ABSTRACT. The recent book Reintroduction of Fish and Wildlife Populations (Jachowski et al. 2016), included a chapter titled The Reintroduction Landscape: Finding Success at the Intersection of Ecological, Social and Institutional Dimensions. The authors of the chapter, representing the U.S. Geological Survey, U.S. Forest Service, and the U.S. Fish and Wildlife Service, coin a new phrase - the reintroduction landscape - that encompasses the integration of human and ecological factors. The chapter authors submit that it is these factors, expressed as ecological, social and institutional dimensions, and the interactions among them, that determine the relative success of species reintroductions. We will examine the various factors within the ecological, social and institutional dimensions and demonstrate the importance of meeting these factors to achieve an appropriate reintroduction landscape. We also note that such considerations can be useful beyond species reintroductions, and apply broadly to important conservation and species recovery actions as a whole.

ABSTRACT. The Colorado River has undergone significant anthropogenic modifications, consequently native fish communities are severely imperiled. We examined temporal patterns in fish community structure over 37 years in Lake Mohave using bi-annual trammel net surveys (spring and autumn) that were initiated by W. L. Minckley in 1974. Specifically, we examined 1) historical changes in fish community structure to determine stability and persistence and 2) long-term abundance trends. Non-native fishes were established prior to surveys, precluding the ability to determine a “normal bounds” of historical fish community structure. The two remaining native fishes, Razorback Sucker, Xyrauchen texanus and Bonytail, Gila elegans, declined precipitously in abundance through time. However, a repatriation program initiated in 1991 prevented Razorback Sucker from extirpation, while reintroduction efforts for Bonytail have failed; wild populations of both species are gone. Total catch per unit effort (CPUE) averaged across seasons (range = 1.77 to 39.57) and species richness (x̅ = 8.08, SD = 1.38) showed a negative relationship with time. Long-term abundance trends indicated three non-native taxa (i.e., Gizzard Shad, Dorosoma cepedianum, Yellow Bullhead, Ameiurus natalis, and Smallmouth Bass, Micropterus dolomieu) increased, eight decreased, and six showed no relationship. Fish community composition shifted directionally through time in multivariate space, with the formation of four significant clusters indicating alternative states and low stability. The native fish community vanished shortly after the introduction of a suite of non-native taxa and Razorback Sucker persists in Lake Mohave only because of continued stocking. The contemporary population of Razorback Sucker is stable albeit less abundant than historically, thus continued adaptive management will be required to preserve the most genetically diverse population in the Colorado River system.

ABSTRACT. Woundfin, Plagopterus argentissimus, has been federally listed as an endangered species since 1970. Successful reproduction and recruitment of Woundfin is limited to a 16.3 mile reach in the upper Virgin River in Utah. Currently, only a small portion of Woundfin live to be greater than 1-year old in the wild; the persistence of Woundfin is dependent on the survival and reproductive success of these young fish. Woundfin abundance and distribution has been limited by multiple factors including non-native fish, drought, altered streamflow regimes, diversions, elevated water temperature, decreased turbidity, water management events, and a decline of spawning and rearing habitat.

Since 2000, the Utah Division of Wildlife Resources has worked through the collaborative Virgin River Program to identify and evaluate these factors limiting Woundfin persistence and recruitment. This presentation will highlight the creative ways we have addressed these factors and enhanced Woundfin populations and habitat recovery in the Virgin River.

ABSTRACT. Bonytail, Gila elegans, and Razorback Sucker, Xyrauchen texanus, are two endangered fishes endemic to the Colorado River Basin. Population declines of both species are attributed to the introduction of non-native fish species and alteration to flow. Each year hatchery-reared Bonytail and Razorback Sucker are reintroduced back into the wild. However post-stocking survival is often poor as offspring are naïve to predation. Artificial structures have been discussed as a potential strategy to improve post-stocking survival but have yet to be evaluated. Therefore the objective of this study was to evaluate three different artificial structures to improve survival of hatchery-reared Bonytail and Razorback Sucker when exposed to predation. Three different structures (artificial macrophytes, large diameter vertical PVC, and small diameter horizontal PVC) and a control treatment (void of any structure) were used in the experiment. A repeated measures design experiment was conducted using Largemouth Bass, Micropterus salmoides, as a model predator and naïve hatchery-reared Bonytail and Razorback Suckers were used as prey. Experiments were conducted within one meter diameter circular tanks for one hour periods. Small diameter horizontal PVC and artificial macrophytes resulted in significantly higher survival for Bonytail compared to both the control treatment and large diameter vertical PVC. There was no significant difference in survival for Razorback Suckers between all treatments. Therefore it appears that artificial structure may play a larger role in post-stocking survival for Bonytail than Razorback Sucker, but future research is needed to confirm these results at a larger scale.

