Prior to anthropogenic modifications, the historic Missouri River provided ecological conditions suitable for reproduction, growth, and survival of pallid sturgeon Scaphirhynchus albus. However, little information is available to discern whether altered conditions in the contemporary Missouri River are suitable for feeding, growth and survival of endangered pallid sturgeon during the early life stages. In 2004 and 2007, nearly 600 000 pallid sturgeon free embryos and larvae were released in the upper Missouri River and survivors from these releases were collected during 2004-2010 to quantify natural growth rates and diet composition. Based on genetic analysis and known-age at release (1-17 days post-hatch, dph), age at capture (dph, years) could be determined for each survivor. Totals of 23 and 28 survivors from the 2004 and 2007 releases, respectively, were sampled. Growth of pallid sturgeon was rapid (1.91 mm day )1 ) during the initial 13-48 dph, then slowed as fish approached maximum length (120-140 mm) towards the end of the first growing season. The diet of youngof-year pallid sturgeon was comprised of Diptera larvae, Diptera pupae, and Ephemeroptera nymphs. Growth of pallid sturgeon from ages 1-6 years was about 48.0 mm year )1 . This study provides the first assessment of natural growth and diet of young pallid sturgeon in the wild. Results depict pallid sturgeon growth trajectories that may be expected for naturally produced wild stocks under contemporary habitat conditions in the Missouri River and Yellowstone River.

Summary We synthesized wild and stocked pallid sturgeon Scaphirhynchus albus capture data collected in four recovery areas of the Missouri River during 1998–2007, providing the first basin‐wide analysis of size structure, growth, and condition. Proportional size distribution (PSD) values ranged from 20 to 33 and were indicative of past stockings given the continued lack of natural recruitment. A new weight‐length regression derived from 2268 captured wild (8%), hatchery‐stocked (75%), and unknown origin (16%) pallid sturgeon had a significantly lower slope and intercept from a previously published model that used only 214 wild fish and a truncated size range. Relative condition (Kn) declined after stocking throughout the basin but stabilized at 0.94 within 3 years. Spatially, Kn of juvenile pallid sturgeon (330–629 mm) was generally highest in the reaches of the Missouri River with large tributaries. In accordance with the latitudinal counter gradient growth hypothesis, similar absolute growth increments (both length and weight) of tagged age‐1 pallid sturgeon in the Upper and Lower Missouri River indicated upstream fish grew at faster rates given the 1.3 fold difference in growing season length. From North to South, von Bertalanffy growth coefficients (k) showed a latitudinal increase while L∞ decreased, providing additional support of the latitudinal counter gradient growth hypothesis. However, growth rates of tagged juvenile pallid sturgeon aged 2–6 years were highest at the two most downstream reaches showing an increased influence of growing season length. In the Missouri River, pallid sturgeon (≤ ages 1–9 or 10 years) exhibited linear growth in the two most upstream reaches (Montana and North Dakota), exhibited logistic growth in the inter‐reservoir reach in South Dakota/Nebraska while a power function best described growth downstream of the lowermost dam (Nebraska, Iowa, Kansas, and Missouri). Differing growth models among reaches highlights the confounding affect of habitat fragmentation by dams in the Missouri River on growth as well as potential latitudinal affects on sexual maturation. Relative condition and growth of pallid sturgeon appears adequate throughout the Missouri River indicating success of past stocking efforts to forestall extirpation.

The Comprehensive Sturgeon Research Project is a multiyear, multiagency collaborative research framework developed to provide information to support pallid sturgeon recovery and Missouri River management decisions. The project strategy integrates field and laboratory studies of sturgeon reproductive ecology, early life history, habitat requirements, and physiology. The project scope of work is developed annually with cooperating research partners and in collaboration with the U.S. Army Corps of Engineers, Missouri River Recovery-Integrated Science Program. The research consists of several interdependent and complementary tasks that engage multiple disciplines. The research tasks in the 2011 scope of work emphasized understanding of reproductive migrations and spawning of adult sturgeon, and hatch and drift of larvae. These tasks were addressed in three hydrologically and geomorphologically distinct parts of the Missouri River Basin: the Lower Missouri River downstream from Gavins Point Dam, the Upper Missouri River downstream from Fort Peck Dam and including downstream reaches of the Milk River, and the Lower Yellowstone River. The research is designed to inform management decisions related to channel re-engineering, flow modification, and pallid sturgeon population augmentation on the Missouri River, and throughout the range of the species. Research and progress made through this project are reported to the U.S.

For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment-visit http://www.usgs.gov/ or call 1-888-ASK-USGS.For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod/.Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. AbstractThe Comprehensive Sturgeon Research Project is a multiyear, multiagency collaborative research framework developed to provide information to support pallid sturgeon recovery and Missouri River management decisions. The project strategy integrates field and laboratory studies of sturgeon reproductive ecology, early life history, habitat requirements, and physiology. The project scope of work is developed annually with collaborating research partners and in cooperation with the U.S. Army Corps of Engineers, Missouri River Recovery Program-Integrated Science Program. The project research consists of several interdependent and complementary tasks that involve multiple disciplines.The project research tasks in the 2014 scope of work emphasized understanding of reproductive migrations and spawning of adult pallid sturgeon and hatch and drift of larvae. These tasks were addressed in three hydrologically and geomorphologically distinct parts of the Missouri River Basin: the Lower Missouri River downstream from Gavins Point Dam, the Upper Missouri River downstream from Fort Peck Dam and downstream reaches of the Milk River, and the Lower Yellowstone River. The project research is designed to inform management decisions related to channel re-engineering, flow modification, and pallid sturgeon population augmentation on the Missouri River and throughout the range of the species. Research and progress made through this project are reported to the U.S. Army Corps of Engineers annually. This annual report details the research effort and progress made by the Comprehensive Sturgeon Research Project during 2014.

Rainbow trout Oncorhynchus mykiss stocked into Flaming Gorge Reservoir, Utah-Wyoming, are thought to be in poor condition and to rarely overwinter. In 2001-2002, we evaluated factors that affect the growth and abundance of rainbow trout, both temporally and spatially, based on a series of field measurements and growth experiments. Based on our field measurements, the growth and condition of rainbow trout in Flaming Gorge Reservoir actually parallel those of rainbow trout of various strains in other systems, and some rainbow trout overwinter as many as 3 years in the reservoir. Overall, rainbow trout appear to be spatially limited by physical factors (e.g., temperature) during only a few isolated times of the year and not in all areas of the reservoir. Although zooplankton were abundant throughout the reservoir, primary and secondary production vary spatially with concordant effects on fish growth and condition. Diet analysis indicated that rainbow trout consume primarily aquatic macroinvertebrates along with some zooplankton and demonstrate an extremely limited switch to piscivory at larger sizes. Rainbow trout reared in netpens and limited to a diet of zooplankton lost weight in all three areas of the reservoir. In addition, the reservoir supports a large population of trophy lake trout Salvelinus namaycush, which probably affects the abundance of rainbow trout directly through consumption and the growth potential of rainbow trout indirectly through risk-averse behavior. The combination of spatial variation in reservoir productivity and habitat type, differing stocking strategies, and behavioral responses caused by predators appears to determine the varying success of stocked rainbow trout in the different areas of the reservoir. Our study suggests that stocking strategies may be most effective when specific characteristics of the prey and predator base, the suitability of different habitats, and the genetic strain are explicitly evaluated within the context of the targeted angler population.