Asian Carp in the Missouri River: Analysis from Multiple Missouri River Habitat and Fisheries Programs

Bighead carp Hypophthalmichthys nobilis, silver carp H. molitrix, black carp Mylopharyngodon piceus, and grass carp Ctenopharyngodon idella, collectively referred to as Asian carps, are invasive species that were either accidentally or intentionally introduced into the Mississippi River basin. The expansion of Asian carp into the Missouri River is not well understood and knowledge of population characteristics within this river were lacking. The objectives of this study were to describe the relative abundance, size structure, and spatial and temporal trends of Asian carp using multiple gears from three long-term fish community monitoring programs in the Missouri River downstream of Gavins Point Dam, South Dakota and Nebraska from 2003 to 2007. A total of 1,307 bighead, 1,280 silver, 624 grass, and 0 black carp were captured. The majority of adult bighead carp were captured in overnight hoop nets (38%) and adult silver (14%) and grass carp (23%) were most commonly caught in overnight experimental gill nets. Mini-fyke nets captured almost exclusively, young of the year Asian carp (≤ 80 mm), while gill, trammel, and hoop nets collected a wide length range of fish (81 – 1,200 mm). The relative abundance of all three Asian carp species did not significantly differ among years; however, spatial trends were found as relative abundance was highest in the Missouri River downstream of the Platte River. Short Asian carp weighed less in the Gavins Point reach compared to downstream of the Grand River in Missouri. Conversely, long Asian carp in the Gavins Point reach attained greater weights than fish of similar length downstream. We found that multiple sampling gears are necessary to monitor Asian carp population characteristics in the Missouri River. Asian carp populations appear to be well established in the Missouri River and it is increasingly important to understand the affects these invasive species have on the native fish community

Asian Carp in the Missouri River: Analysis from Multiple Missouri River Habitat and Fisheries Programs

Bighead carp Hypophthalmichthys nobilis, silver carp H. molitrix, black carp Mylopharyngodon piceus, and grass carp Ctenopharyngodon idella, collectively referred to as Asian carps, are invasive species that were either accidentally or intentionally introduced into the Mississippi River basin. The expansion of Asian carp into the Missouri River is not well understood and knowledge of population characteristics within this river were lacking. The objectives of this study were to describe the relative abundance, size structure, and spatial and temporal trends of Asian carp using multiple gears from three long-term fish community monitoring programs in the Missouri River downstream of Gavins Point Dam, South Dakota and Nebraska from 2003 to 2007. A total of 1,307 bighead, 1,280 silver, 624 grass, and 0 black carp were captured. The majority of adult bighead carp were captured in overnight hoop nets (38%) and adult silver (14%) and grass carp (23%) were most commonly caught in overnight experimental gill nets. Mini-fyke nets captured almost exclusively, young of the year Asian carp (≤ 80 mm), while gill, trammel, and hoop nets collected a wide length range of fish (81 – 1,200 mm). The relative abundance of all three Asian carp species did not significantly differ among years; however, spatial trends were found as relative abundance was highest in the Missouri River downstream of the Platte River. Short Asian carp weighed less in the Gavins Point reach compared to downstream of the Grand River in Missouri. Conversely, long Asian carp in the Gavins Point reach attained greater weights than fish of similar length downstream. We found that multiple sampling gears are necessary to monitor Asian carp population characteristics in the Missouri River. Asian carp populations appear to be well established in the Missouri River and it is increasingly important to understand the affects these invasive species have on the native fish community

Size-Dependent Trophic Patterns of Pallid Sturgeon and Shovelnose Sturgeon in a Large River System

This study compared patterns of d15N and d13C enrichment of pallid sturgeon Scaphirhynchus albus and shovelnose sturgeon S. platorynchus in the Missouri River, United States, to infer their trophic position in a large river system. We examined enrichment and energy flow for pallid sturgeon in three segments of the Missouri River (Montana/North Dakota, Nebraska/South Dakota, and Nebraska/Iowa) and made comparisons between species in the two downstream segments (Nebraska/South Dakota and Nebraska/Iowa). Patterns in isotopic composition for pallid sturgeon were consistent with gut content analyses indicating an ontogenetic diet shift from invertebrates to fish prey at sizes of .500-mm fork length (FL) in all three segments of the Missouri River. Isotopic patterns revealed shovelnose sturgeon did not experience an ontogenetic shift in diet and used similar prey resources as small (,500-mm FL) pallid sturgeon in the two downstream segments. We found stable isotope analysis to be an effective tool for evaluating the trophic position of sturgeons within a large river food web

