Truman Reservoir Grass Carp Ecology

Truman Reservoir is the largest reservoir in Missouri and was formed by the damming of the Osage River near Warsaw, Missouri in 1979 [34 ] by the U.S Army Corps of Engineers. Truman Reservoir has a surface area of > 22,500 ha and four major tributaries, the Osage River, Pomme de Terre River, South Grand River, and Tebo Creek (Fig 1). Another major tributary, the Sac River, empties into the Osage River just above the reservoir at river kilometer 80 (rkm, river kilometers upstream from Truman Dam). Grass carp have likely been present since the formation of the reservoir via inundation of ponds in the watershed that were stocked with grass carp for vegetation control, and potentially through natural recruitment or continued escapement from ponds in the watershed where grass carp are stocked for vegetation control [35 , 36 (link)]. Because the reservoir was filled before triploid grass carp production technology was developed, and the production and stocking of diploid grass carp remains legal in Missouri [30 ], all escapees from ponds inundated by the initial filling of the reservoir would have been fertile, diploid fish. Many fish that later escaped from ponds in the watershed would also have been fertile. The Missouri Department of Conservation, which manages the Truman Reservoir fishery, does not stock grass carp into the reservoir [20 (link)]. With the discovery of successful spawning through the collection of fertilized eggs on four Truman Reservoir tributaries [20 (link)], it became evident that natural recruitment has likely increased the population in the system.