Resumen

MIRANDA CHUMACERO, Guido. Altitudinal distribution, relative abundance and density of fishes in Rio Huarinilla system (Cotapata, Bolivia). Ecología en Bolivia [online]. 2006, vol.41, n.1, pp.79-93. ISSN 1605-2528.

Altitudinal ranges, density, abundance, and biology of most fishes of Andean rivers are little known. For this reason, between June and August 2003, using an electrofishing gear, I sampled the fish fauna in the lower basin (1.040-1.700 m elevation) of the Rio Huaranilla and its tributaries, located in the Cotapata National Park, Bolivia. I recorded eight species belonging to seven genera and six families. On average, Hemibrycon beni was the most abundant of the species (relative abundance 61.9%), even though I did not record it at elevations above 1.360 m. The genus Astroblepus (made up of two sibling species, possibly more) made up 31.4% of the individuals captured and reached up to 1.560 m in elevation. Trichomycterus sp.1 contributed many fewer individuals (3.4% of the total) and was found from the lowest to the highest sampled points. Other species found (Knodus cf. heteresthes, Ancistrus sp., Parodon nasus, Tetragonopterinae sp. 1 y Rhamdia quelen) did not extend above 1.300 m in elevation and represented less than 2% of the relative abundance. Ephemeroptera and Diptera were the most abundant items in stomachs observations in most species. Possibly, spawning occurs before the rain season (July to November). Additionally, I estimated density and distribution in the basin of each species.

Palabras clave : Mountain fishes; Yungas; rain forest rivers; streams; electrofishing.

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