Abstract

The instantaneous natural mortality rate is estimated for toothfish (Dissostichus eleginoides) using empirical models, with the emphasis on an evaluation of the precision of the estimates. The results are compared with estimates obtained per age classes and obtained through an analytical model. The growth parameters and the size at first maturity available for toothfish are used in order to consider the error in the input parameters, and after the prediction error in the variance computation of the estimates. The M values were estimated with low precision, with coefficients of variation ranging between 41 y 60%, and confidence intervals at 95% fluctuating between 0.04 y 0.39 yr-1. The median of the estimates ranged between 0.1 and 0.14 yr-1, and they were closed to the average of the M values obtained per age classes (M = 0.11 yr-1). It is recommended to use M = 0.1 yr-1 for stock assessment models applied to the resource, since centesimal values make no sense for an imprecise parameter.