Publications / 2015 Didymo Survey - Second Annual Report

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As a follow up to research initiated in 2014, Colorado Mountain College Natural Resource Management program (CMC NRM) monitored the Fryingpan River for didymo presence three times during 2015. The first sampling event was in May prior to spring runoff and peak flows, the second was in July following peak flows, and the third was in October to represent baseflow conditions. 

Didymo is a native, nuisance species in rivers and streams throughout Colorado. A fast growing diatom, didymo covers substrate and has the potential to alter historic macroinvertebrate habitat. Creating effective mechanisms to prevent the spread or introduction of invasive and nuisance species is important for maintaining the health of the Fryingpan River ecosystem and fishery. The continued education of anglers and river users is important to reducing the spread of didymo to other water bodies in the watershed and around the Colorado. Wader washing stations can help reduce the spread of didymo and the introduction of new non-native or nuisance species. 

This study suggests that increased flushing flows at or above 700 cfs during the spring simulate natural snowmelt conditions and promote bedload migration and the removal of didymo from the substrate. Results indicate increased didymo at all reference sites compared to the 2014 data. Responsible management and consistent dialog between the Bureau of Reclamation, water managers, water stewards, and recreational businesses will assist with flow control for environmental and recreational purposes. 

Continued monitoring of fish populations, benthic invertebrates, and water quality for nutrient concentrations throughout the Fryingpan could help describe the relationship of didymo in the aquatic ecosystem. An ongoing monitoring strategy is recommended for the Fryingpan River to include sampling of five key sites (Site 1, 8, 12, 15, and 20) three times annually, plus three reference sites upstream of Ruedi Reservoir (Appendix I). This sampling should be complimented with a comprehensive 5 year study at all sites. 

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