The Status of Fishes in the Missouri River, Nebraska: Lake Sturgeon \u3ci\u3e(Acipenser fulvescens)\u3c/i\u3e

Lake Sturgeon (Acipenser fulvescens) occurrences in the Missouri River along Nebraska’s eastern border are historically sporadic and rare. Presently, the wild Lake Sturgeon population in this river reach may be extirpated. A Recovery Program initiated by the Missouri Department of Conservation (MDC) has stocked almost 150,000 hatchery-reared Lake Sturgeon into the lower Missouri River at several sites in Missouri. As a result, the number of Lake Sturgeon collected has increased. Since monitoring began in 2003, no Lake Sturgeon have been collected above Gavins Point Dam while 40 fish were collected downstream of Gavins Point Dam. The majority of captures occurred in the lower channelized reach downstream of the confluence of the Platte and Missouri rivers. All fish collected are assumed to be progeny of MDC’s Recovery Program as either they were hatchery marked or their size (mean fork length = 764 mm, range = 602–997 mm) correlated with the expected growth rates. At present, their rarity warrants continued listing as a state threated species

The Status of Fishes in the Missouri River, Nebraska: Lake Sturgeon \u3ci\u3e(Acipenser fulvescens)\u3c/i\u3e

Lake Sturgeon (Acipenser fulvescens) occurrences in the Missouri River along Nebraska’s eastern border are historically sporadic and rare. Presently, the wild Lake Sturgeon population in this river reach may be extirpated. A Recovery Program initiated by the Missouri Department of Conservation (MDC) has stocked almost 150,000 hatchery-reared Lake Sturgeon into the lower Missouri River at several sites in Missouri. As a result, the number of Lake Sturgeon collected has increased. Since monitoring began in 2003, no Lake Sturgeon have been collected above Gavins Point Dam while 40 fish were collected downstream of Gavins Point Dam. The majority of captures occurred in the lower channelized reach downstream of the confluence of the Platte and Missouri rivers. All fish collected are assumed to be progeny of MDC’s Recovery Program as either they were hatchery marked or their size (mean fork length = 764 mm, range = 602–997 mm) correlated with the expected growth rates. At present, their rarity warrants continued listing as a state threated species

Emigration of hatchery‐reared Pallid Sturgeon, Scaphirhynchus albus (Forbes and Richardson), through a Missouri River dam

The middle Missouri River (MMR; Fort Randall Dam, SD to Gavins Point Dam, NE‐SD) is stocked with hatchery‐reared pallid sturgeon, Scaphirhynchus albus (Forbes and Richardson), from upper Missouri River broodstock to aid recovery of this federally endangered species. Emigration of these fish through Gavins Point Dam restores genetic connectivity that likely existed pre‐impoundment but could lead to outbreeding depression in the future. Recapture data of hatchery‐reared pallid sturgeon stocked in the MMR were evaluated to improve understanding of pallid sturgeon emigration. From 2004 to 2015, 219 emigrants were caught: 4 stocked at age ≥2 years and 215 stocked at age ≤1 year. Emigration of the 2001‐2007 year classes stocked at age 1 was a consistent phenomenon and appeared higher than emigration of year classes stocked at ages 2–3. Little evidence suggested emigration was associated with an unusually high‐water event in 2011. The annual emigration probability of individuals stocked at age 1 estimated from multi‐state mark–recapture models was 0.05 [95% confidence interval = 0.04–0.06] for fish ages ≥1 year. This study suggests that alterations to stocking practices (e.g. stocking age) may affect emigration rates and, therefore, connectivity among pallid sturgeon populations

The Status of Fishes in the Missouri River, Nebraska: Sauger (\u3ci\u3eSander canadensis\u3c/i\u3e)

Early fisheries investigation of the Missouri River fish community indicated that Sauger were common throughout Nebraska, including all major Missouri River tributaries. However due to many factors, their current range is restricted to the Missouri River and the lower reaches of a few tributaries. Hesse (1994) recommended listing Sauger as a state endangered species but this recommendation was never implemented. Therefore, the objective of this paper is to reevaluate the current population status of Sauger in the Missouri River along Nebraska’s border. Over 2,100 Sauger have been captured from the Missouri River along Nebraska’s eastern border since 2003. Sauger were most frequently captured in the riverine reach above Gavins Point Dam where they comprised 10% to 14% of the adult fish community captured. Sauger populations appear to be relatively stable throughout this reach over the past decade. Sauger were infrequently captured below Gavins Point Dam, representing less than two percent of the adult fish community. The Sauger population below Gavins Point Dam is highly variable making any long-term trends difficult to determine. The Sauger population reacted positively to the extreme flood conditions throughout the Missouri River in 2011, especially below Gavins Point Dam. As river management has not changed over the past half century, Sauger are just one of several native fish species experiencing greatly diminished population levels and rage contraction due to major river modifications

The Status of Fishes in the Missouri River, Nebraska: Blue Sucker Cycleptus elongatus

