02005naa a2200229 a 450000100080000000500110000800800410001910000210006024500870008126000090016852014160017765000090159365000100160265000140161265000090162665000100163565300140164565300150165965300160167470000240169077300610171417919302017-04-05       1990    bl ---       0--  u    #d1 aRODRIGUEZ, M. A.  aDiversity and species composition of fish communities of Orinoco floodplain lakes.  c1990  aFish communities of Neotropical floodplains are often characterized as higly variable in space and time, but basic patterns of species diversity, distribution, abundance, and temporal dynamics are still poorly described. To document these patterns and to quantify the relative magnitudes of spatial and temporal variation in spcies composition, floodplain fish communities in Venezuela were studied for two years. Fish were collected from 20 lakes in one blackwater and two whitewater regions along a 400-km stretch of the lower Orinoco River. Characoids and catfishes predominated in the collection of 170 species, followed by knifefishes and cichlids. Patterns of species richness hardly varied from year to year. Year-to-year variation in species composition of individual lakes was small compared with spatial variation among lakes. Most of the spatial avariation in species composition was due to differences betwen the blackwater region and the two whitewater regions; the two whitewater regions hardly differed from each other, even though they were 400 km apart. The main finding is that species richness and species composition were strikingly constant from year to year at three levels: individual lakes, regions, and whole basin. The authors suggest that site-specific enviroenmental attributes vary slowly with time and constrain the potentially high rates of changes in floodplain fish communities.  afish  alakes  aVenezuela  aLago  aPeixe  aCommunity  aComunidade  aRio Orinoco1 aLEWIS JUNIOR, W. M.  tNational Geographic Researchgv.6, n.3, p.319-328, 1990.