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Ecología en Bolivia

On-line version ISSN 2075-5023

Abstract

ECHEVERRIA, Aldo; POUILLY, Marc  and  REJAS, Danny. Isotopic niche width variation of three fish species in a resource availability gradient. Ecología en Bolivia [online]. 2020, vol.55, n.1, pp. 6-15. ISSN 2075-5023.

To study the effect of resource availability on the trophic niche width of fishes in the Bolivian Amazon basin, we compared isotopic niche widths (as a surrogate for trophic niche) of three fish species (Acestrorhynchus altus, Hoplias malabaricus and Pygocentrus nattereri) in a gradient of prey availability. We sampled fishes in lakes located in the floodplain of the rivers Blanco (low prey availability), Iténez (intermediate prey availability) and San Martín (high prey availability), analyzed them for ratios of stable isotopes (δ13C and δ15N), and estimated the standard ellipse and isotopic niche width using the SIBER package in R. Acestrorhynchus altus behaved as an optimal forager, showing wider isotopic niche where prey were less abundant, and less wide isotopic niche in rivers with intermedíate and high prey availability. P. nattereri showed wider trophic niche at intermedíate prey densities and H. malabaricus showed no effect of prey availability on isotopic niche width. This indicates that, for these species, factors such as prey selectivity, water transparency, mouth size or feeding habits, may be more important than prey availability in determining trophic niche width.

Keywords : Amazonia; Bolivia; SIBER; Stable isotopes; Trophic ecology.

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