Longitudinal patterns of fish assemblages in a large tropical river in southeastern Brazil: evaluating environmental influences and some concepts in river ecology |
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Authors: | Francisco Gerson Araújo Benjamin Carvalho Teixeira Pinto and Tatiana Pires Teixeira |
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Institution: | (1) Laboratório de Ecologia de Peixes, Universidade Federal Rural do Rio de Janeiro, Km 47 Antiga Rod Rio S?o Paulo, Seropedica, RJ, 23851-970, Brazil |
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Abstract: | This study aimed to evaluate environmental influences on fish distribution and to assess the extent to which concepts in river
ecology accommodate levels of spatio-temporal heterogeneity of fish assemblages in a 1,080-km long tropical river. A total
of 25 sites were sampled between November 2002 and March 2003 in two seasons (summer/wet versus winter/dry). A thermal gradient
separating the upper reaches from the lower reaches was detected. The middle-upper reaches showed higher conductivity and
lower dissolved oxygen and pH levels compared with the other reaches. Although some significant associations were found between
some fish abundance and environmental variables, the most abundant species (Tilapia rendalli, Geophagus brasiliensis, and Oligosarcus hepsetus) occurred in most sites and under most environmental conditions. Fish community structure varied more in space (longitudinal)
than through time (seasonal). The community in the lower reach species was more diverse in comparison with the other reaches.
Differences in the fish assemblage structure among the longitudinal river sections appear to have been influenced by the effects
of damming, and seem to be partially consistent with the Serial Discontinuity Concept, which views dams as discontinuities
within the river continuum. Only the lower river reach showed seasonal differences in the fish community structure, attributable
to the influence of flooding. Management plans and biodiversity conservation will benefit by considering the effects of dam
disruption and flood increased connectivity to the lotic systems.
Handling editor: J. Trexler |
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Keywords: | Fish distribution Environmental variables Fish community Neotropical fishes Ichthyofauna |
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