Trouts (IMAGE) Penn State Caption The difference between a wild brook trout (top) and a hatchery-raised brook trout is striking, and the wild fish have evolved to survive in harsh, small-stream environments. Despite many decades of stocking by the state, in this one watershed at least, wild fish had very few genes from hatchery trout. Credit Shannon White, Penn State 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.