Backwater Habitats Research Articles

Evaluating the efficacy of using GPS satellite transmitters to assess movement of bigheaded carp in a riverine system

Abstract We have evaluated the feasibility of using GPS satellite transmitters on invasive bigheaded carp species, silver carp and bighead carp, that could determine patterns of movement, identify potential feeding and spawning areas, and inform a comprehensive monitoring and commercial removal program in the Illinois River Waterway system in the United States. Despite a wealth of information on bigheaded carp movement from acoustic and radio telemetry, a finer‐scale approach to understand habitat use and daily surfacing trends in movement would strengthen management efforts. Custom Fastloc™‐GPS data‐logging transmitters (with radio telemetry capability) manufactured by Sirtrack™ were tethered to adult bigheaded carp in field experiments. Sixteen field‐deployed transmitters were recovered and yielded 490 individual GPS waypoints when transmitters were attached to fish. We observed movement rates within the Dresden Island Reach of the Illinois River Waterway of approximately 16 river km, and movement in and out of backwater habitats and the warm‐water discharge of a nuclear generating station. We have demonstrated the use of this technology to monitor bigheaded carp and will use the information gained from this study to inform future work with remotely accessed, real‐time, Argos satellite linked prototypes. Fine‐scale accuracies, fast acquisition speeds and the ability to gather real‐time data make this a promising tool and is one the first uses of GPS technology to track fish movement in a riverine system. Continued exploration to improve tag retention efficiency will enhance its utility for continued invasive carp management.

Environmental drivers of cyanobacterial abundance and cyanotoxin production in backwaters of the Upper Mississippi River

AbstractHigh densities of cyanobacteria in aquatic ecosystems can cause impacts to ecosystem services because they serve as a poor‐quality food resource, produce toxins and can indirectly cause a variety of other negative impacts to water quality. There are many hypotheses about the potential environmental drivers of variation in cyanobacterial abundance and toxicity, but these hypotheses have rarely been considered in combination and rarely been examined in large river ecosystems. Here, we use monthly data from backwater habitats of the Upper Mississippi River (UMR) to evaluate associations between environmental conditions and cyanobacterial abundance and toxicity (microcystin and anatoxin‐a) that would be expected based on several hypotheses. Backwaters in the Mississippi River vary in flushing rate, temperature, turbidity, nutrient availability, water depth, and vegetative cover. We find support for hypotheses that suggest physical conditions in backwaters (flushing rate, temperature, turbidity, rooted vegetation cover, and water depth) and nutrient availability influence cyanobacterial abundance and toxicity. We then used structural equation modeling to incorporate several hypotheses into a causal modeling framework, which indicated that backwater connectivity (flushing) strongly influences cyanobacterial abundance via the regulation of water temperature, and that nutrient availability strongly influences the presence of microcystin concentrations above our detection limit. Our data suggest that management of backwater connectivity could influence cyanobacterial abundance and toxicity in UMR backwaters. Reconnecting backwaters (via alteration of levees) could serve as a local adaptation to minimize the effects of climate change and excessive nutrient loading.

Rare Potamogeton species can establish in restored Danish lowland stream reaches

Abstract Freshwater biodiversity is severely threatened, and despite many efforts to halt biodiversity loss the decline continues. Here, we used a transplantation approach to explore whether failure to reverse this trend for freshwater plants reflects that restoration measures applied to streams are inadequate for restoring suitable habitat conditions for plant species in decline. We identified declining species within the plant genus Potamogeton and introduced five of these (Potamogeton compressus L., Potamogeton gramineus L., Potamogeton lucens L., Potamogeton praelongus Wulfen., and Potamogeton pusillus L.) into five restored lowland stream reaches in three different habitat types to examine species establishment and growth. We found that plant establishment varied among streams and species, but we did not see any effect of habitat type within streams on either species growth or survival. Potamogeton compressus and P. pusillus failed to overwinter, while P. gramineus, P. lucens, and P. praelongus were all able to establish viable stands and to overwinter successfully in several of the experimental streams. Our results suggest that suitable habitats are available for declining Potamogeton species in restored stream reaches in Denmark, but their continued growth may be challenged by limited overwintering success. Consequently, we find it likely that dispersal constraints prevent declining Potamogeton species from naturally recolonising restored stream reaches. Understanding the importance of life history traits, such as overwintering and dispersal, can be crucial for the recovery of plant diversity in streams. Here we show that species that survived during winter were those with extensive growth of roots and rhizomes making them more adapted to withstand high flows than species relying on seeds and turions for overwintering. The creation of calmer backwater habitats can therefore be crucial when restoring stream reaches since these habitats may facilitate overwintering of species lost from the main channel during winter.

