The number of individuals (actually, as a percentage) surviving in a population over a period of time. Often measured by the ratio of the number of adult fish to the number of putrescents.

An indicator (usually expressed as a percentage) of the total number of fish from natural spawning or released stock (caviar, fry, fingerlings, etc.) that have reached puberty. For example, if 100 carp fingerlings are stocked and only 50 survive to adulthood in the reservoir, the survival rate is 50%. Commercial survival is an indicator (usually expressed as a percentage) of the number of adult fish that can be obtained by fishing in natural reservoirs from the amount of source material (caviar, fry, fingerlings, etc.). For example, if the survival rate is 30%, then out of 100 fingerlings of the source material, the fishery can get 30 adult fish in the catch.