An augmented Clark model for stability of populations.

A simple modification of a frequently employed age-structured model for population dynamics is presented. This augmented formulation allows the assessment of the impact of age-dependent harvest mortality on population stability. The characteristic frequencies of the predicted oscillations are discussed. The period of oscillation is almost independent of survival and the exact functional form of the recruitment function, and it is not equal to twice the mean age of mature animals, as suggested earlier. It is shown that increased survival before reproduction has a destabilizing influence for populations exhibiting an overcompensatory recruitment function.