ABSTRACT. Nonnative fishes, such as Channel Catfish, Ictalurus punctatus, potentially have negative impacts on native fishes, but their effects on native communities can be difficult to quantify. Specifically, predation on native fishes will likely vary spatially and temporally based upon prey availability and abiotic conditions, thus quantifying a predator’s ability to diminish native fishes needs to incorporate multiple spatial and temporal scales. To quantify the predatory threat of Channel Catfish on native fishes, stomach fullness, stomach evacuation rates, and diets were quantified throughout the San Juan River, NM, CO, and UT over both fine (24 hour) and broad (seasonally) temporal scales. Stomach fullness varied both spatially and seasonally but contrary to our expectations, no diel differences in fullness were observed. Stomach evacuation rates, measured in a laboratory setting, increased with water temperatures and fish prey items took 7-75 hours to digest to 50% of their initial wet weight. Lastly, diets were composed of both aquatic (~60%) and terrestrial (~40%) materials, of which fish remains were in a relatively low frequency (0-0.25) of stomachs and native fishes represented 52% of the total fish prey consumed by Channel Catfish. Identifying nonnative predator impacts on native species across multiple scales may help develop management strategies to minimize negative interactions between native and nonnative fishes.

ABSTRACT. Characterizing spatial and temporal variation in communities can provide insight into main factors driving community structure. Samples across space can capture variation attributed to environmental gradients, such as stream size, and samples across time can capture responses to variation in hydrologic conditions, including extreme events such as flooding and drought. Because disturbance is often unpredictable by nature, capturing the effects of a natural disturbance can be quite difficult, unless a study is already in progress. Two wildfires and an extreme monsoon occurred mid-way through a 2008-2016 study on the spatial and temporal variation in aquatic communities in the Gila River of New Mexico, providing an opportunity to witness how these events might structure macroinvertebrate communities. Aquatic macroinvertebrate community structure varied spatially along an elevational gradient with high elevation sites distinguished with higher abundance of two caddisfly families Polycentropodidae and Philopotamidae and low elevation sites characterized by higher abundance of the dragonfly family Libellulidae. Overall insect diversity decreased following the wildfires, although a few families, such as Chironomidae, were unaffected or increased in total biomass. Variable discharge over the 8-year study also had an effect, with Empididae, Nemouridae, and Taeniopterygidae becoming more abundant in flood years relative to other macroinvertebrate taxa. Responses of macroinvertebrate taxa was concordant with general patterns of habitat use; some riffle dwelling species performed well in wet years and some pool dwelling species performed well in dry years. Collectively, these patterns of variation might be used to predict benthic macroinvertebrate community response to spatial and temporal variation in environmental conditions.

ABSTRACT. The northwestern extreme of the desert region includes several endorheic or terminal lake basins in Oregon, northeastern California, and northwestern Nevada (Fort Rock, Chewaucan, Goose, Warner, Catlow, Alvord, Malheur, Coyote lakes, and Quinn River). This region supports remnant fish faunas that once inhabited extensive pluvial Pleistocene lakes.

Oregon State University is re-evaluating the taxonomy of the Torrent Sculpin (Cottus rhotheus) in Oregon, Washington, Idaho and Montana. Results suggest that there are two or three species subsumed under the one current name separated along molecular, morphological and geographic lines. The lab is testing whether the very similar Cottus gulosus and Cottus perplexus are actually distinct species in Oregon, and working on a review paper that will highlight and summarize taxonomic needs for the fishes of Oregon.

Lake County Umbrella Watershed Council (LCUWC) has designed and planned three conservation projects benefitting Warner Sucker and Redband Trout in the Warner basin, and three fish passage projects in the Goose Lake Basin that will benefit nine native Goose lake fishes. Several partner organizations and agencies have formed a “Warner Basin Aquatic Habitat Partnership” with the council to develop fish passage solutions for Warner Suckers, Redband Trout, and other aquatic life. The Western Native Trout Initiative has developed a portfolio of projects, including Warner basin projects, to use in advocating conservation to potential supporters.

