As global tilapia production grows, it is important to characterize varieties available for production and generate data on environmental tolerances. This study generated data on tolerances, adaptabilities and production characteristics of four tilapia varieties. Goals of this study were to: (1) compare growth of four tilapia varieties in two types of recirculating systems, (2) evaluate juvenile growth of seven tilapia varieties in fresh and brackishwater mesocosms, and (3) estimate cold tolerance of juveniles of four tilapia varieties in fresh and brackishwater. Nile tilapia (Oreochromis niloticus), blue tilapia (Oreochromis aureus), Mississippi commercial strain tilapia (MCS), and Florida red tilapia (FRT) were grown in a clear-water recirculating system for eight months. Blue tilapia yields were greater (P¡Ü 0.05) than those of Nile tilapia and FRT. Yields of Nile tilapia, MCS, and FRT were not significantly different. Seven tilapia varieties: Nile, blue, FRT, MCS, blue x FRT, Mozambique x Nile, and Nile x blue were grown in fresh and brackishwater mesocosms. Nile tilapia was stocked in three freshwater pools. Every other variety was stocked into six pools, in three of which salinity was increased to 23 ppt over 14 days. In freshwater, yield of MCS was greater (P¡Ü 0.05) than that of all other varieties. Four tilapia varieties: Nile, blue, FRT and MCS were subjected to three temperature reduction regimes: rapid (-0.5 C/ 5 h), moderate (-1 C/ 24 h) and gradual (-1 C/ 48 h) and to the moderate reduction regime at three salinities (0, 5 and 10 ppt). No significant differences were observed in cold tolerance among varieties within temperature reduction regimes. Salt did not improve the cold tolerance of blue, Nile and MCS but slightly improved that of FRT. Performance of four tilapia varieties: Nile, blue, MCS and FRT in four culture systems was ranked to develop index values. Cold tolerance of four tilapia varieties was described from an environmental standpoint, with no significant differences found between varieties. The influence of the temperature reduction regimes on cold tolerance was significant.

Waterfowl managers in Minnesota and other states are concerned that increased kill rates associated with the use of spinning-wing decoys (SWDs) may negatively affect local breeding populations of mallards (Anas platyrhynchos). I conducted 219 experimental hunts to evaluate hunting vulnerability of mallards to SWDs during the 2002 duck-hunting season in Minnesota. Following experimental hunts, I asked volunteer hunters to complete post-hunt questionnaires to document their hunting experience, and their use and opinions of SWDs. Finally, I used stable isotope methodology to determine natal origins of HY mallards killed during experimental hunts. I found that mallard flocks (≥1 duck) were 2.91 times more likely to respond (i.e., approached within 40 m of hunters) when SWDs were turned ON. Sizes of responding mallard flocks were 1.25 times larger, on average, when SWDs were turned ON than OFF. Mallards killed/hr/hunter/hunt averaged 4.71 times higher (P < 0.05) when SWDs were turned ON than OFF. More HY and AHY mallards were killed when SWDs were turned ON than OFF; however, AHYs were relatively less likely than were HYs to be killed with SWDs turned ON. Based on my stable isotope analysis, more local and migrant HY mallards were killed by hunters when SWDs were turned ON than OFF, but local HY mallards were not relatively more likely than were migrant HY mallards to be killed by hunters using SWDs in Minnesota. I found no evidence that SWDs reduced crippling nor allowed hunters to harvest relatively more drakes than hens. I estimated that if 46% and 79% of Minnesota hunters used SWDs in 2000 and 2002, respectively, Minnesota mallard harvest would increase by factors of 2. However, increasing use of SWDs may result in a partial re-distribution of annual mallard harvests if naïve ducks are harvested upon initial exposures to SWDs, and those ducks that survive migrations to wintering areas become habituated to SWDs, as suggested by my results. My study was confined to a single hunting season in Minnesota, and thus, did not assess whether vulnerability of mallards to hunters using SWDs varies among years or geographically. A multi-year, flyway-wide study is needed to make stronger and more rigorous inferences regarding potential changes in annual harvest rates of mallards due to increasing use of SWDs by hunters in North America.

