My research efforts are focused on factors affecting population and community dynamics of freshwater fish and invertebrates, especially the role of disturbance in community dynamics, impacts of introduced species in aquatic ecosystems and conservation of aquatic ecosystems. As part of this work, I attempt to bridge the gap between studies done at small spatial scales and the larger spatial scales necessary to understand how disturbance and movement affect population and community dynamics in stream ecosystems.
The Ozark Plateau is located at the southern extent of native Smallmouth Bass Micropterus dolomie... more The Ozark Plateau is located at the southern extent of native Smallmouth Bass Micropterus dolomieu range and water temperature and drought conditions during summer months may potentially affect growth of Smallmouth Bass in this region. Groundwater streams in the region do not warm to the same extent as runoff streams during summer months and could provide a thermal refuge habitat for Smallmouth Bass from high summer temperatures and drought conditions. Our study objective was to examine differences in body condition and diet of Small-mouth Bass through summer months between groundwater and runoff streams. We sampled Smallmouth Bass from eight streams across two the flow regimes monthly from June-September from 2014 to 2016 in the Ozark Plateau of Arkansas and Missouri. Relative weights were calculated and diet contents were examined for each fish. Linear mixed model analyses indicated that relative weights declined in both stream types in 2014 and 2015, but not in 2016. Surprisingly, there was no significant difference in change in relative weights between runoff and groundwater streams in any year. No diet shifts over the course of the summer were noted in any year, and no differences were seen between
Crayfish are abundant and important consumers in aquatic food webs and crayfish invasions have de... more Crayfish are abundant and important consumers in aquatic food webs and crayfish invasions have demonstrated strong effects of crayfish on multiple trophic levels. Density may be an important factor determining the role of omnivorous crayfish in benthic communities, especially if density alters the strength of trophic interactions. The effect of crayfish density on a simple benthic food web using ceramic tiles was examined in three treatments (crayfish exclusion cage, cage control (open to crayfish), and exposed ceramic tiles) in mesocosms stocked with 6, 12, or 18 crayfish·m-2. We hypothesized that at low densities crayfish consumption of herbivorous chironomids would increase algal abundance, but at high densities crayfish would reduce both periphyton and invertebrates. In the experiment, periphyton and chironomid abundance increased with declining crayfish biomass on day 30 but not day 15. The magnitude of crayfish effects on day 15 periphyton chlorophyll a abundance increased with crayfish biomass, but crayfish effects on day 30 periphyton chlorophyll a or chironomid biomass did not increase with crayfish biomass. In this experiment there was little evidence for a trophic cascade at low crayfish densities and strong omnivory by crayfish dominated trophic dynamics.
Abstract The crayfish Orconectes neglectus chaenodactylus has recently been introduced into the S... more Abstract The crayfish Orconectes neglectus chaenodactylus has recently been introduced into the Spring River drainage in southern Missouri and northern Arkansas and appears to be displacing the native species O. eupunctus. To determine if O. eupunctus and O. neglectus chaenodactylus compete for habitat, we examined if either species shift habitats when in the presence of one another. Habitat use of juvenile and adult crayfish was determined in six habitat types (backwater, pool, riffle, run, stream margin and vegetation) with a quadrat sampler during July/August 2003 at three sites: (1) an upstream site where O. neglectus chaenodactylus occurs, (2) a zone of overlap where both species occur and (3) a downstream site where O. eupunctus occurs. Habitat selection was determined by comparing habitat use to habitat availability. Redundancy Analyses were used to determine the relationship between crayfish densities and measured environmental variables (current velocity, water depth and percent boulder, cobble, pebble and sand). Orconectes eupunctus showed no shift in habitat use, habitat selection and species-environmental relationships between the downstream site and the zone of overlap. However, O. neglectus chaenodactylus did show a shift in habitat use and habitat selection between the upstream site and the zone of overlap, although no shift in species environmental relationships was found. Competition for habitat between O. eupunctus and O. neglectus chaenodactylus did not appear to cause the habitat shift by O. neglectus chaenodactylus since O. neglectus chaenodactylus shifted into habitats used and selected by O. eupunctus. This study suggests that O. eupunctus and O. neglectus chaenodactylus may not compete for habitat. It is possible that habitat is not limiting in this system or that competition is taking place, but at a microhabitat level. Further study is needed to examine other potential mechanisms causing the displacement of O. eupunctus.
