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Research about Louisiana

Source-linked reports with geographic coverage including Louisiana.

At least 667 records · Page 37Linked to original sources
USGS1998

Survival of female northern pintails wintering in southwestern Louisiana

The North American breeding population of northern pintails ( Anas acuta ) has reached previously unprecedented low numbers 4 times since 1983. Because pintails show high fidelity to wintering areas, regional survival estimates and identification of factors influencing survival are needed to guide management of wintering pintails. We used radiotelemetry to estimate survival rates of female pintails wintering in southwestern Louisiana. We tested for variation in survival and hunting mortality rates in relation to age (immature or adult), winter (1990-91, 1991-92, 1992-93), time period (prehunting season, first hunting season, time between split hunting seasons, second hunting season, posthunting season), body condition (body mass when released, adjusted for body size), and region (southwestern Louisiana or elsewhere on the Texas-Louisiana Gulf Coast or Mississippi Alluvial Valley). Within southwestern Louisiana, the 147-day (5 Oct-28 Feb) survival rate of adults (0.714 ± 0.045; x̅ ± SE) was greater ( P = 0.02) than that of immatures (0.550 ± 0.068), primarily because immatures had higher hunting mortality. Female survival was lower ( P s < 0.01) during hunting than during nonhunting seasons but did not differ between first and second hunting seasons ( P = 0.58) or among non-hunting seasons ( P s >0.25). Survival did not differ in relation to winter or condition ( P s > 0.12). Hunting mortality did not differ ( P s > 0.13) in relation to winter, condition, or region, but hunting mortality of immatures (0.287 ± 0.046) was greater ( P < 0.001) than that of adults (0.130 ± 0.025). Despite conservative hunting regulations (30-day seasons and 1 pintail daily), hunting mortality rates of pintails in southwestern Louisiana were high. Pintails in southwestern Louisiana rely on a small number of key refuges for protection but feed almost exclusively in privately owned agricultural fields. If increased winter survival of female pintails in southwestern Louisiana is desired, we recommend that managers increase food available.

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USGS1998

Shot prevalences and diets of diving ducks five years after ban on use of lead shotshells at Catahoula Lake, Louisiana

Catahoula Lake, central Louisiana, is a RAMSAR Convention Wetland of International Importance and among the most important wintering and staging areas for waterfowl in North America. To evaluate exposure rates in Catahoula Lake waterfowl 5 years after a ban on use of lead shot, we determined the prevalence of ingested shot and diets of canvasbacks ( Aythya valisineria ) and lesser scaup ( A. affinis ) salvaged from commercial fishing nets in winter 1992-93. Plant material composed >77% of the midwinter diet of canvasbacks. Consumption of belowground plant material (e.g., chufa flatsedge [ Cyperus esculentu s] and arrowhead [ Sagittaria spp.] tubers) exceeded 47% in 1992-93, but was lower than in 1987-88. Male lesser scaup fed almost exclusively on plant material, especially bearded sprangletop ( Leptochloa fascicularis ) and millet ( Echinochloa spp.). Prevalence of ingested lead or steel shot was similar in canvasbacks (38%) and lesser scaup (34%) in spite of differences in foraging behavior, suggesting that ducks actively selected shot as grit. Shot (lead or steel) prevalence in diving ducks at Catahoula Lake was similar in winters 1987-88 and 1992-93, but the proportion of birds with lead in their gizzards was greatly reduced in 1992-93 (6%) compared to 1987-88 (27%). Because ingestion of lead shot deposited in wetlands prior to steel shot regulations remains a problem at some sites, we suggest that provision of nontoxic grit may serve to reduce lead shot prevalence in waterfowl at contaminated sites.

