title: Colossal aggregations of giant alien freshwater fish as a potential biogeochemical hotspot.
abstract: The ubiquity and fascinating nature of animal aggregations are widely recognised. We report here consistent and previously undocumented occurences of aggregations of a giant alien freshwater fish, the Wels catfish (Silurus glanis). Aggregative groups were on average composed of 25 (± 10 SD, ranging from 15 to 44) adults with estimated average total biomass of 651 kg (386 - 1132) and biomass density of 23 kg m(-2) (14 - 40). Aggregations always occurred within the same location. No foraging, reproductive or anti-predator behaviour were observed during the aggregations. A mass-balance model estimated that these colossal aggregations of an alien species can locally release, through excretion only, up to 70 mg P m(-2) h(-1) and 400 mg N m(-2) h(-1), potentially representing the highest biogeochemical hotspots reported in freshwater ecosystems and another unexpected ecological effect of alien species.
authors: UMR 5245 EcoLab, Laboratoire Écologie Fonctionnelle et Environnement, Université de Toulouse, UPS, INP, Toulouse, France.
authors: Stéphanie
authors: S
authors: Boulêtreau
authors: Julien
authors: J
authors: Cucherousset
authors: Sébastien
authors: S
authors: Villéger
authors: Rémi
authors: R
authors: Masson
authors: Frédéric
authors: F
authors: Santoul
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D002397:Catfishes; D005260:Female; D005618:Fresh Water; D058865:Introduced Species / Q000706:statistics & numerical data*; D008297:Male; D015233:Models, Statistical; D011157:Population Dynamics; D011235:Predatory Behavior