MEPS 586:127-139 (2018)  -  DOI: https://doi.org/10.3354/meps12426

Predator declines and morphological changes in prey: evidence from coral reefs depleted of sharks

Neil Hammerschlag1,2,*, Shanta C. Barley3,4, Duncan J. Irschick5, Jessica J. Meeuwig3, Emily R. Nelson1, Mark G. Meekan

1Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149, USA
2Leonard and Jayne Abess Center for Ecosystem, Science and Policy, University of Miami, Coral Gables, FL 33146, USA
3School of Biological Sciences and the Oceans Institute, University of Western Australia, 35 Stirling Highway, Crawley, Perth, WA 6009, Australia
4Australian Institute of Marine Science, The Oceans Institute, University of Western Australia, 35 Stirling Highway, Crawley, Perth, WA 6009, Australia
5Department of Biology, 221 Morrill Science Center, University of Massachusetts at Amherst, Amherst, MA 01003, USA
*Corresponding author:

ABSTRACT: Evidence from the wild as to the ecological and evolutionary consequences of top predator depletions remains limited, especially in marine systems. Given the pace and extent of predator loss, an understanding of these processes is important. Two sets of adjacent coral reef systems off north-western Australia have similar biological, physical and environmental conditions, but one of the reef systems has been exposed to nearly exclusive commercial fishing of sharks. Across reefs where sharks have been depleted, prey fishes have significantly smaller caudal fins and eyes compared to the reefs with intact shark populations (up to 40 and 46% relative difference in standardized means). These patterns are consistent across 7 teleost prey species (N = 611 individuals) that vary in behavior, diet and trophic guild. We hypothesize that these morphological patterns are primarily driven by differences in shark predation. Morphological differences are not consistent with plausible alternative explanations (habitat complexity, temperature, light, current, food availability, prey targets, competition) as primary drivers. These results provide field evidence of morphological changes in prey potentially due to predator depletions consistent with ecological predictions; specifically, predator loss caused a reduction in the size of prey morphological traits associated with predator detection and evasion. While our analysis cannot differentiate between rapid evolutionary change versus morphological plasticity due to shark depletions, either possible outcome would indicate that predator removals may have profound effects on body shapes of prey communities. This is particularly significant in the case of sharks, given that the consequences of their widespread removal have been a topic of significant speculation, debate and concern.


KEY WORDS: Fishing · Morphology · Predation risk · Predator-prey interactions · Shark · Trophic cascades


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Cite this article as: Hammerschlag N, Barley SC, Irschick DJ, Meeuwig JJ, Nelson ER, Meekan MG (2018) Predator declines and morphological changes in prey: evidence from coral reefs depleted of sharks. Mar Ecol Prog Ser 586:127-139. https://doi.org/10.3354/meps12426

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