Quantification of The Effects of Coral Reef Degradation On Butterflyfish Populations in The Southern Great Barrier Reef

Abstract

Because of their wide abundance on coral reefs, butterflyfishes’ presence or absence can function as an indicator for overall reef health. A survey of both healthy and degraded coral reef flats off Heron Island in Queensland, Australia was conducted to determine the effects of decreasing coral cover on corallivorous fishes. During a four-day period at the end of October, 2013, four species of butterflyfish – two obligate and two facultative corallivorous butterflyfish species – were tallied along two transects in the reef flats. From a total of 291 individuals, there was a significant difference in habitat composition choice between healthy and degraded habitats seen by a p= 2.234e-10. Additionally, means extracted from log-transformed data suggest that the twelve percent decrease in live coral between transects of the healthy habitat caused a disproportionate decrease in fish abundance. This suggests that a minor loss of coral cover can result in a dramatic loss of fish abundance and diversity and may point towards a threshold where living coral can no longer sustain original population abundances of coral reef communities.