reference to a study by Moos (1978). Actually, Moos reports that he captured ‘spent’ shovelnose sturgeon in the Missouri, it was not known if the sturgeon spawned in the Missouri or in tributaries, such as the James and Vermillion rivers. (If the sturgeon reproduced in the Missouri, they were reproducing without a spring rise downstream of Gavins Point Dam.) There have been numerous observations of sturgeon spawning in the tributary streams. It is generally believed the major exogenous cue to sturgeon spawning is water temperature. This is not unexpected as fish are cold blooded and all their activities are closely tied to temperature. Based on a review of information, temperature is the apparent cue for spawning for most Missouri River fishes. Jorgensen (2003, p. 11) using the Missouri River fish identified by Galat and Clark (2002) reviewed the spawning characteristics of these fishes. Jorgensen concluded based on the information collected that temperature was the major spawning cue for the sturgeons and other Missouri River fish. USFWS (2000, p. 103) states “Current research; however, indicates that pallid sturgeon spawning is directly linked to water temperature”. This conclusion supports the detailed temperature and flow data presented by Berg (1981, fig. 22) that strongly suggests that temperature, not flow, cues sturgeon spawning. The Berg data showed initiation of spawning at 18
C. Most observations on spawning of sturgeon indicate that the spawning
temperatures for pallid and shovelnose sturgeons are between 16.2 and 21.5o C. Not withstanding that numerous observation indicate that the pallid and shovelnose sturgeon spawn in the tributaries, not withstanding that there is little suitable substrate for spawning in the main stem of the Lower Missouri River, the relation of temperature to flow was investigated. Temperature - stage hydrographs, such as figure 11 and those in Appendix B, can give insight into the occurrences of temperature and stage for the ‘natural’ hydrograph.
Many persons state that the “natural’ hydrograph was the ideal hydrograph for the successful recruitment of terns and plovers on the Missouri River. The least terns are opportunistic nesters and migrate to and through the area from late April to early June and usually leave by early September (USFWS, 2000, p. 74). Least terns can reproduce in about 50 days if not interrupted by rises in the river stages or other perturbations (USACE, 1999, p. 9). If the nests are flooded, the birds may leave the area, or they may seek more suitable nesting locations either near or just off the river. Least terns start migrating south in August and typically all are gone by early September (USFWS, 2000, p. 74).
Piping plovers, which are opportunistic nesters, migrate to and through the area from late April through early June. Nest initiation may begin by late April and continue through early July (USACE, 1998). Piping plover can reproduce in about 60 days if not disturbed by flooding or other perturbations. If flooded, the birds may continue migration, or attempt to nest again on other less desirable sites adjacent to the river. Re-nesting results in additional hazards to the birds, especially from predators. Piping plover start migration southward in July or early August. Generally, all piping plover birds have departed by late August (USFWS, 2000, p.82).