Native Aquatic Species

St. Vrain Creek is a transitional stream dominated by gravel substrate and intermediate temperatures. This makes it a hotbed for fish diversity. As stated by Colorado Parks and Wildlife’s (CPW) native aquatic species biologist Boyd Wright, the St. Vrain is a priority for CPW because many fish species still exist in the St. Vrain while they’ve been extirpated in most other parts of the state.

Trees (both living and dead) are not only important to mammals and birds, but also to fish and other aquatic species. Tree canopy will help keep the river temperature down and downed trees will provide areas for small fish to hide from predators. While deadfall within the river may not allow as much water to pass as in a “clean” river, some woody debris is important for the functioning of a healthy aquatic ecosystem and given that the urban reach of the St. Vrain has been given a grade of C+ for fish diversity, it is imperative to maintain, at the very least, that level of diversity.

While the urban reach of the St. Vrain has been given a C+ grade, upstream of the Beckwith diversion at Golden Ponds has earned a grade of F+. This is because this diversion, used for agriculture, is impassable by our native fishes. Therefore, the Beckwith diversion, as well as other impediments to fish movement within Longmont, should either be removed entirely or should be altered so that it/they allows/allow fish to travel upstream. Not just the riparian corridor surrounding the St. Vrain but the St. Vrain itself, is a wildlife movement corridor. Not allowing habitat connectivity leads to bottlenecks in genetic diversity and, potentially, local extirpation or even extinction.