Butler and Moon receive honors at the Texas Chapter of TWS

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Dr. M. Butler proudly displaying the award

The Texas Chapter of the Wildlife Society met in February 2016 and recognized Dr. Matthew Butler as lead author for the “Best Technical Publication“. Specifically, the publication is the I&M protocol for surveying  whooping cranes at and around Aransas National Wildlife Refuge in Texas  (get protocol). Co-authors include: Cinthia Eichhorn, the talented Data Manager and GIS expert for USFWS southwest, and Brad Strobel, now the head biologist at Necedah National Wildlife Refuge in Wisconsin.

 

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Dr. J. Moon establishing equipment to measure sea  level rise

 

Dr. Jena Moon, Texas Gulf Coast Zone Biologist, was voted in as the Vice President of the Texas Chapter of the Wildlife Society! Jena is an excellent selection for the Board, given her hard work, dedication to wildlife management, and effective collaboration with the public, private landowners, state and federal agencies, and non-profit organizations. In her role, Jena is anticipated to promote a positive public image for the U.S. Fish and Wildlife Service, the Texas Chapter of the Wildlife Society, and the wildlife profession.

Congratulations to Matt, Cinthia, Brad and Jena!

Southwest Inventory and Monitoring Program assists with U.S. Fish and Wildlife Service banding program

During the month of August 2014, Region 2 Division of Biological Science’s Jeremy Edwardson (Wildlife Biologist, Okmulgee, OK), partook in U.S. Fish and Wildlife Service’s high priority waterfowl banding program in Canada. The waterfowl banding program is a large-scale effort that is essential in monitoring migrating waterfowl and provides crucial information on migratory bird hunting and harvest assessments. U.S. Fish and Wildlife Service representatives and other organizations from across North America gather to assist with the banding program every year and is part of a cooperative agreement among Canada, United States, and Mexico.

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Big Grass Crew preparing for a banding session

Jeremy participated on the banding crew based at Big Grass Marsh near Plumas, Manitoba. This 12,400 acre marsh is owned and managed by Ducks Unlimited, and was the first large scale Ducks Unlimited restoration project in Canada. The crew also consisted of Chad Carlson (Biological technician, Sand Lake NWR), Seth Fisher (Wildlife Biologist, Tensas River NWR), and crew leader, Rob Spangler (USFWS Pilot – Wildlife Biologist, Lakewood, CO). In addition, the crew was supported by Canadian Wildlife Service employee, Darin Walker.  During the 2014 Big Grass Marsh banding season, a total of 287 trap nights (August 6-26) resulted in 4,109 ducks banded (870 Mallards, 2,893 Blue-winged Teal, 180 Redheads, 90 Canvasbacks, 50 Wood Ducks, 10 Northern Pintail; 4 American Green-winged Teal, 4 Ruddy Ducks, 3 American Black Ducks, 3 Mallard – American Black Duck hybrids, 1 Northern Shoveler, and 1 Lesser Scaup).

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A full trap of ducks near Big Grass Marsh, Manitoba

This detail provided program participants hands on training and strengthened teamwork characteristics. Specifically, Jeremy was able to develop a larger network of contacts, improved waterfowl identification and capture techniques, strengthened live bird handling experience, and provided opportunities at obtaining airboat operating hours towards his airboat operator certification. All of which will support his role of supporting Oklahoma refuges and the Division of Biological Sciences.

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Jeremy Edwardson with a banded American Black Duck

Despite varying challenges, crews scattered throughout Canada were able to work together and resulted in a successful banding effort for 2014. The crews’ efforts played a significant role in assisting one of U.S. Fish and Wildlife Services’ main mission of managing waterfowl.

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Crews overcame high water challenges and focused efforts on more productive locations

Visit www.flyways.us for more information on the banding program and other projects that are vital to waterfowl management

Monitoring Ocelots in Tamaulipas Mexico

In 2012, the USFWS entered into a binational partnership with the Civil Society for the Conservancy and Development of Natural Areas (CDEN), Friends of Laguna Atascosa National Wildlife Refuge, Gladys Porter Zoo, and (in 2013) the San Antonio Zoo. This partnership was formed to locate a large population of ocelots in northern Tamaulipas, Mexico, to assess if it might be able to serve as a potential source for translocation to smaller, at-risk populations such as the ones located in south Texas.

