Geology topics

Dana L. Winkelman

Publications and source records attributed to Dana L. Winkelman.

At least 19 recordsLinked to original sources

USGS2025

Riverscape genetics of nonnative Brook Trout to inform native cutthroat trout conservation

Objective Understanding how riverscape features influence gene flow is critical for managing population connectivity in freshwater species. We examined how landscape and stream characteristics shape the spatial genetic structure of nonnative Brook Trout Salvelinus fontinalis in a headwater stream network proposed for reintroduction of federally threatened Greenback Cutthroat Trout Oncorhynchus virginalis stomias . Brook Trout were studied to evaluate the suitability of this habitat for supporting a native trout metapopulation. Methods We genotyped 757 Brook Trout from 22 sites across a 60-km stream network using 12 microsatellite loci. Spatial genetic structure was assessed using clustering analysis (program STRUCTURE) and pairwise differentiation metrics ( F ST and Jost’s D ). A spatial network modeling approach was used to quantify the effects of riverscape features (e.g., stream gradient, stream order, waterfalls, and flow direction) on trout gene flow. Results Genetic clustering identified four distinct tributary groups, while estimates of pairwise genetic differentiation indicated some genetic connectivity across the network (mean F ST = 0.04; mean Jost’s D = 0.06). Trout gene flow was impeded by waterfalls, steep stream gradients, and increased hydrologic distance. Higher stream order and downstream flow direction were associated with stronger gene flow, and stream segments containing waterfalls and steeper gradients showed greater asymmetries between upstream and downstream gene flow. Conclusions Brook Trout populations in this stream network are spatially structured, but gene flow persists and is mediated by physical riverscape features and hydrologic distance. The observed patterns of genetic connectivity suggest that this habitat can support connectivity among populations of reintroduced Greenback Cutthroat Trout. In future native trout reintroduction efforts, prioritizing habitats with gradual stream gradients and fewer waterfalls would promote population connectivity.

Transactions of the American Fisheries Society↗

USGS2025

Hatchery rearing density affects poststocking survival

Objective Research has indicated that salmonids raised in a hatchery and stocked into the wild have lower future survival and reproductive success than wild fish. Understanding whether hatchery rearing practices affect populations after stocking can help to maximize the quality, quantity, and economic value of fish stocked for conservation and recreational purposes. The goal of our study was to test whether and to what extent rearing density affects poststocking survival of Rainbow Trout Oncorhynchus mykiss when stocked into a put-grow-and-take fishery. Methods Rainbow Trout were raised for 3 months in the hatchery at two densities (high = 51,948–13,072 fish/m 3 , rearing index 2.0, 1,260 metric units; low = 12,987–3,268 fish/m 3 , rearing index 0.5, 315 metric units). A subset of the fish were PIT-tagged and stocked into Parvin Lake, Red Feather Lakes, Colorado. Recaptures of tagged fish occurred every 2 weeks for the first 2 months poststocking and at 7 and 12 months poststocking. Results At the time of stocking, there were no statistical differences in Fulton’s condition factor, total length, weight, or hepatosomatic index for each treatment. Recapture data indicated that there was no difference in Fulton’s condition factor and hepatosomatic index after stocking. Apparent poststocking survival was higher for fish raised at low density in the hatchery compared with those raised at high density. Conclusions Our study suggests that rearing density affects fingerling Rainbow Trout poststocking survival. Stocking more fish due to fish being reared at higher densities within the hatchery did not result in more total fish remaining after a year in the lake compared with the low-density treatment. Rearing fish at high densities does not provide a benefit of more fish after stocking and may result in more disease risk in the hatchery.

