Papers by Andrew F Casper
BioScience, 2010
Assignment of values for natural ecological benefits and anthropocentric ecosystem services in ri... more Assignment of values for natural ecological benefits and anthropocentric ecosystem services in riverine landscapes has been problematic, because a firm scientific basis linking these to the river's physical structure has been absent. We highlight some inherent problems in this process and suggest possible solutions on the basis of the hydrogeomorphic classification of rivers. We suggest this link can be useful in fair asset trading (mitigation and offsets), selection of sites for rehabilitation, cost-benefit decisions on incremental steps in restoring ecological functions, and general protection of rivers.
Sampling in non-wadeable rivers presents methodological challenges for monitoring fish species. C... more Sampling in non-wadeable rivers presents methodological challenges for monitoring fish species. Changing
environmental conditions may affect the ability to accurately capture species (i.e., detection) and consequently
may lead to inappropriate inferences on occupancy rates. We used hierarchical Bayesian multiseason mixture
models to estimate occupancy and detection of 41 of 52 fish species in the Kankakee River, Illinois, by using data
from a standardized monitoring program. Fish were sampled with AC boat electrofishing and shoreline seining
over 7 years. Some centrarchids (e.g., Smallmouth Bass Micropterus dolomieu) were efficiently sampled by boat
electrofishing, whereas most other species had low detection probabilities. Moderate changes in environmental
conditions, such as water velocity and temperature, produced moderate changes in detection and occupancy.
Generally, when species had high detection probabilities, changes in environmental conditions produced relatively
small changes in the estimated detection probabilities. Our results also suggested that some sport fishes collected
from rivers with only moderate environmental fluctuations are unlikely to produce strongly biased estimates of
detection and occupancy among years. However, many species had detection probabilities that were low, imprecisely
estimated, or both. Overall, we demonstrate that long-term fisheries monitoring can effectively detect some
species at levels that are often relevant for management, but assessments of species with lower and more uncertain
detection probabilities may not provide adequate information for management decisions. We recommend the use of
sampling designs that allow the estimation of both detection and occupancy.
The American Midland Naturalist, 2016
OCEANS 2009, MTS/ …, Oct 26, 2009
Rivers, estuaries, reservoirs, and lakes are multi-use systems that supply water for agricultural... more Rivers, estuaries, reservoirs, and lakes are multi-use systems that supply water for agricultural, industrial, and human consumption while simultaneously assimilating both point-and non-point source discharges. Existing methods of data collection are generally limited to snapshots in space and time while a comprehensive view of spatial variability remains elusive. Accelerating the integration of existing in-situ sensors, geospatial analysis techniques, and reliable autonomous sampling platform technologies provide immediate ...
Estuaries and Coasts, Dec 2014
On-going shifts in the arctic climate and landscape have the potential to increase terrestrial pa... more On-going shifts in the arctic climate and landscape have the potential to increase terrestrial particulate organic matter (POM) transported to the Mackenzie delta and coastal Beaufort shelf. If increased terrestrial/freshwater material exports to the coastal zone can be assimilated by the pelagic food web, then this represents a new pool of carbon for the regional food web and could result in a shift in the nature of carbon supporting pelagic productivity. Analysis of the δ 13C of POM from the riverine, estuarine, and marine (shelf) zones of the Mackenzie delta shows that the signatures of terrestrial/freshwater carbon does extend onto the shelf, although it diminishes with distance from the Mackenzie River. δ 13C values of calanoid copepods, mysid shrimp, and two species of Amphipods varied depending on their environment (river, estuary, or marine) and local POM δ 13C signature. From this, we conclude that exported terrestrial POM can be a subsidy for portions of both the estuarine and marine pelagic food web. However because the response of consumer δ 13C depended on both species and location, we also conclude that the response to increased riverine POM will be different for estuarine versus marine biota. The implication is that increases in exported terrestrial carbon represent a significant potential shift in coastal pelagic ecosystem structure and function.