Environmental factors associated with silver carp presence and relative abundance near an invasion front to inform removal efforts

Management of invasive fishes has relied heavily upon understanding their spatial distributions and habitat use at fine spatial scales to guide treatments and removals. In the USA, targeted removal is used in management of bigheaded carps (Hypophthalmichthys spp.) in the Mississippi River system to reduce invasion potential into the Laurentian Great Lakes from the upper Illinois Waterway. Our study tested factors linked to fine-scale spatial distributions of the most prevalent bigheaded carp species—silver carp (Hypophthalmichthys molitrix)—in the upper Illinois River to increase effectiveness of removal efforts. Bi-monthly mobile hydroacoustic sampling was conducted from 2017 to 2018 and paired with continuous environmental data collection in the two northern-most invaded reaches of the upper Illinois River. Model selection was used to describe habitat conditions associated with silver carp presence and density. Depth was the most consistent predictor of silver carp presence and density, with shallower depths consistently associated with higher abundance. During summer months, shallow areas in large backwater habitats with lower temperature and higher dissolved oxygen concentration held more silver carp. These results may help managers focus targeted removal efforts through time, increase harvest effectiveness, and reduce the potential for further invasion toward the Laurentian Great Lakes.

Operational Impacts of a Water Management Structure on the Surrounding Fish Assemblages in a Restored Backwater and a Large Floodplain River

Water management structures (WMS) are used to regulate water levels between large floodplain river backwaters and their adjacent river systems offering a balance between maintaining quality backwater habitat and providing benefits to the river systems. The design and operation of these WMS is dependent on unique management goals, and their impacts on the surrounding ecosystem are understudied. From 2016–2018 we quantified the response of the surrounding fish assemblages (i.e., backwater and river abundance and composition) to the WMS operation at the Emiquon Preserve, a 2723 ha restored floodplain lake located adjacent to the main channel of the Illinois River, U.S.A. Environmental conditions were recorded, and fish were collected using boat electrofishing on both sides of the WMS under three operational levels: closed and no flow, gravity flowing water, and mechanically pumping water to the river. Multivariate analyses determined that there was no difference in fish community composition within the Emiquon Preserve among operation levels. Within the river there were differences in community composition when the WMS was closed and mechanically pumping water. Environmental parameters varied seasonally and WMS operation level varied but indicated an increase in chlorophyll-a in the river when the WMS was mechanically pumping water, although the chlorophyll-a decreased within 200 m downstream of the WMS in the Illinois River. This study suggests that managed connections between restored backwater and habitats operated like this WMS have variable, spatially isolated impacts on fish communities despite supplying chlorophyll-a to large river ecosystems.

