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Marine Ecology Progress Series

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MEPS 533:163-176 (2015)  -  DOI:

Effects of simulated human exploitation of a key grazer, Patella vulgata, on rocky shore assemblages

C. D. G. Borges1,4,*, S. J. Hawkins1,2, C. P. Doncaster1, T. P. Crowe3

1Centre for Biological Sciences, University of Southampton, Life Sciences Building 85, Highfield, Southampton SO17 1BJ, UK
2Ocean and Earth Science, National Oceanography Centre, Waterfront Campus, European Way, University of Southampton, Southampton SO14 3ZH, UK
3School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland
4Present address: CIIMAR- Centro Interdisciplinar de Investigação Marinha e Ambiental, Laboratório de Biodiversidade Costeira, Rua dos Bragas 289, 4050-123 Porto, Portugal
*Corresponding author:

ABSTRACT: Exploitation of key consumers can have major consequences for community and ecosystem functioning. Limpets are key grazers exploited in regions such as Macaronesia, southern Africa, Chile and California. Here we describe a field experiment designed to simulate human exploitation of British limpets that are unexploited and used as model populations. Our aim was to evaluate the effects of size-selective harvesting on the composition of the rocky shore community of non-target species. Limpet populations were subjected to simulated exploitation of large size classes for 18 mo at 2 locations in the southwest of England, by systematic removal at 2 different intensities: low and high exploitation compared with unexploited plots. The exploitation of limpets led to establishment of Fucus spp. to differing degrees at each location, but while variation in percentage cover of Fucus spp. decreased over the course of the experiment in unmanipulated control plots, it increased in plots with either low or high exploitation. Multivariate analyses showed that communities at the 2 locations responded differently to the same intensity of exploitation: unmanipulated controls were similar to low-exploitation treatments at Constantine, while at Trevone low-exploitation treatments were similar to high-exploitation treatments. This was mainly due to increases in percentage cover of F. vesiculosus var. evesiculosus with exploitation, indicating that site-specific differences in assemblage structure and the size structure of the harvested populations will determine its assemblage-level responses. Therefore, reductions in density of grazers may have divergent consequences for different rocky shore communities.

KEY WORDS: Assemblage structure · Exploitation · Grazers · Key species · Rocky shore

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Cite this article as: Borges CDG, Hawkins SJ, Doncaster CP, Crowe TP (2015) Effects of simulated human exploitation of a key grazer, Patella vulgata, on rocky shore assemblages. Mar Ecol Prog Ser 533:163-176.

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