For bivalves, somatic growth is often inferred from shell measurements alone. However, shell grow... more For bivalves, somatic growth is often inferred from shell measurements alone. However, shell growth may not always reflect changes in soft tissue due to confounding factors such as seasonal or ontogenetic asynchrony between shell and tissue, flexible energy allocation, or population differences. This study compares the relationship between shell growth, changes in soft tissue mass, and RNA/DNA ratio in the zebra mussel (Dreissena polymorpha) and quagga mussel (Dreissena bugensis) from contrasting riverine and brackish estuarine environments. Reciprocal transplantation indicated that shell growth in late summer was consistently lower for the estuarine source zebra mussels while the RNA/DNA ratio was highest for zebra mussels independent of either geographic source or destination. Shell growth of the river source quagga mussels was almost two times greater than zebra mussels at the river site, but both shell growth and final tissue mass were lower in the estuarine environment. While there were no differences in final RNA/DNA ratios between zebra and quagga mussels from the same source, the RNA/DNA ratio of zebra mussels from the estuary and transplanted to the estuary was higher than that of all other zebra mussel treatments. This study suggests that shell growth does not always accurately reflect tissue growth and that the shell and tissue growth of quagga mussels is greater than that of zebra mussels in fresh but not brackish waters, and that physiological plasticity can have a fixed geographic component.
Fundamental to the inter-Agency effort to protect coral reefs in southwestern Puerto Rico is the ... more Fundamental to the inter-Agency effort to protect coral reefs in southwestern Puerto Rico is the assumption that soil eroded from land in the Guánica/Rio Loco watershed is carried out of Guánica Bay and into coral reef zones and may even be pushed by currents to the west, where it could affect coral reef communities near La Parguera and beyond. Terrestrial soil particles, with their associated contaminants and nutrients, can stress corals and negatively impact reef health. At least some of this assumption is true. There is strong evidence that eroded soil is being discharged into Guánica Bay (Fig. 1), even to the point of changing the Bay’s bathymetry. There is also evidence that at least some of that eroded soil is carried out of the Bay into the coastal zone, although how much is not well known and is currently under investigation by UPR-Mayaguez scientists. It is not known where the soil ends up. Does it settle on reefs outside of Guánica Bay, is it carried to La Parguera reefs, or does it simply drift out to sea? [more]
Ephemeral and intermittent headwater streams are under increasing pressure from disturbance and d... more Ephemeral and intermittent headwater streams are under increasing pressure from disturbance and development. Rapid, repeatable assessment techniques are needed in order to gauge the condition of these stream systems.Several attributes of these headwater streams constrain the use of the most widely used macroinvertebrate or water quality stream assessment techniques.The hydrogeomorphic (HGM) functional assessment is a reference-based alternative technique.Toevaluatethisalternative,repeated
assessments were conducted in eight high-gradient headwaters in WestVirginia by four independent teams. Across-site and measurement variance among teams was assessed using a coefficient of variation (CV, expressed as percent). Avariability of > 50%CV,which suggests less repeatable results, occurred in only 13.8% of measurements, primarily associated with 2 of the 9 variables examined (snag density and substrate size). Between site measurement variance was the greatest at more highly disturbed sample locations, particularlywith regard to the large woody debris, tree species richness, and channel bank erosion variables. Variables with the lowest CV were tree diameter, detrital cover, canopy cover, and channel embeddedness. Based on these results, measurements included when applying HGM approach to these streams should focus on direct measurements or directed estimates that yield a large response range across a spectrum of sites while maintaining consistent repeatability among different teams,with special attention paid to their use in highly disturbed sites.
1.In situ exclosure experiments in the Mississippi and Ohio Rivers determined the importance of f... more 1.In situ exclosure experiments in the Mississippi and Ohio Rivers determined the importance of fish predation in regulating zebra mussels (Dreissena polymorpha), an increasingly important constituent of the benthic invertebrate assemblages in both rivers.
2. We evaluated the effects of predatory fish on the density, biomass and size distribution of zebra mussels in a floodplain reach of the upper Mississippi River and in a naturally constrained reach of the Ohio River. Fifty, six-sided, predator-exclusion cages and fifty ‘partial’ cages (mesh at the upstream end only) were deployed, with half the cages containing willow snags and half clay tiles suspended 12–16 cm above the bottom. A single snag or tile sample unit was removed from each cage at approximately monthly intervals from July to October 1994. Types and relative abundances of molluscivorous fish were evaluated by electrofishing near the cages in both rivers. Actual and potential recruitment of young zebra mussels on to the substrata were measured using benthic samples in both rivers and estimated (Ohio River only) from counts of planktonic veligers.