Colorado↗

USGS2025

Non-lethal detection of Renibacterium salmoninarum in Greenback Cutthroat Trout Oncorhynchus clarkii stomias comparing mucus, blood, and ovarian fluid samples to kidney tissues

Objective Renibacterium salmoninarum , the causative agent of bacterial kidney disease, poses a major threat to both wild and aquaculture salmonid populations. Traditional detection methods typically involve lethal sampling to collect kidney tissues but are often impractical for species of conservation concern. This study evaluates nonlethal sampling techniques for detecting R. salmoninarum in Greenback Cutthroat Trout Oncorhynchus clarkii stomias by comparing mucus, blood, and ovarian fluid samples to conventional kidney tissue. Methods During the 2019 spawning season, we collected samples from 781 adult fish and tested for R. salmoninarum via direct fluorescent antibody test (DFAT) and quantitative polymerase chain reaction (qPCR). Results A total of 25 and 256 kidney tissues were positive by DFAT and qPCR, respectively. Of the three nonlethal samples tested, mucus swabs showed the highest percent correlation for detection with positive kidney tissues (DFAT = 47.6%, qPCR = 41.7%). Blood and ovarian fluid samples showed a lower percent correlation with positive kidney tissues (blood: DFAT = 12.0%, qPCR = 1.2%; ovarian fluid: DFAT = 12.5%, qPCR = 21.4%). Conclusions Our results suggest that nonlethal mucus swabbing could serve as a practical alternative for monitoring R. salmoninarum, especially in conservation efforts where minimizing fish mortality is critical.

Colorado↗

USGS2025

Sinoatrial contracaeciasis in Johnny Darters ( Etheostoma nigrum ) and Plains Topminnow ( Fundulus sciadicus ) from the South Platte drainage, Colorado

Intra-sinoatrial nematodes were incidentally recognized in wild-caught Colorado Johnny Darters ( Etheostoma nigrum , JD) in 2020–2021 and in Colorado Plains Topminnow ( Fundulus sciadicus , PTM) in 2023-2024. PTM and JD were evaluated histologically. Nematodes dissected from PTM were used for morphologic evaluation and molecular identification. The first and second internal transcribed spacers (ITS1 and ITS2) of ribosomal DNA were sequenced. Sinoatrial nematodes were found in two of 1232 JD (0.2%) and nine of 110 PTM (8.2%). Worms caused dilation or aneurysm of the sinus venosus. One JD had severe sinus venosus phlebitis. Morphologic, histologic and molecular features were diagnostic for Contracaecum spp. This is the first identification of larval Contracaecum in PTM, the first record of an intravascular nematode in this species, and the first documentation of vascular localization of Contracaecum larvae in JD. Vascular pathology could result in increased susceptibility to predation and favour the completion of the nematode life cycle. Parasites could become detrimental to population survival, especially those that are stressed by ecological and anthropogenic factors.

Colorado↗

USGS2025

Histological progression and bacterial load dynamics of Renibacterium salmoninarum in Chinook salmon Oncorhynchus tshawytscha

Renibacterium salmoninarum , the cause of bacterial kidney disease (BKD), severely impacts salmonid populations. Much of our understanding of the BKD pathology in salmonids comes from evaluating fatal infections in wild populations or spawning Pacific Northwest salmonids. Our study investigated the histological progression and bacterial load dynamics of R. salmoninarum infection in Chinook salmon following intraperitoneal injection to enhance understanding of the disease’s dynamics. Seventy presmolt salmon were injected with the ATCC-33209 isolate of R. salmoninarum and monitored over 10 wk. Histological signs of disease were observed in spleen and liver tissues at 1 wk post-injection and in kidney tissues at 4 wk post-injection, with signs of disease increasing over time. Additionally, histopathological analysis revealed splenic and hepatic capsulitis (coelomitis), individual hepatocyte necrosis, progressive granulomatous hepatitis, splenitis, and nephritis with necrosis. Gram staining confirmed the presence of Gram-positive bacteria within macrophages and extracellularly in infected tissues. Quantitative PCR revealed significant increases in bacterial loads in both kidney and liver tissues over the study period, with higher bacterial loads observed in the kidney tissue. Bacterial load was strongly correlated with disease stage, with peak bacterial burdens coinciding with the most severe histological changes. Our study provides a comprehensive account of R. salmoninarum infection and disease progression in Chinook salmon after intraperitoneal injection.