Biological invasions have major environmental and economic impacts, and pose a serious threat to ... more Biological invasions have major environmental and economic impacts, and pose a serious threat to global biodiversity. Invasive crayfish species are one of the greatest threats to native crayfish biodiversity. Additionally, almost 50% of US and Canadian species are considered at risk, making crayfish one of the most imperiled taxonomic groups in the world. Small‐scale (extralimital) invasions are often overlooked and may be more common than large‐scale (extraregional) invasions. One example of an extraregional and extralimital invader is the Ringed Crayfish (Faxonius neglectus), which has been independently introduced multiple times to drainages throughout the United States, including those adjacent to its native range. Traits related to invasiveness, such as chelae size, are suggested to differ between invasive crayfish from extralimital and extraregional source populations with larger size related to increased invasiveness. We examined morphological traits related to invasion poten...
Crayfish use of intermittent streams is especially important to understand in the face of global ... more Crayfish use of intermittent streams is especially important to understand in the face of global climate change. We examined the influence of stream permanence and local habitat on crayfish occupancy and species densities in the Ozark Highlands, USA. We sampled in June and July 2014 and 2015. We used a quantitative kick–seine method to sample crayfish presence and abundance at 20 stream sites with 32 surveys/site in the Upper White River drainage, and we measured associated local environmental variables each year. We modeled site occupancy and detection probabilities with the software PRESENCE, and we used multiple linear regressions to identify relationships between crayfish species densities and environmental variables. Occupancy of all crayfish species was related to stream permanence. Faxonius meeki was found exclusively in intermittent streams, whereas Faxonius neglectus and Faxonius luteus had higher occupancy and detection probability in permanent than in intermittent streams, and Faxonius williamsi was associated with intermittent streams. Estimates of detection probability ranged from 0.56 to 1, which is high relative to values found by other investigators. With the exception of F. williamsi, species densities were largely related to stream permanence rather than local habitat. Species densities did not differ by year, but total crayfish densities were significantly lower in 2015 than 2014. Increased precipitation and discharge in 2015 probably led to the lower crayfish densities observed during this year. Our study demonstrates that crayfish distribution and abundance is strongly influenced by stream permanence. Some species, including those of conservation concern (i.e., F. williamsi, F. meeki), appear dependent on intermittent streams, and conservation efforts should include consideration of intermittent streams as an important component of freshwater biodiversity.
The ability to colonize new habitat is essential for wild populations affected by disturbance or ... more The ability to colonize new habitat is essential for wild populations affected by disturbance or other forms of habitat change. For aquatic insects in small streams, overland flight is an important strategy for dispersal when barriers to in-stream migration exist and when populations are isolated in upland habitats. Two Ozark-endemic water beetles (Heterosternuta sulphuria and Heterosternuta phoebeae) have shown little overlap in distributions, with the former frequently occurring in small upland watersheds and the latter occurring in aquatic habitats farther downstream in larger watersheds. Because H. sulphuria has been associated with perennial aquatic habitats, we hypothesized that H. sulphuria individuals could exhibit low capacity for flight, thereby affecting population distributions over time. Laboratory flight observations showed that zero individuals of H. sulphuria flew (n = 67), whereas 17 of 76 individuals of H. phoebeae were observed to fly. Stream habitat drying experi...