3. Zebra mussels were consumed by at least three fish species in the upper Mississippi River (mostly carp, Cyprinus carpio, and redhorse suckers, Moxostoma sp.) and five species in the Ohio River (primarily smallmouth buffalo, Ictiobus bubalus, and channel catfish, Ictalurus punctatus), but potential recruitment seemed adequate to replace consumed mussels, at least in the Ohio River. The number of juvenile benthic mussels showed no apparent link with the density of veligers soon after initiation of reproduction. Recruitment of juveniles on snags and tiles was not affected by cage type (thus eliminating a potentially confounding ‘cage effect’).
4. Fish significantly influenced mussel populations, but the impact was often greatest among low density populations in the upper Mississippi. Density and biomass differed in both rivers for cage type (higher inside cages), substratum (greater on tiles), and date (increased over time). Presumed size-selective predation was present in the Mississippi (greater on larger size classes) but was not evident in the Ohio. We hypothesize that fish in the Mississippi can more easily select larger prey from the low density populations; whereas size-selective predation on tightly packed zebra mussels in the Ohio would be difficult.
5. Although fish can reduce numbers of Dreissena polymorpha in the two rivers, current levels of fish predation seem insufficient to regulate zebra mussel densities because of its great reproductive capacity. The recent invasion of zebra mussels, however, could lead to larger fish populations while promoting greater carbon retention and overall ecosystem secondary production.
As changes in landuse and the demand for water accelerate, regulators and resource managers are i... more As changes in landuse and the demand for water accelerate, regulators and resource managers are increasingly asked to evaluate water allocation against the need for protection of in-stream habitat. In the United States, only a small number of river basins have the longterm hydrograph data needed to make these assessments. This paper presents an example of how to bridge the conceptual and physical divide between GIS-based watershed modelling of basin-discharge and in-stream hydraulic habitat models. Specifically, we used a Soil andWater Assessment Tool (SWAT) model for the Hillsborough River to produce data for use in a Physical HABitat SIMulation (PHABSIM) model of the same river. This coupling of models allowed us to develop long-term discharge data in ungauged river systems based on watershed characteristics and precipitation records. However this approach is not without important limitations. Results confirm that accuracy of the SWAT-predicted hydrograph declines significantly when either the DEM resolution becomes too coarse or if DEM data are resampled to a coarser or finer resolution. This is due to both changes in the size and shape of the river basin
with the varying DEMs and subsequent shifts in the proportions of land use, soils and elevation. Results show the use of 30m DEMs produced hydrographic patterns amenable for using in-stream habitat protocols like PHABSIM model, especially where little or no hydrographic and land use information exists.
The zebra mussel, Dreissena polymorpha, is widespread in the St. Lawrence River while the conspec... more The zebra mussel, Dreissena polymorpha, is widespread in the St. Lawrence River while the conspecific quagga mussel, Dreissena bugensis, is found only in the Lake Ontario outflow region of the river. This situation provided an opportunity to evaluate in situ environmental and interspecific heterogeneity in shell and tissue growth. Shell dry weight, carbon content, and shell strength of D. polymorpha from the four spatially discrete water masses differed significantly. For instance, D. polymorpha total and tissue mass increased over the summer in the shallow fluvial Lac Saint-Pierre but decreased in the upstream and downstream water masses. Standardized shell mass and strength of D. polymorpha was lowest where the mussels experienced salinity or low calcium. Although the response pattern of mass and glycogen content for D. polymorpha was spatially complex, mussels from the stressful oligohaline estuary population had the weakest shells and lowest glycogen content, even though their standardized tissue mass was the heaviest. This disparity in shell and tissue response suggests that some aspect of shell physiology alone may be limiting these mussels in estuarine environments. Tissue characteristics of D. polymorpha and D. bugensis were similar at the site where both were present, but the shell strength of D. bugensis was only equivalent to the weakest of D. polymorpha. We also conclude that lighter shells might make D. bugensis more susceptible to predation or mechanical damage but may also offer a bioenergetic advantage that is contributing to its
rapid displacement of D. polymorpha where the two species co-occur.
