CPW explains threat of non-native fish species posed to native, threatened fish populations COLORADO SPRINGS, Colo. (KRDO) -- Colorado Parks and Wildlife says that the introduction of non-native fish species into local lakes and other waterways is a common occurrence but one that is nearly impossible to stop or enforce. The matter took on a sense of urgency this month when CPW began draining Mack Mesa Reservoir, north of Grand Junction, because of the appearance of Great northern pike -- a predator that eats other fish and endangers four endangered or threatened native species repopulating in...