Aquatic habitat changes within the channelized and impounded Arkansas River, Arkansas, USA

AbstractRiver‐wide changes in morphologic character following channelization and impoundment alter the occurrence and distribution of surface water and available habitats for aquatic organisms. Quantifying patterns of creation, redistribution or disappearance of habitats at river‐wide and decadal spatiotemporal scales can promote understanding regarding trajectories of different habitat types following alteration and prospects of direct habitat enhancement projects within altered alluvial rivers. Newly available remote‐sensing tools and databases may improve detection of river‐wide changes in habitat through time. We used a combination of remote‐sensing data and generalized linear models to assess changes in surface water coverage from 1984 to 2015 among aquatic habitats of 496 km of the Arkansas River within Arkansas, USA. Changes through time in surface area of permanent and episodically inundated areas — and thus the availability of aquatic habitat — were variable along the river. Overall, the river lost a total 2.1% of permanent and 12.1% of episodic water surface area. The general trend of loss of off‐main‐channel habitat and increased coverage of permanent water along main‐channel habitats may indicate a long‐term transition (i.e. ramp‐type disturbance) within areas of the Arkansas River where backwaters are transitioning to terrestrial environments, and habitat heterogeneity in the main channel is decreasing. As such, a decadal‐scale change of channel form and backwater habitats may be the dominant pattern with limited regeneration of diverse habitat types. Understanding changes to permanent and episodic water availability may aid predictions regarding ecological effects of channelization and impoundments, including both increases and decreases in riverine productivity, biotic diversity and population abundances through space and time. Water resource managers and biologists can use information regarding river‐wide changes in habitat availability obtained through remote sensing data to direct river management practices, including dredging and side‐channel construction, and to assess ecological responses to such changes.

Bluegill Habitat Use in the Upper Mississippi River

Anthropogenic modifications to the environment have had damaging effects on the wildlife that depend on those natural ecosystems. Specific to Upper Mississippi River fishes, channelization, dams, and loss of floodplain connectivity have all been purported as deleterious. In the face of these habitat modifications, understanding habitat requirements of native species is needed to help guide management and restoration efforts. Furthermore, bluegill (Lepomis macrochirus) are an important indicator species that may provide insight to habitat needs of the broader fish community (e.g., “canary in a coal mine”). Prior research suggests bluegill require a mosaic of habitats throughout all life stages (e.g., main channel to backwater connection). As such, the objective of this study was to identify the habitat needs of bluegill in the Upper Mississippi River. We evaluated bluegill habitat use via electrofishing conducted by the U.S. Army Corps of Engineers’ Long-Term Resource Monitoring (LTRM) element. Electrofishing events (n = 4868) were conducted at three field sites throughout the Upper Mississippi River from 1993 to 2017. Our analysis of catch data (n = 83,352) indicates that bluegill prefer backwater macrohabitat over main channel and side channel habitats. Bluegill abundance varied between microhabitat characteristics. Bluegill catch rates were highest in low-flow areas, with velocities ranging from 0 to 0.09 m/sec. In general, catch rates were highest across all pools in moderately shallow depths (0–1.5 m) and in silty substrates. Management efforts that focus on the preservation of backwater habitat and connectivity to the main channel should help to sustain bluegill populations in the Upper Mississippi River. The information garnered in this study can be used to help direct management efforts that not only favor bluegill, but also other members of the Upper Mississippi River fish community.

Using Geomorphology to Better Define Habitat Associations of a Large-Bodied Fish, Common Snook Centropomus undecimalis, in Coastal Rivers of Florida

To adequately protect habitat for economically important fishes, the habitats used must first be identified and described. Coastal geomorphology is often overlooked as an influential parameter of fish habitat use in favor of readily available data taken at the time of sampling. We hypothesized that river dynamics (e.g., length, watershed, floodplain connectivity) and mesohabitat categories based on geomorphology (e.g., backwater, river bend) were at least as important as fine-scale microhabitat (e.g., depth, shore type) for describing the distribution and habitat affinities of Common Snook Centropomus undecimalis (hereafter referred to as snook) in coastal rivers of the Atlantic coast and Tampa Bay, Florida. Contrary to previously studied rivers where adult snook abundance increased during a seasonal prey pulse, adult snook abundance in the study rivers differed little between seasons and the rivers were used as nurseries by juveniles. Mesohabitat categories were important for describing snook distribution. For example, the smallest snook (≤ 250 mm total length, TL) strongly selected for backwater habitats while the largest (≥ 851 mm TL) selected river bends. Detailed microhabitat data collected at individual capture locations were helpful in describing the habitat associations of the smallest size group of snook (shallow depths and aquatic macrophytes with various shore types) and for characterizing river bends (high flow, deep water, and lower salinities) but were not strongly associated with other snook sizes or mesohabitat categories. Thus, broader scale habitat features were found to be equally as important as detailed microhabitat and should be considered when informing conservation efforts.

