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USGS2013

Landscape-level estimation of nitrogen removal in coastal Louisiana wetlands: potential sinks under different restoration scenarios

Coastal eutrophication in the northern Gulf of Mexico (GOM) is the primary anthropogenic contributor to the largest zone of hypoxic bottom waters in North America. Although biologically mediated processes such as denitrification (Dn) are known to act as sinks for inorganic nitrogen, it is unknown what contribution denitrification makes to landscape-scale nitrogen budgets along the coast. As the State of Louisiana plans the implementation of a 2012 Coastal Master Plan (MP) to help restore its wetlands and protect its coast, it is critical to understand what effect potential restoration projects may have in altering nutrient budgets. As part of the MP, a spatial statistical approach was developed to estimate nitrogen removal under varying scenarios of future conditions and coastal restoration project implementation. In every scenario of future conditions under which MP implementation was modeled, more nitrogen ( ) was removed from coastal waters when compared with conditions under which no action is taken. Overall, the MP increased coast-wide average nitrogen removal capacity (NRC) rates by up to 0.55 g N m −2 y −1 compared with the “future without action” (FWOA) scenario, resulting in a conservative estimate of up to 25% removal of the annual + load of the Mississippi-Atchafalaya rivers (956,480 t y −1 ). These results are spatially correlated, with the lower Mississippi River and Chenier Plain exhibiting the greatest change in NRC. Since the implementation of the MP can maintain, and in some regions increase the NRC, our results show the need to preserve the functionality of wetland habitats and use this ecosystem service ( i.e . Dn) to decrease eutrophication of the GOM.

Louisiana↗

USGS2014

Spatial distribution of loggerhead turtle ( Caretta caretta ) emergences along a highly dynamic beach in the northern Gulf of Mexico

As coastlines change due to sea level rise and an increasing human presence, understanding how species, such as marine turtles, respond to alterations in habitat is necessary for proper management and conservation. Survey data from a major nesting beach in the northern Gulf of Mexico, where a revetment was installed, was used to assess spatial distribution of loggerhead emergences. Through use of Quadrat analysis and piecewise linear regression with breakpoint, we present evidence to suggest that nest site selection in loggerheads is determined in the nearshore environment, and by characteristics such as wave height, alongshore currents, depth and patterns of erosion and accretion. Areas of relatively dense nesting were found in areas with relatively strong alongshore currents, relatively small waves, a steep offshore slope and the largest historical rates of erosion. Areas of relatively dense nesting also corresponded to areas of low nesting success. Both nesting and non-nesting emergences were clustered immediately adjacent to the revetment and at other eroding sites along the beach. These results suggest that alterations to the nearshore environment from activities such as construction of a jetty, dredging or installation of pilings, may impact sea turtle nest distribution alongshore. We also show that piecewise linear regression with breakpoint is a technique that can be used with geomorphological and oceanographic data to predict locations of nest clumping and may be useful for managers at other nesting beaches.

Florida↗

USGS2025

Laying sequence and oceanographic factors affect egg size in Scripps's Murrelets Synthliboramphus scrippsi at Santa Barbara Island

Egg size is an important avian life history parameter, with larger eggs indicating greater investment of resources in the chick. Prey availability can affect such investment. We investigated the effects of oceanographic conditions and laying sequence on Scripps's Murrelet Synthliboramphus scrippsi egg size at Santa Barbara Island, California during 2009-2017. We evaluated oceanographic covariates characterizing marine productivity for their effect on egg size, including large-scale oceanographic indices such as the Pacific Decadal Oscillation (PDO) index, Oceanic Niño Index (ONI), and North Pacific Gyre Oscillation (NPGO) index. We also evaluated a larval anchovy catch-per-unit-effort (ANCHL) index and the Biologically Effective Upwelling Transport Index (BEUTI) as region-wide indices, and sea surface temperature (SST) as a local index. We evaluated oceanographic conditions over the entire year and during the breeding season only. We also considered the contribution of lagged effects to oceanographic conditions. Our results generally ran counter to our hypothesis that increased ocean productivity should increase egg size. Based on Akaike's Information Criterion, the four top-ranked models provided support for an association between larger eggs and conditions indicative of lower oceanographic productivity, including lower values of BEUTI and NPGO, and higher values of ONI, PDO, and SST. The only result that supported our hypothesis was a positive relationship between ANCHL and egg size, although the 95% confidence interval for the effect included 0. The strongest relationship detected was between laying sequence and egg size, as second eggs were considerably larger than first eggs. Our results indicate substantial complexity in the relationship between ocean productivity and seabird demography. A better understanding of how ocean productivity affects seabird breeding outcomes through multiple mechanisms will help improve predictions of how seabirds will respond to changing ocean conditions.

