Colossal Aggregations of Giant Alien Freshwater Fish as a Potential Biogeochemical Hotspot

Stéphanie Boulêtreau (1) , Julien Cucherousset (2) , Sébastien Villéger (2) , Rémi Masson (1) , Frédéric Santoul (1)

1 LEFE - Laboratoire Ecologie Fonctionnelle et Environnement
2 EDB - Evolution et Diversité Biologique

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

Mots clés: Excretion; Diet; Predation; Foraging; Ecosystems; Fresh water; Freshwater fish; Catfish

Domaines: Biologie animale; Ecosystèmes

Stéphanie Boulêtreau, Julien Cucherousset, Sébastien Villéger, Rémi Masson, Frédéric Santoul. Colossal Aggregations of Giant Alien Freshwater Fish as a Potential Biogeochemical Hotspot. PLoS ONE, 2011, vol. 6, ⟨10.1371/journal.pone.0025732⟩. ⟨hal-00912411⟩