Spring movements of paddlefish in a prairie reservoir system

Paddlefish (Polyodon spathula) movements and habitat use were monitored in the Keystone Reservoir System, Oklahoma during 1996-1998 to determine repro ductive activity patterns. Paddlefish spring spawning migrations were more dependent on water flows than water temperature or photoperiod. Paddlefish moved up the Cimarron River and Arkansas River in 1997 and 1998 when spring flows increased. However, they did not migrate up the rivers in 1996, a ye ar with extremely low flows. Suitable spawning substrate was found in the S alt Fork River, a major tributary of the Arkansas River, and the tailwaters of Kaw Dam on the Arkansas River. Paddlefish were located over suitable sp awning substrate in the Salt Fork River; however, no larvae were collected. Although paddlefish migrate up the Cimarron River in spring, minimal spawn ing habitat may limit successful spawning in that river. In 1998, paddlefis h moved into the Salt Fork River rather than. the Kaw Dam tailwaters, presu mably because there was limited flow from Kaw Dam that spring. Paddlefish i n the Keystone Reservoir system appear to have adapted to the high spring w ater temperatures and fluctuating flows enabling successful reproduction. The paddlefish (Polyodon spathula) is native to large midwestern rivers in the central United States, including the Arkansas River and the Cimarron Ri ver, which combine to make Keystone Reservoir in northcentral Oklahoma. Pad dlefish populations have diminished in numbers during the last century due in part to destruction of spawning grounds and dam construction (Graham 199 7). Paddlefish traditionally migrate up rivers in spring (Unkenholz 1982, R ussell 1986), where spawning occurs in flowing water over silt-free gravel (Purkett 1961) at water temperatures of 10-18 degrees C (Pitman 1991). Howe ver, gravel is sparse in prairie rivers of the southcentral and southwester n U.S., and paddlefish may be required to spawn over other substrates (Boni slawsky 1977). In the last 50 years, impoundments have, in many cases, diminished the size of paddlefish populations because they block fish from their spawning grou nds or inundate the spawning areas altogether. In addition, river stage and discharge are usually highly regulated and may not mimic natural spring fl ow regimes (Unkenholz 1986), which may prohibit paddlefish spawning. Howeve r, some paddlefish populations, including the one in Keystone Reservoir, ha ve survived and even flourished (Paukert 1998). Our objective was to determ ine spring movement patterns associated with reproductive activity of paddl efish in the Keystone Reservoir system, Oklahoma.