Merona de Bernard auteur aut IRD Mol J. auteur aut IRD Vigouroux R. auteur aut IRD Chaves P. D. auteur aut IRD text journalArticle eng text/pdf born digital access Fish species are known for their large phenotypic plasticity in life-history traits in relation to environmental characteristics. Plasticity allows species to increase their fitness in a given environment. Here we examined the life-history response of fish species after an abrupt change in their environment caused by the damming of rivers. Two reservoirs of different age, both situated on the Guiana Shield, were investigated: the young Petit-Saut Reservoir in French Guiana (14 years) and the much older Brokopondo Reservoir in Suriname (44 years). Six life-history traits in 14 fish species were studied and compared to their value in the Sinnamary River prior to the completion of Petit-Saut Reservoir. The traits analyzed were maximum length, absolute and relative length at first maturation, proportion of mature oocytes in ripe gonad, batch fecundity and mean size of mature oocytes. The results revealed a general increase of reproductive effort. All species showed a decrease in maximum length. Compared to the values observed before the dam constructions, eight species had larger oocytes and three species showed an increased batch fecundity. These observed changes suggest a trend towards a pioneer strategy. The changes observed in Petit-Saut Reservoir also seemed to apply to the 30 years older Brokopondo Reservoir suggesting that these reservoirs remain in a state of immaturity for a long time. specialized South America Reproduction Strategy Tactic Fecundity Oocyte size 034 7 4 683-692 2009 1679-6225 https://www.documentation.ird.fr/hor/fdi:010049255 10.1590/S1679-62252009000400018 1679-6225 [F B010049255] https://www.documentation.ird.fr/hor/fdi:010049255 https://www.documentation.ird.fr/intranet/publi/2010/02/010049255.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2010-03-10 2017-08-23 fdi:010049255 fre