Complex size-dependent habitat associations in potamodromous fish species

Abstract

Knowledge of the distribution of species life stages at multiple spatial scales is fundamental to both a proper assessment of species management and conservation programmes and the ability to predict the consequences of human disturbances for river systems. The habitat requirements of three native cyprinid species-the Iberian barbel Barbus bocagei Steindachner, the Iberian straight-mouth nase Pseudochondrostoma polylepis (Steindachner), and the Northern straight-mouth nase Pseudochondrostoma duriense (Coelho)-were examined at 174 undisturbed or minimally disturbed sites in 8 river catchments across western Iberia, by modelling occurrence and counts of species life stages at two spatial scaleslarge (regional) and instream (local)-using hurdle models.All the life stages of the barbel showed a negative association with upstream high-gradient river reaches, whereas juvenile P. duriense favoured such areas. Stream width and openness were negatively related with the occurrence of juvenile and small adult barbel, but not with large adults. Juvenile nase, on the other hand, were found to be mainly confined to fast-flowing habitats with high instream cover and coarser substrata. Advanced life stages of the barbel were mainly associated with the ''pure'' regional and shared components, whereas the purely local attributes accounted for much of the model variation among nases, in particular juveniles, and juvenile barbel. The results of this study are useful for setting or refining management goals, and highlight the need to separately consider life stages

Prioritizing barrier removal to improve functional connectivity of rivers

“…Variables associated with large spatial scales similar to the ones used in the present study tend to have a higher explanatory capacity, in term of species distribution compared to local‐scale variables (Roth, Allan & Erickson ; Marsh‐Matthews & Matthews ; Santos et al . ). Of course, there may have been other ‘local’ factors which were not accounted for in the present study, such as instream habitat and/or water quality variables which might have improved habitat suitability analyses.…”

Importance of considering riparian vegetation requirements for the long-term efficiency of environmental flows in aquatic microhabitats

“…The habitat increase in calandino during this period can be ecologically tricky due to the habitat plasticity of this species (Doadrio, 2011;Gomes-Ferreira et al, 2005), as well as its characteristic adoption for an rselection strategy as an evolutionary response to frequently disturbed environments (Bernardo et al, 2003). Above all, one should not ignore the fact that the relationships between fish assemblages and habitat are extremely complex (e.g., Diana et al, 2006;Hubert and Rahel, 1989;Santos et al, 2011), a consequence of the actual natural conditions (Poff and Allan, 1995;Poff et al, 1997) that when disrupted may allow the expansion of more generalist and opportunistic fauna (Poff and Ward, 1989).…”

Structural microhabitat use by endemic cyprinids in a Mediterranean‐type river: Implications for restoration practices

“…This method was adopted to avoid pushing the anode forward in the water causing displacement of fish from their original position. To account for ontogenetic differences in microhabitat use, species were divided into size classes based on length-at-age structure reported in the literature (Ribeiro et al, 2003;Santos et al, 2011): 60-150 mm, >150-200 mm and ≥200 mm TL for barbel, roughly corresponding to the life stages of juveniles, small adults, and large adults, respectively; 30-120 and ≥120 mm TL for nase and 20-50 and ≥50 mm for calandino, both size classes corresponding to juveniles and adults, respectively. The sampling crew moved upstream, zigzagging across the stream to guarantee complete coverage of all habitats.…”