Dynamic model and simulation analysis of the genetic impact of population harvesting

In this paper the impact of exploitation of a sexually reproducing population is investigated by means of a selection model. Our aim is to find genetic systems for which the fishing results in selection effect, provided that the growth and reproduction rates of individuals are genetically determined. To this end a complex dynamic model is presented, providing long-term predictions both on the size structure and on the genetic composition of the population. For a minimal nontrivial model, the two-locus two-allele case is considered, where the survival, transition and reproduction rates depend on size and genotype. For each size class and genotype the corresponding density is a state variable. The mating system is supposed to be totally panmictic and the gamete production is described in terms of the meiosis matrix. Based on the above model, an in silico analysis is carried out. The simulation results show that the long-term behaviour of the genetic structure can be characterized by a cyclic convergence, which means that the state sequences corresponding to different phases of the reproduction cycle tend to an asymptotic genotype distribution. For an illustration of the effect of exploitation on the genetic composition the "fishing effort" model is considered. If the totally homozygous genotype possesses the best phenotype, fishing does not seem to influence the genetic distribution in the long term. The same is true in case of heterozygote advantage. In some situations, however, fishing modifies the genetic distribution of the population. Meanwhile there is a significant change in the size of the harvested individuals. This result points out to the importance of the genotype-phenotype correspondence while building up fishing strategies. (C) 2010 Elsevier Inc. All rights reserved.