This paper analyses some aspects on the length/weight relation ship of Sardinella brasiliensis and its variations as a function of their reproductive cycle and displacements along the Brazilian coast between 23ºS and 28ºS. The area surveyed was divided into five sub-areas, each one covering one degree of latitude. The relationship and its variations between shoals were studied for each sub-area at different seasons and for the sub-areas at the same season. The absence of a variation pattern for the length/weight relationship has shown to be the result of seasonal changes in the physiological aspects of fish (as a function of their reproductive cycle) as well as result of behaviour of individuals in two main areas: 23ºS-25ºS and 26ºS-28ºS, which are spawning areas, spawning occuring during spring and summer at the first and only during spring at the latter. After spawning the young (from both areas) more at different times to a common trophic area where they find suitable conditions (25ºS26ºS), returning to their original sub-areas at different occasions, following their first sexual maturation. Although spawning takes place at different times and sites, with the convergence of young to a common nursery, mixing might occur. Further studies on meristics and body proportions are being developed regarding the existence of different populations.