Length-Weight Relationships for Three Asian Carp Species in the Missouri River

Bighead carp (Hypophthalmichthys nobilis), silver carp (Hypophthalmichthys molitrix), and grass carp (Ctenopharyngodon idella), collectively referred to as Asian carp, are invasive species that have been introduced into the Mississippi River basin. The expansion of Asian carp into the Missouri River is not well understood and knowledge of population characteristics within this river are lacking. The objectives of this study were to describe the length-weight relationships (condition) of Asian carp from 2003 to 2007 in the Missouri River downstream of Gavins Point Dam, South Dakota and Nebraska to St. Louis, Missouri. All total, 388 bighead, 75 silver, and III grass carp were measured and weighed. Short bighead carp weighed significantly less in the upper Missouri River from Gavins Point Dam to the Platte River compared to fish of the lower Missouri River from the Grand River to the Mississippi River. Conversely, long bighead carp in the upper Missouri River attained greater weights than fish of similar length downstream. Though not significant, condition similarly varied between the upper and lower Missouri River for silver carp and grass carp

Comparison and Validation of Two Linear Back-Calculation Models Used to Estimate Fish Growth

Back-calculation, a useful tool in fisheries management, provides biologists with entire growth histories of fish from bony structures sampled at one point in time. Objectives of this study were to: assess and validate the Fraser-Lee and Weisberg back-calculation models using known growth histories of fish from scales and otoliths in laboratory and field settings, quantify the effect of scale measurement error on back-calculations for both models, and to compare the effects of different y-intercept values (i.e., correction factors) on back-calculated lengths in the Fraser-Lee model. In the laboratory, growth validations were conducted by simulating annuli using oxytetracycline hydrochloride (OTC) to mark the bony structures of bluegills (Lepomis macrochirus), bluegill X green sunfish hybrids (L. macrochirus X Lepomis cyanellus), and rainbow trout (Oncorhynchus mykiss) multiple times. In the field, smallmouth bass (Micropterus dolomieu) and walleyes (Stizostedion vitreum) were tagged in spring (i.e., at time of annulus formation) and later recaptured to assess growth. In the laboratory, OTC marking success of scales was not 100%; marking was lower for OTC-fed bluegills (46%) and OTC-fed rainbow trout (25%) than for OTC-fed hybrid sunfish (82%). Marking success was greatest for the hybrid-sunfish but differed by administration method; success was higher for fish fed OTC (82%) compared to OTC injection (74%). No back-calculations were performed with the rainbow trout because OTC marking success was low and the majority of scales were regenerated. For OTC-fed bluegills and hybrid sunfish, Fraser-Lee back-calculated lengths (BCLs) were within 6.0% of actual lengths except for a 13.9% deviation for OTC-fed bluegills at mark one. For OTC-fed hybrid sunfish, the bluegill standard intercept of 20 mm provided more accurate BCLs than the green sunfish standard intercept of 10 mm. For OTC-injected hybrid sunfish, neither the Fraser-Lee nor the Weisberg model consistently provided the more accurate BCLs when using scales. For all OTC marks in scales, Fraser-Lee and Weisberg BCLs were within 4.8 and 2.7% respectively, of the actual lengths. In comparison, BCLs with otoliths were generally less accurate and less precise than scales for both models. However, the Fraser-Lee model was generally more accurate and always more precise than the Weisberg model for otolith back-calculations. The effect of scale measurement error on BCLs for both the Fraser-Lee and Weisberg models was small; mean BCLs changed only 1.5 mm for the Fraser-Lee model and 1.6 mm for the Weisberg model as a result of a mean measurement error of 2.6 circuli. Each circulus corresponded to a measurement error in BCL of 1.73 mm for both models. The OTC marks did not correspond directly to circuli in OTC-fed bluegills and OTC-fed or OTC-injected hybrid sunfish thus raising questions about scale physiology. In all fish, the OTC marks cut across 3 to 5 circuli in the anterior region and 7 to 10 circuli in the lateral region of the scale. Marks from the OTC-injected hybrid sunfish appeared to 'bleed' in toward the scale focus and displayed fluorescence along the entire cross section, suggesting that the fibrillary layer of the scale was calcified. For wild caught fish in spring, the Fraser-Lee back-calculation model was more accurate and precise than the Weisberg model. Nearly all Fraser-Lee BCLs underestimated the actual lengths but no consistent bias existed for Weisberg model estimates. For the Fraser-Lee model, standard intercepts provided more accurate BCLs than biological intercepts (defined as the body length at scale formation) . Ratios of known body and known scale growth for marked and recaptured fish were not directly proportional (i.e., an isometric 1:1 ratio) and all simple linear regressions of known body growth ratios on known scale growth ratios were significantly different than the expected 1:1 ratio. However, the coefficient of determination (r^2 ) always decreased when all known growth ratios were used from fish recaptured multiple times compared to regressions with one randomly selected known ratio per fish. Lower r^2 values indicated the Weisberg Model assumption of independence for successive scale increments in fish may not be valid. The Fraser-Lee model is recommended over the Weisberg model for back-calculation because Fraser-Lee estimates were as accurate as the Weisberg model, were more precise and had a consistent bias towards underestimation.Department of Biology and the Wisconsin Cooperative Fishery Research Unit at the University of Wisconsin-Stevens Poin