California Department of Fish and Wildlife (CDFW) completed projects in Pine Creek and Eagle Lake of northeast California for the conservation and management of Eagle Lake Rainbow Trout (ELRT), a native Rainbow Trout subspecies. Currently, CDFW is reestablishing natural production and assessing genetic integrity, while supplementing with hatchery reared Rainbow Trout. CDFW also collected genetic samples for genetic analysis and inbreeding within ELRT and evaluation of the level of genetic distinctiveness of extant populations. CDFW used video to document upstream spawning migrations in Pine Creek. CDFW assessed Brook Trout distribution in Pine Creek to plan Brook Trout removal.

Oregon Department of Fish and Wildlife (ODFW) provided updated information on Redband Trout surveys conducted in the Warner and Abert lakes basins. ODFW also facilitated the capture and transfer of several Foskett Speckled Dace to the High Desert Museum for an educational display. These fish are in addition to eleven Warner Suckers that ODFW provided to the museum in 2016.

BLM conducted a habitat enhancement project at Foskett Spring. Management actions and a commitment to conservation were conducive to the US Fish and Wildlife Service’s decision to propose delisting the Foskett Speckled Dace from the ESA list. The public comment period for the proposed delisting has concluded and a final decision will be published December to early January. ODFW conducted population estimate of Borax Lake Chub in 2016 and 2017 and observed a rather large population change (low of 1,200 fish in 2016 to 78,000 fish in 2017). The US Fish and Wildlife Service is also proposing to delist the Borax Lake Chub, from the ESA list. The proposal will publish with an open public comment period mid-October.

ABSTRACT. Green Sunfish Lepomis cyanellus are exceptional invaders and have become widespread throughout watersheds of the Southwest, largely due to their ability to tolerate the extreme physical and biological conditions characteristic of desert aquatic systems. Green Sunfish are frequently linked to declining native fish populations as a result of competitive and predatory interactions. Consequently, managers of desert fishes have put substantial resources into mechanical removal efforts intended to eradicate nonnative Green Sunfish, with varying degrees of success. We sought to evaluate factors that contributed to the success of mechanical removal of Green Sunfish across eradication efforts in Arizona. We compared six Green Sunfish removal efforts in Arizona that occurred between 2012 and 2018. We considered a number of factors that likely influence success of removal efforts including whether removal reaches were isolated from invasion, watershed size, removal reach length, and initial relative abundance. We used logistic regression to evaluate which factors contributed to removal success. We found that successful removals were characterized by low initial relative abundance and isolation from an invasion source. By identifying factors contributing to successful outcomes for removal efforts, we can focus our limited resources for nonnative fish control on systems where mechanical removals are likely to be successful.

ABSTRACT. In the Owens Valley, native fish conservation is limited by suitable habitat; open waters are invaded by non-native species and refuge habitats are scarce. We investigated the potential for success of a multi-species native fish refuge using a mesocosm experiment to assess interactions between Owens Speckled Dace, Rhinichthys osculus ssp., and two size classes of hybridized Owens Tui Chub, Siphateles bicolor snyderi X S. obesa, (a surrogate for the listed subspecies). We tested the effects of interspecific interactions (e.g. competition and predation) on body condition, growth, and survivorship using five different combinations of species and sizes with a control treatment, each replicated 8 times. Mesocosms were inoculated with benthic substrate and invertebrates from the proposed refuge habitat. Two hypotheses were evaluated, (1) that the large size class of chub would prey upon dace, and (2) that interspecific competition between smaller size classes of fish would negatively affect body condition for both species. We did not find support for our first hypothesis, of predation by chub on dace, however, dace body condition was negatively affected by competition with small chub which partially supported our second hypothesis. Growth and body condition of large and small chubs were not affected by the presence of dace. Our results suggest that competition with small chub is more important than predation by large chub for dace growth and survival. Restoring sympatric populations of the two species may be possible if the habitat complexity allows for the rapid growth of chubs or if habitat complexity reduces the potential for interactions.

