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Tuesday, January 30 • 2:20pm - 2:40pm
STURGEON, ESOCIDS & COREGONIDS: Shifting Population Dynamics of the Commercially Exploited Shovelnose Sturgeon (Scaphirhynchus platorynchus) in the Wabash River

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AUTHORS. Jessica L. Thornton, Eastern Illinois University; Leslie D. Frankland, Illinois Department of Natural Resources; Craig Jansen, Indiana Department of Natural Resources; Jana Hirst, Illinois Department of Natural Resources; Vaskar Nepal KC, Virginia Institute of Marine Science; Rob Colombo, Eastern Illinois University

ABSTRACT. The shovelnose sturgeon population in the Wabash River provides an important recreational sport and commercial caviar fishery for both Illinois and Indiana. In fact, it is one of the last commercially viable populations for roe harvest. The Wabash offers vital habitat for shovelnose sturgeon who complete their life cycle in the river. Previous studies have shown that increased harvest pressure in this species can slow maturation and result in recruitment overfishing. Therefore, it is important to closely monitor exploited populations over time. Over the past decade, shovelnose sturgeon were sampled with boat electroshocking, drifting gill nets, hoop nets, trotlines, and trawls. Fish captured between the years 2007 and 2016 had an overall average fork length of 668 ± 0.6mm, and an average weight of 1193 ± 3.41g. The mean relative weight was 87, falling within the target range (80-90), but condition significantly declined over the years. The overall proportional size structure indices for quality, preferred, memorable, and trophy size fish were 100, 98, 70, and 1 respectively. Overall size structure and condition are reflective of a healthy population, but not a stable one, with declines in condition and the proportion of memorable sized fish over time. We also observe greater estimates of mortality (25-35%) in this population driven by just a couple years of data. Gravid F-IV females, the fish directly impacted by roe harvest, also showed a significant decline in both condition and mean fork length over time. This implies that slower-growing and less-rotund females are now being selected for as an effect of commercial harvest pressure placed on larger, better condition females. Further monitoring is necessary to maintain a sustainable population and to support continued sport and commercial shovelnose sturgeon fishing in the Wabash River.

Tuesday January 30, 2018 2:20pm - 2:40pm CST