Diseases of Aquatic Organisms↗

USGS2025

Leveraging detection uncertainty to estimate Renibacterium salmoninarum infection status among multiple tissues and assays

Effective disease surveillance relies on accurate pathogen testing and robust prevalence estimates. Diagnostic specificity (DSp), the probability that an uninfected animal tests negative, is high when false positives are low. Diagnostic sensitivity (DSe) is the probability an infected animal tests positive; higher DSe means fewer false negatives. However, sensitivity and false negatives are harder to estimate without a "gold standard", an assay that can detect between 90 - 100% of true positive infections. Occupancy estimation of infection prevalence offers one solution by allowing for imperfect detection of the pathogen. Testing potentially infected tissues multiple times allows for the use of a Bayesian multistate occupancy model to estimate the probability of pathogen infection in tissues [Formula: see text] and detection probabilities [Formula: see text] for different assays. Using [Formula: see text] and [Formula: see text] from the posterior distribution, the conditional probability of detecting the pathogen can be modeled, allowing for the calculation of DSe. Renibacterium salmoninarum is a bacterial pathogen causing bacterial kidney disease among salmonid species and was the model pathogen we used to train our model. The current testing standard for salmonids combines initial screening for antibodies using direct fluorescent antibody test (DFAT) with polymerase chain reaction (PCR) confirmation to detect R. salmoninarum. However, detection of R. salmoninarum still varies between species, tissues, and assays. Here, a multi-state occupancy model was used to estimate detection probability among individual and dual kidney/liver infections with DFAT and qPCR in fish with an unknown infection status. Both assays produced false negatives, but qPCR had fewer than DFAT and a higher DSe. Infection state was often misclassified, but multiple surveys per individual or combining tissues for testing improved DSe for both assays.

conterminous United States↗

USGS2025

Genetics of wild, whirling disease resistant rainbow trout populations in Colorado

Introduction: Myxobolus cerebralis , the parasite responsible for salmonid whirling disease, was unintentionally introduced to and became established in Colorado in the 1990s. Mortality of young-of-year fish due to infection by M. cerebralis resulted in recruitment failure and subsequent significant declines in Rainbow Trout ( Oncorhynchus mykiss ) populations. The complex multistage lifecycle of M. cerebralis makes it difficult to eradicate and manage, and hatchery control strategies do not work in the wild. A viable method that has been utilized for wild populations is enhancing host resistance. Myxobolus cerebralis resistant Rainbow Trout were discovered at a hatchery in Germany and subsequently incorporated into Colorado's brood stock program. Since 2004, M. cerebralis resistant strains have been stocked into all major Colorado coldwater drainages to re-establish Rainbow Trout populations after whirling disease-related declines, with documented survival and reproduction of stocked disease resistant fish. Methods and results: Genetic population assignment tests (via putatively neutral microsatellite markers) were used to monitor the stocked populations and indicated that, after only a few years, many of the individuals in these populations unexpectedly assigned to genetic strains that were historically susceptible to M. cerebralis . To further investigate the genetic composition of these fish, a single nucleotide polymorphism (SNP) panel was used to determine the percent genetic composition of resistant strain in these individuals. Microsatellites and SNPs provided similar results, indicating a low percentage of ancestry from the resistant strain in these fish, but they continued to survive exposure to M. cerebralis , suggesting that these individuals possessed genetic loci necessary for resistance. Finally, a quantitative trait locus (QTL) region (termed WDRES-9) was used to identify individuals with alleles associated with disease resistance. Implementation of the WDRES-9 QTL test allowed for more accurate determination of M. cerebralis resistant individuals within wild populations and better described their variability in resistance.