Otoliths Reveal Spawning Ecology and Early Life History of Sympatric Catostomids

AbstractDifferences in spawning ecology and early life history may influence the recruitment success of three sympatric catostomids in the Colorado River basin: the Bluehead Sucker Catostomus discobolus, Flannelmouth Sucker C. latipinnis, and federally endangered Razorback Sucker Xyrauchen texanus. In the San Juan River, all three species annually produce larvae, but only Bluehead and Flannelmouth suckers regularly recruit to the juvenile phase and older. Otolith microstructure analysis can determine age, growth rates, and spawning periodicity and may elucidate possible reasons for differences in recruitment among species. Larval suckers were collected from low‐velocity habitats in the San Juan River in 2011; fish were measured, and ontogenetic phase and fish age were determined from otolith increment counts. Otolith age was used to determine hatch dates and spawning periodicity, calculate daily growth rates, and develop three candidate growth functions relating fish age and body length. Relative to Bluehead and Flannelmouth suckers, Razorback Suckers had a shorter spawning period, lower growth rate, and a higher proportion of the least developed ontogenetic phase. The small size of Razorback Suckers relative to other suckers may result in higher predation and lower prey acquisition, thus restricting their transition to more developed phases and limiting recruitment to the juvenile phase. Model ranking based on Akaike's information criterion (corrected for small sample size) was nearly identical for all growth functions. The early life history information we provide may guide flow releases in this regulated system to provide suitable backwater habitat and warmer water temperatures compatible with reproduction, growth, and survival of native catostomids, including the endangered Razorback Sucker. However, due to the limited temporal and geographic extent of samples used in this study, data presented herein are not inclusive of all conditions under which suckers may be present in the San Juan River.

Modelling bioenergetic and population‐level impacts of invasive bigheaded carps (Hypophthalmichthys spp.) on native paddlefish (Polyodon spathula) in backwaters of the lower Mississippi River

Abstract While invasions of large rivers by exotic fish species are well documented, assessing actual or potential impacts on native species is a challenge. Rapid assessments may be possible through the application of a combination of bioenergetic and population dynamic models. Paddlefish (Polyodon spathula) is a native species in the central USA with a history of population decline due to waterway development and overharvesting for roe. It is not known whether paddlefish are impacted by resource competition from invasive bigheaded carp populations, including silver (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis), which have expanded dramatically in the Mississippi River. We used bioenergetic models to project the potential impact of invasive silver and bighead carp on zooplankton density and paddlefish somatic growth in backwater habitat. Bioenergetic outputs were translated to impacts on fecundity, becoming inputs for 50‐year metapopulation simulations of backwater habitat connected to the main‐stem Mississippi River by episodic flood events. Competition with carp reduced growth and increased the risk of population decline for paddlefish. Impacts increased disproportionately with increased carp abundance and were further exacerbated in scenarios with increased diet overlap or decreased zooplankton abundance. We also analysed paddlefish condition data collected at sites near the lower Mississippi River with varying histories of carp invasion. These data give credence to the bioenergetic model output; paddlefish had reduced body condition at sites with long‐established, high‐density carp populations. We conclude that invasive bigheaded carps have great potential to reduce paddlefish growth, fecundity, and abundance. The pairing of bioenergetics and population models is likely to be broadly useful in assessing the risks posed by other invasive species.