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USGS1998

Water use and quality of fresh surface-water resources in the Barataria-Terrebonne Basins, Louisiana

Approximately 170 Mgal/d (million gallons per day) of ground- and surface-water was withdrawn from the Barataria-Terrebonne Basins in 1995. Of this amount, surface water accounted for 64 percent ( 110 MgaVd) of the total withdrawal rates in the basins. The largest surface-water withdrawal rates were from Bayou Lafourche ( 40 Mgal/d), Bayou Boeuf ( 14 MgaVd), and the Gulf Intracoastal Waterway (4.2 Mgal/d). The largest ground-water withdrawal rates were from the Mississippi River alluvial aquifer (29 Mgal/d), the Gonzales-New Orleans aquifer (9.5 Mgal/d), and the Norco aquifer (3.6 MgaVd). The amounts of water withdrawn in the basins in 1995 differed by category of use. Public water suppliers within the basins withdrew 41 Mgal/d of water. The five largest public water suppliers in the basins withdrew 30 Mgal/d of surface water: Terrebonne Waterworks District 1 withdrew the largest amount, almost 15 MgaVd. Industrial facilities withdrew 88 Mgal/d, fossil-fuel plants withdrew 4.7 MgaVd, and commercial facilities withdrew 0.67 MgaVd. Aggregate water-withdrawal rates, compiled by parish for aquaculture (37 Mgal/d), livestock (0.56 Mgal/d), rural domestic (0.44 MgaVd), and irrigation uses (0.54 MgaVd), totaled about 38 MgaVd in the basins. Ninety-five percent of aquaculture withdrawal rates, primarily for crawfish and alligator farming, were from surface-water sources. >br> Total water-withdrawal rates increased 221 percent from 1960–95. Surface-water withdrawal rates have increased by 310 percent, and ground-water withdrawal rates have increased by 133 percent. The projection for the total water-withdrawal rates in 2020 is 220 MgaVd, an increase of 30 percent from 1995. Surface-water withdrawal rates would account for 59 percent of the total, or 130 Mgal/d. Surface-water withdrawal rates are projected to increase by 20 percent from 1995 to 2020. Analysis of water-quality data from the Mississippi River indicates that the main threats to surface water resources are from the herbicide atrazine and excessive nutrients. Atrazine concentrations in the Mississippi River at Baton Rouge briefly exceed the U.S. Environmental Protection Agency maximum contaminant level of 3.0 micrograms per liter during periods in the late spring and early summer. Trace metals in bottom material collected from Bayou Lafourche indicate that the reach of Bayou Lafourche from Donaldsonville to Golden Meadow is adversely affected by low-level contamination. Dissolved nitrate had a mean concentration of 1.4 milligrams per liter in the Mississippi River near Bayou Lafourche and can contribute to excessive plant growth. Long-term salinity records near Bayou Lafourche indicate no pronounced trends, with the exception of the Gulf Intracoastal Waterway at Houma. At this site, salinities remained low until 1961, when the Gulf Intracoastal Waterway was connected to the Gulf of Mexico by the Houma Navigation Canal. The sources of saltwater are variable. Some saltwater has entered Bayou Lafourche south of the Gulf Intracoastal Waterway; at other times saltwater has moved up the Houma Navigation Canal and has flowed east in the Gulf Intracoastal Waterway, north into Company Canal, and southeast in Bayou Lafourche towards Larose, Louisiana.

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USGS1998

Water resources data, Louisiana, water year 1997

Water resources data for the 1997 water year for Louisiana consists of records of stage, discharge, and water quality of streams; stage, contents, and water quality of lakes and reservoirs; and water levels and water quality of ground water. This report contains records for water discharge at 67 gaging stations; stage only for 45 gaging stations and 6 lakes; water quality for 37 surface-water stations (including 22 gaging stations) and 95 wells; and water levels for 243 observation wells. Also included are data for 113 crest-stage and flood-profile partial-record stations. Additional water data were collected at various sites not included in the systematic data-collection program, and are published as miscellaneous measurements. These data represent that part of the National Water Data System operated by the U.S. Geological Survey and cooperating State and Federal agencies in Louisiana.

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USGS1998

Use of mini-refuges by female northern pintails wintering in southwestern Louisiana