Colorado↗

USGS2024

A genetic assessment of natural barriers for isolating a habitat network proposed for Greenback Cutthroat Trout reintroduction

Objective: Native inland trout conservation efforts rely on physical barriers to exclude nonnative salmonids from target habitats. We used genetic techniques to evaluate a series of natural waterfalls for their potential to serve as barriers to prevent nonnative salmonids from entering a proposed reintroduction area for federally threatened Greenback Cutthroat Trout Oncorhynchus virginalis stomias . Methods: Genetic samples were collected from nonnative Brook Trout Salvelinus fontinalis at 11 sampling reaches above and below natural waterfalls (height: ~1–3 m under base flow conditions) along a 33-km segment of Colorado's upper Cache la Poudre River near the outflow of the proposed reintroduction area. To evaluate whether upstream movement of Brook Trout is restricted by any of these waterfalls, we characterized longitudinal trends in genetic diversity along the river corridor and examined patterns of genetic differentiation and population structure in relation to waterfall locations using a panel of microsatellites. Result: We found no evidence that the waterfalls served as complete movement barriers for nonnative Brook Trout based on genetic clustering analyses, estimates of population differentiation, and longitudinal genetic patterns. Our multilocus assessment did not identify alleles restricted to downstream reaches, and the river segment was genetically homogenized. Conclusion: Our evaluation suggests that the existing waterfalls do not fully prevent upstream movement by nonnative Brook Trout, and thus barrier modification would be needed to establish an isolated Greenback Cutthroat Trout population in the proposed wilderness area.

Colorado↗

USGS2023

Biotic and abiotic factors affecting short-term survival of two age-0 Rainbow Trout strains in Colorado streams

Both biotic and abiotic factors can influence the survival and growth of age-0 salmonids. Diseases, such as whirling disease, can also affect salmonid demographics and population dynamics. Here, we conducted a supplementary analysis and evaluated specific stream characteristics that may have been responsible for the differences in growth and survival of two whirling disease resistant Rainbow Trout Oncorhynchus mykiss strains observed by Avila et al. (2018). We used regression modeling to analyze the influence of the biotic and abiotic characteristics of nine streams on the short-term apparent survival and growth of two Rainbow Trout strains, 5,000 German Rainbow Trout and 5,000 German Rainbow Trout × Colorado River Rainbow Trout in each stream. Akaike's information criterion (AIC c ) model selection was used to identify the factors that most affected short-term survival and growth. Average stream temperature had the largest (positive) effect, β temp = 0.060, on short-term survival. Rainbow Trout strain, average stream temperature (β temp = 1.55), competitor biomass (β competitor biomass = −0.002), and predator number (β predator number = 0.01) additively affected short-term growth. Our results indicate that both biotic and abiotic factors are important short-term determinants of Rainbow Trout poststocking performance and may account for the differences in survival and growth that we observed among stocking locations.

North American Journal of Fisheries Management↗

USGS2023

Temperature and winter duration requirements for reproductive success in johnny darter Etheostoma nigrum in the South Platte River basin, Colorado

