On an unseasonably hot July day, Jerrod Bowman peers into the water flowing through a box-like passage for endangered fishes, checking their route is clear. Bowman works as a fish biologist for the Navajo Nation, based west of Farmington, where the San Juan River borders the reservation. A small dam here forms a barrier to the seasonal migration of two rare fish species, the razorback sucker and the Colorado pikeminnow. On the south side of the river a narrow, rocky channel leading to a concrete bypass serves as a passage around the dam. “I’m just trying to give them the chance to move upstream,” Bowman says. Historically, Colorado pikeminnows traveled hundreds of miles through the free-flowing rivers of the Colorado River Basin, from Wyoming to northern Mexico. Razorback suckers also migrated seasonally to spawn through a similar range.