Climate change vulnerability assessment for Pacific Lamprey in rivers of the Western United States

Pacific Lamprey (Entosphenus tridentatus) are a native anadromous species that, like salmon, historically returned to spawn in large numbers in watersheds along the west coast of the United States (U.S.). Lamprey play a vital role in river ecosystems and are one of the oldest vertebrates that have persisted over time likely influencing the evolution of many aquatic species. Pacific Lamprey have declined in abundance and are restricted in distribution throughout Washington, Oregon, Idaho and California. A key uncertainty influencing Pacific Lamprey status is the impact of climate change. We modified the NatureServe Climate Change Vulnerability Index (CCVI) to accommodate climate predictions from the International Panel on Climate Change. Using downscaled information, we characterized changes in 15 rivers occupied by Pacific Lamprey in the western U.S. We evaluated this risk under Representative Concentration Pathways (RCP) 4.5 and 8.5 for two time periods (mid-century 2040–2069 and end-century 2070–2099). The CCVI scores generally increased when going from RCP 4.5 to RCP 8.5 in three Global Climate Models for both mid-century and end-century, which our analyses forecasts degraded stream temperature and hydrologic conditions under increasing greenhouse gas emissions. The geographically assessed results suggest that climate change impacts to Pacific Lamprey vulnerability are magnified in highly altered rivers. If we continue to observe greenhouse gas emission levels associated with the RCP 8.5, Pacific Lamprey will be at greater risk to climate change impacts. In order to mitigate the risk from climate change toward the end of the century, additional actions will need to be prioritized to rapidly reduce the impact of these threats such as increasing flow, creating backwater habitat, restoring riparian vegetation and reducing stream disturbances. The findings revealed the patterns of vulnerability for Pacific Lamprey across their U.S. range are informative for prioritizing river restoration actions when paired with regional implementation plans.

Spatial variation in bluegill population demographics in a highly modified large river system

Population demographics are used by biologists and managers to determine the quality of a fishery and set regulations to achieve desired management goals. Regulating a large river system fishery that spans a substantial geographical region is often complicated by spatially variable environmental factors that affect fish population dynamics (e.g. habitat, water quality); these dynamics are rarely examined within an entire system. In this study we compared spatial differences in population age and length at capture, growth, fecundity and body condition of bluegill Lepomis macrochirus among two different river reaches (e.g. basin width, gradient, velocity) of the Illinois River (Illinois, USA) and a disconnected floodplain lake, the Emiquon Preserve. Variations in selected population demographics were evaluated in relation to well-documented habitat characteristics (e.g. water quality, aquatic vegetation, backwater availability). Differences in bluegill demographic traits between the disconnected floodplain lake and river reaches were distinct, and variations between river reaches were sex specific. The floodplain lake generally had older bluegill that expressed a higher maximum length at age and a lower growth rate and fecundity than bluegill in river reaches. River bluegill differed between river reaches in male growth, and fecundity in both sexes. Body condition was not significantly different among bluegill populations. Early research on floodplain lakes indicates that this habitat supports greater fish growth and higher reproductive fitness than mainstem habitat. We conclude that increasing the availability of quality backwater habitat, even within a highly modified large river system like the Illinois River, could substantially increase the quality and stability of bluegill populations.

Black Carp in North America: a Description of Range, Habitats, Time of Year, and Methods of Reported Captures

AbstractBlack Carp Mylopharyngodon piceus are considered invasive in North America. Since the first wild capture in 2003, collection records have increased, yet information summarizing successful collection methods is lacking. Reported capture methods throughout the Black Carp's native and introduced ranges vary providing minimal aid for determining control and monitoring methods. Here, we describe the current species range and the spatial and temporal variation among captures. The size of fish can affect capture; thus, we report captured fish and gear dimensions and recommend appropriate scientific collection methods. We focus on collection data from 302 Black Carp ranging from 410 to 1,607 mm total length received from 2011 to February 2019. The reported range of Black Carp has expanded in the Cumberland, Illinois, Mississippi, Missouri, Ohio, and Tennessee rivers. Captures most frequently occurred in channel (41%), side‐channel (24%), and backwater (22%) habitat types, with increased records in May, June, and July. Most records were commercial captures, of which hoop net (51%) and gill net (26%) were most common. Results suggest that standard scientific methods for sampling fish in large rivers and standing water by hoop net and gill net may be used to monitor Black Carp, but a robust study design needs to be applied to determine gear selectivity and to determine if catch rates are density dependent or incidental.

