The description of fish population demographic can be carried out with the estimate of key parameters: asymptotic length and weight (L∞ and W∞ ), growth constant (K), initial number of each cohort at times zero (N0) and mortality coefficient (Z). If the base information was obtained from samples taken with fishing gears with similar efficiencies, it would be possible to evaluate the population's historical changes or to carry out comparisons among populations of different water body. Both

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... ions are difficult to approach. Performance indices more used were presented like a simple tool of growth parameters integration with the purpose of facilitating the comparison. In this paper, the parameter T (maximum biomass time or age) and its standardization for the silverside is presented. This index may be used as tool to evaluate how far or close a population is regarding the standard values of growth and survival. So, it can be combining with performance indices in order to accepting the differences when T is next to the standard values for this species and to reject them when it moves away from T standard values.