Influence of the flood regime on the reproduction of fish species with different reproductive strategies in the Cuiabá River, Upper Pantanal, Brazil

Abstract

This study evaluated the influence of the flood regime of the Cuiabá 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.

Seasonal changes in the gonadossomatic index, allometric condition factor and sex ratio of an auchenipterid catfish from eastern Amazonia

“…By analyzing both the frequency distributions of gonadal maturation stages and the seasonal variation of the GSI, we suggest an extended spawning period for A. longimanus population in rivers of the Caxiuanã National Forest, a pattern similar to the already described for other auchenipterids (Araújo et al, 1999;Bailly et al, 2008). The reproductive period was identified with greater intensity during the flood period, in which the flooded forest forms a rich environment for fish (Goulding, 1980), suggesting the flood pulse as the primary environmental factor influencing fish recruitment (Zeug & Winemiller, 2008).…”

“…By contrast, Bailly et al (2008) found that the gonadal development of three auchenipterid fishes (Auchenipterus osteomystax, A. nigripinis, and Parauchenipterus galeatus (= Trachelyopterus galeatus) were not affected by the hydrological cycle in the Brazilian Pantanal wetlands. These results emphasize that auchenipterid species can show different strategies in relation to the reproductive site and natural environmental cycle, and more studies on these species are in need to allow the understanding of the group framework.…”

“…Goulding, 1980), the floodplain provides feeding sites, nursery areas and protection from predators for many fish species. According to the flood pulse concept, proposed by Junk et al (1989), the annual floodplain inundation triggers blooms of primary and secondary production, and the fish species in these complex systems have reproductive ecologies adapted to exploit this pulse of production (Bailly et al, 2008).…”

“…Within teleost, several recent studies have demonstrated the important role played by seasonal floods on theses reproductive parameters both in temperate (Zeug & Winemiller, 2007 and tropical rivers (Agostinho et al, 2004;Bailly et al, 2008). Nevertheless, the available studies on the biology and ecology of Auchenipteridae catfishes focus on few species (Araújo et al, 1999;Silva & Viana, 2003;Bailly et al, 2008) and insufficient information are available for the driftwood catfish Auchenipterichthys longimanus (Günther, 1864).…”

“…Nevertheless, the available studies on the biology and ecology of Auchenipteridae catfishes focus on few species (Araújo et al, 1999;Silva & Viana, 2003;Bailly et al, 2008) and insufficient information are available for the driftwood catfish Auchenipterichthys longimanus (Günther, 1864).…”