Spatial and temporal changes in species composition of submersed aquatic vegetation reveal effects of river restoration

We examined temporal changes in spatial patterns of submersed aquatic vegetation (SAV) in response to the restoration of geomorphic habitat in Navigation Pool 8 of the Upper Mississippi River from 1998 to 2016. The frequency of occurrence and species composition of SAV at sampling sites were spatially interpolated for each year to create annual maps. Linear models were fitted to temporal changes in SAV within each map pixel. The frequency of occurrence of SAV (across all species) increased over time in much of the impounded region of the pool, including areas near restored islands. However, impounded areas maintained a relatively consistent species composition over time, with species known to be tolerant of higher flow velocities (>0.10 m/second) and wind fetch distances (>1,000 m) (e.g. Vallisneria americana) being most abundant. In contrast, areas protected by newly constructed islands transitioned from V. americana to species found in other protected backwater habitats and known to be intolerant of high flow velocities and wind fetch distances (e.g. Ceratophyllum demersum). The results suggest that previously reported improvements in water clarity may have improved growing conditions for all SAV species, especially in the lower impounded portion of the pool, while island restoration created more backwater‐like habitats and facilitated changes in species composition. Assessing changes in SAV occurrence alone offers only a partial view of local‐scale river restoration (e.g. island building), while analyses of species composition are likely to be more indicative of the types of changes (i.e. reduced flow velocity and wind fetch) associated with restoring geomorphic habitat.

Connectivity and habitat typology drive CO2 and CH4 fluxes across land–water interfaces in lowland rivers

AbstractLowland rivers are assumed to be a net source of carbon dioxide (CO2) and methane (CH4). However, little is known about the contribution of marginal permanent and temporary riverine aquatic systems to river carbon metabolism. Elevation, in relation to flooding, hydro‐morphological, and ecological features of such habitats, can affect the gas fluxes across the water–atmosphere interfaces and the periodically air‐exposed riverbeds. This hypothesis was investigated in the lowland sector of the Po River (Northern Italy) from May to September 2008. Five different aquatic habitats were considered: the main river course; a backwater habitat; and three lateral lentic waterbodies—an oxbow and two quarry lakes of different age. The water mass was always CO2 and CH4 supersaturated, and gas fluxes were from the water to the atmosphere. In the highly dynamic river course and backwaters, CO2 emission rates were nearly one order of magnitude greater than in the lentic and hypoxic oxbow and quarry lakes. By contrast, CH4 fluxes peaked in the lentic, deeper, and permanent water bodies. At sediment–atmosphere interfaces, the CO2 emissions increased along an organic matter, a water saturation, and a chlorophyll a gradient, attaining the maximum rates in the periodically air‐exposed riverbed and marginal sandy sediments. These differences in gas fluxes resulted from either the submersion persistence or the alternation of submersion and emersion phases, which were ultimately due to the gap between elevation and river water variations. All this stresses the critical role of marginal aquatic habitats for river C budget.