CDEN Cat Collage

A collage of  a few representative photographs of the wild felines photographed as part of the study in coastal Tamaulipas, Mexico.

Ocelots are endangered in the Texas mostly due to a loss of their habitat, most of which occurred from the 1930’s to the 1960’s.  Collisions with vehicles also pose a threat.  While both of these issues are being countered with efforts in Texas, the looming threat of a significant loss of their genetic diversity, that occurred over a long period of time, needs to be addressed.  Studies suggested that the most appropriate source for re-establishing the historic genetic diversity of ocelots in Texas would be from the state of Tamaulipas, Mexico, and translocation of wild ocelots has been suggested as an option to achieve this goal.

As with any reintroduction project, there are several items that must be considered carefully.  Among those considerations are the appropriateness of the genetics of the individuals to be introduced, an assessment of disease presence and risk from both recipient and source populations, and arguably most importantly, maintaining the integrity of the source population.

A relatively dense population of ocelots was discovered about 3 hours south of the Texas/Mexico border, in the low sierras along the coast of Tamauliaps.  The great diversity of species in the area is a sign of the quality of the habitat – including jaguar, puma, jaguarundi, bobcat, white-tailed deer, javelinas, and turkey among others.

Ocelot 5 with Kitten 23 Tamaulipas

An adult female ocelot and her kitten photographed as                   part of the study in Tamaulipas.

CDEN, our partners in Tamaulipas, used game cameras to capture photographs of ocelots and identified individuals based on fur patterns.  They counted 20 ocelots in a relatively small area, equating to a density of 1 ocelot/4.92km2.  An estimate of the surrounding ocelot habitat and an extrapolation of the ocelot density provided a very conservative estimate of 117 ocelots in the metapopulation of the surrounding area.

A series of simulations of scenarios with and without translocation of ocelots from this source population were conducted as part of a Population Viability Analysis and the results were only a very low occurrence of negative effects to the source population. over 500 years.

The partnership has provided the data and a report to the government of Mexico on May 27, 2014, as requested in 2013, so that that they can assess the design, analysis and conclusions, and we will wait for their review.  The partnership remains committed to maintaining an effective monitoring effort for this important ocelot population as well as the other species in this rich wildlife community.

tamaulipas ocelot up close

 

 

 

 

 

Little River Inventory and Monitoring Plan is Approved

Little River NWR completed their Inventory and Monitoring Plan (IMP) with a team including Refuge Manager David Weaver, Refuge Forester John Stephens, Zone Biologist Paige Schmidt, Regional I&M Coordinator Kris Metzger, Lead Biologist for National I&M Program Peter Dratch, Zone Biologist for Central and Eastern Texas Jim Mueller, Zone Biologist for Great Plains Bill Johnson, and Wildlife Refuge Specialist at Caddo Lake NWR Jason Roesner. This effort served as the pilot IMP for Region 2 and was the first IMP approved in the region. Further, Mark Chase presented this IMP to Rowan Gould when he briefed him on the National I&M policy. Service staff can log into ServCat at https://ecos.fws.gov/ServCat/ to download a copy of the Plan or to search other approved IMPs.

Little River IMP

The photo shows (from left to right) David Weaver, Bill Johnson, Paige Schmidt, Kris Metzger and Peter Dratch checking out a freshwater mussel bed after completion of the IMP pilot workshop.

Tides, Marsh Tales, and Mud Pies?

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As a child my mother told me I would never have a career that kept me playing in the mud…..well she was only partially right. The mud of Texas coastal marshes hold the secrets of times gone past. We are currently starting a study of sediment depositions and elevation levels to understand past and current perturbations from widespread weather events such as hurricanes and long-term trends of climate change.

The Gulf Coast has suffered extensive loss of coastal marshes since human settlement. Where marsh loss has not been directly caused by rising sea level and other anthropogenic activities, it has been caused by a shift from emergent wetland vegetation to mudflats and open water due to salt water intrusion. Sea level rise, subsidence, and anthropogenic hydrological alterations have changed the environmental parameters that historically regulate coastal marsh function, resulting in their degradation. Global climate change additionally poses significant long-term threats to coastal marsh habitats and species that are dependent on those habitats along the Texas coast.

So how do we measure changes in marsh elevations? We measure elevation changes in coastal marsh with a Surface Elevation Table (SET for short).