California↗

USGS2024

Sampling for disease surveillance: Assessing effects on blue-winged teal survival and recovery

Outbreaks of highly pathogenic avian influenza virus in wild animals highlight the need for disease surveillance in wild birds to improve our understanding of their role as reservoirs and dispersers, and potential threats to domestic poultry and wild bird populations. Surveillance for avian influenza varies in its approach, objectives, and coordination with other monitoring efforts. For waterfowl, a common host to avian influenza viruses, banding represents a concerted effort of capturing and marking thousands of individuals annually to estimate survival and harvest rates, but users of these data have generally taken a conservative approach to remove any banded birds from analyses that had a sample taken for disease surveillance during capture. We tested for differences in survival and encounter probabilities of blue-winged teal ( Spatula discors ) marked ( n = 21,702 teal) and sampled for disease surveillance ( n = 4,216) during the nonbreeding season in Louisiana, USA, from 2016 to 2023. Although we found no consistent effect of collecting biological samples on survival probability, including an additional test showing no detectable effects of sampling for disease surveillance with oropharyngeal and cloacal swabs versus sampling with swabs and a syringe-drawn blood sample, wide 95% credible intervals on the posterior survival estimates (mean 0.36 difference between upper and lower values across all year-sex-sampling groups; 0.44 for sampling type groups) indicated low statistical power to detect an effect. Seber recovery probability during the first interval following sampling was lower among birds sampled using swabs only, but we assume this stems from low sample sizes rather than an effect of collecting biological samples. Because recovery probabilities can vary as a function of individual covariates, we also examined direct recovery probabilities and observed no meaningful effect of disease surveillance sampling type but strong effects of capture date, suggesting the effect on Seber recovery probability may have been due to heterogeneity in exposure to natural and harvest mortality risks. Although we suggest that aligning disease surveillance sample collection efforts with landscape-scale waterfowl banding efforts may have little effect on observed demographic rates, additional studies with larger sample sizes are likely needed to provide the statistical power necessary to formally conclude no effect of biological sampling on survival probabilities.

Louisiana↗

USGS2019

The expectations and challenges of wildlife disease research in the era of genomics: Forecasting with a horizon scan-like exercise

The outbreak and transmission of disease-causing pathogens are contributing to the unprecedented rate of biodiversity decline. Recent advances in genomics have coalesced into powerful tools to monitor, detect, and reconstruct the role of pathogens impacting wildlife populations. Wildlife researchers are thus uniquely positioned to merge ecological and evolutionary studies with genomic technologies to exploit unprecedented ‘Big Data’ tools in disease research; however, many researchers lack the training and expertise required to use these computationally intensive methodologies. To address this disparity, the inaugural ‘Genomics of Disease in Wildlife’ workshop assembled early to mid-career professionals with expertise across scientific disciplines (e.g., genomics, wildlife biology, veterinary sciences, and conservation management) for training in the application of genomic tools to wildlife disease research. A horizon scanning-like exercise, an activity to identify forthcoming trends and challenges, performed by the workshop participants identified and discussed five themes considered to be the most pressing to the application of genomics in wildlife disease research: i) “Improving Communication”, ii) “Methodological and Analytical Advancements”, iii) “Translation into Practice”, iv) “Integrating Landscape Ecology and Genomics”, and v) “Emerging New Questions”. Wide-ranging solutions from the horizon scan were international in scope, itemized both deficiencies and strengths in wildlife genomic initiatives, promoted the use of genomic technologies to unite wildlife and human disease research, and advocated best practices for optimal use of genomic tools in wildlife disease projects. The results offer a glimpse of the potential revolution in human and wildlife disease research possible through multi-disciplinary collaborations at local, regional, and global scales.