The natural flow regime is considered the “master variable” in lotic systems, controlling structu... more The natural flow regime is considered the “master variable” in lotic systems, controlling structure and function at organismal, population, community, and ecosystem levels. We sought to estimate forested headwater stream metabolism across two dominant flow regimes (Runoff and Groundwater) in northern Arkansas and evaluate potential differences in, and drivers of, gross primary production, ecosystem respiration, and net ecosystem metabolism. Flow regimes differed in intermittency, substrate heterogeneity, hyporheic connectivity, and dominant water source (subsurface runoff vs. groundwater), which we expected to result in differences in primary production and respiration. Average daily gross primary production (GPP) and ecosystem respiration (ER) estimated from field data collected from May 2015-June 2016 tended to be greater in Groundwater streams. Respiration was positively related to discharge (R2= 0.98 p< 0.0001) and net metabolism became more heterotrophic with increasing aver...
Abstract - Given the importance of crayfish in stream ecosystems, gaining insight into the role o... more Abstract - Given the importance of crayfish in stream ecosystems, gaining insight into the role of stream permanence in maintaining predator–prey interactions is critical. Our objectives were to determine the influence of stream permanence and season on crayfish predation and assess the role of stream permanence and crayfish density on the presence of predators, while accounting for imperfect detection. We conducted surveys of crayfish density, mammalian scat, and environmental variables within 10 intermittent and 10 permanent streams in the Ozark Highlands. We used occupancy modeling to assess the relationship between predator presence, crayfish density, and environmental variables. Stream permanence did not play a role in determining relative frequency of occurrence or percent volume of crayfish prey in mammalian diets. However, percent volume and relative frequency of crayfish prey found in scats differed by season, with both highest in spring and summer. The relative frequency and percent volume of fish prey showed a significant interaction of season by stream permanence, which may be the first instance of this observation. Procyon lotor (Raccoon) had the highest detection probability (p = 0.39), whereas Neovison vison (American Mink; p = 0.15) and Lontra canadensis (River Otter; p = 0.03) had low detection probabilities. Further study into predator–prey interactions in the context of hydrology, particularly when related to imperiled groups like freshwater crayfishes, is needed since climate change is expected to alter hydrologic patterns.
Environmental flows are defined as the quantity, timing, and quality of stream flows required to ... more Environmental flows are defined as the quantity, timing, and quality of stream flows required to maintain the function of particular organisms in a system or overall ecosystem structure and function. We developed ecological flow-response relationships in the Ozark Highlands, in conjunction with a new hydrologic classification of streams into natural flow regimes for this region. We sampled within the perennial groundwater flow regime at 21 USGS-gauged sites, stratifying by habitat type. We collected fish and crayfish using three-pass backpack electro-fishing, benthic macroinvertebrates qualitatively and quantitatively, and habitat, geomorphological, and water quality data. We used hydrologic data to derive metrics based on magnitude, frequency, duration, and timing of flow, and calculated a hydrologic disturbance index (HDI) for all sites. In preliminary analysis of fish community data, we found significant negative relationships between Simpson's diversity and HDI and percent i...
Environmental flows are defined as the quantity, timing, and quality of stream flows required to ... more Environmental flows are defined as the quantity, timing, and quality of stream flows required to maintain the function of organisms in a system or overall ecosystem structure and function. We developed ecological flow-response relationships in the Ozark Highlands based on a hydrologic classification of streams into natural flow regimes. We collected fish, crayfish, macroinvertebrates, habitat, geomorphological, and water quality data at 21 USGS-gauged sites in streams within the groundwater flow regime. We calculated hydrologic metrics based on magnitude, frequency, duration, timing and change rate of flow, and calculated a hydrologic disturbance index (HDI) for all sites. We found significant negative relationships between fish Simpson's diversity and HDI and percent intolerant individuals and HDI, and a significant positive relationship between number of intolerant species and rapid habitat assessment score. We found the best model for predicting Simpson's diversity and pe...