SET Diagram

SET Diagram

SETs use a stable platform and a rotating horizontal arm to detect changes in elevation of the marsh surface. The arm is a portable mechanical leveling device for measuring relative sediment elevation changes. The arm has a series of pins that are dropped to the soil surface and then provide researchers with accurate and precise measurements (mm resolution) that are always taken in the exact location.

Douglas Head gently moves vegetation in preparation for SET measurement.

Douglas Head gently moves vegetation in preparation for SET measurement.

Over time these measurements can be mapped and then can provide trends of surface change over time.

This work is important because most climate change models are predicting appreciable sea-level rise along the Texas Gulf Coast. NOAA National Water Level Observation Network tide stations indicate that sea-level rise is not occurring at congruent levels along the entirety of the Texas Coast. Sea-level rise estimates from the Port Isabel tide station indicate a sea-level rise of 1.97 mm, well under the global average of 3.1 mm per year. However, tide stations near Galveston, Texas estimate sea-level rise to be occurring at 6.84 mm per year, over twice the global average. Because the rate of sea level rise for the upper Texas Coast is greater than the global average, it likely reflects the additional impact of local land subsidence due to oil and gas activities or ground water extraction. This information will allow the I&M program to improve climate modeling efforts on National Wildlife Refuges to improve species specific management such as those for whooping cranes and mottled ducks. Additionally, it will allow biologists and managers to better plan and carry out future conservation efforts.

Ches Vervaeke (USGS) measures inidvidual pins on SET measuring arm.

Ches Vervaeke (USGS) measures inidvidual pins on SET measuring arm.

In addition to SETs, coastal I&M staff have assisted in the collection of soil cores for vertical profiling of Cesium-137. Cesium occurs in distinct layers due to fall-out from nuclear testing in the 1940s-early 1960’s. In 1963 the Test Ban Treaty outlawed nuclear testing, which now is allowing geologists to use this unique signature within the soil profile to map long-term soil changes, aggradation and subsidence rates in coastal marshes.

Douglas Head and Tom Doyle extrude a soil core for Cesium-137 dating.

Douglas Head and Tom Doyle extrude a soil core for Cesium-137 dating.

We have collected several samples from Chenier National Wildlife Refuges Complex, Texas Mid-Coast Refuges Complex, and Aransas National Wildlife Refuge for analysis.  This project aims to further our understanding of the impacts of sea-level rise, altered hydrology, and subsidence on coastal marshes by establishing a series of SET benchmarks and vegetation monitoring sites on coastal National Wildlife Refuges.  The collected data will be compared to local rates of sea-level rise as observed through the National Water Level Observation Network tide stations.  he data collected for this project should be able to measure minimum detectable changes in aggradation and subsidence that are significantly less than this observed rate of sea-level rise, and will provide valuable site level information regarding the effects of these processes in a variety of marsh types as well as insight to potential impacts on their future condition. Information collected will be used to improve conservation planning and management actions (e.g., restorative efforts, prescribed burning, etc.) within the coastal zone and to improve climate models (e.g., Sea-level Affecting Marshes Model).

A SET will be installed at this location on Brazoria NWR in the Fall.

A SET will be installed at this location on Brazoria NWR in the Fall.

Linking “the clouds” to endangered songbird habitat conservation and management

Getting the big picture

Light Detection and Ranging airborne remote sensing technology, widely known as “LiDAR,” is being used more frequently as data collection and computing power for processing it become more affordable. It is often used to create a very detailed model of elevation and topography that can be used in a geographic information system (GIS). A LiDAR instrument sends thousands of infrared laser light pulses toward the ground from an airplane or helicopter and then simply records the x, y and z coordinates marking the return location for each beam of light. When viewed with specialized computer software, the points resemble a cloud, known as a “point cloud” that describes the height of objects. Detailed LiDAR “Bare Earth” models of topography are commonly at a much greater spatial resolution and vertical and horizontal accuracy than those developed through traditional methods such as aerial photography, making them well suited for civil engineering, geology, and hydrology applications.

LiDAR 3D point cloud showing an open area and adjacent trees.

LiDAR 3D point cloud showing an open area and adjacent trees.

Hillshade map of LiDAR bare Earth elevation.

Hillshade map of a LiDAR bare Earth elevation.

