Age class structure

Age class structure in fisheries and wildlife management is a part of population assessment. Age can be determined by counting growth rings in fish scales, otoliths, cross-sections of fin spines for species with thick spines such as triggerfish, or teeth for a few species. Each method has its merits and drawbacks. Fish scales are easiest to obtain, but may be unreliable if scales have fallen off the fish and new ones grown in their places. Fin spines may be unreliable for the same reason, and most fish do not have spines of sufficient thickness for clear rings to be visible. Otoliths will have stayed with the fish throughout its life history, but obtaining them requires killing the fish. Also, otoliths often require more preparation before ageing can occur.

Analyzing fisheries age class structure

An age class structure with gaps in it, for instance a regular bell curve for the population of 1-5 year-old fish, excepting a very low population for the 3-year-olds, implies a bad spawning year 3 years ago in that species.

Often fish in younger age class structures have very low numbers because they were small enough to slip through the sampling nets, and may in fact have a very healthy population.

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

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Age class structure

Analyzing fisheries age class structure

See also