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The influence of simulated exploitation on Patella vulgata populations: protandric sex change is size-dependent

The influence of simulated exploitation on Patella vulgata populations: protandric sex change is size-dependent
The influence of simulated exploitation on Patella vulgata populations: protandric sex change is size-dependent
Grazing mollusks are used as a food resource worldwide, and limpets are harvested commercially for both local consumption and export in several countries. This study describes a field experiment to assess the effects of simulated human exploitation of limpets Patella vulgata on their population ecology in terms of protandry (age-related sex change from male to female), growth, recruitment, migration, and density regulation. Limpet populations at two locations in southwest England were artificially exploited by systematic removal of the largest individuals for 18 months in plots assigned to three treatments at each site: no (control), low, and high exploitation. The shell size at sex change (L50: the size at which there is a 50:50 sex ratio) decreased in response to the exploitation treatments, as did the mean shell size of sexual stages. Size-dependent sex change was indicated by L50 occurring at smaller sizes in treatments than controls, suggesting an earlier switch to females. Mean shell size of P. vulgata neuters changed little under different levels of exploitation, while males and females both decreased markedly in size with exploitation. No differences were detected in the relative abundances of sexual stages, indicating some compensation for the removal of the bigger individuals via recruitment and sex change as no migratory patterns were detected between treatments. At the end of the experiment, 0–15 mm recruits were more abundant at one of the locations but no differences were detected between treatments. We conclude that sex change in P. vulgata can be induced at smaller sizes by reductions in density of the largest individuals reducing interage class competition. Knowledge of sex-change adaptation in exploited limpet populations should underpin strategies to counteract population decline and improve rocky shore conservation and resource management.
Human exploitation, limpets, protandry, sex change, size at sex change, size-selective harvesting
514-531
Borges, Carla D.G.
6bf45691-2527-41fd-9d72-807d77f3140c
Hawkins, Stephen J.
758fe1c1-30cd-4ed1-bb65-2471dc7c11fa
Crowe, Tasman P.
9ce97cbc-c45f-426b-8e28-c4c93a500593
Doncaster, C. Patrick
0eff2f42-fa0a-4e35-b6ac-475ad3482047
Borges, Carla D.G.
6bf45691-2527-41fd-9d72-807d77f3140c
Hawkins, Stephen J.
758fe1c1-30cd-4ed1-bb65-2471dc7c11fa
Crowe, Tasman P.
9ce97cbc-c45f-426b-8e28-c4c93a500593
Doncaster, C. Patrick
0eff2f42-fa0a-4e35-b6ac-475ad3482047

Borges, Carla D.G., Hawkins, Stephen J., Crowe, Tasman P. and Doncaster, C. Patrick (2016) The influence of simulated exploitation on Patella vulgata populations: protandric sex change is size-dependent. Ecology and Evolution, 6 (2), 514-531. (doi:10.1002/ece3.1872).

Record type: Article

Abstract

Grazing mollusks are used as a food resource worldwide, and limpets are harvested commercially for both local consumption and export in several countries. This study describes a field experiment to assess the effects of simulated human exploitation of limpets Patella vulgata on their population ecology in terms of protandry (age-related sex change from male to female), growth, recruitment, migration, and density regulation. Limpet populations at two locations in southwest England were artificially exploited by systematic removal of the largest individuals for 18 months in plots assigned to three treatments at each site: no (control), low, and high exploitation. The shell size at sex change (L50: the size at which there is a 50:50 sex ratio) decreased in response to the exploitation treatments, as did the mean shell size of sexual stages. Size-dependent sex change was indicated by L50 occurring at smaller sizes in treatments than controls, suggesting an earlier switch to females. Mean shell size of P. vulgata neuters changed little under different levels of exploitation, while males and females both decreased markedly in size with exploitation. No differences were detected in the relative abundances of sexual stages, indicating some compensation for the removal of the bigger individuals via recruitment and sex change as no migratory patterns were detected between treatments. At the end of the experiment, 0–15 mm recruits were more abundant at one of the locations but no differences were detected between treatments. We conclude that sex change in P. vulgata can be induced at smaller sizes by reductions in density of the largest individuals reducing interage class competition. Knowledge of sex-change adaptation in exploited limpet populations should underpin strategies to counteract population decline and improve rocky shore conservation and resource management.

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e-pub ahead of print date: 9 January 2016
Published date: January 2016
Keywords: Human exploitation, limpets, protandry, sex change, size at sex change, size-selective harvesting
Organisations: Ocean and Earth Science, Centre for Biological Sciences

Identifiers

Local EPrints ID: 385701
URI: https://eprints.soton.ac.uk/id/eprint/385701
PURE UUID: 95931bb0-7ca9-4a81-b2ae-545623434ad6
ORCID for C. Patrick Doncaster: ORCID iD orcid.org/0000-0001-9406-0693

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Date deposited: 11 Jan 2016 11:07
Last modified: 15 Aug 2019 00:54

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Contributors

Author: Carla D.G. Borges
Author: Tasman P. Crowe

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