PUB00108 - Laserfiche WebLink

Home Browse Search

2. Aquatic Biology I I I I I I I I I I I I I I I I I I I 11-4 candidate species for listing by the Federal government and has the potential to occur in the St. Vrain Basin. Several other plant species of special con- cern to the state have the potential to occur in the Study Area. These include Bell's twinpod and a little bluestem community. A total of 24 sites of critical plant associations and nine sites of rare plants are identified in Boulder County in the Comprehensive Plan (Boulder County, 1984). Wildlife species that are I isted as threatened or endangered species by the Federal government that have the potential to occur in the St. Vrain Basin include the peregrine falcon and the American bald eagle. Peregrine falcon habitat exists alon9 Boulder Creek from the middle north fork confluence downstream to the confluence of south Boulder Creek. Thirty-seven separate areas are identified as critical wi Idlife habitat in Boulder County in the Boulder County Compre- hensive Plan (Boulder County, 1983). Aquatic habitats in the mountain zone include streams, alpine lakes, and a limited number of reservoir-so Habitats generally may be charact- erized by cold temperatures, low productivi ty and low suspended and dissolved solids levels. In addition, streams have high gradients, variable flows and limited substrate variabi lity. Aquatic fauna consist mainly of trout species and invertebrates at low population densities. The foothi I Is zone aquatic ecosystems consist mainly of streams and a few reservoi rs. Both streams and reservoi rs in this zone generally would have habitat characteristics simi lar in some respects to mountain zone resources except the temperatures, productivity and solids levels would be slightly higher. Stream flow would be less variable, gradients would be lower and substrates more diverse than streams at higher elevations. The aquatic biota of the foothi lis zone would be expected to be dominated by cold water trout species. The fishery and invertebrate communities would be more diverse and populations would be more dense than mountain zone communities. Warm water reservoirs and streams provide most of the aquatic habi- tat in the plains zone. These communities generally may be characterized by seasonal temperature variation, high productivity and high suspended and dis- solved sol ids. Streams are typically low gradient streams with I imited sub- strates and variable flows as a result of irrigation. Aquatic biota consist of a variety of warm water fishes dominated by the minnow species and many invertebrates adapted to sand and si It substrates. Sport fisheries in the Siting Area are variable. The best sport fishing would typically be in the lakes and streams of the foothi I Is zone and lower elevations of the mountain zone. The poorest sport fisheries exist in the lower portions of the various streams in the plains zone. The sport fish- eries of the Little Thompson River, Left-Hand Creek and Four Mi Ie Creek gener- ally are considered of lower quality than those of St. Vrain and Boulder Creeks.