We estimated numbers of individuals for each species, using a backpack electroshocker with standard electrofishing procedures. We used block nets to provide closure at the ends of the segment during years when the stream reach was flowing. We used a two-pass removal depletion method to estimate abundances within segments. After placing captured fish in aerated coolers filled with stream water, we identified fish to species and categorized them by life stage (juvenile or adult) based on standard length, and then returned the fish to the same section of stream. In 2011 (the first year), size data for R. balteatus were only available for the first 30 fish caught (sampling in 2011 was focused mainly on R. osculus, and L. copei, for a mark-recapture study that is reported elsewhere). However, we recorded number captured of R. balteatus for each segment and pass of the stream reach. We calculated the ratio of adult to juvenile life stages of the first 30 fish, and used that ratio to estimate the R. balteatus life stage distribution (adult or juvenile) for additional segments for 2011 only. To estimate abundances, we used a maximum-likelihood population estimator (Microfish, Van Deventer 1998). The data has been given both as the estimate generated by the maximum-likelihood population estimate, as well as a log transformed version of the original estimate. 

Climate change projections in the western United States suggest that snowpack levels and winter precipitation will decline, but mean annual precipitation levels will remain unchanged. Mountain streams that once saw a constant source of water from snowpack will begin to see large seasonal variation in flow. Increased stream intermittency will create significant conservation risks for fish species; however, few studies have examined the abundance responses of fish in high elevation streams to the shift from perennial to intermittent flow. To determine the effects of stream intermittency on fish abundance in a montane stream, we quantified changes in abundance for five species over a five-year period that exhibited extreme variation in streamflow. Responses varied by species and life stage, suggesting that the shift from perennial to intermittent flow will cause significant declines in abundance for some species. Northern leatherside chub, may experience large decreases in their range as the availability of perennial streams decreases. The study of drought effects on fish abundance will be crucial to the conservation of biodiversity in montane regions of the world.

Data is provided in a .xlsx file. It can be opened on Excel, Google Sheets, or Apple Numbers.