As cool Autumn air flows along the winding Sacramento River, thousands of sleek and graceful North American green sturgeons swim along the riverbed after spawning upriver last spring. Amongst those making their migratory journey this fall are 25 fish that will play an important role in growing their species’ numbers, albeit with some help from U.S. Army Corps of Engineers planners. For the past four years, fish biologists with USACE’s Sacramento District Planning Division have spent Mondays and Fridays from September through October on the 300-mile-long river where it passes through Hamilton City, angling in a 20-foot fishing hole favored by the ancient bottom-dwellers. But they’re not there for sport. They’re there to help recover the species that since 2006 has been listed as threatened under the Endangered Species Act.