INFLUENCE OF THE FLOOD REGIME ON THE REPRODUCTION OF FISH SPECIES WITH DIFFERENT REPRODUCTIVE STRATEGIES IN THE CUIABA RIVER, UPPER PANTANAL, BRAZIL

This study evaluated the influence of the flood regime of the Cuiaba River on the reproductive dynamics of fish species with different reproductive strategies. Sampling was carried out at ten sites in the basin, between March 2000 and April 2004. The reproductive strategies evaluated were long-distance migrant (LM), short-distance migrant (SM), sedentary with parental care (PC) and sedentary or SM with internal fertilization (IF). Period, duration and intensity of floods were the flooding attributes considered. Duration and time of spawning were evaluated using the index of reproductive activity (IRA), and inferences concerning reproductive allocation were based on the analysis Of gonad weight. Reproductive success was evaluated based on the annual catch of young-of-the-year of each species. Reproductive dynamics and flood regime were closely correlated; the reproductive peaks of fishes using all four strategies always preceded flood peaks. Intense floods favoured gonadal development of LM and PC, but were less important for IF. In relation to juvenile survival, the occurrence of floods appeared to be crucial for the strategies of LM, PC and IF, because such floods increased fish survival in the period of initial development. In contrast, SM appeared to be less dependent on floods for reproduction. These results indicate that, except for SM, floods have an important role in the recruitment of species using other reproductive strategies, and influence spawning success as well as juvenile survival. Copyright (C) 2008 John Wiley & Sons, Ltd.