Are Missouri River Macrhybopsis Spp. Pelagophils, Litho-Pelagophils, or Lithophils?

To develop a better understanding of the reproductive biology and early life history of three Lower Missouri River chub species (Sicklefin Chub M. meeki, Sturgeon Chub M. gelida , and Shoal Chub M. hyostoma), we studied whether laboratory reproduction could occur and which methods were most productive. We tested two temperature regimes and three hormone treatments on all three species; however, only Sicklefin Chub spawned successfully. All treatments produced spawns, but two treatments had similar success rates at 44 and 43%, where a constant temperature of 23^oC and no hormone treatment was the first, and daily fluctuations of temperatures between 20-23^oC and a water hormone treatment was the second. Spawns consisted of multiple successful demersal circular swimming spawning embraces interspersed with circular swims without embraces. The most spawns observed for one female was four and on average, 327 eggs were collected after each spawn. The water-hardened eggs were semibuoyant and nonadhesive, the first confirmation of this type of reproductive guild in a Missouri River Macrhybopsis sp. Using average water velocity and laboratory development time, we determined drift distance for eggs and larvae could be 468 to 592 km in the Lower Missouri River.