A relative-length-frequency study, in the Gulf of Nicoya, Costa Rica from May 1980 to April 1981, showed that in Anchoa panamensis there are two age groups per year, with maximum spawning peaks during the rainy season, May and October. The asymptotic total llength (L=) and weight (W=) were 160.1 mm and 27.1 g, respectively. The total mortality rate was calculated as 5.240 and we conclude that the population is being underexploited.