ABSTRACT. In 1985 and 1986, Robert Hershler and Don Sada conducted a comprehensive survey for springsnails on and near the newly-established Ash Meadows National Wildlife Refuge. They documented the distribution of 11 species of springsnails, including nine newly-described species, and included field water quality data and a brief description of the habitat at each spring. In the previously surveyed 47 springs, one spring was dry (Mexican Spring), and springsnails occurred in 36. The relatively widespread Pyrgulopsis micrococcus was the only springsnail found in 9 springs. One or more of the remaining ten species (Tryonia variegata, Tryonia angulata, Tryonia ericae, Tryonia elata, Pyrgulopsis erythropoma, Pyrgulopsis crystalis, Pyrgulopsis nanus, Pyrgulopsis isolatus, Pyrgulopsis fairbanksensis, and Pyrgulopsis pisteri) were found in 27 springs. Here, we present a 2017 resurvey of 26 springs with endemic springsnails previously visited by Hershler and Sada (the 27th spring is Devils Hole, which has regular surveys of all invertebrates). Our methods include the enumeration of individuals by genus (Tryonia or Pyrgulopsis), basic field water quality measurements, habitat description and the observation of potential environmental stressors. Samples were also collected for future genetic analysis. Seven of the 26 resurveyed springs were dry. Two species (T. elata and P. isolatus) were not found in the springs where previously reported as endemic. In addition, Tryonia occurred in only one of the two springs where T. ericae was found in the original survey, and only a single individual Pyrgulopsis was found is the spring where P. crystalis previously occurred. Our results show that springsnail presence is generally robust geographically over approximately 30 years, however, the distribution of some species can change significantly over that time, even within a protected area. More surveys and species-level identification are needed to verify non-detections reported in the 2017 survey.

ABSTRACT. Designer flow optimization for dammed rivers is a powerful approach for balancing ecological objectives and competing societal demands for water. How designer flows, which use flow events to target select species of interest, affect non-target ecosystem components has been largely overlooked. Using empirically-parameterized population models based on the Verde River, Arizona ecosystem, we found tradeoffs associated with designer flow regimes targeting riparian vegetation, fishes, and invertebrates. The different event frequencies associated with each designer flow regime resulted in some nontarget ecosystem components becoming functionally extinct in as little as 50 years. By incorporating multiple flow frequencies, the natural flow regime enabled a balanced response of the three components. Although returning to a natural flow regime may no longer be viable in highly managed rivers, designing river flows to support entire ecosystems must begin from natural flow regime principles.

ABSTRACT. Bonytail Gila elegans and Razorback Sucker Xyrauchen texanus are both listed as endangered by the United State Fish and Wildlife Service. A stocking initiative by the Bureau of Reclamation, Lower Colorado River Multi-Species Conservation Program has maintained these native species in parts of their historic range, including below Palo Verde Dam in the area around Blythe, CA. Since 2007, 21,749 Razorback Sucker and 18,475 Bonytail have been stocked in the area with passive integrated transponder (PIT) tags implanted in them. The focus of stockings has been 5 primary “backwaters”. These backwater habitats are connected to the main river channel, allowing stocked fish to disperse into the main channel of the Colorado River. Since 2016, 38 subadults of each species and 20 adult Razorback Sucker were surgically implanted with acoustic telemetry tags so manual and passive tracking of movement could take place. Biologists from Marsh & Associates have monitored the movements of the stocked fish via PIT tag scanners, Submersible Ultrasonic Receiver, and an acoustic hydrophone and receiver. Collection efforts from this year resulted in contacting 1,234 unique Razorback Sucker (5.6%) and 535 Bonytail (2.8%). 103 Razorback Sucker contacted this year were stocked prior to this year, whereas there were no Bonytail contacted that were released prior to this year. PIT scanning effort in the main stem was increased this past year which resulted in 9 Razorback Sucker and 6 Bonytail contacts. Mean days at large was 156.5 for Razorback Sucker and 27.8 for Bonytail.

ABSTRACT. Stocking of hatchery-raised fish or repatriation has been the primary means of maintaining populations of the endangered Razorback Sucker Xyrauchen texanus throughout its historic range. In the lower Colorado River basin, populations in the thousands have been established and maintained in Lake Havasu and Lake Mohave by stocking over a half million subadult to adult Razorback Sucker over the last three decades. Since 2006 all Razorback Sucker released in these reservoirs are injected with a 134.2 kHz passive integrated transponder (PIT) tag. These fish are monitored using traditional capture methods (e.g. annual netting activities) and remote sensing via deployment of remote PIT tag scanning units. Remote PIT tag scanning has resulted in orders of magnitude more contact data than traditional methods. To date, 19,713 Razorback Sucker have been contacted via remote PIT scanning in the lower Colorado River basin. These data have been used to refine estimates of population size and post-stocking and adult survival using mark-recapture models. However, there has been little formal assessment of how these estimates correlate to results from traditional capture methods. A discrete time population model was developed to compare estimates of post-stocking and adult survival and frequency distributions of annual Razorback Sucker stockings in Lake Havasu and Lake Mohave with single-census estimates of abundance. We also extend the population model to include tag loss and compared ratios of tagged to untagged fish calculated from netting events to determine if natural recruitment at low levels was likely occurring without detection. The results were then compared to model results for Lake Mead, the third reservoir in the lower Colorado River basin which has no formal stocking program and limited natural recruitment.

