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Marine Ecology Progress Series

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MEPS 641:145-157 (2020)  -  DOI:

When sharks are away, rays will play: effects of top predator removal in coral reef ecosystems

C. Samantha Sherman*,1,2, Michelle R. Heupel3, Stephen K. Moore1, Andrew Chin1,3, Colin A. Simpfendorfer1

1Centre for Sustainable Tropical Fisheries and Aquaculture, College of Science and Engineering, James Cook University, QLD 4811, Australia
2AIMS@JCU, DB17-063, James Cook University, Townsville, QLD 4811, Australia
3Australian Institute of Marine Science, Cape Cleveland, QLD 4810, Australia
*Corresponding author:

ABSTRACT: Shark abundances are decreasing on many coral reefs, but the ecosystem effects of this loss are poorly understood. Rays are a prevalent mesopredator in tropical coral reef ecosystems that are preyed upon by top predators like sharks. Studies have suggested reduced predator abundances lead to increases in mesopredator abundance (mesopredator release). We examined the relationship between top predator abundances and the abundance and behaviour of 2 small benthic ray genera using baited remote underwater video systems (BRUVS) across 6 countries. Where predators were more abundant, 2 genera of small benthic rays were sighted less often, possibly because of lower abundances. Small ray behaviour was also significantly affected by predator abundance. Individuals of focal ray species visited BRUVS significantly fewer times at sites with higher predator abundances. Where predators were less abundant, rays spent significantly more time in the video frame, and were more likely to feed from bait bags. In addition to predator abundance, small ray presence was significantly influenced by reef relief and depth. Neotrygon spp. were more abundant on deeper, lower relief habitats, while Taeniura spp. were more prevalent in reef-associated shallow, high relief habitats. Overall, this study found that predator abundance had a significant effect on small benthic ray abundance and behaviour in the presence of BRUVS. Results demonstrate that changes in both abundance and behaviour associated with predator loss may make the interpretation of phenomenon like mesopredator release more difficult to identify unless behavioural effects are considered.

KEY WORDS: BRUVS · Predator-prey relationship · Mesopredator release · Stingrays · Individual identification · Behavior · Predator avoidance · Batoid

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Cite this article as: Sherman CS, Heupel MR, Moore SK, Chin A, Simpfendorfer CA (2020) When sharks are away, rays will play: effects of top predator removal in coral reef ecosystems. Mar Ecol Prog Ser 641:145-157.

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