Cross-Sectional Analysis of Sediment and Organic Matter from Transects Across the Lower Unchannelized Missouri River

The United States Army Corps of Engineers, U.S. Geological Survey, and Nebraska Game and Parks Commission cooperated in 1989 to obtain physical data from cross-section transects along the unchannelized Missouri River in northeastern Nebraska. Bed-sediment samples were collected from locations along these transects and taken to the laboratory. Mean particle-size and standard deviation were determined by weighing material retained on seven U.S. Standard sieves after being on a sieve shaker for six minutes. Organic matter content of each sample was obtained by ashing an aliquot in a muffle furnace to remove the organic portion. A new system for coding sediment mixtures was developed, and coded sediment and organic matter content were compared with depth and velocity in a regression analysis. The most common mean particle-size was determined to be medium sand; however, some samples were as coarse as fine gravel. Organic-matter content was less then 3% for the most part; however, it was measured as high as 20%. Sediment and organic matter were related to depth and velocity; however, r-square values were low, suggesting that other factors contribute to the observed variability in the sediment mixtures and organic matter content

Cross-Sectional Analysis of Sediment and Organic Matter from Transects Across the Lower Unchannelized Missouri River

The United States Army Corps of Engineers, U.S. Geological Survey, and Nebraska Game and Parks Commission cooperated in 1989 to obtain physical data from cross-section transects along the unchannelized Missouri River in northeastern Nebraska. Bed-sediment samples were collected from locations along these transects and taken to the laboratory. Mean particle-size and standard deviation were determined by weighing material retained on seven U.S. Standard sieves after being on a sieve shaker for six minutes. Organic matter content of each sample was obtained by ashing an aliquot in a muffle furnace to remove the organic portion. A new system for coding sediment mixtures was developed, and coded sediment and organic matter content were compared with depth and velocity in a regression analysis. The most common mean particle-size was determined to be medium sand; however, some samples were as coarse as fine gravel. Organic-matter content was less then 3% for the most part; however, it was measured as high as 20%. Sediment and organic matter were related to depth and velocity; however, r-square values were low, suggesting that other factors contribute to the observed variability in the sediment mixtures and organic matter content

Niobrara-Missouri River Fishery Investigations

The Niobrara River heads in the table lands of eastern Wyoming and flows 786 kilometers (km) eastward across Nebraska joining the Missouri River near the town of Niobrara, Nebraska. The Niobrara is the largest Missouri River tributary between the last two mainstem impoundments (Lake Francis Case and Lewis and Clark Lake). Fish movement up the Niobrara is prevented by Nebraska Public Power District\u27s (NPPD\u27s) Spencer Hydroelectric Dam, 63.3 km upstream from the river mouth. The lower reach of the river is turbid and carries a considerable load of sand, silt, and organic debris into the Missouri River. The mean annual flow is 49.5 m3/s. The mean annual flow through Spencer Dam for the period September 1976 through September 1977 was 37.7 m3/s. Silt, sand, and debris settle into the reservoir behind Spencer Dam. Periodic flushing is needed to prevent damage to the turbines. Quarterly flushings have resulted in significant fish kills downstream from Spencer Dam (Hesse 1976, Hesse 1977, Wallace 1976). Niobrara River fish populations have not been studied previously. In contrast, the fishery of the Missouri River-L.ewis and Clark Lake system was studied by the U.S. Fish and Wildlife Service from 1962- 1974 (Walburg 1976). Walburg alluded to the beneficial relationship that potentially exists between the Niobrara and Missouri river systems. The fishery in Lewis and Clark Lake has been declining since 1959 for reasons that are well defined (Walburg 1964, Walburg 1976). The Niobrara is a major tributary and may offer a better spawning and nursery environment than the Missouri-Lewis and Clark system. This study was designed to distinguish the relationship existing between the fisheries of these two systems and establish a baseline of life history data for Niobrara fishes for future reference. This information is especially valuable, since proposals by the U.S. Bureau of Reclamation would create an impoundment on the Niobrara (O\u27Neill-Norden Dam Irrigation Project) approximately 208 km upstream from the mouth of the river. Should this project become reality, flows in the Niobrara at Norden, Nebraska, would be reduced from the 21.9 m3/s mean annual flow for the period 1964-73 (Nebraska Natural Resources Commission 1976). Projected flow through Norden Dam would be 5.7 m3/s for 60% of the time {personal communication with Roger Andrews, U.S. Bureau of Reclamation). Reduced flow will surely restrict fisheries habitat in the lower Niobrara. If the Niobrara River is a significant contributor to the fishery of the Missouri River - Lewis and Clark Lake system, a loss of fish habitat in the Niobrara could have a detrimental effect on the fishery of the larger system. Collection of data at this time will aid in the assessment of such losses if they occur

