Spotfin Chub Research Articles

Long‐Term Population Dynamics and Habitat Association of the Federally Threatened Spotfin Chub in the Little Tennessee River

AbstractUnderstanding the population dynamics of rare and endangered species can be difficult, particularly when a species has a narrow geographic range. The Spotfin Chub Erimonax monachus is both federally and state (North Carolina) listed as threated and is endemic to the Tennessee River basin in the southeastern United States. The Spotfin Chub was once found throughout the Tennessee River basin, but its range has been reduced to four river systems. The Little Tennessee River contains the only known population of Spotfin Chubs in North Carolina. However, current efforts are ongoing to restore populations in the Cheoah River (Little Tennessee River basin). The goal of this study was to evaluate the status of Spotfin Chubs in the Little Tennessee River and to determine potential information gaps to guide future studies. Specifically, we evaluated temporal trends of the Spotfin Chub in the river using a state–space model that incorporated multiple data sources. We additionally evaluated current habitat availability to better understand how habitat could be driving site‐level variation in abundance. We found an overall increasing trend in Spotfin Chub abundance over time, but there was substantial variation across years. By linking abundance trends to current habitat availability, we found that sites with generally more bedrock also had the highest estimated abundance. The Spotfin Chub population appears to be stable; however, determining more specific population demographics (e.g., recruitment and mortality) would improve our understanding of this threatened species.

Population Estimate of the State and Federally Threatened Spotfin Chub Using Underwater Observations

AbstractDetermining the population demographics of threatened or endangered species can be difficult if the methods that are used must be minimally invasive. However, knowing the population status of species that are of conservation interest must be understood for successful management. We used underwater observations (i.e., snorkeling) to determine population estimates for Spotfin ChubErimonax monachusin the Cheoah River in North Carolina, a species that is listed as threatened at both state (North Carolina) and federal levels. Seven sites were randomly selected between the Santeetlah Dam and the confluence with the Little Tennessee River. Each site was surveyed by three snorkelers who completed multipass snorkeling from July 17 to 25, 2019. The population estimates were generated with anN‐mixture model and incorporated site‐specific habitat. Four hundred and sixty‐six observations of Spotfin Chub were recorded across all of the sites and passes. The simple model without covariates of abundance estimated a total population size of 12,139 (95% credible interval [CRI] = 9,821–15,453). Incorporating site‐specific percentage of bedrock improved model fit and indicated that the percentage of bedrock was positively related to site‐specific abundance. The total population size as estimated with the covariate model was 13,905 (95% CRI = 11,620–22,181). Our results yielded new insight into the status of a threatened species while confirming previous knowledge about its microhabitat use. Locally, the results of this work suggest that Spotfin Chub are well established in the Cheoah River and maintain a substrate affinity to bedrock. Broadly, the field methods that were used here are logistically feasible, cost efficient, and minimally stressful for the fish. We suggest that this methodology be considered when total and site‐specific population estimates are needed to manage species of concern. Additionally, more detailed site‐specific habitat can improve model estimates by explaining site‐specific variability in abundance, resulting in more precise total population estimates.

Riverscape correlates for distribution of threatened spotfin chub Erimonax monachus in the Tennessee River Basin, USA

Riverscape correlates for distribution of threatened spotfin chub Erimonax monachus in the Tennessee River Basin, USA

Variation in microhabitat use of the threatened spotfin chub (Erimonax monachus) among stream sites and seasons

Abstract – The spotfin chub Erimonax monachus is a rare cyprinid fish endemic to the Tennessee River drainage, and it is federally listed as threatened in the USA. Microhabitat use of spotfin chubs was studied via stream snorkelling in the Emory River watershed, Tennessee, one of the last remaining populations of this species. We used a Bayesian generalised linear mixed model to evaluate microhabitat covariates related to the presence/absence of spotfin chubs among eight stream sites across three seasons (early summer, late summer and fall). In general, spotfin chubs were more likely to be present in microhabitats characterised by boulder/bedrock substrates, medium to high velocity, and medium depth (typical of the run habitat). However, the patterns were not necessarily consistent among seasons or stream sites, due partly to interactions between microhabitat and macrohabitat covariates. Specifically, spotfin chubs were more selective of bedrock and boulder substrate at smaller stream sites where they were less abundant, and they were more selective of higher velocity at warmer stream temperatures (early and late summer). Our data indicate that spotfin chubs may exhibit flexible microhabitat use to some extent, and their microhabitat use may differ by macrohabitat characteristics such as stream size and water temperature. This study provided a refined understanding of microhabitat use of spotfin chubs and suggests that effective conservation of this declining species should identify and protect available suitable habitat across space and time.

