Production Modeling Using Mortality Estimates

Abstract

Two new approaches to applying the logistic model to fisheries data are suggested; these do not employ information on fishing effort, but use the overall mortality rate (Z) for the population as a direct index of fishing mortality rate (F). The first approach suggests fitting a parabola between annual yield and mean annual Z, and provides an independent estimate of natural mortality M; the second suggests fitting a straight line directly between catch rate and mean annual Z. Both approaches use data sources that are statistically independent and encourage a smooth transition from an early use of production models in a developing fishery into the use of more elaborate analytical models as the data base accumulates.Key words: Theory of production modeling, logistic population growth, use of mortality parameters in fitting