Early on, LiDAR points returned from trees, buildings, and other objects above the ground were considered a nuisance to be removed before producing good topographic data. Nevertheless, scientists and natural resource managers quickly understood the value of LiDAR point clouds and potential to create highly detailed information about vegetation structure, habitat conditions, human infrastructure, geomorphology, and other land features that can vary substantially across large landscapes. This potential is now gaining the attention of many private, county, state, and federal entities who are finding LiDAR to be an essential tool for managing natural resources, urban growth, flood control, water management, disaster mitigation, and other purposes, naturally driving down the cost of acquiring LiDAR data.

 Gaining ground for songbird conservation

Currently, LiDAR is opening new doors for characterizing and managing wildlife habitat for the US Fish and Wildlife Service (USFWS) Southwest Region Inventory and Monitoring (I&M) Program, starting with endangered songbirds. A common theme contributing to songbird declines is loss and fragmentation of habitat caused by agricultural development and urbanization. The Golden-cheeked Warbler (Setophaga chrysoparia) and Black-capped Vireo (Vireo atricapilla) were listed by the USFWS as Endangered in 1990 and 1987, respectively. The 25,000 acre Balcones Canyonlands National Wildlife Refuge (BCNWR) was established in 1992 to protect habitat for these two species. Both birds are Neotropical migrants, spending winter months in Mexico and Central America while occupying a narrow breeding range in the southwestern USA during the spring and summer. The warbler prefers older oak (Quercus spp.) and Ashe juniper (Juniperous ashei) woodlands while the vireo prefers semi-open shrublands.

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Balcones Canyonlands National Wildlife Refuge is made up of large and small parcels of land purchased from private citizens and resides within the breeding range of the Golden-cheeked Warbler and Black-capped Vireo. Breeding habitat for the vireo (not shown) extends north to Oklahoma and south to northern Mexico.

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Typical habitat conditions preferred by the golden-cheeked warbler in oak-juniper woodlands.

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Typical habitat conditions preferred by the black-capped vireo in semi-open shrublands.

BCNWR managers and I&M needed a way to determine where the most suitable habitat conditions exist for warblers and vireos on and off Refuge lands. Specifically, we wanted to know how future land acquisitions, habitat restoration, and protection activities can best be prioritized to make the most of resources allocated to warbler and vireo conservation.

Translating point clouds to habitat

In 2012, the first BCNWR-wide bird point count survey was conducted following a protocol developed by I&M Zone Biologist Dr. Jim Mueller. Drawing on modern sampling techniques from published studies, a total of 250 randomly selected locations were surveyed to record presence, distance, and time of detection of the Golden-cheeked Warbler and the Black-capped Vireo, and potential nest predators such as the Brown-headed Cowbird (Molothrus ater), Western Scrub-jay (Aphelocoma californica), and Blue Jay (Cyanocitta cristata), at four separate occasions during the breeding season. Detections for the Northern Bobwhite (Colinus virginianus), a species of conservation concern, were also recorded.

LiDAR and on-the-ground bird surveys are now beginning to play a role in estimating woodland conditions that are most important to the warbler and vireo, and eventually map locations across the landscape where they are likely to exist or which habitats are likely to be colonized in the future. Of considerable advantage, the state of Texas maintains substantial LiDAR data archives for many of the counties known to maintain warbler and vireo populations. In addition, the US Department of Agriculture National Agricultural Imagery Program (NAIP) acquires high-quality and high spatial-resolution color-infrared (CIR) aerial photography for the entire state of Texas every 2 to 3 years.  Each of these data sources is freely available through the Texas Natural Resource Information System (TNRIS) and important to developing relationships between songbirds and habitat characteristics such as woodland vegetation composition and structure.

Remotely sensed data must first be processed, often using sophisticated computational techniques that require fast computers to translate them into information that is useful for conservation planning and management. However, results can be astonishingly accurate and simple to interpret for making management decisions.  For the warbler, we have developed highly accurate vegetation height, density, and canopy cover data layers from LiDAR that can be mapped and quickly be related to preferred habitat conditions by songbirds.

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LiDAR derived vegetation height useful for identifying older oak-juniper woodlands (darker green to blue color) important to the golden-cheeked warbler.

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LiDAR derived relative vegetation density for trees between 5 and 10m tall. Height breaks can be used to determine both overstory and understory vegetation density important to songbirds.

