Parrotfish Body Size As An Indicator of Diurnal Fish Species Richness On Fringing Coral Reefs in Barbados

Background: Coral reefs around the world are host to some of the most condensed and varied ecosystems. However, over the past decades, their biodiversity has alarmingly decreased. A rapid and reliable way of assessing their status is urgently needed to monitor and prevent their decline. The purpose of this study is to assess whether or not family Scaridae (common name: parrotfish) body size can be used as an index to evaluate the diurnal fish diversity on coral reefs. Methods: We selected 6 accessible reefs on the West coast of Barbados and measured the size of parrotfish we encountered, as well as the number of fish species present on the reef; this data was then plotted and statistically analyzed to establish a possible correlation. Results: Our results show that reef fish species richness is strongly correlated to both the ratio of large to small parrotfish and the average parrotfish size. It is however the large to small ratio that exhibited the strongest relationship. Further analysis revealed that the population size of large parrotfish correlates with reef biodiversity with a Pearson’s r coefficient of 0.97. Conclusion: This relationship could be due to the fact that large parrotfish (greater than or equal to 20 cm) have increased grazing rates compared to smaller ones, this increased grazing promotes coral polyp recruitment, thereby benefiting the diversity observed on coral reefs. Further research is needed to elucidate whether these results can be extended to other areas of the Caribbean and provide conservation efforts with an easy tool to survey and protect coral reef ecosystems.