Spatial and temporal patterns and the influence of abiotic factors on larval fish catches in the lower Niobrara River, Nebraska

The Niobrara River has a natural hydrograph and temperature regime with the lower 32 km protected under the National Wild and Scenic River system managed by the National Park Service. The largest threat to this river is decreased instream flows due to water withdrawals for agriculture. The Niobrara River a large tributary to the Missouri River may positively influence fish production. However, no information exists regarding phenology of fish spawning or what abiotic factors may influence spawning. Our objectives were to examine the taxonomic composition and the spatial and temporal patterns of the larval fish assemblage in relation to environmental variables in the lower Niobrara River. Larval fish sampling occurred weekly from April to August in 2008 and May to August 2009 with drift nets set in the Niobrara River at two sites: the mouth and 63 kilometers upstream. Each year, larval fish first appeared in the drift during the second week of May and were collected until the third week of August. Larval river carpsuckers Carpiodes carpio were the most abundant species in the drift during early-June, followed by red shiners Notropis lutrensis and sand shiners Notropis stramineus in late-June to mid-August, with Lepomis spp. appearing during late-June to late-July. No diel cycle in occurrence of larval fish in the drift was observed and likely resulted from the naturally high turbidity (mean nephelometric turbidity unit [NTU] \u3e 74). Larval fish densities were 24% higher in 2009 compared to 2008. Spatially, the greatest numbers of larval fish for most fish species were collected at our upstream site located immediately downstream of Spencer Dam. Differences in environmental variables were found among sites and years as mean water temperature, velocity, and turbidity were higher and dissolved oxygen was lowest at the mouth site in 2009. The results of canonical correspondence analysis found red shiners and sand shiners were associated with high water temperatures with low stable flows found late summer. Larval flathead chubs Platygobio gracilis and common carp Cyprinus carpio abundance was positively related to dissolved oxygen and water velocity and negatively with water temperature. River carpsuckers were associated with high water velocities and moderate water temperatures while Lepomis spp. were positively associated with high conductivity and high water temperatures. Fish species that successfully spawned in the lower Niobrara River are adapted to extreme temperatures, high variability in discharge, turbidity, and sediment load. Based on the importance of abiotic factors affecting larval fish abundances, a reduction in in-stream flows would likely jeopardize native fish populations and eliminate some productivity of fish in this river

Movement Patterns of Age-1 and Age-7 Pallid Sturgeon Within the Missouri River During Record 2011 Discharges Downstream of Fort Randall Dam

During the summer of 2011, the Missouri River system experienced the largest discharge levels ever recorded from Fort Randall Dam, (\u3e 4,247 m3s-1 sustained from 25 June to 31 July of 2011), which was approximately four fold above normal. Our objective was to determine movement patterns of pallid sturgeon Scaphirhynchus albus in the inter-reservoir riverine reach between Fort Randall and Gavins Point dams, South Dakota, during this record discharge period. Fifty-one hatchery reared pallid sturgeon implanted with ultrasonic transmitters from two size classes, large (age-6 at tagging; n = 24) and small (age-1; n = 27), were at large during the flood. Small age-1 fish ranged from 352 – 389 mm fork length (FL; mean = 369 mm) and 165 – 235 g (mean = 193 g), while fish in the large size class ranged from 564 – 723 mm (mean = 652) and 700 – 1,600 g (mean = 1,154 g). After discharge increased in late May, 67% of large pallid sturgeon were relocated at least once with 10 fish relocated multiple times, whereas only 11% of small fish were relocated. Mean net movement between six relocation surveys for both pallid sturgeon size groups pooled was positively correlated with discharge (r2 = 0.77, p = 0.07). Mean net movement of the large size class (r2 = 0.82, p = 0.04) was positively correlated to changes in net discharge, with two fish moving in the main channel to within 6.5 river km of Fort Randall Dam when flows exceeded 4,000 m3s-1. Small pallid sturgeon also demonstrated upstream movement with increasing discharge but to a lesser extent. No fish were found on the inundated floodplain or during one survey in late May of Lewis and Clark Lake. Overall, pallid sturgeon remained in the main river channel and generally moved upstream during record discharges out of Fort Randall Dam; however other factors such a temperature and food availability may have also contributed to their movements

