Abstract
Interspecific competition is recognised as a major impact to biodiversity conservation. The upper part of the Cabriel River harbours the most important population of Júcar nase, a fish species in imminent danger of extinction; nowadays this species cohabits with several non-native species such as the Iberian nase and the bermejuela. The potential habitat competition with these non-native species was studied by analysing the overlapping of the suitable microhabitats. Generalized Additive Models (GAMs) were developed to model microhabitat selection and these GAMs were used to assess habitat suitability under several flows simulated
with River-2D. The competition for microhabitats was assessed as low because habitat selection seemed to differ among species and the hydraulic model encompassed a river stretch mostly unsuitable for the Júcar nase. Nevertheless, the Júcar nase would compete firstly with bermejuela, secondly with small Iberian nase
and lastly with large Iberian nase. Though the study suggested low microhabitat competition it was considered necessary to inspect the potential competition between these cohabiting species.
