Browsing by Subject "recruitment"
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Item Blue Crab Population Ecology and Use by Foraging Whooping Cranes on the Texas Gulf Coast(2012-02-14) Greer, Danielle MarieIn 2002, a proposal was submitted to divert water from the confluence of the Guadalupe and San Antonio Rivers to San Antonio, Texas. To investigate the potential impacts of diverting water from the Guadalupe Estuary, my research focused on the foraging ecology of the crane and population ecology of the blue crab, a documented crane food. During winters 2004-2005 and 2005-2006, I examined diets and optimal foraging patterns of territorial adult cranes at Aransas National Wildlife Refuge, Texas. To identify foods of greatest benefit to cranes, I used currencies of optimization to evaluate foraging gain, cost, and efficiency. Foraging benefit differed among foods, depending on the foraging currency used and resource targeted (e.g., energy). Wolfberry fruit, snails, and insects were consumed in the highest quantities, required the least foraging effort, and were generally associated with the highest foraging efficiency. Blue crabs and clams were important sources of protein and biomass. During September 2003-October 2005, I used novel artificial settlement substrates and modified methods of standard deployment to investigate the spatio-temporal patterns of blue crab terminal settlement and recruitment rates. Monitoring rates in shallow bay habitat and ponds of the interior salt-marsh revealed megalopal crabs were developmentally advanced when arriving to study sites and the extent to which young crabs infiltrated the salt-marsh increased with age. Such findings suggested sites represented optimal terminal settlement habitat and consequently critical nursery habitat. Model selection indicated water temperature before and during embryonic development was the best predictor of megalopal settlement, whereas juvenile recruitment was most influenced by recent precipitation. I studied the size-specific abundance patterns of blue crabs in and around mature salt-marsh. Using drop-trapping and throw-trapping methods, I collected monthly samples in several habitats during October 2004-March 2006. Interior-marsh habitats contained fewer but larger crabs than bay habitat. Crabs contributing greatest to biomass were smallest (11-30 mm carapace-width) in bay habitat, larger (31-80 mm) along interior-marsh pond edges, and largest (41-130 mm) in interior-marsh open water. Model selection revealed crab density was most influenced by micro-site characteristics (habitat, water column structure type and structural complexity). Overall, shallow bay provided important nursery habitat for young blue crabs and interior marsh ponds were important for dispersing juvenile and adult crabs.Item Demographic and trophic dynamics of fishes in relation to hydrologic variation in channel and floodplain habitats of the Brazos River, Texas.(2009-06-02) Zeug, Steven ChristopherLarge rivers in North America have been subjected to a variety of hydrologic alterations that have negatively impacted aquatic fauna. These impacts have triggered restoration efforts, including management of flows, to restore or maintain ecological integrity. Ecological data relevant to flow management and habitat restoration is scarce, and conceptual models of ecosystem function have been widely applied to large rivers despite a lack of quantitative evaluation of these models. Here, I examine demographic and trophic dynamics of fishes with divergent life histories and trophic guilds in relation to habitat heterogeneity and flow variability in a relatively unaltered floodplain system: the Brazos River, Texas. Reproductive activity of fishes with three divergent life history strategies was positively associated with long-term river hydrology, although species with alternate strategies exploited different portions of the hydrograph (peak flow versus increasing flow). Despite the positive association with hydrology, low-flow periods were favorable for recruitment, and food resources for larvae and juveniles were denser during these periods. Some species used both oxbow and channel habitats during some point in their life cycle, whereas other species appeared to be almost entirely restricted to one habitat type. Terrestrial C3 macrophytes accounted for a significant fraction of the biomass of most consumer species examined. Small-bodied species in oxbow lakes assimilated large fractions of biomass from benthic algae, whereas this pattern was not observed in the river channel. Frequent flow variations in the river channel may reduce algal standing stocks, and significant contributions from autochthonous algal sources may only occur during low-flow periods. Trophic positions of detritivores indicated that terrestrial carbon sources were assimilated, for the most part, via invertebrates rather than by direct consumption. My results indicate that current conceptual models are too vague to provide accurate predictions for restoration strategies in rivers with variable flow regimes. Flow and habitat management strategies that focus on reproducing key features of historical fluvial dynamics are likely to be more successful than strategies that focus on single indicator species or flow dynamics that differ from the historical hydrograph.Item Factors Associated with Recruitment and Retention Rates of Minority Youth 4-H Members as Perceived by Adult Club Leaders and County Extension Agents in Texas(2012-12-05) Gonzales, Nicole 1989-According to enrollment data from the National 4-H Headquarters, minority participation in Texas 4-H clubs has declined over the past five years. This descriptive study measured the perceptions of 4-H adult leaders and county Extension agents about minority youth recruitment and retention in Texas 4-H