These data are the primary data used to model rainbow trout growth in Glen Canyon. Fish growth data were collected from nighttime boat electrofishing field campaigns conducted five to six times per year in April, July, September, and January, from April 2012 through November 2021 for a total of 9798 observations of mark-recapture-based growth. Sampling was conducted in a five km reach in the lower portion of the Glen Canyon tailwater (3.7-8.9 km upstream of Lees Ferry, AZ). Two nights of sampling occurred on each trip, with the central 2-3 km of the reach sampled on both nights. After capture, fish were kept in aerated 40-L buckets and transported to a central processing ___location. Groups of 10-15 fish were anesthetized and rainbow trout ≥ 75 mm were scanned and injected with a passive integrated transponders (PIT) tag if they had not been previously tagged. Fork length was measured to the nearest mm, and weight was measured to the nearest gram for fish ≥ 150 mm and to the nearest 0.1 g for smaller fish. Provided are tabulated data for fish forklength and weight at capture and recapture as well as estimates of rainbow trout biomass at each trip interval. We evaluated the effects of discharge, water temperature, competition for prey, solar insolation, soluble reactive phosphorus concentration, and the presence of absence of two experimental flows on growth rates of rainbow trout. These seven covariates were selected based on findings from previous modeling efforts and hypotheses regarding how experimental flows affect the rate of prey delivery, metabolic and foraging costs, foraging efficiency, and prey availability. Covariates are compiled as tabulated mean values for each reach and sampling trip and corresponding data sources.