The Gulf Coast Joint Venture of the North American Waterfowl Management Plan began contracting private agricultural lands (hereafter mini-refuges) in 1988 to expand existing sanctuaries for northern pintails ( Anas acuta ) in southwestern Louisiana. Previous research suggested that mini-refuges may prove more attractive to pintails than permanent, open-water pools (pools) on refuges because mini-refuges provide sanctuary and food during the day, whereas pools generally provide only sanctuary (Rave and Cordes 1993). We used radiotelemetry to compare diel use of mini-refuges and pools (Lacassine Pool and Amoco Pool) by female pintails in southwestern Louisiana during winters of 1991-1992 and 1992-1993. We examined variation in use of these areas in relation to female age (immature or adult), time period (prehunting season, first hunting season, time between split hunting seasons, second hunting season, and posthunting season), and winter (1991-1992 and 1992-1993). Diurnal use of min-refuges and pools differed among time periods, but differences were not consistent between winters. Mini-refuges accounted for <2% of diurnal use by pintails in 7 of 10 time-period and winter comparisons. Diurnal use of mini-refuges was lower than that of Lacassine Pool in 8 of 10 time-period and winter comparisons. Diurnal use of mini-refuges was lower than tha of Amoco pool during first hunting season in 1992-1993, but use of these areas did not differ within other time periods and winters. Nocturnal use of mini-refuges and pools did not differ in relation to female age, time period, winter, or individual bird. Nocturnal use of mini-refuges did not differ from that of Lacassine Pool. In contrast to predictions and findings by Rave and Cordes (1993), we found that: (1) female pintails did not use mini-refuges more than pools, and (2) female pintails used mini-refuges at night. We believe that use of mini-refuges by pintails could be increased if mini-refuges were (1) located in areas of traditionally high pintail use, (2) increased in size, (3) flooded immediately prior to hunting season, and (4) cleared of dense vegetation by rolling, disking, or burning.

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USGS1998

Resource management of forested wetlands: Hurricane impact and recovery mapped by combining Landsat TM and NOAA AVHRR data

A temporal suite of NOAA Advanced Very High Resolution Radiometer (AVHRR) images, transformed into a vegetation biomass indicator, was combined with a single-date classification of Landsat Thematic Mapper (TM) to map the association between forest type and hurricane effects. Hurricane effects to the forested wetland included an abrupt decrease and subsequent increase in biomass. The decrease was associated with hurricane impact and the increase with an abnormal bloom in vegetation in the impacted areas. Impact severity was estimated by differencing the biomass maps before and immediately (3 days) after the hurricane. Recovery magnitude was estimated by differencing the biomass maps from immediately (3 days) after and shortly (1.5 months) after the hurricane. Regions of dominantly hardwoods suffering high to moderate impacts and of dominantly cypress-tupelos suffering low impacts identified in this study corroborated findings of earlier studies. Conversely, areas not reported in previous studies as affected were identified, and these areas showed a reverse relationship, i.e., highly impacted cypresstupelo and low or moderately impacted hardwoods. Additionally, generated proportions of hardwood, cypress-tupelo, and open (mixed) forests per each 1-km pixel (impact and recovery maps) suggest that regions containing higher percentages of cypress-tupelos were more likely to have sustained higher impacts. Visual examination of the impact map revealed a spatial covariation between increased impact magnitudes and river corridors dominated by open forest. This spatial association was corroborated by examining changes in the percentage of open forest per 1-km impact pixel; the percentage of open forest peaked at moderate to high impacts. The distribution of recovery supported the impact spatial distribution; however, the magnitudes of the two indicators of hurricane effects were not always spatially dependent. Converse to univariate statistics describing a11 forested area within the basin, higher recoveries tended to be related to higher percentages of hardwoods. Lower recoveries, on the other hand, tended to be related to forests with nearly equal percentages of hardwoods and cypress-tupelo.

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USGS1997

Massive sediment bypassing on the lower shoreface offshore of a wide tidal inlet: Cat Island Pass, Louisiana

Analysis of a series of historical bathymetric and shoreline surveys along the Louisiana coast west of the Mississippi River mouth detected a large area of deposition in water depths of 2.0–8.5 m offshore of a 9-km-wide tidal inlet, the Cat Island Pass/Wine Island Pass system. A 59.9 · 106 m 3 sandy deposit formed from the 1930s–1980s, spanning 27 km in the alongshore direction, delineating the transport pathway for sediment bypassing offshore of the inlet on the shoreface. Bypassing connected the shorefaces of two barrier island systems, the Isles Dernieres and the Bayou Lafourche. The processes responsible for formation of this deposit are not well understood, but sediment-transport modeling suggests that sediment is transported primarily by wind-driven coastal currents during large storms and hurricanes. Deposition appears to be related to changes in shoreline orientation, closing of transport pathways into a large bay to the east and the presence of tidal inlets. This newly documented type of bypassing, an offshore bypassing of the inlet system, naturally nourished the immediate downdrift area, the eastern Isles Dernieres, where shoreface and shoreline erosion rates are about half of pre-bypassing rates. Erosion rates remained the same farther downdrift, where bypassing has not yet reached. As this offshore bypassing continues, the destruction of the Isles Dernieres will be slowed.

