Evolutionary consequences of age-specific harvesting: age at first reproduction

The aim of this paper is to investigate harvest-induced evolution in life-history strategies of a harvested single-species population. In particular, we analyze evolution of the trait age at first reproduction. The population is grouped into four age classes, namely, zero-year-olds (newborns), one-year-olds (juveniles), two-year-olds (small adults), and individuals aged three years or older (large adults). The population is assumed to consist of a ‘resident’ group and a ‘variant’ group that are identical except that the resident group usually first reproduces as a large adult and the variant group usually first reproduces as a small adult. The effect of various age-dependent harvesting strategies on the dynamics is studied both analytically and numerically. It is shown that age-dependent harvesting strategies can cause evolution from the resident group to the variant group. In addition, we show that a limit on the harvesting of the resident group can yield a sustainable fishery of the commercially preferred resident group.