SPATIAL-ORGANIZATION AND POPULATION-DENSITY OF THE FISH COMMUNITY OF THE LITTER BANKS WITHIN A CENTRAL AMAZONIAN BLACKWATER STREAM

Results of a study of the fish community of the leaf litter banks in the lower reaches of the Taruma‐Mirim, a small central Amazonian stream is presented. The Taruma‐Mirim is an acidic, blackwater, forest stream which flows through igapo forest and enters the Rio Negro close to Manaus. The commonly held view that these blackwaters hold an impoverished ichthyofauna is challenged. The studied litter banks hold about 20 species of fish, all of which were found to live within distinct subregions of the habitat. Average fish density was about 100 individuals m−2. Absolute population sizes were found to be remarkably small; within a 200 m2 area the most abundant species had a population size of about 104 and the least abundant <102 individuals. It is argued that high species richness linked to specialized habitat requirements and small population size indicates considerable population stability. The factors leading to the evolution of such species richness are discussed. Copyright © 1990, Wiley Blackwell. All rights reserved