Changes in fish populations in the Lower Canyons of the Rio Grande

The Lower Canyons of the Rio Grande suffer from environmental degradation that has negatively impacted native fish populations and their distributions. Macrhybopsis aestivalis (speckled chub), Notropis jemezanus (Rio Grande shiner), Rhinichthys cataractae (longnose dace) and Cycleptus elongatus (blue sucker) populations appear to have suffered recent declines. Although diminished water quantity is likely an important factor in these declines, related changes in channel morphology precipitated by massive stands of Arundo donax (giant reed) and Tamarix sp. (salt cedar) may also be responsible. These invasive exotics have essentially channelized the river, disrupted normal sediment distribution and reduced shallow, low-velocity habitats. Much of the Lower Canyons of the Rio Grande are devoid of sandy sediment and most riffles are now composed of gravel and cobble.Integrative Biolog

An Annotated Checklist of the Freshwater Fishes of Texas, with Keys to Identification of Species

Forty-five families and 247 species of fishes are known to inhabit the freshwaters of Texas. We report on the distribution and status of these fishes and provide a key to their identification. Of the native fishes originally found in Texas, five taxa, Notropis orca (phantom shiner), Notropis simus simus (Rio Grande bluntnose shiner), Cyprinella lutrensis blairi (Maravillas red shiner), Gambusia amistadensis (Amistad gambusia) and Gambusia georgei (San Marcos gambusia) are apparently extinct, and three, Oncorhynchus clarki virginalis (Rio Grande cutthroat trout), Hybognathus amarus (Rio Grande silvery minnow) and Gambusia senilis (blotched gambusia) appear to be extirpated from the state. More than 20 percent of the remaining primary freshwater species appear to be in some need of protection.Integrative Biolog

Status Assessment and Watershed Planning for Plateau Shiner, Nueces River Shiner, and Nueces Roundnose Minnow in the Upper Nueces River Basin

NOTE: Though this report states "Vouchers of all species collected were preserved, fixed in 10% formalin and preserved in 75% ethanol and placed for curation in the Texas Natural History Collection at the University of Texas at Austin", as of 22 August, 2018, the specimens had not been catalogued in that collection and searches for them by collection staff and the authors failed to find them.The Upper Nueces River Basin is composed of three main tributary systems: the Nueces, Frio, and Sabinal rivers. All three rivers were designated as Ecologically Significant Stream Segments by the Texas Water Development Board in regional water planning. The Texas Comprehensive Wildlife Conservation Strategy (Texas Parks and Wildlife Department 2005) and The Nature Conservancy (The Nature Conservancy 2004) have also designated the three rivers as high priorities. Additionally, about 60% of the Edwards Aquifer recharge water comes from the upper portion of the Nueces River basin, making riparian health important for plant, animal, and human communities throughout the region. It is thought riparian integrity in these rivers has declined, posing a threat to priority species and habitats, not to mention human use. One possible indicator of this decline is the apparent decrease in range and abundance of several fish species, notably but not exclusively, the plateau shiner (Cyprinella lepida), Nueces River shiner (Cyprinella sp.), and the Nueces roundnose minnow (Dionda serena). These species are thought to depend on perennial relative flows of clear water, and thus serve as an indicator of hydrologic function and water quality. We provide information on the status and range of these three species and their utility as indicators of hydrological integrity and watershed health. We also provide data that can be useful for a community-based action plan to help maintain the ecological integrity in critical portions of the three river basins.The Nature Conservancy, Austin, TexasIntegrative Biolog

Force distributions in a triangular lattice of rigid bars

We study the uniformly weighted ensemble of force balanced configurations on a triangular network of nontensile contact forces. For periodic boundary conditions corresponding to isotropic compressive stress, we find that the probability distribution for single-contact forces decays faster than exponentially. This super-exponential decay persists in lattices diluted to the rigidity percolation threshold. On the other hand, for anisotropic imposed stresses, a broader tail emerges in the force distribution, becoming a pure exponential in the limit of infinite lattice size and infinitely strong anisotropy.Comment: 11 pages, 17 figures Minor text revisions; added references and acknowledgmen

Conservation genetics of cyprinid fishes in the upper Nueces River basin in central Texas

Sequences of the mitochondrial (mt) NADH dehydrogenase subunit 5 gene (ND5) were acquired to assess genetic diversity and female effective population size (Nef) of two forms of Cyprinella (C. lepida and C. sp. cf lepida) and two species of Dionda (D. serena and D. texensis) in headwaters of three rivers in the upper Nueces River basin in central Texas. As documented in prior studies, two divergent clades of haplotypes of mtDNA were found in both genera: one in the Frio and Sabinal rivers, representing C. lepida and D. serena; one in the Nueces River, representing C. sp. cf lepida and D. texensis. Levels of variation in mtDNA from C. lepida in the Sabinal River and D. serena in the Frio and Sabinal rivers were comparable to or considerably lower than values documented for populations of several threatened or endangered cyprinids. Estimates of Nef for C. lepida in the Frio River and C. sp. cf lepida in the Nueces River were low, suggesting that adaptive genetic variation through time may be compromised. Of all populations sampled, only D. texensis in the Nueces River appears at present to be genetically stable demographically. An unexpected finding was two individuals resembling C. lepida in the Frio River with a haplotype referable to C. sp. cf lepida; the origin of these individuals is unknown. Two other individuals resembling C. lepida but with haplotypes of mtDNA referable to C. venusta were found in the Frio River and presumably represent relatively recent hybrids. Results of our study indicate that C. lepida, C. sp. cf lepida, and D. serena in the upper Nueces River basin, especially in the Sabinal River drainage, are at appreciable genetic risk

An Overview of the Space Environments and Spacecraft Effects Organization Concept

The National Aeronautics and Space Administration (NASA) is embarking on a course to expand human presence beyond Low Earth Orbit (LEO) while also expanding its mission to explore our Earth, and the solar system. Destinations such as Near Earth Asteroids (NEA), Mars and its moons, and the outer planets are but a few of the mission targets. Each new destination presents an opportunity to increase our knowledge on the solar system and the unique environments for each mission target. NASA has multiple technical and science discipline areas specializing in specific space environments fields that will serve to enable these missions. To complement these existing discipline areas, a concept is presented focusing on the development of a space environment and spacecraft effects (SESE) organization. This SESE organization includes disciplines such as space climate, space weather, natural and induced space environments, effects on spacecraft materials and systems, and the transition of research information into application. This space environment and spacecraft effects organization will be composed of Technical Working Groups (TWG). These technical working groups will survey customers and users, generate products, and provide knowledge supporting four functional areas: design environments, engineering effects, operational support, and programmatic support. The four functional areas align with phases in the program mission lifecycle and are briefly described below. Design environments are used primarily in the mission concept and design phases of a program. Environment effects focuses on the material, component, sub-system, and system-level response to the space environment and include the selection and testing to verify design and operational performance. Operational support provides products based on real time or near real time space weather to mission operators to aid in real time and near-term decision-making. The programmatic support function maintains an interface with the numerous programs within NASA, other federal government agencies, and the commercial sector to ensure that communications are well established and the needs of the programs are being met. The programmatic support function also includes working in coordination with the program in anomaly resolution and generation of lessons learned documentation. The goal of this space environment and spacecraft effects organization is to develop decision-making tools and engineering products to support all mission phases from mission concept through operations by focusing on transitioning research to application. Products generated by this space environments and effects application are suitable for use in anomaly investigations. This paper will describe the scope and purpose of the space environments and spacecraft effects organization and describe the TWG's and their relationship to the functional areas