ABSTRACT. Bonefish (Albula spp.) are a prized sportfish among avid anglers worldwide. Two morphologically indistinguishable species of bonefish (Albula vulpes and Albula goreensis) occur in coastal areas of the tropical western Atlantic. Growth rates of A. vulpes, which supports an economically important sport fishery, differ among locations where they have been studied, but many locations have not yet been examined. To investigate bonefish growth in Cuba, specimens were obtained from 3 regions around the periphery of the island from November 2016 to January 2017. Sagittal otoliths (for aging) and fin clips (for genetics) were collected from each fish, and sex was determined by examining gonads. A total of 222 bonefish were collected for this study. Comparisons of distribution patterns, von Bertalanffy growth curves and age at maturity of different species in different regions will be presented. The insight of different growth patterns between A. vulpes and A. goreensis allows for better management of the species, and further distinguishes differences in the biology of A. vulpes and A. goreensis.

ABSTRACT. Here we report the results of over 100 kilometers of electrofishing stream surveys to assess the distributions of Owens Valley fishes, including Owens Sucker (Catostomus fumeiventris), and Owens Speckled Dace (Rhinichthys osculus sp.). Surveys were conducted in valley-bottom streams and ditches from Round Valley (north of Bishop, CA) to Tinnemaha Reservoir (south of Big Pine, CA). Hierarchical clustering was used to identify five species assemblages comprised of native+nonnative, and wholly nonnative, fish communities. Fish assemblages were compared with water quality, geomorphic, and land-use data to better understand species distribution within the watershed. Comparing the historic site record with the current distribution survey, we conclude the two native species remain widespread. However, Owens Speckled Dace appear to have undergone a substantial range contraction, whereas Owens Sucker distribution has remained stable. The persistence of Owens Suckers is likely due to the presence of large adults which exceed the gape-limit of sympatric, co-occurring brown trout.

ABSTRACT. Bluehead Sucker occurring in the Bonneville Basin and Snake River Basin have been determined to be genetically distinct from those occurring in the Colorado River drainage. As such, the few disjunct populations that occur across parts of Utah, Idaho, Nevada, and Wyoming have become increasingly necessary to protect. This study aged Bonneville Bluehead Sucker from fin ray samples taken in five disjunct sections of the Weber River (Weber, Davis, Morgan, and Summit counties UT) as well as Snake River Bluehead Sucker from the Raft River (Box Elder County, UT). Age structure information from this study will allow managers to make better informed decisions related to the effects of missing age classes, max age, growth, and reproductive maturity which differs within each population due to differing habitat characteristics.

ABSTRACT. Salt Creek and San Felipe Creek are two drainages that constitute much of the existing habitat for Desert Pupfish (Cyprinodon macularius) outside of their occurrence in the Salton Sea, agricultural irrigation systems and refuges. Salt Creek is a natural drainage supplemented by mitigation water. San Felipe Creek is an entirely natural drainage that includes the only designated Critical Habitat for the species. As the Salton Sea increases in salinity, the Sea will become unsuitable for the species to utilize, isolating the two watersheds.   Management challenges have been changing during the past five years in these watersheds, and this talk discusses these changes and the subsequent actions taken by California Department of Fish and Wildlfe and by partner entities.

ABSTRACT. Razorback Sucker Xyrauchen texanus is an endangered species endemic to the Colorado River Basin. In the lower Colorado River, recruitment in the wild is nonexistent and adult survival is low due to habitat alterations and negative interactions with nonnative species. Topock Marsh is a large (1618 hectares) backwater adjacent to the Colorado River. Preliminary Remote PIT scanning in 2016 determined that 551 Razorback Sucker of the original 3244 stocked in 2010 still persist in the Marsh. Due to this persistence, a telemetry study was implemented in the Winter of 2016. A total of 20 wild fish captured in Topock Marsh and 20 hatchery fish were implanted with acoustic telemetry tags and tracked for one year post release to determine survival and utilization of the Marsh. A combination of active tracking with directional and omnidirectional hydrophones and passive tracking with Submersible Ultrasonic Receivers (SUR) determined that a total of 2 hatchery fish and 8 wild fish survived to the end of the study. Kaplan-Meier survival estimates (95% CI) were 0.62 (0.38-0.82) and 0.51 (0.29-0.73) for hatchery fish and wild fish respectively. Although survival was not significantly different between hatchery and wild fish, several of the hatchery fish were lost to the study therefore inflating their survival estimates. The SUR network determined that fish utilized the whole Marsh during the winter months, and in the summer months concentrated where cool fresh water is delivered into the Marsh from the Colorado River. Given the relatively high survival of fish in Topock Marsh, particularly the 2010 stocking cohort, it has the potential to be an important recovery habitat. Using the information that was learned from the telemetry study, the population in Topock Marsh will continue to be monitored and information will be used to aid in the recovery of Razorback Sucker.