Effects of Electroshock on Cyprinid Embryos: Implications for Threatened and Endangered Fishes

AbstractThe purpose of this study was to evaluate the effects of electroshock on survival to hatching in embryos of Cyprinidae, which includes numerous fish species designated as threatened or endangered under the U.S. Endangered Species Act. Embryos of three cyprinids were exposed for 20 s to a homogeneous electric field (DC or 60‐Hz pulsed DC [PDC], 3‐ms pulse width) at voltage gradients similar to those used during electrofishing. Exposure occurred only once and was at a specific stage of development. Zebrafish Danio rerio were electroshocked at numerous stages of embryonic development, and the most sensitive developmental stage was determined and used to guide subsequent experiments. Embryos of two minnows native to the southeast United States, the spotfin chub Erimonax monachus and whitetail shiner Cyprinella galactura, were exposed to a range of DC (3‐15 V/cm) and 60‐Hz PDC (8‐15 V/cm) voltage gradients, and survival to hatching was evaluated. Additionally, the potential for electrofishing to induce premature hatching in late‐stage cyprinid embryos was investigated by exposing eyed spotfin chub embryos to 8‐V/cm DC electroshock. Embryos were most vulnerable to electroshock‐induced mortality early in development, particularly near epiboly, and DC was more harmful than 60‐Hz PDC. At older developmental stages, embryos were less vulnerable to electroshock‐induced mortality, although premature hatching was induced in some older developmental stages of electroshocked spotfin chub embryos. Whitetail shiner embryos were more vulnerable (lethal voltage gradient predicted to induce 50% mortality [LV50], 5 V/cm) to electroshock‐induced mortality than were spotfin chub embryos (LV50, 6 V/cm). Results indicate that cyprinid embryos can be killed by DC electroshock at electric field intensities commonly generated by electrofishing equipment, and electrofishing near spawning grounds of threatened or endangered cyprinids should be avoided when embryos are present.

Effects of Suspended Sediment on Whole-Body Cortisol Stress Response of Two Southern Appalachian Minnows, Erimonax Monachus and Cyprinella Galactura

Abstract Total immunoreactive corticosteroid (IRC) levels (adjusted for fish mass; ng/g) were measured in whole-body homogenates of 2- and 8-months old Whitetail Shiners (Cyprinella galactura) and 4-months old federally threatened Spotfin Chubs (Erimonax monachus) exposed for 48 hours to varying suspended sediment concentrations (SSC; 0, 25, 50, 100, and 500 mg/L). Hydrophobic fractions were extracted from individual frozen fish after sonication and centrifugation of tissues. Extracts were resuspended in a buffer compatible with a commercially available enzyme-linked immunosorbent assay (ELISA) kit. Serially diluted concentrations of cortisol and extracts collected from unstressed fish were used to standardize the assay. Two-months old C. galactura had the highest resting level of whole-body IRC at 0 mg/L SSC. They also elicited the greatest response (three- to four-fold increase) when exposed to SSCs greater than 25 mg/L. Resting whole-body IRC levels were lowest in 8-months old C. galactura. For these f...

Reintroduction of Four Imperiled Fishes in Abrams Creek, Tennessee

This project's goal was to restore populations of four rare fishes into Abrams Creek, Blount County, TN. These species, all on the US Endangered and Threatened Wildlife List, include two catfishes, the smoky madtom (Noturus bailey) and the yellowfin madtom (N. flavipinnis), the duskytail darter (Etheostoma percnurum) and the spotfin chub (Erimonax monachus). Captive propagation, reintroduction, and non-invasive monitoring techniques were used for this restoration effort, which began in 1986. By 2000, there was evidence of reproduction for all four species. As of 2003, the number of these species stocked in Abrams Creek was 3167 smoky madtoms, 1574 yellowfin madtoms, 3430 duskytail darters, and 11,367 spotfin chubs. Increasing population sizes were indicated for three of the four fishes, and smoky madtom and duskytail darter abundances were nearly comparable to native populations in Citico Creek, Monroe County, TN.

