RETROSPECTIVE ANALYSIS OF THE ASSESSMENT OF THE CHILEAN HAKE (MERLUCCIUS GAYI) BY USING A TUNING SEQUENTIAL POPULATION ANALYSIS

Abstract

A retrospective analysis of the stock assessment of the Chilean hake resource off central-southem Chile (30°S-40°S) is carried out. The objective is to identify bias in the annual stock assessment by using an ad hoc tuning Sequential Population Analysis (SPA), which considers catch per unit effort data as auxiliary information. The retrospective analysis showed a consistent over estimation of the fishing mortality for the recruits and younger ages for each terminal year and, therefore, an under estimation of the abundance for the same ages. This is due to the exploitation pattem, estimated for the most recent year. A procedure to estímate variance from the SPA, using a parametric form of the bootstrap method, showed that the exploitation pattem in the terminal year has a great incidence on the results of the evaluation. It is recommended to improve the auxiliary information and to consider the posibility of estímating the fishing mortality separately for each age class in the most recent year, being necessary to use fishing effort data or another abundance índex as obtained from surveys.