Estrutura populacional e aspectos reprodutivos de Potamorhina latior (Characiformes: Curimatidae) (Spix, 1829) dos lagos tributários do Rio Acre-Amapá e Pirapora.

Abstract

The aim of this work is a comparative study of the populations of Potamorhina latior (Characiformes: Curimatidae) (Spix. 1929) in the Amapa and Pirapora lakes, located in municipality of Rio Branco, seeking to gather data about structural and reproductive aspects as well as their interrelations with the environment. The initial presuposition was the both populations would show diffrent structures, due to the strong process of anthropomorphization affecting the Amapa lake, but not yet observed in the Pirapora lake. The data were collected in the periodo from April 2000 to March 2001, and comprised climatological, limnological and fish population variables expected to provide information on possible interrelations or differences between the populations. The results showed that the climatological variables kept the same pattern of unifomity observed in earlier years, but the wareer features were remarkably diffrent concerning transparency, turbidity, dissolved oxygen and conductivity. They also exhibited important diffrences in the population composition in the two lakes: the number of fish was much larger in the Pirapora; the males outnumbered the females in both lakes, though the difference was statiscally relevant only in the Amapa; the females achieved higher values in length and average weight in both lakes; both males and females in Pirapora were bigger and heavier. Moreover, in the Pirapora lake fish size for the first maturation was smaller even to males and females, and the same relation was maintained concerning size and reproduction maturity for all individuals considered. In the analysis of species fecundity conducted with females from Pirapora, diameter basis for oocytes elimination during egg laying was 0,40 mm, and fecundity ranged from 33,843 to 140,198 oocytes. Spawning was of the total type, occurring in the rainy season, probably between December and February, in accordance with observed reproductive effort defined by gonadosomatic index. According to the results found mainly for the Pirapora population, ther seems evident the need for developing further studies with this species to obtain more and deeper knowledge of its biology.