Summer habitat relationships of barbels in south-west Spain

An analysis was made of the associations with local habitat features of barbels (Barbus sp.) of a Mediterranean river basin. The analysis was based on the presence data from sampling the upper, middle, and lower reaches of 31 rivers in the middle Guadiana River basin (south-west Spain). Numerous local habitat variables were determined, including the river's size and substratum, physico-chemical variables of water, and the aquatic and riparian vegetation. For each species, a univariate analysis was performed using preference indices, and logistic regression was used to construct a parsimonious multivariate model and Gaussian response models with the most influential variables, quantifying the species' limits of tolerance. Distinct habitat associations for every species were obtained, mainly relating Barbus comiza to the larger habitats and higher water levels, Barbus nucrocephalus to the maintenance of lotic conditions and Bat-bus sclateri to more fluctuating rivers. Barbus steindachneri showed a different habitat relationship from that of the genetically almost identical B. comiza. Cover played a significant role in all but B. comiza. (c) 2005 The Fisheries Society of the British Isles