Journal of Heredity↗

USGS2010

Structured decision-making and rapid prototyping to plan a management response to an invasive species

We developed components of a decision structure that could be used in an adaptive management framework for responding to invasion of hemlock woolly adelgid Adeleges tsugae on the Cumberland Plateau of northern Tennessee. Hemlock woolly adelgid, an invasive forest pest, was first detected in this area in 2007. We used a structured decision-making process to identify and refine the management problem, objectives, and alternative management actions, and to assess consequences and tradeoffs among selected management alternatives. We identified four fundamental objectives: 1) conserve the aquatic and terrestrial riparian conservation targets, 2) protect and preserve hemlock, 3) develop and maintain adequate budget, and 4) address public concerns. We designed two prototype responses using an iterative process. By rapidly prototyping a first solution, insights were gained and shortcomings were identified, and some of these shortcomings were incorporated and corrected in the second prototype. We found that objectives were best met when management focused on early treatment of lightly to moderately infested but relatively healthy hemlock stands with biological control agent predator beetles and insect-killing fungi. Also, depending on the cost constraint, early treatment should be coupled with silvicultural management of moderately to severely infested and declining hemlock stands to accelerate conversion to nonhemlock mature forest cover. The two most valuable contributions of the structured decision-making process were 1) clarification and expansion of our objectives, and 2) application of tools to assess tradeoffs and predict consequences of alternative actions. Predicting consequences allowed us to evaluate the influence of uncertainty on the decision. For example, we found that the expected number of mature forest stands over 30 y would be increased by 4% by resolving the uncertainty regarding predator beetle effectiveness. The adaptive management framework requires further development including identifying and evaluating uncertainty, formalizing other competing predictive models, designing a monitoring program to update the predictive models, developing a process for re-evaluating the predictive models and incorporating new management technologies, and generating support for planning and implementation.

Journal of Fish and Wildlife Management↗

USGS2020

Resolving species boundaries in the critically imperiled freshwater mussel species, Fusconaia mitchelli (Bivalvia: Unionidae)

Species are a fundamental unit of biology, and defining accurate species boundaries is integral to effective conservation and management of imperiled taxa. Freshwater mussels (Bivalvia: Unionidae) are among the most imperiled groups of organisms in North America, yet species boundaries remain uncertain for many taxa. The False Spike, Fusconaia mitchelli (Simpson in Dall, 1895), is a freshwater mussel considered to be endemic to central Texas (Brazos, Colorado, and Guadalupe drainages). Recent research revealed significant intraspecific genetic variation between geographically separated populations of F . mitchelli , which could be indicative of speciation; however, small sample sizes for several of the populations precluded formal taxonomic revision. Here, we increase taxon sampling and use multilocus DNA sequence data and traditional morphometrics to re‐evaluate species boundaries in F . mitchelli . We sequenced three loci: the protein‐coding mitochondrial DNA genes cytochrome c oxidase subunit 1 and NADH dehydrogenase 1 , and the nuclear internal transcribed spacer 1 . Phylogenetic analyses depicted deep genetic divergence between F . mitchelli in the Guadalupe and those in the Brazos and Colorado drainages, which was further supported by available biogeographic information. Morphometric analyses and coalescent‐based species delimitation models integrating both DNA sequence and morphological data provided strong support for the divergence observed between the two geographically isolated clades of F . mitchelli . Based on these results, we revise taxonomy accordingly by elevating the junior synonym Fusconaia iheringi (Wright, 1898) to represent the Brazos and Colorado populations and restrict the distribution of F . mitchelli to the Guadalupe River drainage. Our findings may impact pending management decisions to protect F . mitchelli under the U.S. Endangered Species Act.

Journal of Zoological Systematics and Evolutionary↗

USGS2018

Cumulative spring discharge and survey effort influence occupancy and detection of a threatened freshwater mussel, the Suwannee Moccasinshell

Freshwater mussels (Unionidae) are among the most imperiled groups of organisms in the world, and the lack of information regarding species distributions, life-history characteristics, and ecological and biological requirements may limit the protection of remaining mussel populations. We examined the influence of hydrologic factors on the occurrence of the Suwannee Moccasinshell Medionidus walkeri, a federally threatened freshwater mussel species, endemic to the Suwannee River Basin in Georgia and Florida. We also evaluated the influence of survey effort on detection of Suwannee Moccasinshell during field surveys. We compiled all recent (2013–2016) mussel survey records in the Suwannee River Basin. We calculated cumulative discharge contributed by upstream springs for each of 220 survey locations. We combined the spring discharge predictor variable with Suwannee Moccasinshell detection and nondetection data from each survey location to develop a suite of occupancy models. Modeling results indicated that detection of Suwannee Moccasinshell during surveys was strongly and positively related to survey effort. Modeling results also indicated that sites with cumulative spring discharge inputs exceeding ∼28 cubic meters per second were most likely (i.e., predicted occupancy probabilities >0.5) to support Suwannee Moccasinshell populations. However, occupancy declined in the lowermost reaches of the Suwannee mainstem despite high spring discharge inputs, presumably due to greater tidal influences and differences in physicochemical habitat conditions. Historical localities where Suwannee Moccasinshell has presumably been extirpated are all devoid of springs in their upstream watersheds. We hypothesize that springs may buffer extremely tannic, and at times polluted, surface waters, in addition to maintaining adequate flows during periods of drought, thereby promoting the persistence of Suwannee Moccasinshell populations. Our study suggests that springs are a critical resource for Suwannee Moccasinshell and may be more important for conservation planning than was previously recognized.