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Golden-cheeked warbler occurrence data collected in 2012 combined with LiDAR derived vegetation height indicating how late successional oak-juniper woodland structure is important habitat.

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Golden-cheeked warbler occurrence data collected in 2012 combined with LiDAR derived canopy cover indicating how relatively closed canopy oak-juniper woodland structure is important habitat.

Synthesizing LiDAR outputs with data collected in the field is not only telling a story about preferred songbird habitat conditions, but also where these conditions exist over large areas. A recent study by Farrell et al. (2013) provides an excellent example of how LiDAR derived vegetation data can be used effectively to identify key habitat for the Golden-cheeked Warbler and Black-capped Vireo on the Fort Hood military installation. We are taking similar steps to develop spatial models of songbird and nest-predator occupancy that will afford important information on where to prioritize conservation and habitat restoration actions both on and off Refuge lands. LiDAR and CIR imagery are also helping to address other questions such as understanding how understory vegetation, heterogeneity in height and canopy structure, successional status, and woodland species composition are related to the presence of warblers and vireos. This information will provide keen insights into how management activities such as hazardous fuels mitigation and other woodland treatments may best enhance habitat conditions and help minimize the negative influence of songbird nest predation. These monitoring and modeling activities are aimed at achieving refuge management goals, consistent with the 2001 Comprehensive Conservation Plan (2001) and Draft Habitat Management Plan (2010).

In the future, larger-scale efforts to characterize habitat conditions throughout the range of these two species may also help to identify locations where conservation credits to private land owners can best meet endangered songbird recovery objectives. Thus, the answer to these and many other questions about wildlife habitat relationships and management might just be in the clouds.

References

Balcones Canyonlands National Wildlife Refuge Comprehensive Conservation Plan. 2001. U.S. Fish and Wildlife Service, Albuquerque, New Mexico.

Balcones Canyonlands National Wildlife Refuge Habitat Management Plan (Draft). 2010. U.S. Fish and Wildlife Service, Marble Falls, Texas.

Farrell, S. L., B. A. Collier, K. L. Skow, A. M. Long, A. J. Campomizzi, M. L. Morrison, K. B. Hays, and R. N. Wilkins. 2013. Using LiDAR-derived vegetation metrics for high-resolution, species distribution models for conservation planning. Ecosphere 4:1-18.

Among the tiniest of snails…

Bitter Lake National Wildlife Refuge is home to 8 species that are listed as Federally Threatened or Endangered, and to several additional species listed as Threatened or Endangered by the State of New Mexico.  Among the Federally Endangered species is a tiny snail, so small it went unnoticed until 1987.  Pecos assiminea (Assiminea pecos) ranges in size from 1.4 to 2.2 mm.  It occurs near the wetted edges (mud-water interface) of certain sinkholes, springs, and spring-runs (also known as cienega) on the Refuge.  Pecos assiminea was listed as Endangered in 2005.  In addition to Bitter Lake NWR, the snail is found on The Nature Conservancy’s Diamond Y Springs in west Texas.

Sketch of Pecos assiminea, excerpted from Taylor, 1987 (Figure 2):

Taylor_AssmineaSketch-Fig2

Due in large part to its tiny size, it is extremely difficult to survey.  Imagine trying to find a small brownish snail that is often less than 2 mm long in a shaded, uneven brown background; this difficulty is compounded because the habitat being searched is also full of small brown seeds, bits and pieces of small brown vegetation, and little mud stained salt crystals.  Search efforts, thus, have traditionally been hindered because they were extremely time-consuming and tedious.  Researchers have to lie on the ground with their face only a few inches above the ground, and several hours might be required to cover only a small area. Additionally, large-scale sampling efforts have been hindered by the lack of a feasible monitoring technique.

Searching for Pecos assiminea along Bitter Creek, Bitter Lake NWR, photo by Patricia Obryon

Searching for Pecos assiminea along Bitter Creek, Bitter Lake NWR, photo by Patricia Obryon.

In 2011, Bitter Lake National Wildlife Refuge decided to pursue a monitoring effort that would help it better understand the species distribution, habitat associations, and density on the refuge.  Field work for this project was largely carried out by Elizabeth (Beth) Roesler, who joined Bitter Lake NWR as an intern working for the Student Conservation Association.  Roesler’s field work involved systematically searching areas of the Refuge where Pecos assiminea is known and suspected to occur.  Roesler searched small quadrats of known size, and the quadrats were regularly spaced in searched habitats.  She also collected habitat information concurrent with each quadrat searched, such as vegetation type, soil texture/saturation, ground temperature, and water quality (from adjacent spring flows).  This information was collected in order to better understand habitat parameters associated with the species, and will eventually be incorporated into models that help predict where the species might occur.  However, even with a scientifically rigorous sampling design, positive finds of Pecos assiminea were few and searches still proved to be a tedious process.

