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Keywords:

  • dynamic response analysis;
  • stock assessment;
  • maximum net productivity level

Abstract

A qualitative determination of whether a population is above or below its MNPL can be carried out under circumstances where the value of the MNPL itself, and other details of the production curve, cannot be estimated. This qualitative assessment may often be sufficient for management decisions. The method proceeds by locally approximating the production curve, in the neighborhood of the present population density, from data on population sizes and harvests, and then determining whether this represents the ascending or descending arm of the curve. When the harvests are small, or when the harvests are a constant fraction of the production, the population-size data need only be relative. With adequate quantities of data, this assessment method can accommodate random measurement error and random perturbations in the dynamics of the population system.