Florida↗

USGS2015

Genetic signatures of historical dispersal of fish threatened by biological invasions: the case of galaxiids in South America

Aim The ecological effects of biological invasions are well documented, but little is known about the effects of invaders on the genetic structure of native species. We examined the phylogeography, genetic variation and population structuring of two galaxiid fishes, Aplochiton zebra and A. taeniatus , threatened by non-native salmonids, and whose conservation is complicated by misidentification and limited knowledge of their genetic diversity. Location Chile and the Falkland Islands. Methods We combined microsatellite and mitochondrial DNA (16S rDNA and COI) markers to compare genetic diversity, effective population size and gene flow of Aplochiton spp. populations differentially affected by salmonid presence. Results We identified two 16S rDNA haplotypes among A. zebra – one dominant in coastal populations and another dominant in inland populations. Populations living on the island of Chiloé displayed a mixture of coastal and inland haplotypes, as well as high microsatellite diversity, as one would expect if the island had been a refugium during the Last Glacial Maximum, or a contact zone among populations. Microsatellite data revealed strong population structuring, indicative of current isolation patterns, and a negative correlation between the genetic diversity of A. zebra and the relative abundance of invasive salmonids. Main conclusions Our study indicates that population structuring of A. zebra reflects the influence of historical patterns of migration, but also the current levels of reduced gene flow among watersheds. Invasive salmonids, known to compete with and prey on native galaxiids, may have had negative impacts on the genetic diversity of Aplochiton spp. The low genetic variation found in some populations, coupled with potential biases in abundance estimates due to species misidentification, highlight the urgent need for more research into the conservation status of the two species of Aplochiton .

Journal of Biogeography↗

USGS2010

Assessing allowable take of migratory birds

Legal removal of migratory birds from the wild occurs for several reasons, including subsistence, sport harvest, damage control, and the pet trade. We argue that harvest theory provides the basis for assessing the impact of authorized take, advance a simplified rendering of harvest theory known as potential biological removal as a useful starting point for assessing take, and demonstrate this approach with a case study of depredation control of black vultures (Coragyps atratus) in Virginia, USA. Based on data from the North American Breeding Bird Survey and other sources, we estimated that the black vulture population in Virginia was 91,190 (95% credible interval = 44,520?212,100) in 2006. Using a simple population model and available estimates of life-history parameters, we estimated the intrinsic rate of growth (rmax) to be in the range 7?14%, with 10.6% a plausible point estimate. For a take program to seek an equilibrium population size on the conservative side of the yield curve, the rate of take needs to be less than that which achieves a maximum sustained yield (0.5 x rmax). Based on the point estimate for rmax and using the lower 60% credible interval for population size to account for uncertainty, these conditions would be met if the take of black vultures in Virginia in 2006 was < 3,533 birds. Based on regular monitoring data, allowable harvest should be adjusted annually to reflect changes in population size. To initiate discussion about how this assessment framework could be related to the laws and regulations that govern authorization of such take, we suggest that the Migratory Bird Treaty Act requires only that take of native migratory birds be sustainable in the long-term, that is, sustained harvest rate should be < rmax. Further, the ratio of desired harvest rate to 0.5 x rmax may be a useful metric for ascertaining the applicability of specific requirements of the National Environmental Protection Act.

Journal of Wildlife Management↗

USGS2025

Evidence for size‐based predation risk during Atlantic salmon (Salmo salar) smolt migration.

