Virtual population analysis

Bharti, Vivekanand (2017) Virtual population analysis. In: Course Manual Summer School on Advanced Methods for Fish Stock Assessment and Fisheries Management. Lecture Note Series No. 2/2017 . CMFRI; Kochi, Kochi, pp. 232-237.

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Abstract

Virtual population analysis (VPA) is a modeling technique commonly used in fisheries science for reconstructing the historical population structure of a fish stock using information on the deaths of individuals in each time step. The time steps are typically annual (though not necessarily) and the deaths are usually partitioned into mortality due to fishing and natural mortality. VPA therefore looks at a population in an historic perspective. The advantage of doing a VPA is that once the history is known it becomes easier to predict the future catches, which is usually one of the most important tasks of fishery scientists. Virtual population analysis calculates the number of fish alive in each cohort for each past year. It is also called cohort analysis because each cohort is analysed separately. VPA relies on a very simple relationship for each cohort. VPA or Cohort analysis was first developed as age-based methods in temperate regions further developed as length-based methods for tropical regions.

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