the growth of atherinella brasiliensis (quoy & gaimard, 1824) was studied through monthly samples taken at tramandaí lagoon, imbé county, rio grande do sul, brazil. animals were captured using a beach seine net. length-weight relationships and age- growth curves for males and females were adjusted. the growth parameters of the von bertalanffy growth formulae are linf=16.0 and k=0.883 for males and linf=17.0 and k=0.825 for females. first reproduction occurred one year after recruitment. once reaching maturity, adults of a. brasiliensis reproduced once more in the next spring with two-year-olds and disappeared soon after from size frequency distributions. a few captured animals showed a size compatible with an age of three years.