Hatchery supplementation is frequently employed during the conservation and recovery of imperilled salmon populations. At the smolt stage, hatchery rearing practices often produce individuals that are larger than wild conspecifics. Under this ‘bigger is better’ strategy, it is assumed that larger fish are less susceptible to predation during migration. We tested this hypothesis on hatchery-reared Atlantic salmon ( Salmo salar ) smolts with fork lengths representative of those of natural and hatchery origins, allowing us to isolate the influence of size from rearing history. From May to June 2023 we characterized predation risk for acoustic-tagged ( n = 50) and tethered ( n = 192) smolts of various sizes through a mostly free-flowing section of the Penobscot River, Maine, USA. Across both methods, more than 50% of smolts were predated, with the majority of predation events being attributed to smallmouth bass ( Micropterus dolomieu ). Tethered smolts of all sizes experienced similar predation risk. In the acoustic telemetry component of this study, smaller, wild-sized smolts incurred greater overall mortality relative to standard hatchery sizes (95% vs. 75%), the majority of which occurred within 3 km of the release site. Collectively, these results allude to a strong predation influence imposed by smallmouth bass on smolts in freshwater sections of the Penobscot River and small-bodied migrants may incur greater predation risk, particularly near stocking sites.

Journal of Fish Biology↗

USGS2015

Impact of experimental habitat manipulation on northern bobwhite survival

Habitat management for northern bobwhite ( Colinus virginianus ) should affect vital rates, but direct linkages with survival are not well documented; therefore, we implemented an experiment to evaluate those responses. We conducted our experiment on a reclaimed surface mine, a novel landscape where conditions were considered sub-optimal because of the dominance of non-native vegetation, such as sericea lespedeza ( Lespedeza cuneata ), which has been reported to provide marginal habitat for northern bobwhite and may negatively affect survival. Nonetheless, these areas have great potential for contributing to bobwhite conservation because of the amount of early successional cover they provide. Our study site, a 3,330-ha reclaimed surface mine in western Kentucky, consisted of 2 tracts (Sinclair and Ken, 1,471 ha and 1,853 ha, respectively) that served as replicates with each randomly divided into a treatment (i.e., habitat manipulation through a combination of disking, burning, and herbicide application) and an undisturbed control ( n  = 4 experimental units). Habitat treatments were applied October 2009 to September 2013. We used radio telemetry to monitor northern bobwhite ( n  = 1,198) during summer (1 Apr–30 Sep) and winter (1 Oct–31 Mar), 2009–2013. We used the known-fate model in Program MARK to evaluate treatment effects on seasonal survival rates. We included biological, home-range, landscape, and microhabitat metrics as covariates to help improve model sensitivity and further elucidate experimental impacts. Survival varied annually, ranging from 0.139 (SE = 0.031) to 0.301 (SE = 0.032), and seasonally (summer, 0.148 [SE = 0.015]; winter, 0.281 [SE = 0.022]). We found a treatment effect ( β  = 0.256, 95% CI = 0.057–0.456) with a seasonal interaction ( β   = −0.598, 95% CI = −0.898 to −0.298) with survival being higher in summer (0.179 [SE = 0.022] vs. 0.109 [SE = 0.019]) and lower in winter (0.233 [SE = 0.025] vs. 0.355 [SE = 0.035]) on treatment than control units. Among habitat covariates, litter depth ( β  = −0.387, 95%CI = −0.5809 to −0.1930) was the most influential effect (negative) on survival. Additional experiments across a wider range of habitat conditions may be required to determine management intensity or duration thresholds required to elicit greater changes in survival for northern bobwhite populations.

Kentucky↗

USGS2024

High genetic diversity, low population genetic structure, strong natal philopatry, and longevity revealed in the Black Swift (Cypseloides niger borealis)

Genetic diversity is a critical cornerstone of biodiversity and is a central goal in management and conservation biology. Such diversity has implications for survivability, adaptability, and resiliency of a species. This study aimed to determine levels of genetic diversity and population genetic structure in the Northern Black Swift ( Cypseloides niger borealis ). This species nests across western North America as far north as Canada and south into Mexico, migrating annually to wintering areas in western Brazil. Colonies occur in isolated areas where appropriate nesting habitat is available, and in many cases, colonies are widely separated from each other. Banding data revealed that adults of this long-lived species return to their same breeding colony annually for many years. Additionally, some females exhibit natal philopatry, returning to and successfully raising offspring at the colony where they were hatched. This allowed us to hypothesize that we might expect some amount of genetic structure in the samples we studied. The life history characteristics of this species suggest that breeding colonies might be more genetically differentiated than other migratory birds that tend to have limited population genetic structure across their ranges. We used newly developed species-specific microsatellite primers to examine levels of genetic diversity and connectivity among 6 Black Swift colonies in the western United States. Levels of genetic diversity were generally high (expected heterozygosity ranging from 0.67 to 0.75) and comparable across 3 breeding sites with sufficient sample sizes ( N > 5). Principal coordinates analysis and STRUCTURE analysis showed no real clustering of individuals in regard to colonies, suggesting one panmictic metapopulation rather than multiple populations that are genetically distinct as we had previously hypothesized based on banding data. This is the first study to elucidate the genetic structure among colonies of Black Swift.

