Updated assessment of hatchery‐reared pallid sturgeon (Forbes & Richardson, 1905) survival in the lower Missouri River

Abstract

As pallid sturgeon, Scaphirhynchus albus (Forbes & Richardson, 1905), natural reproduction and recruitment remains very minimal in the lower Missouri River from Gavins Point Dam (river kilometer [rkm] 1305.2) to the confluence with the Mississippi River (rkm 0.0), hatchery supplementation and river-wide monitoring efforts have continued. Annual survival estimates of hatchery-reared pallid sturgeon stocked in the lower Missouri River were previously estimated during 1994–2008. Low recapture rates prior to 2006 limited the data available to estimate survival, which resulted in considerable uncertainty for the estimate of annual survival of age-1 fish. Therefore, the objective was to provide more precise estimates of annual survival of pallid sturgeon using five additional years of stocking and sampling. The Cormack-Jolly-Seber model structure provided in program MARK was used to estimate the age-specific survival estimates. Over 135 000 hatchery-reared pallid sturgeon were released during 1994–2011 and recaptured at a rate of 1.9%, whereby estimates for the annual survival of age-0 (Ø = 0.048) and >age-1 (Ø = 0.931) were similar to those previously reported, but the age-1 (Ø = 0.403) survival estimate was 52% lower. Post hoc analysis using time-specific survival estimates indicated lower survival for age-1 fish post-2003 year classes, relative to the pre-2002 year classes. An analysis confirms that hatchery-reared pallid sturgeon continue to survive in the wild. However, low survival during the first 2 years of life is a management concern as efforts are aimed at maximizing genetic diversity and population growth. A follow-up analysis also demonstrated the variability of capture rates and survival over time, which reinforces the need to continue to monitor and evaluate mark-recapture data. The mark-recapture efforts have provided demographic parameter estimates that remain a critical component for species recovery as these data are incorporated into population models.