Water diversion reduces abundance and survival of two Mediterranean cyprinids

• Published in: Ecology of freshwater fish Vol. 27; no. 1; pp. 481 - 491
• Main Authors: Merciai, Roberto, Bailey, Larissa L., Bestgen, Kevin R., Fausch, Kurt D., Zamora, Lluís, Sabater, Sergi, García‐Berthou, Emili
• Format: Journal Article
• Language: English
• Published: Malden Wiley Subscription Services, Inc 01.01.2018
• Subjects: Abundance; Aquatic ecosystems; Barbus meridionalis; Bypasses; Cyprinidae; Drought; Drying; Ecosystems; Fish; Fish populations; Freshwater; Freshwater ecosystems; Freshwater fish; Freshwater fishes; hydrologic alteration; Hydrology; Inland water environment; Man-induced effects; mark‐recapture study; population density; Populations; Probability theory; Rivers; Squalius laietanus; Stream discharge; Stream flow; Survival; Threatened species; Water conservation; Water depth; Water diversion; Water flow
• ISSN: 0906-6691; 1600-0633
• DOI: 10.1111/eff.12363

Water flow is a fundamental characteristic required for the ecological integrity of stream ecosystems. However, populations of many freshwater fishes in the Mediterranean region are threatened by man‐induced drought due to water diversion. Mark‐recapture methodology is an effective tool for estimating fish abundance and survival probability, but it has been seldom used with Mediterranean freshwater fish. We tagged over 2,400 individuals of two threatened cyprinids (Mediterranean barbel Barbus meridionalis and Catalan chub Squalius laietanus) inhabiting an Iberian stream affected by water diversion, and used mark‐recapture methods to evaluate the effects of flow, temperature and depth on their apparent survival and abundance at hydrologically altered and perennial reaches. Based on estimates over the summer drying season, survival of Mediterranean barbel was more than six times higher in an upstream reach with permanent flow than a middle reach impacted by water diversion. Water depth was the most important habitat feature accounting for differences in survival, with both barbel and chub exhibiting higher survival and abundance at permanent sites farther downstream where flow had been restored and in an unaltered tributary. Our results show clear negative impacts of water diversion on fish populations. Both species, but particularly barbel, have life‐cycle characteristics that may allow populations to recover quickly if natural streamflow was restored by conserving water and reducing water diversion.