Rainbow Trout (IMAGE) Cary Institute of Ecosystem Studies Caption Blackflies are an important food source for rainbow trout, a popular species among recreational anglers in the Colorado River. Credit Credit: US Geological Survey/Freshwaters Illustrated-Dave Herasimtschuk Usage Restrictions May be used to promote this press release. License Licensed content 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.