diverse and characterized by smaller fish and lower biomass inside of the lagoons, the report said.

Scientists at the Khaled bin Sultan Living Oceans Foundation conducted extensive underwater surveys, which found that Palau’s reefs had the highest live coral cover of all the reefs studied on the Global Reef Expedition, a scientific research mission to assess the health and resiliency of coral reefs around the world.

The Global Reef Expedition came to Palau in 2015. An international team of scientists and local experts spent nearly a month at sea surveying coral reefs in 10 states across Palau.

Scientists found that the average live coral cover recorded in Palau was over 45 percent and reached 60 or 70 percent in some marine protected areas. This coral cover is very high, even among the world’s best coral reefs.

“Palau’s coral cover is truly exceptional,” said Alexandra Dempsey, the director of Science Management at KSLOF and one of the report’s authors. “It indicates a robust benthic coral reef community with high coral cover and species diversity.”

Although the quantity and quality fell short of expectations, the repotr concluded that, “The fish communities of Palau were in relatively good condition, with similar reef fish biomass and density as other nearby countries surveyed in the south and western Pacific.”

“Within Palau, fish biomass and density were higher outside of the lagoonal sites across states when compared to inside, as was the proportion of large fish. Across all states, diversity, biomass, and fish size were generally smaller inside of the lagoon; fish density did not show a clear pattern between sites inside and outside of the lagoon. The differences in fish biomass were driven by differences in fish size rather than abundance,” the report said.

Based on the findings from the research mission, the scientists made the following recommendation:

“Many of the conservation and protected areas focus restrictions within the lagoon and require special use permits for non-Palauan’s and tourism, with some areas requiring fishing permits. Implementing fisheries management regulations such as fish size and catch limits, as well as additional gear restrictions will help curb the overexploitation of these nearshore lagoonal reefs.

“It may be prudent to consider increasing protection in areas adjacent to large population centers, such as around Koror to be more restrictive and expand no-take, no-entry area size to allow for recovery of fish populations.”

These coral reefs have likely benefited from Palau’s efforts to conserve their natural marine heritage. Palau has a long history of marine conservation.

Key is the traditional policy of “bul”—a moratorium on catching particular species or fishing on certain reefs to protect habitats that are critical to the community’s food security. Conservation of the country’s reefs was further boosted in 2015 by the establishment of the Palau National Marine Sanctuary, which delivered one of the world’s largest protected areas of ocean.

“Unsurprisingly, this long-term commitment to marine conservation has delivered some of the most vibrant reefs the Foundation encountered on its Global Reef Expedition,” said Dr. Sam Purkis, KSLOF’s chief scientist as well as Professor and Chair of the Department of Marine Geosciences at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science. “Given that Palau’s efforts are yielding tangible conservation results, the country might serve as a role model to other countries in the South Pacific and beyond.”

“Fish are a critical component of a robust coral reef community. They’re important not only ecologically, but for the people who depend upon the reefs food or income,” said Renée Carlton, Marine Ecologist at KSLOF and lead author on the report.

Carlton said the research team saw some warning signs regarding reef fish communities, but just the same, they hope that “by expanding current fisheries management regulations and establishing more no-take no-entry areas, Palau’s reef fish communities could become some of the best in the world.”

“The commitment Palauans have made to conserving their reefs is highly commendable and I hope they’re able to use the findings in this report to continue preserving their natural resources for future generations,” Carlton added.

The foundation noted that although several years have passed since the expedition, data from the research mission will be critical for monitoring changes to the reefs over time and help managers identify priority sites for conservation action.