Positive Periodic Solution and Numerical Optimization in the Harvesting Effort for a Single-Species Stage-Structured System with Birth Pulses

In this paper, we consider a single-species stage-structured model with birth pulses and the harvesting of the species. Especially, we assume that the species can be divided into the immature and the mature, which exhibit different death rates. The mature species reproduces at fixed moments each year because the birth of many species is seasonal or occurs in a regular pulse, and the species is harvested not during the whole year but during a single period of the year. For such a system, we obtain conditions which guarantee the existence of a stable positive periodic solution. This implies that sustainable exploitation of the species can be maintained if we use the proper strategy in the harvesting effort and timing. Further, in order to get the maximum annual sustainable yield, we optimize the harvesting using numerical analysis; in addition, we find that the harvesting timing affects the maximum annual sustainable yield. Lastly, we show the effects of birth rate and harvesting effort on the dynamical complexity of the system with the help of a bifurcation graph.