The total number of individuals of a certain species present in an area, generally estimated by sampling methods (such as capture–recapture), and which may vary according to competition, predation, and resources.
An index of abundance is a relative measure of the size of a population or sub-unit of the population, such as a year class. The abundance, for example, of fish may be measured as number/weight of fish caught per standard unit of fishing effort, in a given area, and for a given time span, and then compared to earlier data. See Pearce and Ferrier (2001) Biol. Conserv. 98, 1 on modelling the relative abundance of species for regional conservation planning.
Subjects: Earth Sciences and Geography.