While the spatial heterogeneity of many aquatic ecosystems is acknowledged, rivers are often mist... more While the spatial heterogeneity of many aquatic ecosystems is acknowledged, rivers are often mistakenly described as homogenous and well-mixed. The collection and visualization of attributes like water quality is key to our perception and management of these ecosystems. The assumption of homogeneity can lead to the conclusion that data collection from discrete, discontinuous points in space or time provide a comprehensive estimate of condition. To counter this perception, we combined high-density data collection with spatial interpolation techniques to created two-dimensional maps of water quality. Maps of four riverine transitions and habitats e wetland to urban, river to reservoir, river to estuary and a groundwater intrusion e were constructed from the continuous data. The examples provided show that the most basic water quality parameters - temperature, conductivity, salinity, turbidity, and chlorophyll florescence - are heterogeneous at spatial scales smaller than those captured by common point
sampling statistical strategies. The 2-dimensional, interpolation-based maps of the Hillsborough River (Tampa, FL) show significant influences of a variety of geographic features including tributary confluences, submarine groundwater inflow, and riparian interfaces. We conclude that many sampling strategies
do not account for the type of patchy heterogeneity observed. The integration of existing in-situ sensors, inexpensive autonomous sampling platforms, and geospatial mapping techniques provides high resolution visualization that can adds a more comprehensive geographic perspective needed for environmental monitoring and assessment programs.
1. Two senior ecologists summarised their experience of the scientific publication process (Statz... more 1. Two senior ecologists summarised their experience of the scientific publication process (Statzner & Resh, Freshwater Biology, 2010; 55, 2639) to generate discussion, particularly among early career researchers (ECRs). As a group of eight ECRs, we comment on the six trends they described.
2. We generally agree with most of the trends identified by Statzner & Resh (2010), but also highlight a number of divergent perspectives and provide recommendations for change. Trends of particular concern are the use of inappropriate metrics to evaluate research quality (e.g. impact factor) and the salami slicing of papers to increase paper count. We advocate a transparent and comprehensive system for evaluating the research.
3. We stress the importance of impartiality and independence in the peer review process.We therefore suggest implementation of double-blind review and quality control measures for reviewers and possibly editors. Besides such structural changes, editors should be confident to overrule biased reviewer recommendations, while reviewers should provide helpful reviews
but be explicit if a submission does not meet quality standards. Authors should always conductathorough literature search and acknowledge historical scientific ideas and methods. Additionally, authors should report low-quality copy editing and reviews to the editors.
4. Both early and late career researchers should jointly implement these recommendations to reverse the negative trends identified by Statzner & Resh (2010). However, more senior scientists will always have to take the lead with respect to structural changes in the publication system given that they occupy the majority of decision-making positions.
The removal of dams is frequently promoted as a cost-effective tool for some forms of river rehab... more The removal of dams is frequently promoted as a cost-effective tool for some forms of river rehabilitation, even though the scientific evidence supporting this approach is relatively rare. Our fifteen-month study assessed initial effects of removal of the Edwards Dam at three sites in the Kennebec River, Maine (USA) on zoobenthos, a critical component of a river's food web. Overall changes in both abundance and generic diversity were analysed in relation to feeding strategy. We also evaluated changes in trophic food webs by analysing stable isotope signatures of carbon and nitrogen for major functional feeding groups. The overall density of zoobenthos increased most dramatically (190 %) at the site closest to the former dam, but measures of taxonomic diversity showed variable responses. Neither generic richness nor evenness were significantly altered by removal of the dam. However, the composition of the community changed, with the addition of eight genera including caddisflies (Neureclipsis and Ithytrichia), mayflies (Tricorythodes and Stenonema), oligochaetes (Arcteonais), and various predatory (Ablabesmyia) and non-predatory chironomid midges. Differences in community similarity between a restored site near the former dam and a control, continuously free-flowing site diminished over time. Changes in stable isotope signatures suggested modification of feeding strategies and possible changes in the abundance of aquatic sources of organic matter. Community structure and ecosystem processes are likely to respond to dam removal in either a categorical (effect vs no effect) or a continuous (gradational) manner depending on the type of organism or process examined and the relationship between sizes of the dam and river.
