In the present study, the age, growth, reproduction and the population dynamics of APHANIUS FASCIATUS were investigated in three different sampling stations in Mesolongi and Etolikon lagoons. The age was determined from the scales and founded six age classes. The study of monthly marginal increment showed that APHANIUS FASCIATUS form their yearly annulus during February. Were founded significantly differences between sexes and between regions with relate to age composition, the slope of length-weight relationships, the mean back-calculated total lengths, the condition factor and the mortality rate. The reproduction season was particularly long. It began in April and ended in July. The spawning was multiple with the production of many clutches. The hydrated oocytes are relatively large with diameter about 2 millimeters and specific gravity 1.0046 grams per cubic centimeters, eggs are entangled in vegetation by means of long filaments. The study of fecundity showed that there are significantly differences between sampling stations, the maximum absolute fecundity was 591 eggs. The overall sex ratio was found 1: 2.44 (males: females) that was changing during the year