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Random retrospective pattern in fish stock assessment

Antonio Vázquez,Mónica Mandado-2010-01-01-DIGITAL.CSIC (Spanish National Research Council (CSIC))

TL;DRAbstract

The retrospective problem is a systematic inconsistency among a series of estimates of population size, or related assessment variables, based on increasing periods of data (Mohn 1999). Legault (2009) studied the retrospective patterns produced by data with a particular characteristic, such as missing catch, an increase in natural mortality or changes in survey catchability. Inconsistency in retrospective results can also be produced by the underlying inaccuracy of input data and incompetence of the assumed VPA model between to explain stock dynamics, however a defined pattern or systematic deviations in retrospective is not expected if such underlying variability is at random. The objective of this paper is quantifying the inconsistency in the case these effects are random, and we will continue to call it “retrospective” even it has not a “pattern”.

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The retrospective problem is a systematic inconsistency among a series of estimates of population size, or related assessment variables, based on increasing periods of data (Mohn 1999). Legault (2009) studied the retrospective patterns produced by data with a particular characteristic, such as missing catch, an increase in natural mortality or changes in survey catchability. Inconsistency in retrospective results can also be produced by the underlying inaccuracy of input data and incompetence of the assumed VPA model between to explain stock dynamics, however a defined pattern or systematic deviations in retrospective is not expected if such underlying variability is at random. The objective of this paper is quantifying the inconsistency in the case these effects are random, and we will continue to call it “retrospective” even it has not a “pattern”.

Keywords

Retrospective cohort studyStock assessmentStatisticsStock (firearms)PopulationEconometricsMathematicsDemography

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