BioScience, Jan 1, 2010
Assignment of values for natural ecological benefits and anthropocentric ecosystem services in ri... more Assignment of values for natural ecological benefits and anthropocentric ecosystem services in riverine landscapes has been problematic, because a
firm scientific basis linking these to the river’s physical structure has been absent.We highlight some inherent problems in this process and suggest
possible solutions on the basis of the hydrogeomorphic classification of rivers.We suggest this link can be useful in fair asset trading (mitigation and
offsets), selection of sites for rehabilitation, cost-benefit decisions on incremental steps in restoring ecological functions, and general protection of
rivers.
Rivers of North America, Jan 1, 2005
Proceedings from the …, Jan 1, 1994
American Midland Naturalist, Jan 1, 1995
Patterns of microhabitat use and overlap among five benthic fish species in a fifth-order stream ... more Patterns of microhabitat use and overlap among five benthic fish species in a fifth-order stream were investigated during two same-year sampling periods characterized by high vs. low discharges. Microhabitat use patterns for Cottus carolinae (banded sculpin), Etheostoma bellum (orangefin darter), E. blennioides (greenside darter), E. maculatum (spotted darter) and E. zonale (banded darter) were similar to literature reports. During high flow most segregation occurred along a depth/substrate roughness gradient while in low flows segregation was more common along a velocity gradient. Less segregation in microhabitat use during low flow was probably due to differences in spatial overlap. Five species pairs exhibited high spatial overlap (>0.60) during high flow whereas one pair exhibited this pattern during low flow. Overall, there was a decrease in spatial breadth (13.91 vs. 10.57) and overlap (0.52 vs. 0.36) of microhabitat use during the low flow period.
River Research and Applications, Jan 1, 2007
While the four-dimensional nature of river ecosystems has been recognized for nearly two decades,... more While the four-dimensional nature of river ecosystems has been recognized for nearly two decades, the role of lateral complexity has rarely been factored into studies of zooplankton ecology. We examined the importance of hydrologic retention areas (slackwaters) near islands and embayments of the St. Lawrence River for densities, fecundity, and diel migration of planktonic microcrustaceans. Densities of cladocera and copepods (nauplii and adult stages of cyclopoids and calanoids) were sampled from surface and deeper layers both at night (2100-0100 h, near the new moon) and during the day (1000-1400 h) for channel (deep-fast), offshore (shallow-slower), and inshore (shallow-stagnant) habitats. Average zooplankton densities increased laterally from the main channel into the slackwaters with the exception of calanoid copepods, which peaked in the intermediate depths and flows of the offshore habitats. Although the ratio of males to females for the calanoid Eurytemora affinis and the cladoceran Bosmina spp. did not differ among habitats, a greater percentage of ovigerous cladoceran females were present in slackwaters than in channel habitats. Densities of microcrustaceans were generally greater during the night than day, suggesting diel vertical migration. By demonstrating both lateral and diel differences in the spatial distribution of riverine zooplankton, we refute the view of large rivers as well-mixed homogenous systems. To the contrary, the two non-random patterns that we document imply that there is an abiotic template that at least microcrustacean potamoplankton can exploit. In turn this suggests more research into the ecological significance of the pelagic structure of other large rivers like the St. Lawrence is justified. Copyright (c) 2007 John Wiley & Sons, Ltd.
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Papers by Andrew F Casper
environmental conditions may affect the ability to accurately capture species (i.e., detection) and consequently
may lead to inappropriate inferences on occupancy rates. We used hierarchical Bayesian multiseason mixture
models to estimate occupancy and detection of 41 of 52 fish species in the Kankakee River, Illinois, by using data
from a standardized monitoring program. Fish were sampled with AC boat electrofishing and shoreline seining
over 7 years. Some centrarchids (e.g., Smallmouth Bass Micropterus dolomieu) were efficiently sampled by boat
electrofishing, whereas most other species had low detection probabilities. Moderate changes in environmental
conditions, such as water velocity and temperature, produced moderate changes in detection and occupancy.
