Harvesting Models for Resource-limited Populations

’Extensive’ herbivore/vegetation models and ’intensive’ grazing models yield two conclusions for sustained-yield harvesting of populations regulated by an interaction with their resources. First, the growth curve for the population, relating growth rate to current density, and the equilibrium yield/effort curve under harvesting, are likely to be asymmetric, with peaks displaced to the right and maximum growth rate and harvest greater then predicted by the symmetrical, single-species logistic model. In general, the growth curve for a consumer has its peak displaced to the right relative to that of its resource. Second, stability of the population and harvest is greater at moderately high harvesting intensities than at low ones, and is greater the more leftward-peaked the resource growth curve.