Wetpixel member Rémi Masson (Plongeur74) has co-authored a paper about the aggregations of Wels catfish (Silurus glanis) that occur in the Rhône River, France. The study shows that the aggregation of these large fish causes the highest biomass of any fresh water species. This in turn, has significant effects in terms of the amount of phosphorus and nitrogen that these animals excrete entering the water.
The study did not find any specific cause for the aggregations, but was able to eliminate it as being due to schooling, reproduction, foraging or anti-predator behaviors. The full paper has been published in the Public Library of Science ONE (PLoS ONE) journal.