Matt Hively

Fish ladder at the Buffalo River hydroelectric facility Streamflows are rising, bugs are hatching, and rainbow trout from Riverside to Island Park Dam are on the move. With less than one month remaining in this year’s spawning migration up the Buffalo River, it’s a good time to take stock of what the data show—and how they fit into nearly two decades of fish ladder monitoring. (See previous blogs1,2 for more background on the Buffalo River fish ladder.) Spawning Female Trapping for the 2025 season began on February 25th, capturing the full span of the spring migration to date. As of May 20th, we have recorded a total of 799 fish passing through the Buffalo River fish ladder, the vast majority of which were Rainbow Trout (72%) (Figure 1). Brook Trout comprised nearly a quarter of the total (23%), while other species (Mountain Whitefish, Mountain Sucker, and Speckled Dace) made up the remainder (5%). This species mix is consistent with previous years and underscores the dominant role of Rainbow Trout in the spring migration, particularly in the context of upstream spawning activity. Figure 1 – Species composition of all fish observed at the Buffalo River fish ladder Feb 25–May 20, 2025.