Generally, when species had high detection probabilities, changes in environmental conditions produced relatively
small changes in the estimated detection probabilities. Our results also suggested that some sport fishes collected
from rivers with only moderate environmental fluctuations are unlikely to produce strongly biased estimates of
detection and occupancy among years. However, many species had detection probabilities that were low, imprecisely
estimated, or both. Overall, we demonstrate that long-term fisheries monitoring can effectively detect some
species at levels that are often relevant for management, but assessments of species with lower and more uncertain
detection probabilities may not provide adequate information for management decisions. We recommend the use of
sampling designs that allow the estimation of both detection and occupancy.
assessments were conducted in eight high-gradient headwaters in WestVirginia by four independent teams. Across-site and measurement variance among teams was assessed using a coefficient of variation (CV, expressed as percent). Avariability of > 50%CV,which suggests less repeatable results, occurred in only 13.8% of measurements, primarily associated with 2 of the 9 variables examined (snag density and substrate size). Between site measurement variance was the greatest at more highly disturbed sample locations, particularlywith regard to the large woody debris, tree species richness, and channel bank erosion variables. Variables with the lowest CV were tree diameter, detrital cover, canopy cover, and channel embeddedness. Based on these results, measurements included when applying HGM approach to these streams should focus on direct measurements or directed estimates that yield a large response range across a spectrum of sites while maintaining consistent repeatability among different teams,with special attention paid to their use in highly disturbed sites.
2. We evaluated the effects of predatory fish on the density, biomass and size distribution of zebra mussels in a floodplain reach of the upper Mississippi River and in a naturally constrained reach of the Ohio River. Fifty, six-sided, predator-exclusion cages and fifty ‘partial’ cages (mesh at the upstream end only) were deployed, with half the cages containing willow snags and half clay tiles suspended 12–16 cm above the bottom. A single snag or tile sample unit was removed from each cage at approximately monthly intervals from July to October 1994. Types and relative abundances of molluscivorous fish were evaluated by electrofishing near the cages in both rivers. Actual and potential recruitment of young zebra mussels on to the substrata were measured using benthic samples in both rivers and estimated (Ohio River only) from counts of planktonic veligers.
3. Zebra mussels were consumed by at least three fish species in the upper Mississippi River (mostly carp, Cyprinus carpio, and redhorse suckers, Moxostoma sp.) and five species in the Ohio River (primarily smallmouth buffalo, Ictiobus bubalus, and channel catfish, Ictalurus punctatus), but potential recruitment seemed adequate to replace consumed mussels, at least in the Ohio River. The number of juvenile benthic mussels showed no apparent link with the density of veligers soon after initiation of reproduction. Recruitment of juveniles on snags and tiles was not affected by cage type (thus eliminating a potentially confounding ‘cage effect’).
4. Fish significantly influenced mussel populations, but the impact was often greatest among low density populations in the upper Mississippi. Density and biomass differed in both rivers for cage type (higher inside cages), substratum (greater on tiles), and date (increased over time). Presumed size-selective predation was present in the Mississippi (greater on larger size classes) but was not evident in the Ohio. We hypothesize that fish in the Mississippi can more easily select larger prey from the low density populations; whereas size-selective predation on tightly packed zebra mussels in the Ohio would be difficult.
5. Although fish can reduce numbers of Dreissena polymorpha in the two rivers, current levels of fish predation seem insufficient to regulate zebra mussel densities because of its great reproductive capacity. The recent invasion of zebra mussels, however, could lead to larger fish populations while promoting greater carbon retention and overall ecosystem secondary production.
with the varying DEMs and subsequent shifts in the proportions of land use, soils and elevation. Results show the use of 30m DEMs produced hydrographic patterns amenable for using in-stream habitat protocols like PHABSIM model, especially where little or no hydrographic and land use information exists.
rapid displacement of D. polymorpha where the two species co-occur.
sampling statistical strategies. The 2-dimensional, interpolation-based maps of the Hillsborough River (Tampa, FL) show significant influences of a variety of geographic features including tributary confluences, submarine groundwater inflow, and riparian interfaces. We conclude that many sampling strategies
do not account for the type of patchy heterogeneity observed. The integration of existing in-situ sensors, inexpensive autonomous sampling platforms, and geospatial mapping techniques provides high resolution visualization that can adds a more comprehensive geographic perspective needed for environmental monitoring and assessment programs.