Assessing Contaminant Sensitivity of Endangered and Threatened Aquatic Species: Part III. Effluent Toxicity Tests

Toxicity tests using standard effluent test procedures described by the U.S. Environmental Protection Agency were conducted with Ceriodaphnia dubia, fathead minnows (Pimephales promelas), and seven threatened and endangered (listed) fish species from four families: (1) Acipenseridae: shortnose sturgeon (Acipenser brevirostrum); (2) Catostomidae; razorback sucker (Xyrauchen texanus); (3) Cyprinidae: bonytail chub (Gila elegans), Cape Fear shiner (Notropis mekistocholas) Colorado pikeminnow (Ptychocheilus lucius), and spotfin chub (Cyprinella monacha); and (4) Poecillidae: Gila topminnow (Poeciliopsis occidentalis). We conducted 7-day survival and growth studies with embryo-larval fathead minnows and analogous exposures using the listed species. Survival and reproduction were also determined with C. dubia. Tests were conducted with carbaryl, ammonia--or a simulated effluent complex mixture of carbaryl, copper, 4-nonylphenol, pentachlorophenol and permethrin at equitoxic proportions. In addition, Cape Fear shiners and spotfin chub were tested using diazinon, copper, and chlorine. Toxicity tests were also conducted with field-collected effluents from domestic or industrial facilities. Bonytail chub and razorback suckers were tested with effluents collected in Arizona whereas effluent samples collected from North Carolina were tested with Cape Fear shiner, spotfin chub, and shortnose sturgeon. The fathead minnow 7-day effluent test was often a reliable estimator of toxic effects to the listed fishes. However, in 21 % of the tests, a listed species was more sensitive than fathead minnows. More sensitive species results varied by test so that usually no species was always more or less sensitive than fathead minnows. Only the Gila topminnow was consistently less sensitive than the fathead minnow. Listed fish species were protected 96% of the time when results for both fathead minnows and C. dubia were considered, thus reinforcing the value of standard whole-effluent toxicity tests using those two species. If the responses of specific listed species are important for management decisions, our study supports the value in developing culture and testing procedures for those species.

Assessing Contaminant Sensitivity of Endangered and Threatened Aquatic Species: Part II. Chronic Toxicity of Copper and Pentachlorophenol to Two Endangered Species and Two Surrogate Species

Early life-stage toxicity tests with copper and pentachlorophenol (PCP) were conducted with two species listed under the United States Endangered Species Act (the endangered fountain darter, Etheostoma fonticola, and the threatened spotfin chub, Cyprinella monacha) and two commonly tested species (fathead minnow, Pimephales promelas, and rainbow trout, Oncorhynchus mykiss). Results were compared using lowest-observed effect concentrations (LOECs) based on statistical hypothesis tests and by point estimates derived by linear interpolation and logistic regression. Sublethal end points, growth (mean individual dry weight) and biomass (total dry weight per replicate) were usually more sensitive than survival. The biomass end point was equally sensitive as growth and had less among-test variation. Effect concentrations based on linear interpolation were less variable than LOECs, which corresponded to effects ranging from 9% to 76% relative to controls and were consistent with thresholds based on logistic regression. Fountain darter was the most sensitive species for both chemicals tested, with effect concentrations for biomass at < or = 11 microg/L (LOEC and 25% inhibition concentration [IC25]) for copper and at 21 microg/L (IC25) for PCP, but spotfin chub was no more sensitive than the commonly tested species. Effect concentrations for fountain darter were lower than current chronic water quality criteria for both copper and PCP. Protectiveness of chronic water-quality criteria for threatened and endangered species could be improved by the use of safety factors or by conducting additional chronic toxicity tests with species and chemicals of concern.

Electroshock‐Induced Injury and Mortality in the Spotfin Chub, a Threatened Minnow

The effects of AC and pulsed DC (PDC) electroshock on mortality and injury (vertebral damage and hemorrhage) of spotfin chub Cyprinella monacha, a threatened minnow, were evaluated in a laboratory experiment. Groups of 18-20 captive-reared fish were either designated as a control or exposed for 3 s to one of five electrical treatments (60-Hz AC at a peak-to-peak voltage gradient of 1.7, 2.5, or 3.3 V/cm or 60-Hz PDC at a peak voltage gradient of 2.5 or 5.0 V/cm). Immobilization, which renders fish susceptible to capture during electrofishing, was the predominant response evoked in the groups exposed to electroshock, with the exception of the 1.7-V/cm AC group. No injury was detected in any fish in the experiment. Mortality was 10% or less in groups exposed to AC, regardless of voltage gradient. There was no significant variation in mortality among the groups exposed to AC (P = 0.487-1.00). Mortality varied significantly in the groups exposed to 60-Hz PDC (2.5 V/cm (0%) versus 5.0 V/cm (25%); P = 0.047). Our results indicate that electroshocking with 60-Hz AC and 60-Hz PDC may be safe for capturing spotfin chub when voltage (thus, voltage gradient) is limited to the immobilization threshold and the exposure period to 3 s. However, AC should be used only in low-conductivity waters (e.g., <80 μS/cm).