Decadal changes in reef fish diversity in the Philippines

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John Whalen, Jemelyn Baldisimo, Eric Garcia and Kent Carpenter, Biological Sciences, Old Dominion University, Norfolk, VA, Abner Bucol and Angel Alcala, Silliman University, Jeffrey T. Williams, Smithsonian Institution, David Catania, California Academy of Sciences

Background/Question/Methods
The Central Visayas of the Philippines is a global epicenter of marine fish biodiversity. Hypotheses attribute this peak of species richness within the Coral Triangle to processes that occur at geological time scales. However, changes in biodiversity may occur on ecological time scales, allowing for the assessment of the potential impact of anthropogenic activities. Low species richness in the Central Visayas has previously been associated with stressors such as habitat degradation, overfishing, and harvesting individuals for the aquarium trade. Many marine protected areas (MPAs) have been established throughout the Philippines in order to mitigate the cumulative negative effect of these stressors. While most of the country’s MPAs lie within the Central Visayas, this region has been termed the “epicenter of conservation adversity” within the Philippines. This study examines patterns of diversity in select reef fish communities within the Central Visayas that were sampled in the 1970s and 2010s. These two surveys used similar sampling methods and were conducted by the Smithsonian Institution and the California Academy of Sciences, respectively. Individual- and sample-based species accumulation and rarefaction curves were used to create snapshots of species diversity from these distinct periods. Changes in community composition of trophic levels were also compared between this fort year period.
Results/Conclusions
Results indicate species richness reductions of 7.4% per decade in the Central Visayas over the past four decades, a greater rate than previously suggested. Multiple sites shifted to a community dominated by planktivores, suggesting that the fishing down the food web process is occurring. Despite observations of increases in species richness at local scales and a high abundance of MPAs, species richness is decreasing in the Central Visayas. An increase in planktivores suggests that the fishing down the food web is occurring. Unless threats to these marine resources are reduced, further declines can be expected.