This study investigated the chemical, physical, and mechanical properties of the bamboo species Phyllostachys pubescens and its utilization potential to manufacture medium density fiberboard (MDF). The result showed holocellulose and alpha-cellulose content increased from the base to the top portion. There was no significant variation in Klason lignin content or ash content from the base to the top portion of the bamboo. The outer layer had the highest holocellulose, alpha cellulose, and Klason lignin contents and the lowest extractive and ash contents. The epidermis had the highest extractive and ash contents and the lowest holocellulose and alpha-cellulose content. Specific gravity (SG) and bending properties of bamboo varied with age and vertical height location as well as horizontal layer. All mechanical properties increased from one year old to five year old bamboo. The outer layer had significantly higher SG and bending properties than the inner layer. The SG varied along the culm height. The top portions had consistently higher SG than the base. Bending strength had a strong positive correlation with SG. In order to industrially use bamboo strips efficiently, it is advisable to remove minimal surface material to produce high strength bamboo composites. Compression properties parallel to the longitudinal direction was significantly higher than perpendicular to the longitudinal direction. As expected, at the same panel density level, the strength properties of the fiberboard increased with the increasing of resin content. Age had a significant effect on panel properties. Fiberboard made with one year old bamboo at 8% resin content level had the highest modulus of rupture (MOR) and modulus of elasticity (MOE) among the bamboo panels, which was largely attributed to a higher compaction ratio as well as a higher percentage of larger fiber size. Fiberboard made with five year old bamboo at 8% resin level had the highest internal bond strength.

Since the accidental introduction of red imported fire ants (Solenopsis invicta Buren, RIFA) into Mobile, Alabama in the 1930s, the invasion of this species into other areas across the southeast has increased drastically. RIFA have been implicated in the disruption of ecosystems and decreases in biodiversity. Most research on effects of RIFA on vertebrates and invertebrates have focused on small spatial scales and single species. I examined established populations of RIFA in relation to native ground-dwelling arthropods and small mammal communities in longleaf-pine and pine-hardwood forests. I evaluated the efficacy of using Amdro® to control RIFA and determined the effect of RIFA predation on arthropod and small mammal communities. RIFA suppression occurred in April, August, and October 2003. In the longleaf-pine forest, RIFA suppression was effective in June between years (P = 0.088) and treatments (P = 0.093). This was consistent with an increase in cotton mice abundance on treated (17.7 ± 2.7) versus control (6.0 ± 2.5) plots (P = 0.035), with 90% of cotton mice captured during the June sampling period. Across seasons, significant differences were observed for Collembola in August between years (P = 0.001) and in December between treatments (P = 0.01). Likewise, abundance of Coleoptera was greater in December between years (P = 0.023) and in May between treatments (P = 0.002). In the pine-hardwood forest, RIFA suppression was effective in April and June (P = 0.001, P = 0.004, respectively) when compared across seasons. No significant differences were observed for any small mammal species captured in the pine-hardwood site. Acari were greater on treated (11.0 ± 1.7) than control (4.7 ± 1.9) plots (P = 0.067); however, no significant differences were observed for any invertebrate group across seasons. Although this study is in the initial phase of a 5-year project, the data suggests that RIFA may potentially affect the abundance of selected faunal species in forested ecosystems.

Northern bobwhite (Colinus virginianus) populations have been declining throughout their range during the past 30 years primarily because of a result of loss of early successional habitat. Specifically, intensive silviculture practices and reduction in the use of prescribed fire has led to this loss. I studied effects of management practices (selective herbicides, mowing, and prescribed fire) on male and covey distribution, and brood-rearing habitats on Jackson-Bienville Wildlife Management Area (JBWMA). Specifically, I used calling surveys to assess landscape characteristics associated bobwhite distribution. I also measured vegetation and arthropod response, using imprinted bobwhite chicks, pitfalls, and sweep nets, to different habitat manipulations. Male bobwhites were closely associated with early successional habitats, and negatively associated with the proportion of landscape variables associated with 16-29 year old pine stands. Several vegetation characteristics were affected by the use of herbicides, mowing, and burning; however, arthropod response was not similar. Imprinted chicks selected arthropod orders similar to wild chicks, although they did not consume a large quantity of arthropods. These data indicates habitats on JBWMA may not be of the quality needed for brood-rearing. Future research should focus on long-term effects of manipulations (selective herbicides, mowing, and burning) on northern bobwhite populations. Managers should focus on creating early successional habitats across forested landscape, and continue to search for methods to enhance these habitats for northern bobwhites.

