Fishing has been identified as a potential cause of the evolution of earlier age and size at maturation in many fish stocks. Several studies have focused on the ecological effects of fisheries on slow-growing, late-maturing hermaphroditic species such as groupers, but few have looked
at the potential evolutionary effects of long-term size-selective fishing on hermaphrodites. We present an individual-based energy-allocation life-history model parameterized for Epinephelus fuscoguttatus Forsskål, 1775. Individual life-history trajectories are specified by three
“genes”: length at 50% probability of maturation and the proportions of available energy allocated to reproduction in the female and male phases. A genetic algorithm finds evolutionarily stable life-history strategies (ESS). Age and size at maturation and sex change are thus emergent
traits. The model predicts that the grouper hermaphroditic life-history strategy should be very sensitive to even low fishing mortalities. Under increasing fishing mortalities, the ESS showed decreased age and size at maturation and sex change and increased female-to-male sex ratios. The model
predicted an alteration in the sex system, under which the population became dioecious (having separate sexes) at intermediate fishing mortalities. The evolutionarily stable yield peaks at fishing mortalities as low as 0.06 yr–1. Fisheries management in the simplest form would,
for such species, include implementing a low fishing mortality and choosing proper size limits for the fishery.
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