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Keenlyne, K. D., C. J. Henry, A. Tews and P. Clancey (1994). Morphometric comparisons of upper Missouri River sturgeons. Transactions of the American Fisheries Society. 123:779-785.

Morphometric comparisons were made among three isolated populations of pallid sturgeon Scaphirhynchus albus and shovelnose sturgeon S. platorynchus from the upper Missouri River. Six measurements were made on 89 pallid and 204 shovelnose sturgeons. Means of several morphometric characteristics were statistically different between populations of both species. Pallid sturgeon means showed proportional trends relative to location on the river. Toward the headwaters, relative head and interrostral lengths were progressively shorter and outer barbel length relatively longer. The only trend observed for the shovelnose sturgeon was that relative head length became longer upriver. This was the opposite of the trend observed for the pallid sturgeon. Morphometric ratios commonly used to differentiate the two species were useful measures for live fish from isolated populations of Missouri River sturgeon but not for the overall sturgeon population. The exclusivity of morphometric ratios currently used to distinguish between the two species did not hold for our larger fish and large sample size. A cumulative morphometric characteristic index is described to aid managers in comparing individual fish within a composite sturgeon population, and the finding of three possible hybrids is discussed