Rainbow Darter (IMAGE) Penn State Caption Jonathan Freedman studied small fish such as the rainbow darter because they have limited movements and specific habitat requirements, making them more susceptible to the effects of dredging. Credit Jonathan Freedman Usage Restrictions non commercial use only 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.