Field experiment (image) University of Basel Share Print E-Mail Caption The researchers released 3000 experimental fish into a natural river habitat without stickleback, exposing them to natural selection. After one year, the remaining fish were recaptured and examined genetically. Credit University of Basel, Dario Moser Usage Restrictions Use of image with proper credit only. Share Print E-Mail 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.