least tern and piping plover used the Missouri River above Sioux City on a regular basis to nest and successfully reproduce.
Another question: Is the June rise of the natural hydrograph is essential to the successful spawning of the fishes of the Missouri River? A review of the spawning characteristics of 85 species found in the Missouri River indicated that 79 of the 85 different species can spawn in lakes and or tributary streams; thus, the necessity of spring rise for spawning Missouri River fish is questionable or marginal (Jorgensen, 2003b). Specifically in reference to successful spawning of the pallid sturgeon, the review indicated that the dominant exogenous spawning cue was most likely temperature. The author could not find any historic references of sturgeon spawning in the lower Missouri River (below Gavins Point Dam); however, several historic references of sturgeon spawning in tributaries were found. For example, Goode (1884, p. 663) states “Shovelnose sturgeon: white sturgeon –Scaphirhynchups platyrhynchus: This species is found in abundance in large rivers in the west and south. It spawns early in May, ascending smaller streams for that purpose.” The Iowa Fish Commission (1892-3, p. 22) states:” Scaphirhynchups platyrhynchus- The shovelnose or white sturgeon is found in the Ohio and Mississippi valleys, extending to the upper Missouri and to the Rio Grand. In the large tributaries of the Mississippi, the species is very common. The maximum length is 8 feet, but is not an important food fish, being but little esteemed. Nothing is recorded of its habits, except that it runs up the small streams in May for the purpose of spawning”. Note, prior to about 1905, the pallid sturgeon and the shovelnose sturgeon were not differentiated. It seems clear that in the two descriptions above that both the pallid sturgeon and the shovelnose sturgeon were being discussed. Barnichol and Starrett (1951, p. 289) report: “ The predominance of males (sturgeons) in the channel in April indicates that the females seek another habitat during the season, returning to the channel by June. According to Harry E. Finley, a commercial fisherman at Andalusia, female shovelnose sturgeons are seldom taken by commercial Fisherman during April and May, which he believes are the months of the spawning season”. Jorgensen and others (2002) reported that there is little or trivial spawning habitat in the Missouri River. The coarse gravel riprap used in channelization structures is a candidate substrate for sturgeon spawning; however, this substrate is usually covered with algae (Jorgensen, 2003b). It has been assumed that the unchannelized river between Gavins Point Dam and Ponca, Nebraska, would be suitable habitat; However Jorgensen and others (2002) show that, in general, suitable spawning substrate does not exist in that reach. The summer low flow has no particular benefit in the Gavins Point Dam to Plattsmouth, Nebraska reach in that it would tend to disconnect the river from the few connected backwaters and lakes that exist in that reach. These observations and others suggest that the Missouri River main stem, especially on the lower Missouri River, was not the site of pallid sturgeon spawning.
It has been assumed in the 2002 biological opinion, without presenting quantitative data and or substantive observations, that the main stem of the