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USGS1986

Mid-winter food use and body weights of mallards and wood ducks in Mississippi

We obtained esophageal food samples from 311 mallards (Anas platyrhynchos) and 94 wood ducks (Aix sponsa) and body weights from 2,118 mallards and 315 wood ducks in western Mississippi during December and January 1979-83. On average, mallards ingested 3.0% animal food, principally aquatic invertebrates, and 97.0% plant food. Rice, soybeans, and seeds of 'moist soil' plants provided 41.3, 41.6, and 10-11% of the total food intake. Wood ducks ingested nearly 100% plant food, of which 23.4% was soybeans and 74.3% was acorns from Nuttall (Quercus nuttallii), water (Q. nigra), and willow oaks (Q. phellos). Mallard food use varied with water conditions; the use of rice decreased and soybeans increased during 1980-81 when cumulative November-January precipitation was < 50% of normal. Wood duck food use varied with habitat; the diet included more acorns at sites having larger acreages of intact bottomland hardwood forest. Mallard and wood duck body weights varied within and among winters. Mallard weights decreased by about 2% from December to January each year. We considered this a regulated loss, whereas we attributed increases and decreases of 4-5% in average weights during wet and dry winters to changes in feeding opportunities associated with winter precipitation. Wood duck weights followed similar trends. We concluded that continued drainage in the Mississippi Delta will adversely affect waterfowl foraging opportunities, and that research on winter feeding ecology will progress more rapidly if we develop an understanding of the foraging efficiencies associated with alternate food resources.

Mississippi↗

USGS1997

Statistical modeling of agricultural chemical occurrence in midwestern rivers

Agricultural chemicals in surface water may constitute a human health risk or have adverse effects on aquatic life. Recent research on unregulated rivers in the midwestern USA documents that elevated concentrations of herbicides occur for 1-4 months following application in late spring and early summer. In contrast, nitrate concentrations in unregulated rivers are elevated during fall, winter, and spring months. Natural and anthropogenic variables of fiver drainage basins, such as soil permeability, amount of agricultural chemicals applied, or percentage of land planted in corn, affect agricultural chemical concentration and mass transport in rivers. Presented is an analysis of selected data on agricultural chemicals collected for three regional studies conducted by the US Geological Survey. Statistical techniques such as multiple linear and logistic regression were used to identify natural and anthropogenic variables of drainage basins that have strong relations to agricultural chemical concentrations and mass transport measured in rivers. A geographic information system (GIS) was used to manage and analyze spatial data. Statistical models were developed that estimated the concentration, annual transport, and annual mean concentration of selected agricultural chemicals in midwestern rivers. Multiple linear regression models were not very successful (R2 from 0.162 to 0.517) in explaining the variance in observed agricultural chemical concentrations during post-planting runoff. Logistic regression models were somewhat more successful, correctly matching the observed concentration category in 61-80% of observations. Linear and multiple linear regression models were moderately successful (R2 from 0.522 to 0.995) in explaining the variance in observed annual transport and annual mean concentration of agricultural chemicals. Explanatory variables that were commonly significant in the regression models include estimates of agricultural chemical use, crop acreage, soil characteristics, and basin topography.

Journal of Hydrology↗

USGS2007

Restoration of wildcelery, Vallisneria americana Michx., in the lower Detroit River of the Lake Huron-Lake Erie Corridor

American wildcelery ( Vallisneria americana Michx .) is a valuable submersed aquatic plant that was negatively affected by pollution and urban runoff in the lower Detroit River for much of the 20th century. Following 25 years of water-pollution and urban-runoff abatement initiated in the early 1970s, we postulated that water clarity had increased and that this would allow restoration of wildcelery in the lower Detroit River. In addition, water clarity increased in the late 1980s due to water filtration and particulate removal by exotic dreissenid mussels ( Dreissena polymorpha and D. bugensis ), which could contribute to potential wildcelery restoration. We sampled wildcelery in 1996–97 and compared these data to wildcelery data from 1950–51 and 1984–85. Over the 48-year period of comparison, areal density of wildcelery tubers decreased 72% (from 51.2 million to 14.4 million tubers) between 1950–51 and 1984–85 then increased 251% (from14.4 million to 50.5 million tubers) between 1984–85 and 1996–97. As a result, overall areal abundance was about the same in 1950–51 as in fall 1996–97. However, tuber densities in spring 1996 were similar to historical low abundances in springs of 1984–85. Then between spring and fall 1996, tuber densities increased 333% and remained relatively abundant through October 1997 indicating the beginning of the restoration of wildcelery in the lower Detroit River. In addition, we believe further reductions of turbidity through continued pollution-abatement programs and water filtration by dreissenid mussels combined with habitat protection and active management of wildcelery will contribute even further to the restoration of wildcelery in the Detroit River in the 21st century.

