Variações espaciais na atividade reprodutiva de peixes com diferentes estratégias reprodutivas antes e depois do represamento de São Salvador, rio Tocantins.

Abstract

In this study was evaluated the reproductive activity of fish with different reproductive strategies along of spatial gradients, in the longitudinal axis of the pre- and postimpoundment phases of São Salvador reservoir, Tocantins River, Tocantins State, Brazil. It is expected that the marked changes in habitats after damming restrict the reproductive activity of migratory strategies, but does not affect the others significantly. The samples were taken at six sampling sites distributed along the main body of the reservoir of São Salvador (R1 to R6 upstream-downstream direction) from September 2007 to August 2008 in the preimpoundment phase (RIO) and in January to December 2013 in the post-impoundment phase (RESERVOIR). Catches taken pre- and post-impoundment phases resulted in 149 species, and was analyzed in the reproductive activity of 48 species in the RIO phase and 46 species in RESERVOIR phase, but only 29 species showed reproductive activity in both phases. The results showed that the RIO phase the highest mean values of reproductive activity for the total species were recorded mainly in the vicinity of the mouth of the Custódio (R4) river, but with intense activity (IAR> 10) at the sites R1 and R2. In the other sampling sites (R3, R5 and R6) reproductive activity was moderate (IAR> 5). In RESERVOIR phase the higher mean values of ARI were recorded on site R1 and smaller in the vicinity of the dam (R6). Considering the reproductive strategies, the higher values at the scene of the IAR occurred at the R1site, regardless of the strategy considered. For migratory species (MLD), the intense reproductive activity was recorded only in the site R1 and at the river mouth Mucambão (R3). The mean values of IAR group of species with parental care (NMC) were low (incipient activity) at the sites R1 and R6 located in the extremes of the sampled area, but increased after damming (high activity). The mean values of the group of non-migratory species of longdistance and without parental care (NMS), with moderate to intense at the different sites of the reservoir, showed a decline in the site R6 vicinity dam. It was found in this study that regardless of the type of reproductive strategy many species of large, medium and small size, tend to reproduce in environments with features lotic, among which mainly include fluvial zone and the lateral tributaries.