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USGS1997

Woody debris decomposition in the Atchafalaya River Basin of Louisiana following hurricane disturbance

The contribution of woody debris to some biogeochemical functions of forested wetlands was examined in the Atchafalaya River Basin in Louisiana following disturbance by Hurricane Andrew. Woody debris decomposition processes were characterized in terms of mass, C, N, and P dynamics. These were compared between different diameters of debris, areas recieving different intensities of disturbance, and between different positions relative to the soil. Disturbance intensity (as defined by canopy closure) had little effect on decomposition processes when compared with soil orientation (i.e., whether in contact with or suspended above the soil). Rates of mass loss varied between 0.055 and 0.068 for suspended and ground-contact coarse woody debris, respectively. Fine woody debris rate coefficients averaged 0.060 and 0.085 for the same respective orientations. In general, woody debris displayed strong source activity for P but a greater tendency toward sink behavior for N. In terms of biogeochemical transformations, these data suggest that woody debris might act as a phosphate source during sheet flow events but could provide short-term retention of inorganic N associated with floodwaters.

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USGS1997

Effect of hydrologic management on marsh surface sediment deposition in coastal Louisiana

High rates of coastal land loss in Louisiana have prompted efforts to maintain or restore coastal wetland habitats, and structural management of marsh hydrology is one of a number of approaches that has been adopted. The aim of this study was to determine the effect of hydrologic management measures on marsh-surface sediment deposition in the Mississippi deltaic plain. Four impoundments, ranging in size from 50 ha to 177 ha and similarly sized control sites were included in the study. At each site, marsh-surface sediment traps were collected approximately biweekly for 3.5 yr to measure changes in sediment deposition. There was no significant difference in sediment deposition between any of the impoundment and control sites during the premanagement period. The results show no significant difference in marsh-surface sediment deposition between management year 1992–1993 and management year 1994–1995, but management year 1993–1994 had significantly lower sediment deposition than either the first or the last year of the study. Management year 1992–1993 showed the highest sediment deposition when it was assessed across all basins, areas, and sites, and this high rate of deposition is accounted for by the impact of Hurricane Andrew. For all management years there were significant differences between impoundment and control sites, with control sites showing higher rates of marsh surface sediment deposition than impoundments. No clear pattern was identified concerning the influence of various types of hydrologic management on rates of sediment deposition. This reduction in sediment deposition indicated that the areas under management in this study are receiving insufficient inorganic sediment deposition to keep pace with sea-level rise.

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USGS1997

Decomposition of saltmeadow cordgrass (Spartina patens) in Louisiana coastal marshes

In Louisiana, plant production rates and associated decomposition rates may be important in offsetting high rates of land loss and subsidence in organic marsh soils. Decomposition of Spartina patens shoot and leaf material was studied by using litter bags in mesohaline marshes in the Barataria and Terrebonne basins of coastal Louisiana. Spartina patens decomposed very slowly with an average decay constant of 0.0007, and approximately 50% of the material remained after 2 years in the field. Material at the Barataria site decomposed faster than did Terrebonne material with trend differences apparent during the first 150 days. This difference might be explained by the higher content of phosphorus in the Barataria material or a flooding period experienced by the Barataria bags during their first 10 days of deployment. Nitrogen and carbon content of the plant material studied did not differ between the two basins. We detected no consistent significant differences in decomposition above, at, or below sediment/water level. Because S. patens is the dominant plant in these marshes, and because it is so slow to decompose, we believe that S. patens shoots are an important addition to vertical accretion and, therefore, marsh elevation.

