Comparaison de methodes de decomposition de distribution polymodales de frequences de longueurs en distributions unimodales successives (NORMSEP-MIX-Maximums successive maximums), application aux "bossus" (Pseudolithus elongatus ) du Congo

Length measurements on Pseudotolithus elongatus ' samples from the Congo were recorded in the 60s. Subsamples were collected in order to be "aged" by otoliths' reading. The size frequency distributions were splitted into successive unimodal distributions by different methods. Their results were compared. The results obtained from the "successive maximums' method" were similar to those from the "otoliths' reading." The programs NORMSEP and MIX gave results far more difficult to interpret biologically speaking in spite of their mathematical quality. Because many length frequency distributions of a cohort are symmetrical in nature, we suggest applying the "successive maximums' method"if there is no evidence of normality