Homing fidelity and reproductive rate for migratory populations

Abstract

Short-term and long-term population growth rates can differ considerably. While changes in growth rates can be driven by external factors, we consider another source for changes in growth rate. That is, changes are generated internally by gradual modification of population structure. Such a modification of population structure may take many generations, particularly when the populations are distributed spatially in heterogeneous environments. Here, the net reproductive rate R0 is not sufficient to char- acterize short-term growth. Indeed, a population with net reproductiverate greater than one couldinitially declinepre- cipitously, or a population with net reproductive rate less than one could initially grow substantially. Thus, we aug- ment the net reproductive rate with lower and upper bounds for the transient reproductive rate, Rl and Ru. We apply these measures to the study of spatially structured salmon populations and show the effect of variable homing fidelity on short-term and long-term generational growth rates.