Transactions of the American Fisheries Society, 2017
AbstractRestrictive angling regulations in tailwater trout fisheries may be unsuccessful if food ... more AbstractRestrictive angling regulations in tailwater trout fisheries may be unsuccessful if food availability limits energy for fish to grow. We examined spatial and temporal variation in energy intake and growth in populations of Brown Trout Salmo trutta and Rainbow Trout Oncorhynchus mykiss within three catch-and-release (C-R) areas in Arkansas tailwaters to evaluate food availability compared with consumption. Based on bioenergetic simulations, Rainbow Trout fed at submaintenance levels in both size-classes (≤400 mm TL, >400 mm TL) throughout most seasons. A particular bottleneck in food availability occurred in the winter for Rainbow Trout when the daily ration was substantially below the minimum required for maintenance, despite reduced metabolic costs associated with lower water temperatures. Rainbow Trout growth rates followed a similar pattern to consumption with negative growth rates during the winter periods. All three size-classes ( 400 mm TL) of Brown Trout experienc...
The Yellowcheek Darter (Etheostoma moorei) is a rare fish endemic to the Little Red River watersh... more The Yellowcheek Darter (Etheostoma moorei) is a rare fish endemic to the Little Red River watershed in the Boston Mountains of northern Arkansas. Remaining populations of this species are geographically isolated and declining, and the species was listed in 2011 as federally endangered. Populations have declined, in part, due to intense seasonal stream drying and inundation of lower reaches by a reservoir. We used a kick seine sampling approach to examine distribution and abundance of Yellowcheek Darter populations in the Middle Fork and South Fork Little Red River. We used presence data to estimate occupancy rates and detection probability and examined relationships between Yellowcheek Darter density and environmental variables. The species was found at five Middle Fork and South Fork sites where it had previously been present in 2003–2004. Occupancy rates were >0.6 but with wide 95% CI, and where the darters occurred, densities were typical of other Ozark darters but highly variable. Detection probability and density were positively related to current velocity. Given that stream drying has become more extreme over the past 30 years and anthropogenic threats have increased, regular monitoring and active management may be required to reduce extinction risk of Yellowcheek Darter populations.
The Ozark Plateau is located at the southern extent of native Smallmouth Bass Micropterus dolomie... more The Ozark Plateau is located at the southern extent of native Smallmouth Bass Micropterus dolomieu range and water temperature and drought conditions during summer months may potentially affect growth of Smallmouth Bass in this region. Groundwater streams in the region do not warm to the same extent as runoff streams during summer months and could provide a thermal refuge habitat for Smallmouth Bass from high summer temperatures and drought conditions. Our study objective was to examine differences in body condition and diet of Small-mouth Bass through summer months between groundwater and runoff streams. We sampled Smallmouth Bass from eight streams across two the flow regimes monthly from June-September from 2014 to 2016 in the Ozark Plateau of Arkansas and Missouri. Relative weights were calculated and diet contents were examined for each fish. Linear mixed model analyses indicated that relative weights declined in both stream types in 2014 and 2015, but not in 2016. Surprisingly, there was no significant difference in change in relative weights between runoff and groundwater streams in any year. No diet shifts over the course of the summer were noted in any year, and no differences were seen between
Crayfish are abundant and important consumers in aquatic food webs and crayfish invasions have de... more Crayfish are abundant and important consumers in aquatic food webs and crayfish invasions have demonstrated strong effects of crayfish on multiple trophic levels. Density may be an important factor determining the role of omnivorous crayfish in benthic communities, especially if density alters the strength of trophic interactions. The effect of crayfish density on a simple benthic food web using ceramic tiles was examined in three treatments (crayfish exclusion cage, cage control (open to crayfish), and exposed ceramic tiles) in mesocosms stocked with 6, 12, or 18 crayfish·m-2. We hypothesized that at low densities crayfish consumption of herbivorous chironomids would increase algal abundance, but at high densities crayfish would reduce both periphyton and invertebrates. In the experiment, periphyton and chironomid abundance increased with declining crayfish biomass on day 30 but not day 15. The magnitude of crayfish effects on day 15 periphyton chlorophyll a abundance increased with crayfish biomass, but crayfish effects on day 30 periphyton chlorophyll a or chironomid biomass did not increase with crayfish biomass. In this experiment there was little evidence for a trophic cascade at low crayfish densities and strong omnivory by crayfish dominated trophic dynamics.