2. We generally agree with most of the trends identified by Statzner & Resh (2010), but also highlight a number of divergent perspectives and provide recommendations for change. Trends of particular concern are the use of inappropriate metrics to evaluate research quality (e.g. impact factor) and the salami slicing of papers to increase paper count. We advocate a transparent and comprehensive system for evaluating the research.
3. We stress the importance of impartiality and independence in the peer review process.We therefore suggest implementation of double-blind review and quality control measures for reviewers and possibly editors. Besides such structural changes, editors should be confident to overrule biased reviewer recommendations, while reviewers should provide helpful reviews
but be explicit if a submission does not meet quality standards. Authors should always conductathorough literature search and acknowledge historical scientific ideas and methods. Additionally, authors should report low-quality copy editing and reviews to the editors.
4. Both early and late career researchers should jointly implement these recommendations to reverse the negative trends identified by Statzner & Resh (2010). However, more senior scientists will always have to take the lead with respect to structural changes in the publication system given that they occupy the majority of decision-making positions.
firm scientific basis linking these to the river’s physical structure has been absent.We highlight some inherent problems in this process and suggest
possible solutions on the basis of the hydrogeomorphic classification of rivers.We suggest this link can be useful in fair asset trading (mitigation and
offsets), selection of sites for rehabilitation, cost-benefit decisions on incremental steps in restoring ecological functions, and general protection of
rivers.
environmental conditions may affect the ability to accurately capture species (i.e., detection) and consequently
may lead to inappropriate inferences on occupancy rates. We used hierarchical Bayesian multiseason mixture
models to estimate occupancy and detection of 41 of 52 fish species in the Kankakee River, Illinois, by using data
from a standardized monitoring program. Fish were sampled with AC boat electrofishing and shoreline seining
over 7 years. Some centrarchids (e.g., Smallmouth Bass Micropterus dolomieu) were efficiently sampled by boat
electrofishing, whereas most other species had low detection probabilities. Moderate changes in environmental
conditions, such as water velocity and temperature, produced moderate changes in detection and occupancy.
Generally, when species had high detection probabilities, changes in environmental conditions produced relatively
small changes in the estimated detection probabilities. Our results also suggested that some sport fishes collected
from rivers with only moderate environmental fluctuations are unlikely to produce strongly biased estimates of
detection and occupancy among years. However, many species had detection probabilities that were low, imprecisely
estimated, or both. Overall, we demonstrate that long-term fisheries monitoring can effectively detect some
species at levels that are often relevant for management, but assessments of species with lower and more uncertain
detection probabilities may not provide adequate information for management decisions. We recommend the use of
sampling designs that allow the estimation of both detection and occupancy.
assessments were conducted in eight high-gradient headwaters in WestVirginia by four independent teams. Across-site and measurement variance among teams was assessed using a coefficient of variation (CV, expressed as percent). Avariability of > 50%CV,which suggests less repeatable results, occurred in only 13.8% of measurements, primarily associated with 2 of the 9 variables examined (snag density and substrate size). Between site measurement variance was the greatest at more highly disturbed sample locations, particularlywith regard to the large woody debris, tree species richness, and channel bank erosion variables. Variables with the lowest CV were tree diameter, detrital cover, canopy cover, and channel embeddedness. Based on these results, measurements included when applying HGM approach to these streams should focus on direct measurements or directed estimates that yield a large response range across a spectrum of sites while maintaining consistent repeatability among different teams,with special attention paid to their use in highly disturbed sites.
