With the closure of commercial fishing for Shovelnose Sturgeon Scaphirhynchus platorynchus in most reaches of the Mississippi and Missouri rivers, harvest may increase in other rivers. We studied the demographics of a commercially exploited Shovelnose Sturgeon population in the lower 322 km of the Wabash River, Illinois. During 2000–2013, 10,734 Shovelnose Sturgeon were captured by using DC and AC electrofishing, gill nets, hoop nets, trotlines, and benthic trawls. Of the captured individuals, 399 fish were recaptured. Electrofishing CPUE was the highest reported in any study on Shovelnose Sturgeon. Captured fish ranged between 61 and 909 mm FL (mean = 662 mm; median = 671 mm), but few fish were smaller than 500 mm. Although the fish were in good condition (mean relative weight = 89.9), there was a decreasing trend in mean condition over time. Shovelnose Sturgeon ranged in age from 0 to 25 years; 90% of the fish were between age 8 and age 19. Fish were fully recruited to the sampling gear at age 10; total annual mortality for fish older than 10 years was 20.6%. An empirical growth rate of 2.67 mm/year was observed for fish larger than 635 mm, with several individuals showing negative growth. The sex ratio was slightly skewed toward males (2.18 males : 1 female). The Shovelnose Sturgeon population in the lower Wabash River was generally healthy and stable and had characteristics comparable to those of the upper Wabash River population, with slow growth, large sizes, good condition, and low mortality.
Received December 19, 2014; acceptedMay 11, 2015