Demography and movements of shovelnose sturgeon in the Middle Wabash River, Indiana

Harvest of Wabash River shovelnose sturgeon (SNS) has greatly increased, and there is great need to better understand this population. We therefore conducted demographic and movement studies of SNS in the middle Wabash River, IN. We necropsied 168 SNS for definitive sex determination and conducted seasonal sampling to describe additional aspects of this population’s demography. We also tagged 15 male and 15 female SNS with ultrasonic tags and tracked their movements using both active and passive techniques. While mean lengths and weights of fish collected in regular sampling were very similar to those reported earlier, sex ratios based on necropsied fish revealed a population much more highly skewed towards males than previously reported. Tagged SNS movements indicated that most males left the spawning area by late June, and the greatest movements detected were 200 miles downriver from the release site. However, nearly all females were undetected after mid-June and may have moved upriver and outside our tracking area. The results of this study suggest that female SNS numbers may be dropping alarmingly fast and that movements of this species may not be consistent with expectations in the Wabash River.