Abstract The crayfish Orconectes neglectus chaenodactylus has recently been introduced into the S... more Abstract The crayfish Orconectes neglectus chaenodactylus has recently been introduced into the Spring River drainage in southern Missouri and northern Arkansas and appears to be displacing the native species O. eupunctus. To determine if O. eupunctus and O. neglectus chaenodactylus compete for habitat, we examined if either species shift habitats when in the presence of one another. Habitat use of juvenile and adult crayfish was determined in six habitat types (backwater, pool, riffle, run, stream margin and vegetation) with a quadrat sampler during July/August 2003 at three sites: (1) an upstream site where O. neglectus chaenodactylus occurs, (2) a zone of overlap where both species occur and (3) a downstream site where O. eupunctus occurs. Habitat selection was determined by comparing habitat use to habitat availability. Redundancy Analyses were used to determine the relationship between crayfish densities and measured environmental variables (current velocity, water depth and percent boulder, cobble, pebble and sand). Orconectes eupunctus showed no shift in habitat use, habitat selection and species-environmental relationships between the downstream site and the zone of overlap. However, O. neglectus chaenodactylus did show a shift in habitat use and habitat selection between the upstream site and the zone of overlap, although no shift in species environmental relationships was found. Competition for habitat between O. eupunctus and O. neglectus chaenodactylus did not appear to cause the habitat shift by O. neglectus chaenodactylus since O. neglectus chaenodactylus shifted into habitats used and selected by O. eupunctus. This study suggests that O. eupunctus and O. neglectus chaenodactylus may not compete for habitat. It is possible that habitat is not limiting in this system or that competition is taking place, but at a microhabitat level. Further study is needed to examine other potential mechanisms causing the displacement of O. eupunctus.
Biological invasions have major environmental and economic impacts, and pose a serious threat to ... more Biological invasions have major environmental and economic impacts, and pose a serious threat to global biodiversity. Invasive crayfish species are one of the greatest threats to native crayfish biodiversity. Additionally, almost 50% of US and Canadian species are considered at risk, making crayfish one of the most imperiled taxonomic groups in the world. Small‐scale (extralimital) invasions are often overlooked and may be more common than large‐scale (extraregional) invasions. One example of an extraregional and extralimital invader is the Ringed Crayfish (Faxonius neglectus), which has been independently introduced multiple times to drainages throughout the United States, including those adjacent to its native range. Traits related to invasiveness, such as chelae size, are suggested to differ between invasive crayfish from extralimital and extraregional source populations with larger size related to increased invasiveness. We examined morphological traits related to invasion poten...
Crayfish use of intermittent streams is especially important to understand in the face of global ... more Crayfish use of intermittent streams is especially important to understand in the face of global climate change. We examined the influence of stream permanence and local habitat on crayfish occupancy and species densities in the Ozark Highlands, USA. We sampled in June and July 2014 and 2015. We used a quantitative kick–seine method to sample crayfish presence and abundance at 20 stream sites with 32 surveys/site in the Upper White River drainage, and we measured associated local environmental variables each year. We modeled site occupancy and detection probabilities with the software PRESENCE, and we used multiple linear regressions to identify relationships between crayfish species densities and environmental variables. Occupancy of all crayfish species was related to stream permanence. Faxonius meeki was found exclusively in intermittent streams, whereas Faxonius neglectus and Faxonius luteus had higher occupancy and detection probability in permanent than in intermittent streams, and Faxonius williamsi was associated with intermittent streams. Estimates of detection probability ranged from 0.56 to 1, which is high relative to values found by other investigators. With the exception of F. williamsi, species densities were largely related to stream permanence rather than local habitat. Species densities did not differ by year, but total crayfish densities were significantly lower in 2015 than 2014. Increased precipitation and discharge in 2015 probably led to the lower crayfish densities observed during this year. Our study demonstrates that crayfish distribution and abundance is strongly influenced by stream permanence. Some species, including those of conservation concern (i.e., F. williamsi, F. meeki), appear dependent on intermittent streams, and conservation efforts should include consideration of intermittent streams as an important component of freshwater biodiversity.
