Longitudinal structure, density and production rates of a neotropical stream fish assemblage:: the river Ubatiba in the Serra do Mar, southeast Brazil

Spatio-temporal variations in the structure, density, biomass and production rates of fish were assessed in the neotropical River Ubatiba (Serra do Mar, southeast Brazil). Electrofishing techniques and the length-frequency method were shown to be reliable for the assessment of fish numbers and production rates in these running waters of medium conductivity. Eighteen fish species of small size and prolonged spawning period were broadly distributed throughout the river catchment. Over the year, the assemblage structure was persistent along the river. Water column omnivore and algae/detritivore species dominated in density (15086-70330 ind. ha(-1)), whereas three omnivores and a piscivorous species accounted for 70% of the production (51.5-250.4 kg ha(-1) yr(-1)). Comparison of production rates among, tropical, temperate and Mediterranean stream fish assemblages indicate lower rates in tropical streams and an inverse relationship between production and species diversity, lower production rates in high-diversity tropical streams vs higher rates in low-diversity Mediterranean streams, with intermediate rates in temperate streams of intermediate diversity.