The Status of Fishes in the Missouri River, Nebraska: Pallid Sturgeon (\u3ci\u3eScaphirhynchus albus\u3c/i\u3e)

Anthropogenic alterations to the Missouri River have placed the Pallid Sturgeon (Scaphirhynchus albus) population in jeopardy and contributed to their listing as an endangered species. Pallid sturgeon were always less common than the sympatric Shovelnose Sturgeon (S. platorynchus); however, Pallid Sturgeon seemed to be more affected by river alterations as the river sturgeon ratio has become more skewed towards Shovelnose Sturgeon. Shortly after listing, population augmentation with hatchery produced Pallid Sturgeon began to supplement the diminishing wild population. Therefore, the objective of this study was to present the current population status of the Pallid Sturgeon in the Missouri River along Nebraska’s border. Moving upstream along Nebraska’s eastern border the population of wild Pallid Sturgeon declines and appears very minimal to non-existent upstream of Gavins Point Dam. The wild Pallid Sturgeon population below Gavins Point Dam appears unchanged over the past decade. Hatchery supplementation has stocked almost 12,000 hatchery-reared Pallid Sturgeon above Gavins Point Dam and over 135,000 below, these hatchery-reared fish are surviving and contributing to the overall population throughout all reaches as the capture frequency has increased annually. Currently, the Pallid Sturgeon population consists primarily of stock (66%) and quality- sized (22%) fish, most of which are of hatchery origin. Mean relative condition of quality and preferred-size Pallid Sturgeon varied spatially and temporally. As the Pallid Sturgeon population increases several population recruitment obstacles still exist. Until the bottleneck preventing natural recruitment is lessened, continued listing of the Pallid Sturgeon as an endangered species is critical to drive river management and restoration efforts which are likely to influence species recovery

River geomorphology and fish barriers affect on spatial and temporal patterns of fish assemblages in the Niobrara River, Nebraska

The Niobrara River in northern Nebraska traverses the heart of the Great Plains with portions of the river protected under the National Wild and Scenic River system managed by the National Park Service. The Niobrara River changes from a narrow, entrenched stream to a wide, highly braided river with four fish barriers and 36 distinct geomorphic segments in the lower 531 river kilometers (rkm). Our objectives were to examine the spatial and temporal patterns of fish assemblages in the Niobrara River related to environmental variables, fish barriers, and river geomorphology. Tote-barge electrofishing occurred monthly from June to September in 2009 at 17 sites downstream of Dunlap Diversion Dam near Hemingford, Nebraska (river kilometer [rkm] 531) to the mouth (rkm 0) where the Niobrara River meets the Missouri River. In all, we collected 33,888 fish from 42 species and 11 families. Species richness was greatest near the mouth (rkm 4) and subsequently declined sharply upstream of the first fish barrier (Spencer Dam; rkm 63). Monthly changes in the fish assemblages were generally low with most differences due to young of the year, large-bodied fish recruiting to the electrofishing gear. Fish barriers, both anthropomorphic and natural, had significant impacts on the fish community by blocking fish migration, creating high abundances downstream of the structures, and species absent above the barriers. Bray-Curtis dissimilarity values between sample sites ranged from 45.4 to 96.5, which indicated high variation in the fish assemblage as river geomorphic features changed. Norden Chute (rkm 193), a natural fish barrier, marked a sharp change in geomorphic structure from a highly braided river with heterogeneous diversity of habitats downstream to a single river channel with a reduced floodplain upstream. Above the chute, the fish assemblage was dominated by insectivores fish species, while downstream occurrence of piscivores increased. Based on our results, fish barriers affected the diversity and abundances of fish both upstream and downstream