Changes in water temperature and its seasonal timing influences the physiological processes of many aquatic ectotherms. Wastewater treatment plants (WWTP) contribute to warmer and more consistent water temperatures in streams draining the North American Great Plains, particularly during winter months. Reduced variation in seasonal water temperature may adversely affect fishes that rely on temperature fluctuation or specific overwintering temperatures for reproductive cues. We used johnny darter Etheostoma nigrum (Family Percidae), a thermally sensitive species native to the South Platte River Basin, as a focal species to assess the effects of winter water temperature regulations in Colorado. Our objective was to evaluate the effects of winter stream temperature and winter duration on reproductive success of johnny darter in the laboratory to inform development of water quality criteria for the South Platte River Basin. Winter duration (60, 90 or 120 days) and temperature (4 or 12°C) were crossed in a factorial design of six treatments that simulated warmed effluent-impacted streams as well as streams with a more natural thermal regime. We defined reproductive success in johnny darter by examining four reproductive endpoints: (1) spawning timing, (2) egg and larvae production, (3) egg success, and (4) egg development. Across the four endpoints, seven main response variables were measured: spawning initiation date, eggs per gram of female per week, live larvae per gram of female per week, fertilisation success, hatching success, egg-to-larva survival and days to hatch. Winter temperature and duration influenced spawning timing and egg development. Earlier spawning initiation dates were observed in fish exposed to 12°C winters and was associated with a higher number of days to hatch. Eggs per gram of female per week, live larvae per gram of female per week, fertilisation success, hatching success, and egg-to-larva survival were similar among winter treatments. Although the State of Colorado chronic winter water temperature standard of 12°C appears to be adequate for egg and larvae production in johnny darter, our results showed that fish exposed to the standard began spawning significantly earlier than fish exposed to 4°C winters. Evaluating reproductive output in the context of seasonal timing is valid because spawning timing has the potential to affect overall production and egg development, and consequently recruitment and population sustainability. Therefore, spawning timing should be considered when making management decisions and revising water temperature standards. The warming of streams and rivers from WWTP effluent is a global issue, especially in areas that are undergoing rapid urbanisation. Fishes are particularly sensitive to water temperature and many fishes worldwide are likely to be experiencing changes in important physiological processes, affecting both reproduction and survival. Our study indicates that reproductive timing could be influenced by stream warming and stresses the need for further studies on the influence of anthropogenic effects on stream warming.

Colorado↗

USGS2023

Impact of wastewater treatment plant effluent on the winter thermal regime of two urban Colorado South Platte tributaries

Wastewater treatment plant effluent can increase stream water temperature from near freezing to 5°C–12°C in winter months. Recent research in the South Platte River Basin in Colorado showed that this warming alters the reproductive timing of some fishes. However, the spatial extent and magnitude of this warming are unknown. Thus, we created winter water temperature models both upstream and downstream of effluent inputs for two urban tributaries of the South Platte River, the Big Thompson River, and St. Vrain Creek. We examined the influence of air temperature, discharge, effluent temperature, and distance downstream on water temperature over the winter period (December–February). The models were also used to predict water temperature in the absence of effluent and based on air temperature predictions in 2052 and 2082. Effluent temperature was the largest driver of water temperature downstream of the effluent, while the impact of air temperature was comparatively small. Streams cooled after an initially sharp temperature increase, though were still predicted to be ∼2°C greater than they would be in the absence of effluent at ∼0.5 km. Predicted air temperatures in 2052 and 2082 had a negligible effect on water temperature, suggesting that mitigating effluent temperature is key to protecting the winter thermal regimes of effluent-impacted rivers. Our models can be used to gain insight into the magnitude and downstream extent of the impact of effluent temperature on small urban streams in winter and provide a baseline for models in other watersheds and at larger scales.

Colorado↗

USGS2023

Vertical transmission of Renibacterium salmoninarum in cutthroat trout (Oncorhynchus clarkii)

Vertical transmission of Renibacterium salmoninarum has been well-documented in anadromous salmonids but not in hatchery-reared inland trout. We assessed whether the bacterium is vertically transmitted in cutthroat trout ( Oncorhynchus clarkii ) from a Colorado, USA hatchery, and assessed the rate of transmission from male and female brood fish. Adult brood fish were killed, tested for R. salmoninarum in kidney, liver, spleen, ovarian fluid, blood and mucus samples , then stripped of gametes to create 32 families with four infection treatments (MNFN, MNFP, MPFN, MPFP; M: male, F: female, P: positive, N: negative). Progeny from each treatment was sampled at 6 and 12 months to test for the presence of R. salmoninarum with an enzyme-linked immunosorbent assay and quantitative polymerase chain reaction. Our study indicated that vertical transmission was high and occurred among 60% of families across all infection treatments. However, the average proportion of infected progeny from individual families was low, ranging from 1% (MNFP, MPFN and MPFP treatments) up to 21% (MPFP treatment). Hatcheries rearing inland salmonids would be well suited to limit vertical transmission through practices such as lethal culling because any amount of transmission can perpetuate the infection throughout fish on a hatchery.