The Status of Nebraska Fishes in the Missouri River. 2. Burbot (Gadidae: \u3ci\u3eLota Lota\u3c/i\u3e)

Burbot harvest represented 5.1% of the fish-harvest in the tailwater of Gavins Point Dam in July 1956, one year after the dam was closed. Harvest increased from 510 in 1956 to 4,280 in 1958, but represented only 2% of the 1958 harvest. By 1961 burbot were no longer routinely caught in the tailwater, and their density decreased in the remainder of Nebraska\u27s portion of the Missouri River. At present they are very rare and should be listed as endangered in Nebraska

The Status of Nebraska fishes in the Missouri river, 3. Channel Catfish (Ictaluridae: \u3ci\u3eIctalurus punctatus\u3c/i\u3e)

The average size of Missouri River channel catfish has declined. The percentage 10 years old or older is 4.8% compared with an unexploited population in which 32% are 10 years and older. From 1944 through 1988 commercial harvest declined as much as 64%. Total mortality was 37% at age 4 and 79% at age 5. The increased mortality occurred as they reached 13 inches and became fully recruited to the commercial fishery. Harvest statistics are not wholly reliable because reports are not verifiable and commercial fishers do not return fish tags. Harvest exceeded a reasonable limit for maximum sustained yield. Commercial minimum-size limits have been ineffective due to their design and because they are not easily enforced. Commercial catfishing was closed in action taken by the Nebraska Game and Parks Commission in November 1990 to take effect 1 January 1992. Since then the mean size has increased from 286 mm total length (TL) to 324 mm TL in 25.4-mm mesh net samples from the channelized section of the Missouri River, and the percentage of fish longer than 330 mm TL increased from 8% in 1987 to 44% in 1993

Velocity Microhabitats in the Edges of the Channelized Missouri River

Mean column velocity in the filling bank of the channelized Missouri River reached a maximum of 0.875 m/s. In these locations nose velocity was 30% less. Increased volume discharge did not result in increased velocity in the filling bank locations studied. Surface velocity did not exceed 0.5 m/s within the first 3 m from the cutting bank at two locations along the channelized Missouri River near Nebraska City and Tekamah, Nebraska. Within column velocity at the Nebraska City site was typically higher than velocity near the surface and nearer the bottom. However, at the Tekamah site surface velocity was frequently higher than ether mid-column or near-bottom velocity. Velocity preferences for native Missouri River fish species were usually much higher than those observed within the filling bank locations and within a quite wide margin along the cutting bank

THE STATUS OF NEBRASKA FISHES IN THE MISSOURI RIVER, 5. SELECTED CHUBS AND MINNOWS (CYPRINIDAE): SICKLEFIN CHUB (\u3ci\u3eMACRHYBOPSIS MEEKl\u3c/i\u3e), STURGEON CHUB (\u3ci\u3eM. GEUDA\u3c/i\u3e), SILVER CHUB (\u3ci\u3eM. STORERIANA\u3c/i\u3e), SPECKLED CHUB (\u3ci\u3eM. AESTIVAUS\u3c/i\u3e), FLATHEAD CHUB (\u3ci\u3ePLATYGOBIO GRACILIS\u3c/i\u3e), PLAINS MINNOW (\u3ci\u3eHYBOGNATHUS PLACITUS\u3c/i\u3e), AND WESTERN SILVERY MINNOW (H. ARGYRITIS)

