Endangered pallid sturgeon (Scaphirhynchus albus) (right) and shovelnose sturgeon (Scaphirhynchus platorynchus) (left) from the Lower Missouri River, captured as part of the USGS Comprehensive Sturgeon Research Program. Early spring sampling for reproductive adult pallid sturgeon on Lower Missouri River. High-resolution multibeam bathymetric map to characterize habitat around tagged sturgeon locations. Microscopic image of sturgeon larval stage. Field researchers capture Scaphirhynchus sturgeon for telemetry studies using baited trotlines.

Organochlorine chemical residues and elemental concentrations were measured in piscivorous and benthivorous fish at 111 sites from large U.S. river basins. Potential contaminant sources such as urban and agricultural runoff, industrial discharges, mine drainage, and irrigation varied among the sampling sites. Our objectives were to provide summary statistics for chemical contaminants and to determine if contaminant concentrations in the fish were a risk to wildlife that forage at these sites. Concentrations of dieldrin, total DDT, total PCBs, toxaphene, TCDD-EQ, cadmium, chromium, mercury, lead, selenium, and zinc exceeded toxicity thresholds to protect fish and piscivorous wildlife in samples from at least one site; most exceedences were for total PCBs, mercury, and zinc. Chemical concentrations in fish from the Mississippi River Basin exceeded the greatest number of toxicity thresholds. Screening level wildlife risk analysis models were developed for bald eagle and mink using no adverse effect levels (NOAELs), which were derived from adult dietary exposure or tissue concentration studies and based primarily on reproductive endpoints. No effect hazard concentrations (NEHC) were calculated by comparing the NOAEL to the food ingestion rate (dietary-based NOAEL) or biomagnification factor (tissue-based NOAEL) of each receptor. Piscivorous wildlife may be at risk from a contaminant if the measured concentration in fish exceeds the NEHC. Concentrations of most organochlorine residues and elemental contaminants represented no to low risk to bald eagle and mink at most sites. The risk associated with pentachloroanisole, aldrin, Dacthal, methoxychlor, mirex, and toxaphene was unknown because NOAELs for these contaminants were not available for bald eagle or mink. Risk differed among modeled species and sites. Our screening level analysis indicates that the greatest risk to piscivorous wildlife was from total DDT, total PCBs, TCDD-EQ, mercury, and selenium. Bald eagles were at greater risk to total DDT and total PCBs than mink, whereas risks of TCDD-EQ, mercury, and selenium were greater to mink than bald eagle.

Cover photographs. A, LANDSAT TM image of the area around the confluence of the Missouri and Yellowstone Rivers on November 11, 2013. B, High resolution multibeam depth data and pallid sturgeon telemetry locations near the confluence of the Missouri and Osage Rivers. C, A researcher lowers an ichthyoplankton sampling net into the

Insufficient food during early life could limit the population growth of endangered Pallid Sturgeon Scaphirhynchus albus in the lower Missouri River. Shallow-water habitat restoration is intended to provide nursery benefits, including food, for young sturgeon, but the effect of shallow-water habitat on their diet is unknown. Age-0 Pallid Sturgeon are rare, providing little opportunity for direct evaluation; however, studying the closely related and abundant Shovelnose Sturgeon S. platorynchus may provide valuable information to guide habitat restoration efforts. We compared diet, body condition (lipid content), and change in body weight (24-h bioenergetics simulation) for postdrift, age-0 sturgeon among five reaches ranging widely in shallow-water habitat availability. Lipid content of satiated and emaciated laboratory-reared individuals were compared with that of wild-caught fish. In general, shallow-water habitat availability appeared to have little effect on the variables examined. Regardless of reach, wild-caught fish primarily consumed chironomids, and empty stomachs were rare. Additionally, differences in prey weight, lipid content, or the modeled change in body weight did not usually correspond to differences in shallow-water habitat availability. Instead, we found annual differences, as prey weight consumed and the percentage of fish with modeled weight gain was often higher in 2015 than 2014, while the opposite was true for the percentage of fish with lipid content values that were comparable with the emaciated laboratory standard. Overall, our findings complement recent suggestions that shallow-water habitat restoration efforts, as previously implemented, may not benefit sturgeon populations. Our results coupled with previous research suggest that the lower Missouri River prey base can support a stable Shovelnose Sturgeon population; however, additional research is needed to determine whether this applies to Pallid Sturgeon.