Journal of Fish Diseases↗

USGS2022

Elevated winter stream temperatures below wastewater treatment plants shift reproductive development of female Johnny Darter Etheostoma nigrum: A field and histologic approach

River water temperatures are increasing globally, particularly in urban systems. In winter, wastewater treatment plant (WWTP) effluent inputs are of particular concern because they increase water temperatures from near freezing to ~7–15 °C. Recent laboratory studies suggest that warm overwinter temperatures impact the reproductive timing of some fishes. To evaluate winter water temperature’s influence in the wild, we sampled Johnny Darter Etheostoma nigrum from three urban South Platte River tributaries in Colorado upstream and downstream of WWTP effluent discharge sites. Fish were collected weekly during the spring spawning season of 2021 and reproductive development was determined from histological analysis of the gonads. Winter water temperatures were approximately 5–10 °C greater ~300 m downstream of the WWTP effluent compared to upstream sites, and approximately 3 °C warmer at sampling sites ~5000 m downstream of the effluent discharge. Females collected downstream of WWTP effluent experienced accelerated reproductive development compared to upstream by 1–2 weeks. Water quality, including total estrogenicity, and spring water temperatures did not appear to explain varying reproductive development. It appears that small increases in winter water temperature influence the reproductive timing in E. nigrum . Further investigations into how shifts in reproductive timing influence other population dynamics are warranted.

Colorado↗

USGS2022

Factors affecting post-challenge survival of Flavobacterium psychrophilum in susceptible rainbow trout from the literature

Infectious bacterial pathogens are a concern for aquaculture as estimates suggest that billions of US dollars are lost annually in aquaculture due to disease. One of the most prevalent salmonid pathogens is the bacterium Flavobacterium psychrophilum that causes bacterial coldwater disease. We reviewed the published F. psychrophilum literature and conducted a Bayesian analysis to examine large-scale patterns in rainbow trout ( Oncorhynchus mykiss ) mortality associated with laboratory challenge. We incorporated factors that were common across a majority of the laboratory exposure studies and these included bacterial dose, culture time, exposure method, bacterial isolate, experimental duration, and fish weight. The comparison showed that injection as the exposure method produced higher mortality than bath immersion, bacterial isolates differed in their effect on mortality, and bacterial dose has an interactive effect with fish weight and exposure method. Our comparison allows for inference on factors affecting rainbow trout mortality due to exposure to F. psychrophilum and suggests avenues to further optimize research protocols to better reach study goals.

Pathogens↗

USGS2022

Population genetics reveals bidirectional fish movement across the Continental Divide via an interbasin water transfer

Interbasin water transfers are becoming an increasingly common tool to satisfy municipal and agricultural water demand, but their impacts on movement and gene flow of aquatic organisms are poorly understood. The Grand Ditch is an interbasin water transfer that diverts water from tributaries of the upper Colorado River on the west side of the Continental Divide to the upper Cache la Poudre River on the east side of the Continental Divide. We used single nucleotide polymorphisms to characterize population genetic structure in cutthroat trout ( Oncorhynchus clarkii ) and determine if fish utilize the Grand Ditch as a movement corridor. Samples were collected from two sites on the west side and three sites on the east side of the Continental Divide. We identified two or three genetic clusters, and relative migration rates and spatial distributions of admixed individuals indicated that the Grand Ditch facilitated bidirectional fish movement across the Continental Divide, a major biogeographic barrier. Previous studies have demonstrated ecological impacts of interbasin water transfers, but our study is one of the first to use genetics to understand how interbasin water transfers affect connectivity between previously isolated watersheds. We also discuss implications on native trout management and balancing water demand and biodiversity conservation.