Seven species of native Missouri River cyprinids have been reduced in abundance by 70 to 98%. Several have been extirpated from the reach upstream from Gavins Point Dam. The reasons for the decline are most likely the alteration of sediment dynamics due to dam construction, the elimination of bankful discharge, and the elimination of critical habitats, such as sandbars and off-channel areas

The Status of Nebraska Fishes in the Missouri River. 1. Paddlefish (Polyodontidae: \u3ci\u3ePolyodon spathula\u3c/i\u3e)

The mean larval paddlefish density was 60 times higher in the upper unchannelized section of the Missouri River in Nebraska compared to the lower unchannelized section, and was three times higher than the channelized section\u27s density. Within the upper unchannelized section, 96.2% of the larvae were collected in the discharge of two tributaries, which lie in the lower one-third of the reach. Survival from larval to young-of-the-year stage (June through August) was highest during 1991 due, in part, to the recent drought. Reduced fluctuation of river stages occurred as a result of reduced runoff, which minimized the need to reduce discharge to prevent flooding in the lower basin. The mean weight of paddlefish captured during the 1991 snagging season increased from 6.89 kg in 1990 to 7.45 kg, while the mean length increased from 739 mm (eye-to-fork length) to 753 mm. The percentage of snagged paddlefish 10 years old or older decreased from 15.3% in 1990 to 9.5% in 1991. When we compared the mean length of snagged paddlefish with the mean length of gillnet-captured paddlefish from tailwater and downriver sites there was no difference as demonstrated by t-test. There was a significant difference (Pt \u3c 0.01) between mean weights. The same relationship regarding length and weight was true when fish gillnetted downriver was compared to fish gillnetted in the tailwater (Pt \u3c 0.0001). These data suggest that larger, sexually mature fish are congregated in the tailwater of Gavins Point Dam, which is a total barrier to fish migration. The quota of 1,600 fish was exceeded in 1989 and 1990 but was not reached in the 1991 or 1992 seasons, which extended the full 30 days. In the Gavins Point Dam tailwater area, total annual man-hours of fishing was up from 5,339 hours in 1990 to 8,563 hours in 1991 and 9,139 hours in 1992. Mean catch rate for 1991 was 0.1 fish per hour of snagging compared with 0.33 fish per hour in 1990; however, catch rate declined to 0.05 during 1992. A protected slot-length limit was imposed in 1992 and was considered successful because there was no indication of excessive mortality associated with catch and release

Status of Selected Fishes in the Missouri River in Nebraska With Recommendations for Their Recovery

Population density of five species of chubs and two species of minnows in the Missouri River in Nebraska has been reduced by as much as 95% since 1971. Burbot have been nearly extirpated, sauger have been greatly reduced, and blue catfish are rare. Reasons for the decline of these species include removal of snags from the river; cessation of organic matter and sediment transport because of the construction of large dams on the mainstem and tributaries; cutoff of floodplain connection through channelization, degradation, and the cessation of flooding; alteration of the natural hydrograph to meet the need for commercial navigation; and reduction of the natural water temperature regime because of deep release of cold water from the large reservoirs. We propose remedial actions for each of these ecological changes, and we propose listing of several species as endangered in Nebraska

Contamination of the Channel Catfish (\u3ci\u3eIctalurus punctatus\u3c/i\u3e) by Organochlorine Pesticides and Polychlorinated Biphenyls in the Missouri River

Channel catfish (lctalurus punctatus) were collected at ten locations from the Missouri River adjoining Nebraska. Fillet samples were found to be contaminated with DDT, PCB, dieldrin, heptachlor, trifluralin, and chlordane. At one location, near Bellevue, concentrations of chlordane exceeded Federal Food and Drug Administration action levels. This indicates channel catfish caught and consumed from the Bellevue area may pose a threat to human health. This study provides baseline information on the contamination of channel catfish in the Missouri River adjoining Nebraska