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.

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.

Pallid Sturgeon Scaphirhynchus albus are endemic to the Missouri and Mississippi river basins and are rare throughout their range. The species was listed as federally endangered with little to no evidence of natural recruitment. Since population augmentation was initiated as a recovery objective in the early 1990s, thousands of hatchery-origin Pallid Sturgeon have been stocked in the lower Missouri River (Gavins Point Dam [river kilometer 1,305.1] to the confluence of the Mississippi River [river kilometer 0.0]). Efforts to discriminate natural reproduction and recruitment of wild-origin Pallid Sturgeon from hatchery-origin fish has been hampered by tag loss in hatchery-origin sturgeon, inconsistent documentation of hatchery parental crosses, and the failure to collect tissue samples for genotyping all broodstock. However, the recent reconstruction of missing parental genotypes from known hatchery-origin progeny and from cryopreserved milt made it possible to examine Pallid Sturgeon recruitment. Therefore, our objectives were to 1) determine the likelihood that unmarked Pallid Sturgeon captured from the lower Missouri River were the result of natural recruitment and 2) examine the length distribution of wild- and hatchery-origin fish to determine if a difference exists by origin and examine the life-stage distribution. Genetic analysis showed that from 2003 to 2015, 358 “presumptive wild-origin” Pallid Sturgeon were captured in the lower Missouri River and the comparison between the length distributions of wild- and hatchery-origin fish did not provide any additional clarification into potential wild-origin fish. Low recruitment may be due to a small breeding population, high mortality of early life stages, hybridization with Shovelnose Sturgeon Scaphirhynchus platorynchus, or transport of drifting free embryos or larvae into inhospitable habitats. Determining what factors are limiting recruitment is the important next step for the recovery of Pallid Sturgeon in the lower Missouri River.

Acipenseriformes (sturgeons and paddlefish) globally have declined throughout their range due to river fragmentation, habitat loss, overfishing, and degradation of water quality. In North America, pallid sturgeon (Scaphirhynchus albus) populations have experienced poor to no recruitment, or substantial levels of hybridization with the closely related shovelnose sturgeon (S. platorynchus). The Lower Missouri River is the only portion of the species' range where successful reproduction and recruitment of genetically pure pallid sturgeon have been documented. This paper documents spawning habitat and behavior on the Lower Missouri River, which comprises over 1,300 km of unfragmented river habitat. The objective of this study was to determine spawning locations and describe habitat characteristics and environmental conditions (depth, water velocity, substrate, discharge, temperature, and turbidity) on the Lower Missouri River. We measured habitat characteristics for spawning events of ten telemetry-tagged female pallid sturgeon from 2008-2013 that occurred in discrete reaches distributed over hundreds of kilometers. These results show pallid sturgeon select deep and fast areas in or near the navigation channel along outside revetted banks for spawning. These habitats are deeper and faster than nearby river habitats within the surrounding river reach. Spawning patches have a mean depth of 6.6 m and a mean depth-averaged water-column velocity of 1.4 m per second. Substrates in spawning patches consist of coarse bank revetment, gravel, sand, and bedrock. Results indicate habitat used by pallid sturgeon for spawning is more common and widespread in the present-day channelized Lower Missouri River relative to the sparse and disperse coarse substrates available prior to channelization.Understanding the spawning habitats currently utilized on the Lower Missouri River and if they are functioning properly is important for improving habitat remediation measures aimed at increasing reproductive success. Recovery efforts for pallid sturgeon on the Missouri River, if successful, can provide guidance to sturgeon recovery on other river systems; particularly large, regulated, and channelized rivers. K E Y W O R D Shabitat, Missouri River, spawning, sturgeon, telemetryThis is an open