Colorado↗

USGS2022

Dual resistance to Flavobacterium psychrophilum and Myxobolus cerebralis in rainbow trout (Oncorhynchus mykiss, Walbaum)

Aquatic pathogens are a major concern for fish hatchery production, fisheries management, and conservation, and disease control needs to be addressed. Two important salmonid pathogens are Myxobolus cerebralis and Flavobacterium psychrophilum that cause whirling disease and bacterial coldwater disease (BCWD), respectively. Innate disease resistance is a potential option for reducing disease-related mortality in hatchery-reared rainbow trout ( Oncorhynchus mykiss , Walbaum). Two experiments were conducted to assess pathogen resistance of first-generation (F1) rainbow trout created by crossing M. cerebralis - and F. psychrophilum -resistant strains. In the first experiment, we exposed two rainbow trout strains and one F1 cross to six treatments: control (no exposure), mock injection, F. psychrophilum only, M. cerebralis only, F. psychrophilum then M. cerebralis , and M. cerebralis then F. psychrophilum . Results indicated that the F1 cross was not resistant to either pathogen. In the second experiment, we exposed five rainbow trout strains and four rainbow trout crosses to F. psychrophilum . The second experiment indicated that at least one rainbow trout cross was F . psychrophilum -resistant. Achieving dual resistance may be possible using selective breeding but only some multigenerational strains are suitable candidates for further evaluation.

Journal of Fish Diseases↗

USGS2022

Incorporating antenna detections into abundance estimates of fish

Autonomous passive integrated transponder (PIT) tag antennas are commonly used to detect fish marked with PIT tags but cannot detect unmarked fish, creating challenges for abundance estimation. Here we describe an approach to estimate abundance from paired physical capture and antenna detection data in closed and open mark-recapture models. Additionally, for open models, we develop an approach that incorporates uncertainty in fish size, because fish size changes through time (as fish grow bigger) but is unknown if fish are not physically captured (e.g., only detected on antennas). Incorporation of size uncertainty allows for estimation of size-specific abundances and demonstrates a generally useful method for obtaining state-specific abundances estimates under state uncertainty. Simulation studies comparing models with and without antenna detections illustrate that the benefit of our approach increases as a larger proportion of the population is marked. When applied to two field data sets, our approach to incorporating antenna detections reduced uncertainty in abundance substantially. We conclude that PIT antennas hold great potential for improving abundance estimation, despite the challenges they present.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS2022

Effects of 17α-ethinylestradiol and density on juvenile fathead minnow survival and body size

Anthropogenic changes have led to the increased use of wastewater treatment plants in stream systems near urbanized areas. Synthetic oral contraceptives, observed in wastewater treatment effluents, can cause negative effects on fish life history metrics. Previous exposures of 17α-ethinylestradiol (EE2) have been shown to affect survival and reproduction of fathead minnows ( Pimephales promelas ). However, density effects were not considered, and additional research is needed to examine the role of density among fish exposed to EE2. Multiple hypotheses indicate the interaction of density with contaminant exposure may ameliorate or exacerbate mortality. We examined how nominal EE2 concentrations of 0 ng/L, 5 ng/L, and 10 ng/L affect body size and mortality at various densities. Fish body size was influenced by density but not EE2 exposure. When density was high, we did not detect an effect of EE2 exposure on mortality. However, when density was low, EE2 exposures increased mortality. Thus, toxic effects of EE2 exposures were observable at low density but at high density, density-dependence in body size and mortality overwhelmed the effect of EE2. The results from our study provide insight into the relationship between density and EE2 exposures on fish survival and can be used to adjust population dynamic parameters for more accurate population dynamic estimates.

Journal of Aquatic Pollution and Toxicology↗