Production rates (P) and biomass (B) of two stream-dwelling fish species from seven sites in the Ubatiba drainage were studied during two years with contrasting rainfall indexes. In order to test the potential correlation between P, B and the Environmental Heterogeneity Index (EHI) of each site, simple correlation analyses were applied. The analyses did not show significant differences (p<0.01). Spatial pattern of P indicated that production rates of both species are highly homogeneous in the studied sites but are low when compared with other stream-dwelling fishes from the Holartic region. Mean P and B values of Astyanax hastatus Myers, 1928 were Prainy = 14.0 kg.ha-1.year-1, Pdry = 24.4 kg.ha-1.year-1 and Brainy = 7.3 kg.ha-1, Bdry = 12.2 kg.ha-1, with significant higher values during the dry year (t (B)= 2.41; p = 0.03 e t (P)= 2.28; p = 0.04). In spite of presenting a tendency similar to that found for A. hastatus, mean P and B values for Geophagus brasiliensis (Quoy & Gaimardi, 1824) did not show significant differences (t (B) = 1.5; p = 0.16 and t (P) = 1.75; p = 0.11) between years: Prainy = 25.2 kg.ha-1.year-1, Pdry = 53.2 kg.ha-1.year-1 and Brainy = 16.6 kg.ha-1, Bdry = 29.7 kg.ha-1. Reduction of P in the rainy year were 57% and 47% for A. hastatus and G. brasiliensis, respectively. Mean values of P/B decreased among larger individuals of both species.
Secondary production; turnover rates; fish; stream
