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Effects of weir construction on fish population structure in theRiver Erro (North of Spain)

Published online by Cambridge University Press:  15 February 2009

R. Miranda
Affiliation:
Department of Zoology and Ecology, Faculty of Sciences, University of Navarra, Irunlarrea s/n, E-31080 Pamplona, Spain
J. Oscoz
Affiliation:
Department of Zoology and Ecology, Faculty of Sciences, University of Navarra, Irunlarrea s/n, E-31080 Pamplona, Spain
P. M. Leunda
Affiliation:
Department of Zoology and Ecology, Faculty of Sciences, University of Navarra, Irunlarrea s/n, E-31080 Pamplona, Spain
C. García-Fresca
Affiliation:
Department of Zoology and Ecology, Faculty of Sciences, University of Navarra, Irunlarrea s/n, E-31080 Pamplona, Spain
M. C. Escala
Affiliation:
Department of Zoology and Ecology, Faculty of Sciences, University of Navarra, Irunlarrea s/n, E-31080 Pamplona, Spain
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Abstract

In 1996, a compound gauging weir was built in Villaveta Township (Navarra, North of Spain) in the river Erro (Ebro RiverBasin). Before and after its construction, fish and physical and chemical variables were examined to determine weir’s impact onthe reach. Fish captured by electrofishing were measured (total length), and population density and length distribution of thespecies were estimated. Species diversity (Shannon’s diversity index), dominance (Simpson’s dominance index) and evennesswere also calculated. The results revealed an increase in fish population density, especially in smaller specimens, but a decreasein the larger fishes. Substrate and shelter alterations could explain the observed variations in the fish community. In order toimprove the consolidation of well-developed fish populations, the placement of great boulders and the restoration of the riparianvegetation are suggested.

Type
Research Article
Copyright
© Université Paul Sabatier, 2005

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