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Age class structure in fisheries and
''www.fao.org''. Retrieved 2018-03-24. 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.
Age class structure in fisheries and wildlife management
Wildlife management is the management process influencing interactions among and between wildlife, its habitats and people to achieve predefined impacts. It attempts to balance the needs of wildlife with the needs of people using the best availab ...
is a part of population assessment. Age class structures can be used to model many populations including trees and fish. This method can be used to predict the occurrence of forest fires within a forest population. Age can be determined by counting growth rings in fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% ...
scales, otoliths, cross-sections of fin spines for species with thick spines such as triggerfish,O’Sullivan, Sandra (2007). ''Fisheries Long Term Monitoring Program''. Brisbane, Australia: Queensland Department of Primary Industries and Fisheries. 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."MANUAL OF FISHERIES SCIENCE Part 2 - Methods of Resource Investigation and their Application"''www.fao.org''. Retrieved 2018-03-24. 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 example of using age class structure to learn about a population is a regular bell curve for the population of 1-5 year-old fish with a very low population for the 3-year-olds. An age class structure with gaps in population size like the one described earlier implies a badspawning
Spawn is the eggs and sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of releasing the eggs and sperm, and the act of both sexes is called spawning. Most aquatic animals, except for aqua ...
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.Haines, Terry A. (1990). ''Intensive Studies of Stream Fish Populations in Maine''. Washington, D.C., USA: U.S. Environment Protection Agency, Office of Acid Deposition, Environmental Monitoring and Quality Assurance. p. 17.
See also
* Identification of aging in fish *Population pyramid
A population pyramid (age structure diagram) or "age-sex pyramid" is a graphical illustration of the distribution of a population (typically that of a country or region of the world) by age groups and sex; it typically takes the shape of a pyramid ...
* Population dynamics of fisheries
References