História de vida de Leporinus piau Fowler, 1941

Abstract

Hydroelectric dams cause physical and biological effects in rivers around the world, such as suppression of downstream ponds and disruption of aquatic assemblages and organism populations. In order to test the influence of hydroelectric dams on the life history of fish populations, we chose the Parnaíba river and the Leporinus piau species as objects for our study. The Parnaíba river has a single dam located about 560 km from the sources, in the municipality of Guadalupe-PI and known as ‘Boa Esperança Dam’. We investigated in the first chapter the physical impact caused by the reservoir through the impoundment in the upstream and downstream sites, at distant points about 80 km from the beginning of the lake and its spillway, respectively. For this, we collected historical data on river level, flow and rainfall in the Hydrological Information System of the Agência Nacional de Águas (ANA) and analyzed them through descriptive statistics to verify the effect of the reservoir on the studied sites. In the second chapter we evaluated this effect on the biology of Leporinus piau, through the analysis of life history and diet characteristics of the species. Leporinus piau is a migratory species of Characiformes, Anostomidae, popularly known as “piau”, “piau-cabeçagorda” or “piau-coqueiro”, an important source of animal protein exploited through artisanal, sports and subsistence fisheries. The results indicated a greater physical effect in the upstream stretch, through the attenuation of the water flow caused by Boa Esperança Reservoir. Downstream we recorded a greater variation of flow and river level, caused by the rainfall that also varied significantly. Regarding the trophic biology of the species, a significant difference was observed in the composition of the diet among the populations in these same sites, as well as in the niche amplitude between sites and seasonal seasons; as for reproduction, it was verified that the individuals of the upstream population were larger and that downstream presented a smaller size of first maturation, thus reflecting in Condition Factor (K) which was also different. There was no positive relationship between the gonadosomatic index (IG) and rainfall, indicating that there is no environmental signaling for the spawning of the species, in a more pronounced way in the downstream population. The set of results indicate that populations of Leporinus piau undergo different environmental pressures at each site, which may cause their conservation status to be lowered from nonthreatened to vulnerable.