Journal of Great Lakes Research↗

USGS2012

Backwaters in the upper reaches of reservoirs produce high densities of age-0 crappies

Reservoir backwaters are aquatic habitats in floodplains of reservoir tributaries that are permanently or periodically flooded by the reservoir. Like many reservoir arms, backwaters are commonly shallow, littoral habitats, but they differ from arms in various respects, including their support of primarily wetland plant assemblages that are tolerant to flooding. Elsewhere, the reservoir floods mainly upland plants that are less tolerant to flooding, producing a band of barren shoreline along the fluctuation zone. We investigated differences in relative abundance of age-0 crappies Pomoxis spp. in backwaters and arms of widely fluctuating flood control reservoirs, examined the effect of water level, and estimated the likelihood and timing with which these habitats are flooded annually. Higher catch rates of age-0 crappies were obtained in backwater habitats than in arm habitats. When inundated during the crappie spawning season, backwaters provided vegetated habitat at lower water levels than arms. Backwaters flooded earlier than arms and remained flooded longer to provide prolonged nursery habitat. Whereas vegetated habitat was inundated almost yearly in backwaters and arms, inundation that was timed to the onset of spawning occurred less regularly. Because of differences in water elevation, vegetated habitats were flooded in time for crappie spawning about every other year in backwaters but only every third year in arms. Recruitment of age-0 crappies was inversely correlated with high water levels during the months preceding the spawning period, perhaps because early flooding degraded the vegetation. Our results suggest that water levels may be managed during late winter and spring to regularly flood wetland vegetation communities in backwaters; however, water levels should be maintained at or below normal pool and should only irregularly flood upland vegetation in reservoir arms to promote the preservation of such vegetation. Furthermore, management efforts to enhance crappie recruitment should consider the enhancement and preservation of backwaters.

Mississippi↗

USGS2010

The aquatic turtle assemblage inhabiting a highly altered landscape in southeast Missouri

Turtles are linked to energetic food webs as both consumers of plants and animals and prey for many species. Turtle biomass in freshwater systems can be an order of magnitude greater than that of endotherms. Therefore, declines in freshwater turtle populations can change energy transfer in freshwater systems. Here we report on a mark–recapture study at a lake and adjacent borrow pit in a relict tract of bottomland hardwood forest in the Mississippi River floodplain in southeast Missouri, which was designed to gather baseline data, including sex ratio, size structure, and population size, density, and biomass, for the freshwater turtle population. Using a variety of capture methods, we captured seven species of freshwater turtles (snapping turtle Chelydra serpentina ; red-eared slider Trachemys scripta ; southern painted turtle Chrysemys dorsalis ; river cooter Pseudemys concinna ; false map turtle Graptemys pseudogeographica ; eastern musk turtle Sternotherus odoratus ; spiny softshell Apalone spinifera ) comprising four families (Chelydridae, Emydidae, Kinosternidae, Trinoychidae). With the exception of red-eared sliders, nearly all individuals captured were adults. Most turtles were captured by baited hoop-nets, and this was the only capture method that caught all seven species. The unbaited fyke net was very successful in the borrow pit, but only captured four of the seven species. Basking traps and deep-water crawfish nets had minimal success. Red-eared sliders had the greatest population estimate (2,675), density (205/ha), and biomass (178 kg/ha). Two species exhibited a sex-ratio bias: snapping turtles C. serpentina in favor of males, and spiny softshells A. spinifera in favor of females.

Missouri↗