The ability to colonize new habitat is essential for wild populations affected by disturbance or ... more The ability to colonize new habitat is essential for wild populations affected by disturbance or other forms of habitat change. For aquatic insects in small streams, overland flight is an important strategy for dispersal when barriers to in-stream migration exist and when populations are isolated in upland habitats. Two Ozark-endemic water beetles (Heterosternuta sulphuria and Heterosternuta phoebeae) have shown little overlap in distributions, with the former frequently occurring in small upland watersheds and the latter occurring in aquatic habitats farther downstream in larger watersheds. Because H. sulphuria has been associated with perennial aquatic habitats, we hypothesized that H. sulphuria individuals could exhibit low capacity for flight, thereby affecting population distributions over time. Laboratory flight observations showed that zero individuals of H. sulphuria flew (n = 67), whereas 17 of 76 individuals of H. phoebeae were observed to fly. Stream habitat drying experi...
The natural flow regime is considered the “master variable” in lotic systems, controlling structu... more The natural flow regime is considered the “master variable” in lotic systems, controlling structure and function at organismal, population, community, and ecosystem levels. We sought to estimate forested headwater stream metabolism across two dominant flow regimes (Runoff and Groundwater) in northern Arkansas and evaluate potential differences in, and drivers of, gross primary production, ecosystem respiration, and net ecosystem metabolism. Flow regimes differed in intermittency, substrate heterogeneity, hyporheic connectivity, and dominant water source (subsurface runoff vs. groundwater), which we expected to result in differences in primary production and respiration. Average daily gross primary production (GPP) and ecosystem respiration (ER) estimated from field data collected from May 2015-June 2016 tended to be greater in Groundwater streams. Respiration was positively related to discharge (R2= 0.98 p< 0.0001) and net metabolism became more heterotrophic with increasing aver...
Abstract - Given the importance of crayfish in stream ecosystems, gaining insight into the role o... more Abstract - Given the importance of crayfish in stream ecosystems, gaining insight into the role of stream permanence in maintaining predator–prey interactions is critical. Our objectives were to determine the influence of stream permanence and season on crayfish predation and assess the role of stream permanence and crayfish density on the presence of predators, while accounting for imperfect detection. We conducted surveys of crayfish density, mammalian scat, and environmental variables within 10 intermittent and 10 permanent streams in the Ozark Highlands. We used occupancy modeling to assess the relationship between predator presence, crayfish density, and environmental variables. Stream permanence did not play a role in determining relative frequency of occurrence or percent volume of crayfish prey in mammalian diets. However, percent volume and relative frequency of crayfish prey found in scats differed by season, with both highest in spring and summer. The relative frequency and percent volume of fish prey showed a significant interaction of season by stream permanence, which may be the first instance of this observation. Procyon lotor (Raccoon) had the highest detection probability (p = 0.39), whereas Neovison vison (American Mink; p = 0.15) and Lontra canadensis (River Otter; p = 0.03) had low detection probabilities. Further study into predator–prey interactions in the context of hydrology, particularly when related to imperiled groups like freshwater crayfishes, is needed since climate change is expected to alter hydrologic patterns.
