Biologia populacional de Pareiorhina rudolphi (Loricariidae, Hypostominae) na microbacia do Ribeirão Grande, serra da Mantiqueira oriental, Estado de São Paulo

Abstract

Pareiorhina rudolphi was sampled in streams of the Ribeirão Grande system, eastern Serra da Mantiqueira (22o 47’ 08’’S, 45o 28’ 17’’ W). Samplings were carried out using an electrofishing device, during the months of July/2001, October/2001, February/2002 and April/2002. Sex-ratio diverged significantly from the expected 1:1 ratio (χ2 = 6.53; p < 0.05), standing at 1.6:1 (female: male). The spawning period for Pareiorhina rudolphi lasts from spring to summer, with the highest observed in October and February by the gonadosomatic index and the relative condition factor coincided with the spawning period. The length at sexual maturity of P. rudolphi is about 4.45 cm for both sexes. The absolute fecundity was low, and ranged from 4 to 11 oocytes. The periphyton was used as a direct food source by the species, which remain attached to the substrate with their large circular lips, and use their conspicuous slightly yellowish teeth to graze the periphyton. The growth parameters, natural mortality rate and survival rate for P. rudolphi were respectively: K = 0.35 year-1 , L∞ = 7.2 cm, tmax = 8.6 years, M = 1.1 year-1 , S = 33%. The characteristics presented by P. rudolphi occur in the environment in function of a population adjustment, and not of species abundance. Key