Changes in the summer composition of fish fauna in the lower Guadiana basin (Southern Iberia) from low to high discharge

In the lower Guadiana basin (southern Iberia) there was a significant chang e in the summer relative abundance of fish species-size combinations from 1 994 (low discharge) to 1996 (high discharge). Notable increases were observ ed in the smaller size classes of repohilic cyprinids (Barbus spp. and Chon drostoma willkommi), but most species, particularly small sizes, presented increased catches.