Random strandboards from mixed southern wood species were manufactured using calcium borate (CB) and zinc borate (ZB) as chemical additives and polymeric methylene diphenylmethane disocyanate (pMDI) as resin. There were four target levels of borate loading and two levels of resin content. Panel properties, including modulus of elasticity (MOE), modulus of rupture (MOR), internal bond (IB) strength, linear expansion (LE), thickness swelling (TS), leachability, and swelling and strength retention properties under cyclic relative humidity, were measured. The influence of borate content, borate type, and resin content on various properties was analyzed. It was found that the addition of borate negatively impacted the mechanical and physical properties of the boards. The influence of ZB and CB on both mechanical and physical properties was similar. The increase of resin content improved the properties significantly, especially TS. A certain portion of borate leached out from test samples under the water-soaking conditions. There was a higher initial leaching rate and the leaching rate decreased with the lapse of leaching time. Panels with higher initial borate loading level had higher leaching rate for all panel types. The leaching rates of ZB and CB treated samples were similar. The increase of resin content helped reduce TS and boron leaching. Compared with PF-bonded boards, leaching rate was significantly reduced for the pMDI-bonded panels. Under cyclic humidity exposure condition, the addition of borate negatively influenced the maximum TS, residual TS, and mechanical properties. The effects of ZB and CB on the maximum TS, residual TS, and mechanical properties were similar. The increase of resin content significantly reduced residual TS, but had no influence on maximum TS and mechanical properties. The addition of borate did not have significant influence on the strength retention of the boards under long term cyclic humidity exposure condition.

I analyzed data from an experimental aerial transect survey, using stratified random sampling, to estimate wintering populations of greater scaup (Aythya marila) and lesser scaup (Aythya affinis) (hereafter scaup) in off-shore waters along the coast of Louisiana during winters 2000-2002. My objectives were to evaluate anecdotal reports of large numbers of scaup in off-shore waters of Louisiana during winter, and to develop estimates and confidence intervals for numbers of scaup in this area. My analysis yielded estimates of 815,700, 420,600, and 791,000 scaup in off-shore Louisiana for years 2000-2002, respectively. Confidence intervals were 1,087,000 to 545,000, 594,300 to 247,000, and 1,351,900 to 230,200 for years 2000-2002, respectively. Although large numbers of scaup were observed off-shore each year, numbers observed in most strata varied widely from year to year. Coefficients of variation (CV) for these estimates ranged from 17 to 35 percent. Highest densities of scaup were found in bays off the central Louisiana coast followed by the southwest and southeast coasts. Highest CVs were found along the southwest and southeast coasts and in the area south of Atchafalaya Bay. The precision of population estimates in these areas could be improved by increasing the number of transects. Comparisons of the number of scaup estimated in off-shore waters and that in the standard midwinter survey indicate that off-shore areas comprise 51 to 85% of the wintering population of scaup each year in Louisiana. When off-shore estimates are combined with in-shore estimates, the annual variability in total scaup is reduced greatly. It is not known whether variation in the proportion of scaup counted off-shore occurred because scaup preference for off-shore and in-shore areas varied annually, or because shorter-term weather conditions differed during surveys. The resulting high variability therefore may mask true trends in wintering scaup populations. I recommend the addition of off-shore surveys for scaup to improve the accuracy of current mid-winter scaup estimates.

Two laboratory feeding trials were conducted to quantify differences in the digestibility and absorption of dietary amino acids provided in intact protein or in purified amino acid mixtures. In the first experiment, 36 channel catfish (346 ± 47 g) were force-fed one of six practical feed ingredients (blood meal, corn meal, fish meal, meat and bone meal, soybean meal or wheat middlings), or a mixture of crystalline amino acids designed to duplicate the amino acid composition of each of the practical ingredients. Apparent digestibility coefficients (ADC) were calculated for 15 amino acids in each practical ingredient and in each amino acid mixture. An average ADC of all amino acids in each treatment also was calculated. Very few differences in the ADCs of individual amino acids were observed. However, in all ingredients but two, the mean ADCs of amino acids in fish fed purified amino acids were significantly higher than the mean ADCs of amino acids in fish fed intact protein. In the second experiment, 468 channel catfish (396 ± 49 g) were force-fed the same ingredients and amino acid mixtures used in the digestibility trial, and blood was collected from the hepatic portal vein at 1-h intervals for 12 h after feeding. In four of the six ingredients tested, postprandial concentrations of 2-8 amino acids in blood plasma were significantly higher and reached peak levels earlier (1-3 h after feeding) in fish fed purified amino acids than in fish fed intact protein. Results indicated that protein was well digested by channel catfish regardless of its source. However, soybean protein appeared to be digested more slowly than the other proteins tested. The efficiency with which supplemental amino acids are utilized might be reduced if slowly digested proteins compose a major portion of the diet, because of temporal differences in the absorption of amino acids from different dietary sources. If so, the effectiveness of amino acid supplementation could vary with the ingredient composition of the diet to a greater extent than has previously been recognized.