clubs. An electronic survey was distributed to 168 adult leaders and 58 county Extension agents who have participated in 4-H for at least two years from clubs in 54 counties across Texas that are comprised of at least 50% minority youth members. The results from this study show slight differences in the demographic makeup and project areas that are chosen among the minority youth members. Statistically significant differences do exist between the perceptions of county Extension agents and 4-H adult club leaders. While the county Extension agents tend to focus more on the competition aspects of 4-H, adult club leaders are more concerned with the views and feelings of the youth members along with the relationships that are developed. It is important to acknowledge decline in minority retention rates and develop new techniques for recruitment to improve future enrollment for the sake of the organization and prospective minority youth throughout the state.Item Habitat use, growth, and mortality of post-settlement lane snapper (Lutjanus synagris) on natural banks in the northwestern Gulf of Mexico(2009-05-15) Mikulas, Joseph JohnThree low-relief banks (Heald Bank, Sabine Bank, Freeport Rocks) in the northwestern Gulf of Mexico were evaluated as lane snapper (Lutjanus synagris Linnaeus, 1758) nursery habitat. Trawl surveys were conducted in three habitat types (inshore mud, shell ridge, offshore mud), designated by side-scan sonar surveys, to determine patterns of distribution and abundance. Heald Bank and Sabine Bank were trawled in 2003 while Freeport Rocks was trawled in 2000 (Freeport A) and 2004 (Freeport B). Density of lane snapper was higher on Sabine Bank (20.8 ? 2.8 ind ha-1) than on Heald Bank (1.1 ? 0.4 ind ha-1), Freeport A (12.7 ? 2.3 ind ha-1) or Freeport B (3.0 ? 1.0 ind ha-1). Habitat-specific differences in density were observed, although patterns were not consistent among banks. Highest densities of lane snapper were found on Heald Bank?s offshore habitat (1.7 ? 1.0 ind ha-1), Sabine Bank?s ridge habitat (26.5 ? 6.9 ind ha-1), and on the inshore habitat of Freeport A and B (17.6 ? 4.9 ind ha-1 and 4.8 ? 3.6, respectively). Otolith microstructure analysis was performed on lane snapper collected in trawl surveys to determine age, hatch-date distribution, growth and mortality of new recruits. Hatch dates ranged from May 1 to August 31, peaking in June for Freeport (A and B) and in July for Heald Bank and Sabine Bank. Growth rates varied from 0.90 mm d-1 at Heald Bank to 1.27 mm d-1 at Sabine Bank, and rates were highest on the ridge habitat of Sabine Bank (1.31 mm d-1). Mortality of post-settlement lane snapper was higher on Sabine Bank (15.2% d-1; Z = 0.165), than on Freeport A (9.2% d- 1; Z = 0.097), and was greatest on the ridge habitat of Sabine Bank (24 % d-1; Z = 0.275). Recruitment potential (G : Z), evaluated on habitats at Sabine Bank, was highest on the offshore habitat, with a value greater than 1.0, indicating higher potential contribution to the adult population. Results indicate Heald Bank, Sabine Bank, and Freeport Rocks all serve as settlement habitat of lane snapper, which appear to be capable of successful settlement across a variety of habitats and banks.Item Interrogating the Lack of Pay Transparency in Library Faculty Job Postings(Texas A&M University System Virtual Library Conference, 2022-06-15) Hight, Alexa; Hernandez, Patricia Lynn; DeForest, LeaItem Self-perceptions of volunteer management:: a texas 4-h volunteer needs assessment(2009-05-15) Torock, Jodi LynnThe purpose of this study was to assess the management of volunteers through self-perceptions of Texas 4-H volunteers. This research was an on-line questionnaire designed to assess volunteers? attitudes toward recruitment, orientation, training, resources, utilization, motivations for continuation of service, and recognition. The population was volunteers enrolled in the Texas 4-H Program during the 2007-2008 program year. The census included 711 Texas 4-H volunteer respondents. This study used a questionnaire designed by the researcher and a team of faculty and staff at a major land grant university and a demographics questionnaire. SPSS? 16.0 for Windows? was used to analyze the data. The study revealed that most Texas 4-H volunteers are oriented and trained in their roles and responsibilities as a volunteer, have additional opportunities for training in their role as club managers or project leaders, have the resources necessary to fulfill their role, and are recognized for their contributions to the Texas 4-H Program. However, as with any program, there is room for improvement. Respondents indicated a need for curriculum development in volunteer and club management. Additionally, 83% of volunteers began volunteering because they had children or family enrolled in the 4-H program; however, volunteers are motivated to continue to serve as volunteers because they want to help youth and support youth development, the 4-H program, agriculture, and family and community development. Respondents indicated they chose to discontinue serving as a 4-H volunteer due to lack of county Extension staff support, lack of time, children aging out of the program, and burnout. The following recommendations for action were based on the findings and conclusions of this study. Volunteer orientation and training programs should become an integral part of all county 4-H volunteer management programs. Curriculum should be developed in the areas of volunteer and club management. In addition, all volunteers should be recognized for their contributions to the program. Orientation, training, and recognition of 4-H volunteers will provide opportunities for volunteers to build an affiliation for the Texas 4-H program, and in turn, motivate volunteers to continue to serve the 4-H youth development program.