ABSTRACT. The Dolores River (southwestern Colorado, southeastern Utah) is an important source of water for agricultural, municipal/industrial, recreational and ecological interests both within and beyond its watershed. It supports an assemblage of endangered, non-listed native and non-native fish species which varies in composition along its longitudinal gradient. Hydrology of the Dolores River is heavily regulated by McPhee Dam although inputs from the San Miguel River provide a relatively dynamic hydrograph in the Dolores River near and downstream of the Colorado/Utah state line. In 2013, a passive interrogation array was installed in the Dolores River about 13 km above its confluence with the Colorado River to monitor use of the tributary by PIT-tagged non-listed native and endangered fishes. As of October 2017, the facility has detected 1,013 individual PIT-tagged fish consisting of 658 Bonytail Gila elegans, 134 Bluehead Sucker Catostomus discobolus, 74 Flannelmouth Sucker Catostomus latippinis, 30 Razorback Sucker Xyrauchen texanus, 26 Colorado Pikeminnow Ptycocheilus lucius, 16 Roundtail Chub Gila robusta and 8 Flannelmouth/Razorback Sucker hybrids. An additional 67 unidentified fish were also detected. Colorado Pikeminnow were detected in the Dolores River primarily during the months of June through September, whereas Razorback Sucker tended to appear in the river during the months of March through May. Except for anecdotal observations, detections of Colorado Pikeminnow during 2015-2017 represent the first substantiated evidence of this species occurring in the Dolores River since 1991. Colorado Pikeminnow and Razorback Sucker capture histories prior to recent detections are complex and geographically extensive. Bonytail detections appeared to be most frequent immediately following stocking events in the Dolores River, however there were a few examples of individual fish detected in the tributary up to three years after stocking. Flow targets intended to maintain and enhance geomorphology of the Dolores River channel went into effect in 2012, but response of the fish community to these flows is very difficult to discern based on available information.

ABSTRACT. This study compares macroinvertebrate communities before and after a sustained high flow event in the Owens River Gorge (ORG). Since the construction of the Long Valley dam in the 1940s, the ORG has experienced dramatically reduced flows, averaging about 0 cfs from 1953 to 1991, and less than 40 cfs annually from 1991 to 2018. From July 2018 to September 2018 the lower six miles of river experienced a moderately high flow of 400 cfs. Replicated samples were collected during spring and summer of 2018 using a Surber sampler at six locations (two above the reach subject to high flows and four within the reach). We detected a significant decline in invertebrate abundance (p<0.05) and species richness between the pre- and post- high-flow invertebrate communities within the lower reach, with varying levels of decline among common taxa. While we observed an initial decline in invertebrate communities immediately following the pulse flow, we believe scouring effects will likely provide increased interstitial habitat for future invertebrate populations. Monitoring the invertebrate communities in ORG will continue throughout the next few years. Ultimately, we hope to see managed high flows imitate a more natural flow regime than the ORG has seen in the past few decades. Monitoring invertebrate and fish communities’ response throughout this process will be crucial for informing the success of varying flow regimes.

ABSTRACT. The Devils River is a groundwater-dominated, semi-arid river in southwest Texas and is considered one of the most pristine rivers in the state. It is one of the last strongholds for multiple species of regionally endemic freshwater fauna including the federally-listed Devils River Minnow and Texas Hornshell. However, the potential for large-scale groundwater pumping in the watershed and prolonged droughts pose threats to groundwater availability and the springflows that sustain river baseflows. Development of a comprehensive basin-wide fish and mussel conservation plan including instream flow recommendations is ideal due to the relatively small size of the watershed. However, challenges include the isolated location of the river and the low proportion of publicly held lands for implementing on-the-ground conservation measures. To best determine science needs, focus resources, and increase informed stewardship of the river, Texas Parks and Wildlife Department has partnered with governmental agencies, universities, non-profit organizations, and landowners interested in preserving this unique resource. Through collaborative research aimed at a better understanding of groundwater-surface water interactions and instream flow needs of endemic species, and by building cooperative partnerships, steps are underway to preserve the aesthetic, ecological, and recreational values of the Devils River.