In fall of 2012, Roesler incorporated a second technique into her sampling efforts.  This technique involved using known dimension wood tiles, and was suggested by Brian Lang, invertebrate biologist with New Mexico Department of Game and Fish.  Known dimension clay tiles are often used to sample aquatic snails, but Lang’s prior experience using clay tiles in attempts to sample Pecos assiminea had proved unsuccessful.  However, since Pecos assiminea are sometimes seen attached to small wood fragments, wood tiles seemed like they warranted a try.

Wood tile used to survey Pecos assiminea

Wood tile used to survey Pecos assiminea.

Initially, wood tiles were placed on the ground only along the edges of Sinkhole 31, which is believed to have the highest densities of Pecos assiminea on the Refuge.  Roesler’s use of wood tiles proved almost immediately successful.  Within a few weeks, Pecos assiminea began to attach to the wood tiles, and detection rates with tiles were much higher than detection rates from visually searching quadrats of known area.

As opportunity would have it…

In 2012, Bitter Lake NWR received an “Invasives with Volunteers” grant, which enabled them to initiate an ambitious phragmites (pronounced frag-mit-ies) plant removal program to restore a 1 mile spring run (approximately 7 acres of cienega habitat), known as Bitter Creek, to conditions that existed prior to phragmites invasion.  One of the goals of removing phragmites was to alter habitat in favor of Pecos assiminea and the 5 other federally listed species that occur there.  Pecos assiminea snails rarely occur in phragmites dominated habitats and declined along Bitter Creek after the spread of this invasive plant species.

Subsequent to receiving the “Invasives with Volunteers” grant, Texas Tech University received a Science Support Grant in partnership with U.S. Geological Survey and the Refuge.  The purpose of this grant was to monitor the response of Pecos assiminea to phragmites removal on Bitter Creek.  As Roesler was already experimenting with two monitoring techniques (visual searches of small quadrats and wood tiles) to monitor this species, and had already fully sampled Bitter Creek the prior year using quadrat searches, she was the best choice to make the leap from Student Conservation Association intern to graduate student.  In spring of 2013 she enrolled as a graduate student at Texas Tech University to work on the Science Support Grant funded project.  Two main goals of her graduate project are to monitor the effects of phragmites removal on Pecos assiminea, and to concurrently examine the efficacy of the two monitoring techniques mentioned above.  Unlike most graduate students in the field of conservation science, Roesler actually entered graduate school as one of the leading experts on her study species.  Thanks to her Student Conservation Association internship, perhaps only 1 or 2 people in the world have observed and sampled more Pecos assiminea than Roesler.

Beth Roesler, current graduate student at Texas Tech University surveying Pecos assiminea along Bitter Creek

Beth Roesler, current graduate student at Texas Tech University, surveying Pecos assiminea along Bitter Creek.  Photo by Patricia Obryon.

So what does Bitter Lake NWR gain from this project?  First, the Refuge aims to benefit an endangered species through its management actions/prescriptions, and the monitoring effort will help the Refuge learn how the species responds.  Secondly, the Refuge will get answers concerning the efficacy of two potentially suitable sampling techniques that can each be used to answer questions about Pecos assiminea distribution and density.  Hopefully one of the techniques can be used for “operational” monitoring for the species.  From a general conservation standpoint, the U.S. Fish and Wildlife Service will get estimates of Pecos assiminea density in multiple habitats, which will be among the first abundance estimates for this species!  Upon completion of the work, the Refuge will have enough information to make reasonable predictions about the response of Pecos assiminea to phragmites control if additional removal efforts are pursued, and, lastly, the Refuge should have enough information to start modeling likely occurrence of Pecos assiminea based on its habitat parameters.  This project is adaptive management at its best.

Citation:  Taylor, D.W.  1987.  Fresh-water mullusks from New Mexico and vicinity.  New Mexico Bureau of Mines and Mineral Resources Bulletin 116.