Application of a Multispecies Approach for Assessing the Population Abundance and the Age–Structure of Fish Stocks

Abstract

Application of a multispecies approach for assessing the population abundance and the age-structure of fish stocks is proposed. The main objective of this approach is to eliminate a bias in the results of cohort analysis (the most frequently used single-species procedure for assessing the fish population age-structure) caused by uncertainties in the external estimates of natural mortality rates. The approach is applicable if fish predation is a major cause for fish natural mortality and all fish species which significantly interact among themselves through predation are taken into account. It is additionally assumed that these fish species do not leave the area under consideration. Compliance with these conditions allows the prediction, on the basis of ecological theory and required field and laboratory data, of a major component of natural mortality, predation mortality, within extended cohort analysis. The paper describes the proposed procedure (extended cohort analysis) and outlines possible ways of collecting the required input data.Key words: assessment, fish population abundance, age-structure, multispecies approach, natural and fishing mortality