Steffensen K.D.,Fisheries Division Nebraska Game and Parks Commission Lincoln |
Powell L.A.,University of Nebraska - Lincoln |
Stukel S.M.,Fish and Parks Yankton |
Doyle W.J.,U.S. Fish and Wildlife Service
Journal of Applied Ichthyology | Year: 2016
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. © 2015 Blackwell Verlag GmbH.