DUGi

Water abstraction affects abundance, sizestructure and growth of two threatened cyprinid fishes

http://dugi.udg.edu/item/http:@@@@hdl.handle.net@@2072@@289382

Hydrologic alteration is a major threat to freshwater biota, and particularly fish, in many rivercourses around the world. We analyzed and compared the effects of water abstraction ontwo threatened cyprinid fishes of contrasting ecology (the Mediterranean barbel Barbusmeridionalis and the Catalan chub Squalius laietanus) in a Mediterranean stream. We comparedabundance, size-structure, growth, and condition of both species across perennialand artificially intermittent reaches affected by water abstraction. Both species were lessabundant, had scarce large individuals, and displayed slower growth rates (length-at-age) inintermittent reaches, showing clear detrimental effects of water diversion. Mixed-effect modelsof scale increments showed variation among individuals and among sites, years and ageclasses for both species. The larger-sized, water-column species (chub) disappeared orwas rare in many intermittent reaches. The barbel present in intermittent reaches showedbetter somatic condition than in sites with permanent flow, perhaps due to reduced competitionafter rewetting or colonization by better fitted individuals. This benthic, rheophilic speciesseems more resilient to moderate water abstraction than chub. Many effects of waterflow intermittency were only detected on fish life-history traits when accounting for natural,often non-linear, variation, along upstream-downstream gradients. Our results suggestthat abundance was the strongest indicator of effects of water abstraction on fish populations,whereas condition was a more labile trait, rapidly recovering from anthropogenicdisturbance

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