ABSTRACT. The endangered Devils Hole Pupfish, Cyprinodon diabolis, whose wild population is limited to a single geothermal pool in the Mojave Desert, has been the subject of conservation and management for more than 50 years. Historically, the establishment of quasi-natural, outdoor refuge populations met only marginal and temporary successes, and ultimately failed due to various logistical and biological reasons. Further, despite decades of attempts, traditional propagation via aquaria has never been fully successful. Here, we report the status of the captive population at the Ash Meadows Fish Conservation Facility (AMFCF), a state-of-the-art aquaculture facility that combines aquaria propagation with a simulated natural refuge habitat. Utilizing eggs collected from Devils Hole, we achieved a greater than 80% larval survival to adulthood. At appropriate size, juveniles and young adults are stocked into a 100,000 gallon refuge tank designed to simulate the challenging conditions of Devils Hole. All life stages, including eggs, larvae, and multiple generations of adults occur in the tank. Although the captive population has produced successive generations, the explosive population growth that was hoped for has not yet been realized, and challenges to successful breeding in aquaria remain. In one example, control of predacious diving beetles in the refuge tank has increased egg recovery significantly. Recovered eggs proved more difficult to rear in laboratory conditions compared to wild-collected eggs, due in part to rapid colonization of eggs and aquaria by microbes, resulting in egg and larval death. New rearing methods were subsequently developed and have been successful in controlling deleterious microbes, resulting in a laboratory population from captive-spawned eggs which will be utilized in captive-breeding trials.

ABSTRACT. Unforeseen interactions of dams and declining water availability have formed new obstacles to recovering endemic and endangered big‐river fishes. During a recent trend of drying climate and declining reservoir water levels in the Southwestern United States, a large waterfall has formed on two separate occasions (1989–1995 and 2001–present) in the transition zone between the San Juan River and Lake Powell reservoir because of deposited sediments. Since recovery plans for two large‐bodied endangered fish species, Razorback Sucker (Xyrauchen texanus) and Colorado Pikeminnow (Ptychocheilus lucius), include annual stockings in the San Juan River, this waterfall potentially blocks upstream movement of individuals that moved downstream from the river into the reservoir. To quantify the temporal variation in abundance of endangered fishes aggregating downstream of the waterfall and determine population demographics, we remotely monitored and sampled in spring 2015, 2016, and 2017 when these fish were thought to move upstream to spawn. Additionally, we used an open population model applied to tagged fish detected in 2017 to estimate population sizes. Colorado Pikeminnow were so infrequently encountered (<30 individuals) that population estimates were not performed. Razorback Sucker captures from sampling (335), and detections from remote monitoring (943) showed high abundance across all 3 years. The Razorback Sucker population estimate for 2017 alone was 755 individuals and, relative to recent population estimates ranging from ~2,000 to ~4,000 individuals, suggests that a substantial population exists seasonally downstream of this barrier. Barriers to fish movement in rivers above reservoirs are not unique; thus, the formation of this waterfall exemplifies how water development and hydrology can interact to cause unforeseen changes to a riverscape.

