Food resources and cyprinid diet in permanent and temporary Mediterranean rivers with natural and regulated flow.

Abstract

Th is study addresses the differences in food availability, diet and feeding activity of the Iberian barbel, between permanent and temporary nonregulated rivers, and the effect of flow regulation on feeding parameters. A total of 267 adult barbels were seasonally collected in four nonregulated and regulated rivers from permanent and temporary basins, and their gut content was analysed. Locally available food sources were evaluated across sites and seasons. Ba rbels from the permanent nonregulated river exhibit a more variable and diversified diet in which invertebrates assumed a large importance, especially during high flow s. Barbels from the temporary nonregulated river presented a more uniform diet composed of plant material and detritus, particular ly in drought seasons. Flow regulation affected different flow components in both systems, but the effects on food resourc es and barbels’ diet were similar, resulting in an intra-annual stabilisation of resource availability and fish diet, with a higher consumption of plants and detritus. Changes in fish diet and feeding activity in both nonregulated and regulated rivers were strongly associated with the seasonal variability of streamflow components, particularly between low- and high-flow periods, and with the reduction in flow variability in the case of dam regulation. Results from this study can be used to improve guidelines for flow requirement implementation.