Abstract

ALVAREZ-BUSTAMANTE, Jonathan; JIMENEZ-SEGURA, Luz F.  and  JARAMILLO-VILLA, Úrsula. Ichthyofauna of cascade reservoirs in the channel of a tropical Andean river. Actu Biol [online]. 2018, vol.40, n.108, pp.46-58. ISSN 0304-3584.  https://doi.org/10.17533/udea.acbi.v40n108a05.

The Serial Discontinuity Concept affirms that the formation of reservoirs in cascade within rivers generates changes in the structure of the aquatic biota that accumulate along the basin. In the Porce River (Magdalena-Cauca River Basin, Colombia) two reservoirs were formed in cascade, Porce II and Porce III. To know the response of the fish assemblage in the sector of the river that was dammed, we collected samples during four periods of abundant rains and four of lesser rains from 2011 to 2013 from sites inside both reservoirs selected according to position on the longitudinal axis (tail, transition and dam). To eliminate the effect of depth, at every site, we took samples from two depths, surface and bottom. 15 species were captured; 12 in Porce II and 10 in Porce III. Differences in the composition and structure of the species of fish were found to vary depending on the location along the river flow (from tail to dam), and also by the water depth (surface to river bottom). In Porce II reservoir, the richness and the abundance of fish diminished in direction tail to dam and the abundance decreased from surface to bottom. In Porce III though the species richness presented the same trend along the longitudinal axis, the abundance was greater on the bottom that at the surface. The characteristics of the assemblage were not associated with the rainfall periods in either reservoir. One concludes that the composition and structure of the assemblage are defined by the morphologic characteristics of the reservoir, as well as the age and time of hydraulic retention.

Keywords : fish assemblage; diversity; freshwater fishes; serial discontinuity; Andean river.

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