Estimating ecosystem production across gradients of river alteration in the Colorado River basin; could contemporary productivity be a limiting factor for native fishes?
March 2021 - February 2023
- Utah Agricultural Experiment Station
The Colorado River Basin (CRB) is one of the most overallocated river networks in the world and is experiencing declining watershed runoff due to climate change. Most fish species native to the CRB are found nowhere else and have declined dramatically coincident with the damming and regulation of the CRB. Substantial resources are invested to recover these fish species with efforts largely focused on restoring physical conditions (i.e., habitat, flow or water temperature) and removing non-native fish species. There has been minimal focus on quantifying changes to the primary (i.e., plants) and secondary production (e.g., insects) that fuel native fish species. In the Grand Canyon segment of the CRB, flow, turbidity and depletion of phosphorous in Lake Powell have been linked to primary production and primary production has been linked to various fish species. However, these linkages have not been studied upriver of Lake Powell despite these upper segments being the focus of recovery efforts for endangered fishes. Based on research in other rivers, we expect primary and secondary production (hereafter river productivity) in the CRB is impacted by river regulation, modified hydrology, and agricultural and municipal runoff, with climate change likely to bring further modifications. If river productivity is limiting fish species, then increasing water temperatures and declining runoff associated with climate change may exacerbate this limitation. Thus, to better predict the impacts of ongoing climate change on the imperiled fish species of the CRB, it is imperative to identify current drivers of river productivity.