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USGS1997

Relative costs of prebasic and prealternate molts for male blue-winged teal

We compared masses of definitive basic and alternate plumages of male Blue-winged Teal ( Anas discors ) to evaluate the hypothesis that nutritional investments in basic and alternate plumages are related to the duration that plumages are worn and to assess the relative costs of prebasic and prealternate molts. Because these plumages are worn by males for approximately equal durations, we predicted that masses of the basic and alternate body plumages would be similar. To assess nutritional stress ( demands greater than available resources ) associated with molt, we examined the relation between remigial length and structural size and compared predicted and observed plum-age masses of Blue-winged Teal and other ducks. If birds were nutritionally challenged during remigial molt, then we predicted remigial length would be influenced by nutrition rather than size, and remigial length and size would be unrelated. Alternate body plumage of male Blue-winged Teal weighed about 10% more than the basic body plumage; however, masses of both plumages were less than that predicted on the basis of lean body mass. We argue that deviations between observed and predicted plumage masses were related to factors other than nutrition. Further, remigial lengths were significantly, albeit weakly, related to structural size. We therefore concluded that, although the potential for molt-induced stress may be greatest in small-bodied waterfowl species, there was no clear evidence that molting male Blue-winged Teal were nutritionally stressed.

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USGS1997

The effects of herbivory on neighbor interactions along a coastal marsh gradient

Many current theories of community function are based on the assumption that disturbances such as herbivory act to reduce the importance of neighbor interactions among plants. In this study, we examined the effects of herbivory (primarily by nutria, Myocastor coypus ) on neighbor interactions between three dominant grasses in three coastal marsh communities, fresh, oligohaline, and mesohaline. The grasses studied were Panicum virgatum, Spartina patens, and Spartina alterniflora, which are dominant species in the fresh, oligohaline, and mesohaline marshes, respectively. Additive mixtures and monocultures of transplants were used in conjunction with exclosure fences to determine the impact of herbivory on neighbor interactions in the different marsh types. Herbivory had a strong effect on all three species and was important in all three marshes. In the absence of herbivores, the impact of neighbors was significant for two of the species ( Panicum virgatum and Spartina patens ) and varied considerably between environments, with competition intensifying for Panicum virgatum and decreasing for Spartina patens with increasing salinity. Indications of positive neighbor effects (mutualisms) were observed for both of these species, though in contrasting habitats and to differing degrees. In the presence of herbivores, however, competitive and positive effects were eliminated. Overall, then, it was observed that in this case, intense herbivory was able to override other biotic interactions such as competition and mutualism, which were not detectable in the presence of herbivores.

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USGS1997

Use of habitats by female northern pintails wintering in southwestern Louisiana

The breeding population of norther pintails ( Anas acuta ) in 1996 was 39% below the long-term average. Because winter habitat quality may influence subsequent breeding population size in pintails, identification of habitats used by wintering pintails and factors influencing use of habitats may be important for managing for population increase. We examined variation in diel use of habitats by radiotagged female pintails ( n = 272) in southwestern Louisiana in relation to age (imm and ad), winter (1991-92 and 1992-93), and time period within winters (pre-hunting season, first hunting season, time between split hunting seasons, second hunting season, and post-hunting season). Diurnal use of refuges was significantly greater during hunting seasons than during immediately preceding or succeeding nonhunting seasons. Consequently, we reject Tamissier's (1976) hypothesis that high diurnal use of refuges by pintails in southwestern Louisiana occurs later in winters. Time-period differences in diurnal and nocturnal use of habitats (large permanent pools, marsh, rice, fallow [idle], and other agriculture [primarily soybeans]) were not consistent between winters. Diel use of refuges or habitats did not differ in relation to female age. Females used fallow and ice agriculture extensively, particularly at night, and these habitats collectively accounted for 68-93% of nocturnal use. Differential use of habitats between winters was related to annual differences in relative abundance of rice and fallow agriculture. Proximity of refuges to agricultural areas should be an important management consideration for wintering pintails and other waterfowl.

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USGS1997

Water resources data, Louisiana, water year 1996

Water resources data for the 1996 water year for Louisiana consists of records of stage, discharge, and water quality of streams; stage, contents, and water quality of lakes and reservoirs; and water levels and water quality of ground water. This report contains records for water discharge at 64 gaging stations; stage only for 41 gaging stations and 5 lakes; water quality for 38 surface-water stations (including 22 gage stations) and 100 wells; and water levels for 235 observation wells. Also included are data for 117 crest-stage and flood-profile partial-record stations. Additional water data were collected at various sites not involved in the systematic data-collection program, and are published as miscellaneous measurements. These data represent that part of the National Water Data System operated by the U.S. Geological Survey and cooperating State and Federal agencies in Louisiana.

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