A question that has consistently garnered significant attention in the field of salmon management is whether salmon can be reintroduced above dams, giving them access to historic habitats that are currently blocked off. Determining the feasibility of such an effort requires understanding the current state and suitability of the river habitats where salmon reintroduction is proposed. To inform such evaluations on the Upper Tuolumne River, FISHBIO conducted surveys to characterize the distribution, abundance, and quality of fish habitat in the area. This information is critical for assessing the feasibility of anadromous salmonid reintroduction, estimating the population size that the habitat could support, and developing engineering alternatives such as fish ladders or collection facilities.
FISHBIO staff rafted through 25 miles of river surveying pools, runs, boulder gardens, cascades, and high- and low-gradient riffles. Particular focus was made to identify pools with the potential to provide holding habitat for adult Chinook salmon during the summer. Drift and substrate samples were collected to survey aquatic insects and other macroinvertebrates that serve as important salmon prey. Data from this survey will be used to create habitat maps of the area and, along with other studies, will be used to evaluate the potential for supporting a salmon and steelhead population in the upper Tolumne River.