Colorado, Idaho, New Mexico↗

USGS2024

Melded integrated population models

Integrated population models provide a framework for assimilating multiple datasets to understand population dynamics. Understanding drivers of demography is key to improving wildlife management, and integrated population models have informed conservation practices for many species of conservation concern. Motivated by multiple surveys of lesser prairie-chicken ( Tympanuchus pallidicinctus ), we developed a flexible integrated population modeling framework for assimilating demographic data with multiple surveys of abundance. Measurements of abundance are derived from aerial and ground surveys that vary in their observational uncertainty, sampling design, temporal coverage, and survey effort. Our proposed integrated population model draws from the strengths of each survey and prevents their sampling biases from compromising inference. We facilitate posterior inference for our integrated population model using chained Markov melding, which induces the joint distribution for all data sources by linking inference across several submodels. Using Markov melding, we extend the modeling framework previously proposed for analyzing the individual data sources while still obtaining joint Bayesian inference. We fit the melded model with a multistage Markov chain Monte Carlo algorithm that decreases run time and improves mixing. We assimilate data from several state and federal wildlife agencies and over a dozen independent researchers to infer lesser prairie-chicken abundance and vital rates across its entire range over the last 18 years. Supplementary materials accompanying this paper appear online.

Colorado, Kansas, New Mexico, Oklahoma, Texas↗

USGS2024

Invisible hand of sampling for management: Underlying needs to survey a threatened seabird can bias aggregated data

Aim Surveying for a species of concern ahead of proposed activities that alter its habitat is routine practice in conservation and management. Such surveys may accumulate large datasets that could further elucidate trends in abundance and distribution. However, the as-needed surveying of proposed activities may impart a sample site selection bias on the data if used for another purpose. Management of a threatened, forest-nesting seabird offered an example of this. Here we assessed how resource management planning and survey requirements can bias clearance monitoring survey data collected prior to proposed timber harvests, if those data are used for other purposes. Location Oregon and Washington, USA. Taxon Marbled Murrelet ( Brachyramphus marmoratus ). Methods To assess how timber planning and other factors influenced marbled murrelet survey location selection, we used logistic regression models to examine habitat associations of marbled murrelet survey sites ( n = 9178) encompassing proposed timber harvests, and the survey stations ( n = 38,923) therein, across the murrelet's inland range in Washington and Oregon, USA between 1989 and 2021. We then simulated the effect this selective sampling might have on assessments of occupancy trends. Results Most habitat characteristics considered did influence where surveys were located, with distance to roads often being the strongest predictor of survey location. The strength of selection for each covariate changed over time, such that a habitat characteristic strongly influenced location selection in a year but was less influential in another year. The simulation analysis suggested that the non-random selection of survey sites could profoundly bias assessments of occupancy trends. Conclusions When using these clearance monitoring survey data– or any data–beyond their original purpose, careful consideration should be given to the scope of inference provided and analytical methods used, to ensure that observed trends are the product of biological processes and not biased by sampling artefacts.