ABSTRACT. Least Chub, Iotichthys phlegethontis, is endemic to the Bonneville Basin of Utah with only six isolated extant populations. One of these populations occurs at Gandy Marsh which is a complex of approximately 50 springheads located in the Snake Valley of Utah. Gandy Marsh provides habitat for least chub as well as Utah Chub, Gila atraria, Speckled Dace, Rhinichthys osculus, Columbia Spotted Frog, Rana lueteventris, and Northern Leopard Frog, Rana pipiens. Portions of this spring complex have been protected as a Bureau of Land Management Area of Critical Environmental Concern since 1992. Two livestock grazing exclosures (12 and 50 acres), which encompass 25 springheads, were built in the early 1990’s to protect the unique ecosystem and habitat of Gandy Marsh. The discharge of these springheads varies seasonally. Open water is primarily restricted to springheads in the summer. In the spring and fall water flows through springbrooks to seasonally flooded basins. Occupancy surveys for Least Chub at the springheads have been conducted every 1 to 3 years in August since the early 1990’s. Declines in least chub occupancy at springheads within the exclosures were documented beginning in 2010, while occupancy at springheads outside the exclosures remained unchanged. This decline was attributed to a buildup of decadent vegetation within the exclosures which clogged the channels, limited open water, and prevented least chub from leaving or returning to the springheads during high water periods. We believed that Least Chub needed to leave the springheads to reach the seasonally flooded basins to spawn and then return to the springheads to overwinter and oversummer. With the buildup of vegetation, the channels were too clogged for Least Chub to complete this portion of their life cycle which led to a loss of Least Chub inside springheads in the exclosures. A prescribed burn was conducted inside both exclosures in October 2017 with the goal of removing vegetation and increasing open water habitat to allow Least Chub to return to the springheads in the exclosures. In monitoring from 2010 to 2016, Least Chub were only found in one exclosure in one year. During monitoring in August 2018, Least Chub were documented in five springheads inside the exclosures. This increase in occupancy indicates that prescribed fire can be an effective tool to remove vegetation, maintain open water, and allow Least Chub to naturally recolonize springheads. We will continue to monitor Least Chub occupancy and vegetation response to determine frequency of future burns or other management efforts needed to help maintain this population.

ABSTRACT. Colorado Pikeminnow, Ptychocheilus lucius, is a long-lived, potamodromous fish that exhibit spawning site fidelity. Following decades of research in the Green River sub-basin, two primary spawning sites have been identified, one in Yampa Canyon(Yampa River) and the other in Gray Canyon (Green River). In July 2018, a suspected spawning aggregation of Colorado Pikeminnow was encountered during non-native fish removal electrofishing in Dinosaur National Monument near the Chew Bridge (river km 508) downstream of Split Mountain Canyon. In response, a remote submersible PIT antenna (Biomark, Inc., Boise, ID) was promptly deployed at this location from 10–30 July 2018. During this time, 50 unique PIT tags were detected, 42 of which were implanted into Colorado Pikeminnow; three were implanted into Razorback Suckers, Xyrauchen texanus, and five remaining tags have not yet been reconciled with an existing record of implantation. Remote submersible PIT antennas may be a valuable tool for investigating life history traits of endangered fishes in place of more intrusive sampling techniques, such as netting and electrofishing, that potentially disrupt spawning behaviors. Future monitoring of this site with submersible PIT antennas should continue in subsequent years and additional research should be conducted to determine when passive detection of PIT tags can be positively attributed to spawning activity.

ABSTRACT. The placid waters of the canyon-bound and alluvial reaches of both the Colorado and Green Rivers immediately upstream of their confluence form a large proportion of the remnant nursery habitat critical to the survival of the endangered Colorado Pikeminnow. This big river fish, endemic to the Colorado River Basin, uses 120 miles of the lower Green River and 110 miles Colorado River for rearing and recruitment of early life stages. The low-velocity habitats selected by these fish exhibit a low level of stability through time. Discharge has a large impact on quality and abundance of low-velocity habitats. Spring runoff frequently inundates these habitats, whereas extreme low water has the tendency to drain habitats or isolate them from the main channel. Monsoonal activity with consequent flow spikes will inundate habitats with fine sediments reducing their value. Complementing natural stochastic events are a suite of anthropogenic influences. Over the past 130 years, human activity has added multiple factors influencing critical rearing habitat. These include water development, establishment of exotic invasive plant and fish species and global climate change.

ABSTRACT. Invasive species can devastate native species and a main threat to endemic biodiversity is hybridization with introduced species. Cyprinodon variegatus is an invasive species that has impacted several other Cyprinodon species through rapid hybridization and genetic introgression. Cyprinodon rubrofluviatilis is native to the Brazos, Wichita and Red Rivers but collections between 2006-2012 showed intermediate morphological traits suggesting hybridization had occurred in the Brazos River. We investigated if C. variegatus was present and hybridizing in the Brazos River and identify the extent of introgression between the two species. We used molecular and morphological approaches to analyze specimens collected between 2013-2017 from the Brazos, Wichita, and Red Rivers and the Gulf of Mexico. In 2014-2015, low levels of introgression were evident, but hybridization was not widespread in the Brazos. In more recent sampling (2016-2017), genetic structure differed from previous years and there were no longer signs genetic signs of hybridization. Morphological analysis showed clear differences between species with little evidence of intermediate phenotypes. Although hybridization between C. variegatus and C. rubrofluviatilis is not currently widespread, there has been a complex pattern of hybridization in the past and it remains a threat to native Cyprinodon in this region.