Virtual population analysis

Virtual population analysis (VPA) is a cohort modeling technique commonly used in fisheries science 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

References

• Shepherd, John G.; John G. Pope (2002). "Dynamic pool models I: Interpreting the past using Virtual Population Analysis". In P. J. B. Hart, J. D. Reynolds (ed.). Handbook of Fish Biology and Fisheries. Vol. 2. Fisheries. Oxford, UK: Blackwell Science. pp. 127–136.  CS1 maint: Uses editors parameter (link)

Fisheries science and wild fisheries Fisheries science Population dynamics of fisheries Shifting baseline Fish stock Fish mortality Condition index Stock assessment Fish measurement Standard weight in fish Fish counter Data storage tag Catch per unit effort Otolith microchemical analysis Biomass Fisheries acoustics Acoustic tag Coded wire tag GIS and aquatic science Pop-up satellite archival tag EcoSCOPE Age class structure Trophic level Trophic cascades Match/mismatch hypothesis Fisheries and climate change Marine biology Aquatic ecosystems Bioeconomics EconMult Ecopath FishBase Census of Marine Life OSTM Fisheries databases Institutes Fisheries scientists Wild fisheries Ocean fisheries Diversity of fish Coastal fish Coral reef fish Demersal fish Forage fish Pelagic fish Cod fisheries Crab fisheries Eel fisheries Krill fisheries Kelp fisheries Lobster fisheries Shrimp fishery Eel ladder Fish ladder Fish screen Migration Salmon run Sardine run Shoaling and schooling Marine habitats Marine snow Water column Upwelling Humboldt current Algal blooms Dead zones Fish kill

Fisheries management, sustainability and conservation Management Fisheries management Fisheries law Monitoring control and surveillance Vessel monitoring system Fishery Resources Monitoring System Catch reporting Fisheries observer Illegal, unreported and unregulated fishing Magnuson–Stevens Act Pulse fishing Fisheries organizations Quotas Catch share Individual fishing quota Minimum landing size Slot limit Bycatch Discards Incidental catch Cetacean bycatch Turtle excluder device Shrimp-Turtle case EU quotas EU MLS Exclusive economic zone Sustainability Sustainable fisheries Maximum sustainable yield List of harvested aquatic animals by weight Sustainable seafood Overfishing Environmental effects of fishing Fishing down the food web Destructive fishing practices Future of Marine Animal Populations The Sunken Billions The End of the Line Conservation Marine Protected Area Marine reserve Marine conservation Marine conservation activism Salmon conservation Grey nurse shark conservation Shark sanctuary Organisations The Black Fish Marine Stewardship Council Aquaculture Stewardship Council Friend of the Sea SeaChoice Seafood Watch Ocean Conservancy Oceana Sea Around Us Project WorldFish Center Defying Ocean's End HERMIONE PROFISH International Seafood Sustainability Foundation Sea Shepherd Conservation Society Greenpeace Related issues CalCOFI Fish slaughter Marine pollution Mercury in fish Shark finning Threatened sharks Threatened rays List of fishing topics by subject Index of fishing articles Fisheries glossary

Fisheries and fishing topic areas
Fisheries	Aquaculture Diversity of fish Fish diseases and parasites Fish farming Fisheries management Fisheries science Individual fishing quota Sustainable fishery Wild fisheries
Fishing	Artisanal fishing Fisherman Fishing vessel History of fishing
Industry	List of harvested aquatic animals by weight By country Commercial fishing Marketing Markets Processing Products Seafood
Recreation	Angling Big-game fishing Catch and release Fishing tournaments Fly fishing
Techniques	Fish trap Fishfinder Fishing net Gathering seafood by hand Handline fishing Spearfishing Trawling
Tackle	Artificial flies Bait Bite indicators Hook Line Lures Rod Sinker
Locations	Fish ponds Fishing banks Fishing villages Marine habitats
Glossary Index Outline Fishing portal Category