2. We evaluated the effects of predatory fish on the density, biomass and size distribution of zebra mussels in a floodplain reach of the upper Mississippi River and in a naturally constrained reach of the Ohio River. Fifty, six-sided, predator-exclusion cages and fifty ‘partial’ cages (mesh at the upstream end only) were deployed, with half the cages containing willow snags and half clay tiles suspended 12–16 cm above the bottom. A single snag or tile sample unit was removed from each cage at approximately monthly intervals from July to October 1994. Types and relative abundances of molluscivorous fish were evaluated by electrofishing near the cages in both rivers. Actual and potential recruitment of young zebra mussels on to the substrata were measured using benthic samples in both rivers and estimated (Ohio River only) from counts of planktonic veligers.
3. Zebra mussels were consumed by at least three fish species in the upper Mississippi River (mostly carp, Cyprinus carpio, and redhorse suckers, Moxostoma sp.) and five species in the Ohio River (primarily smallmouth buffalo, Ictiobus bubalus, and channel catfish, Ictalurus punctatus), but potential recruitment seemed adequate to replace consumed mussels, at least in the Ohio River. The number of juvenile benthic mussels showed no apparent link with the density of veligers soon after initiation of reproduction. Recruitment of juveniles on snags and tiles was not affected by cage type (thus eliminating a potentially confounding ‘cage effect’).
4. Fish significantly influenced mussel populations, but the impact was often greatest among low density populations in the upper Mississippi. Density and biomass differed in both rivers for cage type (higher inside cages), substratum (greater on tiles), and date (increased over time). Presumed size-selective predation was present in the Mississippi (greater on larger size classes) but was not evident in the Ohio. We hypothesize that fish in the Mississippi can more easily select larger prey from the low density populations; whereas size-selective predation on tightly packed zebra mussels in the Ohio would be difficult.
5. Although fish can reduce numbers of Dreissena polymorpha in the two rivers, current levels of fish predation seem insufficient to regulate zebra mussel densities because of its great reproductive capacity. The recent invasion of zebra mussels, however, could lead to larger fish populations while promoting greater carbon retention and overall ecosystem secondary production.
with the varying DEMs and subsequent shifts in the proportions of land use, soils and elevation. Results show the use of 30m DEMs produced hydrographic patterns amenable for using in-stream habitat protocols like PHABSIM model, especially where little or no hydrographic and land use information exists.
rapid displacement of D. polymorpha where the two species co-occur.
sampling statistical strategies. The 2-dimensional, interpolation-based maps of the Hillsborough River (Tampa, FL) show significant influences of a variety of geographic features including tributary confluences, submarine groundwater inflow, and riparian interfaces. We conclude that many sampling strategies
do not account for the type of patchy heterogeneity observed. The integration of existing in-situ sensors, inexpensive autonomous sampling platforms, and geospatial mapping techniques provides high resolution visualization that can adds a more comprehensive geographic perspective needed for environmental monitoring and assessment programs.
2. We generally agree with most of the trends identified by Statzner & Resh (2010), but also highlight a number of divergent perspectives and provide recommendations for change. Trends of particular concern are the use of inappropriate metrics to evaluate research quality (e.g. impact factor) and the salami slicing of papers to increase paper count. We advocate a transparent and comprehensive system for evaluating the research.
3. We stress the importance of impartiality and independence in the peer review process.We therefore suggest implementation of double-blind review and quality control measures for reviewers and possibly editors. Besides such structural changes, editors should be confident to overrule biased reviewer recommendations, while reviewers should provide helpful reviews
but be explicit if a submission does not meet quality standards. Authors should always conductathorough literature search and acknowledge historical scientific ideas and methods. Additionally, authors should report low-quality copy editing and reviews to the editors.
4. Both early and late career researchers should jointly implement these recommendations to reverse the negative trends identified by Statzner & Resh (2010). However, more senior scientists will always have to take the lead with respect to structural changes in the publication system given that they occupy the majority of decision-making positions.
firm scientific basis linking these to the river’s physical structure has been absent.We highlight some inherent problems in this process and suggest
possible solutions on the basis of the hydrogeomorphic classification of rivers.We suggest this link can be useful in fair asset trading (mitigation and
offsets), selection of sites for rehabilitation, cost-benefit decisions on incremental steps in restoring ecological functions, and general protection of
rivers.
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