Fish species composition before and after construction of a reservoir on the Guadalete River (SW Spain)
Rodríguez Ruiz, A.
Archiv für Hydrobiologie Volume 142 Number 3 (1998), p. 353 - 369
published: Jul 7, 1998
ArtNo. ESP141014203005, Price: 29.00 €
The completion of the Zahara-El Gastor dam on the Guadalete River during the autumn winter of 1991 meant the final step in the spatial fragmentation of the river's headwaters, in the Grazalema Natural Park (SW Spain). Fish were sampled above and below the dam until its closing, in the reservoir and up- and down-stream after the closing. The new reservoir has had a strong effect on the structural composition of the river community. Up to 1991, all the species captured were endemic. Studies prior to the dam's closing showed a predomination of the Iberian barbel in the basin of the reservoir and downstream, while upstream the Iberian chub was dominant. From 1991, the percentages of the different species upstream of the dam varied (depending on the hydrological conditions of the year), while in the reservoir and downstream the Iberian nase became dominant. In addition, non-native species have been captured, in both the reservoir and the river, which had never before been captured in the headwaters of the Guadalete. This small-scale study newly supports the idea that even though a dam may not radically alter the thermal or hydrological regimens of the river, it can have a strong effect on the native ichthyofauna (in both composition and percentage of frequency of the different species forming the fish community).