Environmental flows are defined as the quantity, timing, and quality of stream flows required to ... more Environmental flows are defined as the quantity, timing, and quality of stream flows required to maintain the function of particular organisms in a system or overall ecosystem structure and function. We developed ecological flow-response relationships in the Ozark Highlands, in conjunction with a new hydrologic classification of streams into natural flow regimes for this region. We sampled within the perennial groundwater flow regime at 21 USGS-gauged sites, stratifying by habitat type. We collected fish and crayfish using three-pass backpack electro-fishing, benthic macroinvertebrates qualitatively and quantitatively, and habitat, geomorphological, and water quality data. We used hydrologic data to derive metrics based on magnitude, frequency, duration, and timing of flow, and calculated a hydrologic disturbance index (HDI) for all sites. In preliminary analysis of fish community data, we found significant negative relationships between Simpson's diversity and HDI and percent i...
Environmental flows are defined as the quantity, timing, and quality of stream flows required to ... more Environmental flows are defined as the quantity, timing, and quality of stream flows required to maintain the function of organisms in a system or overall ecosystem structure and function. We developed ecological flow-response relationships in the Ozark Highlands based on a hydrologic classification of streams into natural flow regimes. We collected fish, crayfish, macroinvertebrates, habitat, geomorphological, and water quality data at 21 USGS-gauged sites in streams within the groundwater flow regime. We calculated hydrologic metrics based on magnitude, frequency, duration, timing and change rate of flow, and calculated a hydrologic disturbance index (HDI) for all sites. We found significant negative relationships between fish Simpson's diversity and HDI and percent intolerant individuals and HDI, and a significant positive relationship between number of intolerant species and rapid habitat assessment score. We found the best model for predicting Simpson's diversity and pe...
Transactions of the American Fisheries Society, 2017
AbstractRestrictive angling regulations in tailwater trout fisheries may be unsuccessful if food ... more AbstractRestrictive angling regulations in tailwater trout fisheries may be unsuccessful if food availability limits energy for fish to grow. We examined spatial and temporal variation in energy intake and growth in populations of Brown Trout Salmo trutta and Rainbow Trout Oncorhynchus mykiss within three catch-and-release (C-R) areas in Arkansas tailwaters to evaluate food availability compared with consumption. Based on bioenergetic simulations, Rainbow Trout fed at submaintenance levels in both size-classes (≤400 mm TL, >400 mm TL) throughout most seasons. A particular bottleneck in food availability occurred in the winter for Rainbow Trout when the daily ration was substantially below the minimum required for maintenance, despite reduced metabolic costs associated with lower water temperatures. Rainbow Trout growth rates followed a similar pattern to consumption with negative growth rates during the winter periods. All three size-classes ( 400 mm TL) of Brown Trout experienc...
The Yellowcheek Darter (Etheostoma moorei) is a rare fish endemic to the Little Red River watersh... more The Yellowcheek Darter (Etheostoma moorei) is a rare fish endemic to the Little Red River watershed in the Boston Mountains of northern Arkansas. Remaining populations of this species are geographically isolated and declining, and the species was listed in 2011 as federally endangered. Populations have declined, in part, due to intense seasonal stream drying and inundation of lower reaches by a reservoir. We used a kick seine sampling approach to examine distribution and abundance of Yellowcheek Darter populations in the Middle Fork and South Fork Little Red River. We used presence data to estimate occupancy rates and detection probability and examined relationships between Yellowcheek Darter density and environmental variables. The species was found at five Middle Fork and South Fork sites where it had previously been present in 2003–2004. Occupancy rates were >0.6 but with wide 95% CI, and where the darters occurred, densities were typical of other Ozark darters but highly variable. Detection probability and density were positively related to current velocity. Given that stream drying has become more extreme over the past 30 years and anthropogenic threats have increased, regular monitoring and active management may be required to reduce extinction risk of Yellowcheek Darter populations.
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