Habitat degradation negatively affects auditory settlement behavior of coral reef fishes

Gordon, Timothy A. C. and Harding, Harry R. and Wong, Kathryn E. and Merchant, Nathan D. and Meekan, Mark G. and McCormick, Mark I. and Radford, Andrew N. and Simpson, Stephen D. (2018) Habitat degradation negatively affects auditory settlement behavior of coral reef fishes. Proceedings of the National Academy of Sciences of the United States of America, 115. pp. 5193-5198. ISSN 0027-8424

Abstract

Coral reefs are increasingly degraded by climate-induced bleaching and storm damage. Reef recovery relies on recruitment of young fishes for the replenishment of functionally important taxa.Acoustic cues guide the orientation, habitat selection, and settlement of many fishes, but these processes may be impaired if degradation alters reef soundscapes. Here, we report spatiotemporally matched evidence of soundscapes altered by degradation from recordings taken before and after recent severe damage on Australia’sGreat Barrier Reef. Postdegradation soundscapes were an average of 15 dB re 1 μPa quieter and had significantly reduced acoustic com- plexity, richness, and rates of invertebrate snaps compared with their predegradation equivalents. We then used these matched re- cordings in complementary light-trap and patch-reef experiments to assess responses of wild fish larvae under natural conditions. We show that postdegradation soundscapes were 8% less attractive to presettlement larvae and resulted in 40%less settlement of juvenile fishes than predegradation soundscapes; postdegradation sound- scapes were no more attractive than open-ocean sound. However, our experimental design does not allow an estimate of how much attraction and settlement to isolated postdegradation soundscapes might change comparedwith isolated predegradation soundscapes. Reductions in attraction and settlement were qualitatively similar across andwithin all trophic guilds and taxonomic groups analyzed. These patterns may lead to declines in fish populations, exacerbat- ing degradation. Acoustic changes might therefore trigger a feed- back loop that could impair reef resilience. To understand fully the recovery potential of coral reefs, we must learn to listen.