Virtual population analysis (VPA) is a
cohort
Cohort or cohortes may refer to:
Cohort Sociological
* Cohort (military unit), the basic tactical unit of a Roman legion
* Cohort (educational group), a group of students working together through the same academic curriculum
Scientific
* Cohort ...
modeling technique commonly used in
fisheries science
Fisheries science is the academic discipline of managing and understanding fisheries. It is a multidisciplinary science, which draws on the disciplines of limnology, oceanography, freshwater biology, marine biology, meteorology, conservation, ...
for reconstructing historical fish numbers at age using information on death of individuals each year. This death is usually partitioned into catch by fisheries and
natural mortality. VPA is virtual in the sense that the population size is not observed or measured directly but is inferred or back-calculated to have been a certain size in the past in order to support the observed fish catches and an assumed death rate owing to non-fishery related causes.
Virtual population analysis was introduced in
fish stock assessment by Gulland in 1965 based on older work. The technique of cohort reconstruction in fish populations has been attributed to several different workers including Professor
Baranov from Russia in 1918 for his development of the continuous catch equation, Professor Fry from Canada in 1949 and Drs.
Beverton and
Holt from the UK in 1957. Because cohort reconstruction is essentially an accounting exercise it was likely independently conceived many times.
Several different software implementations of cohort reconstruction for fish populations exist including ADAPT, which is often used in Canada and the USA, and XSA which is commonly used in Europe. The back-calculations in these implementations work the same way but they differ in the statistical methods used for "tuning" to indices of population size.
See also
*
Population dynamics of fisheries
A fishery is an area with an associated fish or aquatic population which is harvested for its commercial or recreational value. Fisheries can be wild or farmed. Population dynamics describes the ways in which a given population grows and shr ...
References
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{{fisheries and fishing
Fisheries science