Oregon, Washington↗

USGS2024

Silver Chub spawning confirmed in the Maumee River, a tributary of Lake Erie

Objective Biodiversity is declining due to invasive species and other factors that can affect individual species differently. Silver Chub Macrhybopsis storeriana are declining in their native range, and their conservation status in the Great Lakes ranges from secure to possibly extirpated. Lake Erie once supported a large Silver Chub population until it crashed in the 1950s. Additionally, the spawning behavior and reproductive guild of Silver Chub in Lake Erie is unknown. Our objective was to document Silver Chub spawning in the Maumee River, a Lake Erie tributary. Methods Invasive Grass Carp Ctenopharyngodon idella are known to spawn in the Maumee River during high-flow events from May to July, and the University of Toledo and U.S. Geological Survey regularly sample the lower 24 km for early life stages using paired bongo nets. Contents from paired bongo nets are returned to the laboratory for processing, and a subset of potential Grass Carp eggs are sent for genetic analysis. Result On June 8, 2022, several potential Grass Carp eggs were captured at two sites on the Maumee River during a high-flow event. Fifteen potential Grass Carp eggs were sent for genetic analysis, and DNA sequencing revealed that six of these eggs were Silver Chub. Discussion This was the first known collection of Silver Chub eggs in a Lake Erie tributary, and our findings indicate that Silver Chub likely belong to the pelagophil reproductive guild. Although Grass Carp and Silver Chub spawn under similar conditions, management actions to control Grass Carp in the Maumee River may be unlikely to affect Silver Chub due to electrofishing settings used in the capture of Grass Carp. The verification of Silver Chub spawning in a Western Erie Basin tributary provides insights into their reproductive biology that could be useful in recovery planning in Lake Erie and throughout the Great Lakes.

Ohio↗

USGS2011

Decision analysis for conservation breeding: Maximizing production for reintroduction of whooping cranes

Captive breeding is key to management of severely endangered species, but maximizing captive production can be challenging because of poor knowledge of species breeding biology and the complexity of evaluating different management options. In the face of uncertainty and complexity, decision-analytic approaches can be used to identify optimal management options for maximizing captive production. Building decision-analytic models requires iterations of model conception, data analysis, model building and evaluation, identification of remaining uncertainty, further research and monitoring to reduce uncertainty, and integration of new data into the model. We initiated such a process to maximize captive production of the whooping crane ( Grus americana ), the world's most endangered crane, which is managed through captive breeding and reintroduction. We collected 15 years of captive breeding data from 3 institutions and used Bayesian analysis and model selection to identify predictors of whooping crane hatching success. The strongest predictor, and that with clear management relevance, was incubation environment. The incubation period of whooping crane eggs is split across two environments: crane nests and artificial incubators. Although artificial incubators are useful for allowing breeding pairs to produce multiple clutches, our results indicate that crane incubation is most effective at promoting hatching success. Hatching probability increased the longer an egg spent in a crane nest, from 40% hatching probability for eggs receiving 1 day of crane incubation to 95% for those receiving 30 days (time incubated in each environment varied independently of total incubation period). Because birds will lay fewer eggs when they are incubating longer, a tradeoff exists between the number of clutches produced and egg hatching probability. We developed a decision-analytic model that estimated 16 to be the optimal number of days of crane incubation needed to maximize the number of offspring produced. These results show that using decision-analytic tools to account for uncertainty in captive breeding can improve the rate at which such programs contribute to wildlife reintroductions.

Journal of Wildlife Management↗

USGS2024

Smaller body size under warming is not due to gill-oxygen limitation in a coldwater salmonid

Declining body size in fishes and other aquatic ectotherms associated with anthropogenic climate warming has significant implications for future fisheries yields, stock assessments and aquatic ecosystem stability. One proposed mechanism seeking to explain such body-size reductions, known as the gill oxygen limitation (GOL) hypothesis, has recently been used to model future impacts of climate warming on fisheries but has not been robustly empirically tested. We used brook trout ( Salvelinus fontinalis ), a fast-growing, cold-water salmonid species of broad economic, conservation and ecological value, to examine the GOL hypothesis in a long-term experiment quantifying effects of temperature on growth, resting metabolic rate (RMR), maximum metabolic rate (MMR) and gill surface area (GSA). Despite significantly reduced growth and body size at an elevated temperature, allometric slopes of GSA were not significantly different than 1.0 and were above those for RMR and MMR at both temperature treatments (15°C and 20°C), contrary to GOL expectations. We also found that the effect of temperature on RMR was time-dependent, contradicting the prediction that heightened temperatures increase metabolic rates and reinforcing the importance of longer-term exposures (e.g. >6 months) to fully understand the influence of acclimation on temperature–metabolic rate relationships. Our results indicate that although oxygen limitation may be important in some aspects of temperature–body size relationships and constraints on metabolic supply may contribute to reduced growth in some cases, it is unlikely that GOL is a universal mechanism explaining temperature–body size relationships in aquatic ectotherms. We suggest future research focus on alternative mechanisms underlying temperature–body size relationships, and that projections of climate change impacts on fisheries yields using models based on GOL assumptions be interpreted with caution.

Journal of Experimental Biology↗