This research demonstrated model development for important wood properties using near infrared spectroscopy (NIR); it considered the effect of outside sources of error, and the ability of NIR to measure fiber morphology. Strength, stiffness, and density were successfully modeled from wood samples taken throughout 10 longleaf (Pinus palustris Mill) trees. Principal components and multiple linear regression were compared for performance in prediction of density, strength, and stiffness. I found both modeling techniques to yield similar prediction accuracies. However, I found that density could be estimated through Beer-Lamberts law since the absorbance at all wavelengths increased with density. Also, 5 of 6 wavelengths needed to predict strength were also needed to predict stiffness lending support that similar chemical morphology controls the covariance between strength and stiffness. Klason lignin, extractives, and microfiber angle (MFA) were also measured throughout the tree. I found extractives, lignin, and MFA to decrease from the pith outward regardless of height. A theoretical model was built attempting to explain how lignin content and MFA co-vary. Theoretical and empirical spectroscopic models both predicted MFA with nearly similar root mean square error and supported that lignin was a probable factor responsible for the covariance in spectra with MFA. Tracheid length was another secondary trait investigated. I demonstrated that tracheid length could be predicted with an R2 of 0.71 due to NIR spectra response with age. Accurate tracheid length prediction was possible due to systematic variation of chemistry with age except for at ring 1 and 4 where some other unknown factor was responsible. Finally, blue stain and machine variability were investigated as two sources of extraneous error. It was of interest to know if the common extraneous error would bias a prediction equation. With proper modeling, I found I could avoid the blue stain variation present in the spectra when modeling modulus of elasticity (MOE), modulus of rupture (MOR), density, lignin, and extractives. However, when a calibration was built from one machine and then applied to a population of scans made from a separate machine, blue stain became problematic and prediction of MOE, MOR, and extractives were biased.

Sustainable management and conservation of the extensive bottomland hardwood forest resource in the southeastern U.S. requires a good understanding of basic structural and competitive relationships within these forests. To gain an insight into these relationships, plot information from stands in Arkansas, Louisiana, and Mississippi were analyzed. The effects of individual tree attributes, distance-dependant, and distance-independent competition measures on 5-yr radial growth of red oak crop trees were examined. Selected species included cherrybark oak (Quercus pagoda Raf.), water oak (Q. nigra L.), and Nuttall oak (Q. nuttallii Palmer). Spatial continuity of tree variables was explored through geostatistical analysis. Finally, spatial distribution patterns of all species, the intraspecific pattern of cherrybark oak, water oak, and sweetgum (Liquidambar styraciflua L.), and the interspecific pattern of their pairs was examined with point pattern analysis. In the analysis of 5-yr radial growth, the crown class score (from Meadows et al. 2001) accounted for a large portion of tree diameter growth. However, average plot-level characteristics failed to account for a significant proportion of the variability in tree growth. The basal area of trees taller than the crop trees and located within 2.5 mean crown radii had the highest negative correlation with crop tree 5-yr radial growth. Red oaks were likely exerting the greatest competition. Crop tree radial growth was also positively associated with the basal area of other red oaks taller than the crop tree and located between 3 and 4 mean crown radii from the crop tree (the indirect neighbors). Geostatistical analysis demonstrated that spatial continuity of unsuppressed tree attributes extended to a distance equal to 4 times the mean crown radius, suggesting that when resources are nonlimiting, multiple trees may be able to coexist and grow well in close proximity. Spatial point pattern analysis indicated that when species were combined, they were frequently aggregated and sometimes overdispersed. Plots with larger trees were more likely to exhibit overdispersion suggesting a shift to this pattern as trees grow. Interspecific and intraspecific pattern analyses suggested that strong interspecific competition resulted in species segregation, while weaker intraspecific competition led to aggregations of conspecifics.