News Release

Colossal aggregations of giant alien freshwater fish as a potential biogeochemical hotspot

Peer-Reviewed Publication

PLOS

Wels Catfish (<I>Silurus glanis</I>) Aggregations (1 of 2)

image: This image shows monospecific circularly moving aggregations. view more 

Credit: Bouleˆtreau S, Cucherousset J, Ville´ger S, Masson R, Santoul F (2011) Colossal Aggregations of Giant Alien Freshwater Fish as a Potential Biogeochemical Hotspot. PLoS ONE 6(10): e25732. doi:10.1371/journal.pone.0025732

Many different types of animals come together to form vast groups – insect swarms, mammal herds, or bird flocks, for example. Researchers in France added another example to the list, reported today in the online journal PLoS ONE: the huge Wels catfish, the world's third largest and Europe's largest fresh-water fish. Researchers observed these fish in the Rhone River from May 2009 to Feb. 2011 and found that they formed dense groups of 15 to 44 individuals, corresponding to an estimated total biomass of up to 1132 kilograms with a biomass density of 14 to 40 kilograms per square meter.

Unlike traditional behavior seen in schools of fish, the catfish in the aggregations did not all point in the same direction and sometimes came into contact with their neighbors. Researchers were not able to determine the reason for this behavior, though they ruled out reproduction, foraging, and safety from predators.

The species originates from Eastern Europe and is not native to the Rhone, so the researchers were curious what effect these large aggregations may have on the local ecosystem. They calculate that the groups of fish could excrete extremely large amount of phosphorous and nitrogen in their waste, creating potentially the highest biogeochemical hotspots reported in freshwater ecosystems.

According to the authors, "our study is unique in identifying unexpected ecological impacts of alien species. Our findings will be ground breaking news for many scientific fields including conservation biology, ecosystem ecology and behavioral ecology and anyone interested in biological invasion and the potential ecological impacts of alien species. Therefore, we believe that our manuscript will stimulate further research and discussion in these fields."

###

This publication is accompanied by a video of the aggregation behavior.

Citation: Bouletreau S, Cucherousset J, Villeger S, Masson R, Santoul F (2011) Colossal Aggregations of Giant Alien Freshwater Fish as a Potential Biogeochemical Hotspot. PLoS ONE 6(10): e25732. doi:10.1371/journal.pone.0025732

Financial Disclosure: The authors have no support or funding to report.

Competing Interest Statement: The authors have declared that no competing interests exist.

Disclaimer: This press release refers to upcoming articles in PLoS ONE. The releases have been provided by the article authors and/or journal staff. Any opinions expressed in these are the personal views of the contributors, and do not necessarily represent the views or policies of PLoS. PLoS expressly disclaims any and all warranties and liability in connection with the information found in the release and article and your use of such information.

About PLoS ONE

PLoS ONE is the first journal of primary research from all areas of science to employ a combination of peer review and post-publication rating and commenting, to maximize the impact of every report it publishes. PLoS ONE is published by the Public Library of Science (PLoS), the open-access publisher whose goal is to make the world's scientific and medical literature a public resource.

All works published in PLoS ONE are Open Access. Everything is immediately available—to read, download, redistribute, include in databases and otherwise use—without cost to anyone, anywhere, subject only to the condition that the original authors and source are properly attributed. For more information about PLoS ONE relevant to journalists, bloggers and press officers, including details of our press release process and our embargo policy, see the everyONE blog at http://everyone.plos.org/media.


Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.