UMR 5245 EcoLab, Laboratoire Écologie Fonctionnelle et Environnement, Université de Toulouse, UPS, INP, Toulouse, France.
PLoS One. 2011;6(10):e25732. doi: 10.1371/journal.pone.0025732. Epub 2011 Oct 5.
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.
动物聚集的普遍性和吸引力是广为人知的。我们在这里报告了一个以前未被记录的巨型外来淡水鱼类——欧鳇（Silurus glanis）聚集的一致发生情况。聚集群体平均由 25 条（±10 SD，范围为 15 至 44 条）成年鱼组成，估计总生物量平均为 651 公斤（386-1132 公斤），生物量密度为 23 公斤/平方米（14-40 公斤/平方米）。聚集总是发生在同一地点。在聚集期间，没有观察到觅食、繁殖或抗捕食行为。质量平衡模型估计，这些外来物种的巨大聚集仅通过排泄就可以局部释放高达 70 毫克 P/平方米/小时和 400 毫克 N/平方米/小时，这可能代表了淡水生态系统中报告的最高生物地球化学热点，也是外来物种的另一个意外生态效应。