Blue Sucker Cycleptus elongatus are a large-bodied, benthic fish that are considered an indicator species for riverine health. A combination of historic commercial fishing and anthropogenic modifications to riverine habitat led to blue suckers being listed as a candidate species for the federal threatened or endangered species list in 1993. However, they were never designated a federally protected species. Locally, Blue Suckers are currently listed as a Nebraska Natural Legacy Project’s Tier 1 species but population changes and trends have not been quantified. Therefore, the objective of this paper was to evaluate the current population status of Blue Sucker in the Missouri River along Nebraska’s border. Over 12,000 Blue Suckers were sampled in Nebraska from 2003 to 2012 as part of a targeted effort to characterize the benthic fish community in the Missouri River. Blue Suckers were rarely sampled upstream of Gavins Point Dam. Sampling results from this reach indicate this remnant population is comprised of mostly large adults with very limited reproduction. Capture frequency increased downstream of Gavins Point Dam with adequate reproduction and recruitment to sustain the population in these reaches. Gill net catch consisted of 14% Blue Suckers in the unchannelized reach downstream of Gavins Point and 23% of the benthic fish community in the channelized reach upstream of the Platte River. Age-0 Blue Suckers were most frequently detected in 2011 during the extreme flooding conditions but were also detected in higher abundance in 2006 when the river remained in its channel. The overall population downstream of Gavins Point Dam appears stable or perhaps slightly increasing. Blue Suckers, as with most native fish populations, were negatively affected when the Missouri River was highly modified through dam construction and channelization. However, reproduction and recruitment is occurring and Blue Sucker are not as imperiled as Pallid Sturgeon Scaphirhynchus albus or the native Macrhybopsis species

The Status of Fishes in the Missouri River, Nebraska: Shoal Chub (\u3ci\u3eMacrhybopsis hyostoma\u3c/i\u3e), Sturgeon Chub (\u3ci\u3eM. gelida\u3c/i\u3e), Sicklefin Chub (\u3ci\u3eM. meeki\u3c/i\u3e), Silver Chub (\u3ci\u3eM. storeriana\u3c/i\u3e), Flathead Chub (\u3ci\u3ePlatygobio gracilis\u3c/i\u3e), Plains Minnow (\u3ci\u3eHybognathus placitus\u3c/i\u3e), Western Silvery Minnow (\u3ci\u3eH. argyritis\u3c/i\u3e), and Brassy Minnow (\u3ci\u3eH. hankinsoni\u3c/i\u3e)

Throughout the past century, the Missouri River has been highly modified which has negatively affected the native fish community. Previous research quantified the reduction of several native Cyprinidae species and made several recommendations to aid in recovery. However, these recommendations were not implemented. Therefore, the objective of this paper is to assess the current population trends of eight native cyprinid species and develop the current management objectives. Over 335,000 fish were collected from the Missouri River along Nebraska’s eastern border with mini-fyke nets and otter trawls from 2003 to 2012. Target Cyprinidae species consisted of less than five percent (n = 14,610) of the total catch with Silver Chubs (n = 11,804) comprising the majority (81%) of target species captured. State-wide all eight species were captured, although localized extirpations may have occurred. These native cyprinid species are extremely rare or extirpated upstream of Gavins Point Dam and populations continue to be limited downstream of Gavins Point Dam. Generally, relative abundance of these fish increased in the channelized reach, compared to the unchannelized reaches, but they no longer dominate the fish community. This shift in species composition and low relative abundance estimates continue to indicate imperilment of the Missouri River system

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

The Shovelnose Sturgeon Scaphirhynchus platorynchus remains the most abundant riverine sturgeon species in North American despite the anthropogenic modifications that have occurred throughout their historic range; however, their populations have declined throughout Nebraska since the construction of Fort Randall and Gavins Point Dams. Therefore, the objective of this study was to present the current status of Shovelnose Sturgeon in the Missouri River along Nebraska’s border. Data was acquired from 2003 to 2012 from all reaches of the Missouri River along Nebraska’s eastern border. Catch rates of Shovelnose Sturgeon increased in a downstream trend and were highest in the reach below the Missouri and Platte River confluence. Based on gill net samples which collected the majority (39%) of Shovelnose Sturgeon, annual catch per unit efforts indicate a declining population above Gavins Point Dam and a stable population below in the open Missouri River. The length frequency distributions of Shovelnose Sturgeon collected were similar across all reaches with the exception of those captured between Fort Randall and the headwaters of Lewis and Clark Lake which were significantly larger than fish captured below the Platte River confluence. Although no age-0 Shovelnose Sturgeon were captured in the unchannelized reaches, age-0 abundance increased in a downstream trend throughout the channelized reaches. Preferred-sized fish (510-640 mm, N = 53,741) were the most common size category of Shovelnose Sturgeon captured throughout all reaches and across all years followed by quality-sized (380-510 mm, N = 12,089) and memorable-sized (640-810 mm, N = 4,569) fish. Our data concludes the overall population of Shovelnose Sturgeon above Gavins Point Dam appears to be slightly declining while the population in the open, lower river appears to be stable

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

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

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