Individual Based Model for Grouper Populations
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Individual Based Model for Grouper Populations Slimane Ben Miled • Amira Kebir Moulay Lhassan Hbid
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Received: 31 May 2010 / Accepted: 28 June 2010 / Published online: 24 July 2010 Ó Springer Science+Business Media B.V. 2010
Abstract Dusky groupers (Epinephelus marginatus) are characterized by a complex sex allocation strategies and overexploitation of bigger individuals. We developed an individual based model to investigate the long-term effects of density dependence on grouper population dynamics and to analyze the variabilities of extinction probabilities as a result of interacting mortalities at different life stages. We conduct several simulations with different forms of sex allocation functions and different combinations of mortality rates. The model was parametrized using data on dusky grouper populations from the literature. The most important insights produced by this simulation study are that density dependence of sex allocation is an evolutionarily stable strategy, increases the population biomass, mitigates the effect of the removal of large male and indicates a need for protection of females and flexible stages.
S. Ben Miled (&) A. Kebir ENIT-LAMSIN, Universite´ de Tunis el Manar, Tunis, Tunisia e-mail: [email protected] A. Kebir e-mail: [email protected] S. Ben Miled Institut Pasteur de Tunis, 13, place Pasteur B.P. 74, 1002 Tunis Belve´de`re, Tunisia A. Kebir DIMACS Center, Rutgers University, 96 Frelinghuysen Road, Piscataway, NJ 08854-8018, USA A. Kebir M. L. Hbid LMDP-Cadi Ayyad University, BP 2390, Marrakech 4000, Morocco M. L. Hbid e-mail: [email protected]
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keywords Individual based model Sequential hermaphroditic Density dependence Sex change Evolutionarily stable strategy ESS Dusky groupers
1 Introduction Sex allocation theory (Charnov 1982) was developed to analyze sex change for hermaphroditic species. One part of sex allocation theory, the size-advantage hypothesis (SAH) (Ghiselin 1969; Warner 1975), is widely used to explain and to understand sex change for sequential hermaphrodites (Munoz and Warner 2003). The SAH are evolutionary models where the direction and timing of sex change are viewed as evolutionary responses to demographic parameters of the entire population (Warner 1988) (i.e. size-specific fecundity, mortality and growth). In this situation, the advantage of sex change for any individual is based on its reproductive value, which depends on the relative size of the individual to the size distribution of the mating group without taking in account the variation of the social group by time (i.e with a constant size structuring), and the possibility of repeated sex change. Indeed, it was thought for a long time that sex change can occur just once in sequential hermaphrodite vertebrates (Charnov 1982; Polikansky 1982), either because there were physiological constraints on sex reversal, or because there was no advantage in reverting to the original sex. This assumption has been overturned by an increasing list of f
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