title: When local extinction and colonization of river fishes can be predicted by regional occupancy: the role of spatial scales.
abstract: BACKGROUND
  Predicting which species are likely to go extinct is perhaps one of the most fundamental yet challenging tasks for conservation biologists. This is particularly relevant for freshwater ecosystems which tend to have the highest proportion of species threatened with extinction. According to metapopulation theories, local extinction and colonization rates of freshwater subpopulations can depend on the degree of regional occupancy, notably due to rescue effects. However, relationships between extinction, colonization, regional occupancy and the spatial scales at which they operate are currently poorly known.
  
  
  METHODS
  And Findings: We used a large dataset of freshwater fish annual censuses in 325 stream reaches to analyse how annual extinction/colonization rates of subpopulations depend on the regional occupancy of species. For this purpose, we modelled the regional occupancy of 34 fish species over the whole French river network and we tested how extinction/colonization rates could be predicted by regional occupancy described at five nested spatial scales. Results show that extinction and colonization rates depend on regional occupancy, revealing existence a rescue effect. We also find that these effects are scale dependent and their absolute contribution to colonization and extinction tends to decrease from river section to larger basin scales.
  
  
  CONCLUSIONS
  In terms of management, we show that regional occupancy quantification allows the evaluation of local species extinction/colonization dynamics and reduction of local extinction risks for freshwater fish species implies the preservation of suitable habitats at both local and drainage basin scales.
authors.affiliation: Department of Hydrosystems and Bioprocesses Research Unit, Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture, Antony, France ; Department of Technology, Architecture and Landscape, hepia Geneva, University of Applied Sciences Western Switzerland, Jussy, Switzerland.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Bergerot
authors.affiliation: Department of Biologie des Organismes et Ecosystèmes Aquatiques, Muséum National d'Histoire Naturelle, Paris, France.
authors.forename: Bernard
authors.initials: B
authors.lastname: Hugueny
authors.affiliation: Department of Hydrosystems and Bioprocesses Research Unit, Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture, Antony, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Belliard
mesh_terms: D000818:Animals; D003247:Conservation of Natural Resources; D053476:Extinction, Biological; D005399:Fishes / Q000254:growth & development*; D045483:Rivers; D062206:Spatial Analysis