Limited nitrate retention capacity in the Upper Mississippi River

The Mississippi River and other large rivers have the potential to regulate nitrogen export from terrestrial landscapes, and thus mitigate eutrophication in downstream aquatic ecosystems. In large rivers, human-constructed impoundments and connected backwaters may facilitate nitrogen removal; however, the capacity of these features is poorly quantified and incompletely incorporated into model frameworks. Using a high-resolution and spatially intensive sampling technique, we assessed the contribution of individual navigation pools, as well as impounded open waters and backwater wetlands within them, to overall nitrate retention by mapping the entire length (1370 km) of the Upper Mississippi River (UMR) main channel. Based on this single spatial survey of water chemistry, the river appeared to act primarily as a passive nitrate transporter, retaining only 12.5% of the incoming load, most of which occurred in the upper 150 km of the river, which includes the largest and only naturally impounded reach of the river. Although reservoirs typically are nitrogen sinks, our data indicate that UMR dams do not impede river flows to the extent necessary to promote substantial changes in water residence times and subsequent nitrogen removal. Backwaters routinely had lower nitrate concentrations than the main channel, but their limited hydrologic connectivity to the through-flowing river channel constrained their influence on downstream export. As a whole, the UMR did not remove a substantial proportion of its nitrate load despite optimal N removal conditions, numerous impoundments, and the presence of extensive backwater habitats. These results suggest that efforts to reduce delivery of nitrogen to the Gulf of Mexico should emphasize mitigation strategies that target upland nutrient sources rather than relying on removal within the Mississippi River.

Long-Distance Movements of Four Polyodon spathula (Paddlefish) from a Remote Oxbow Lake in the Lower Mississippi River Basin

Short-term movements of adult Polyodon spathula (Paddlefish) are well-documented, but long-term movements are underreported. In this study, we describe extraordinary distances traveled by 4 Paddlefish that were captured, tagged, and released in Moon Lake, a remote oxbow lake in Coahoma County, MS. After 8–24 months at large, the 4 fish were recaptured in the Missouri, Mississippi, and Ohio rivers, having traversed 1408–2433 km from Moon Lake through multiple waterways downstream to the Mississippi River at Vicksburg, MS, and then upriver to 4 geographically disparate locations. The multiple waterways used by these fish and the extensive distances traveled demonstrate the potential importance of backwater habitats located away from the mainstem river, and also underscore the need for interstate cooperation to protect Paddlefish populations.

Gradients in Catostomid Assemblages along a Reservoir Cascade

AbstractSerial impoundment of major rivers leads to alterations of natural flow dynamics and disrupts longitudinal connectivity. Catostomid fishes (suckers, family Catostomidae) are typically found in riverine or backwater habitats yet are able to persist in impounded river systems. To the detriment of conservation, there is limited information about distribution of catostomid fishes in impounded rivers. We examined the longitudinal distribution of catostomid fishes over 23 reservoirs of the Tennessee River reservoir cascade, encompassing approximately 1600 km. Our goal was to develop a basin‐scale perspective to guide conservation efforts. Catostomid species composition and assemblage structure changed longitudinally along the reservoir cascade. Catostomid species biodiversity was greatest in reservoirs lower in the cascade. Assemblage composition shifted from dominance by spotted sucker Minytrema melanops and buffalos Ictiobus spp. in the lower reservoirs to carpsuckers Carpiodes spp. midway through the cascade and redhorses Moxostoma spp. in the upper reservoirs. Most species did not extend the length of the cascade, and some species were rare, found in low numbers and in few reservoirs. The observed gradients in catostomid assemblages suggest the need for basin‐scale conservation measures focusing on three broad areas: (1) conservation and management of the up‐lake riverine reaches of the lower reservoirs, (2) maintenance of the access to quality habitat in tributaries to the upper reservoirs and (3) reintroductions into currently unoccupied habitat within species' historic distributions. Copyright © 2017 John Wiley & Sons, Ltd.

Restoration Versus Invasive Species: Bigheaded Carps' Use of A Rehabilitated Backwater

AbstractKnowledge of how invasive species use invaded habitats can aid in developing management practices to exclude them. Swan Lake, a 1100‐ha Illinois River (USA) backwater, was rehabilitated to restore ecosystem functions, but may provide valuable habitat for invasive bigheaded carps [bighead carp (Hypophthalmichthys nobilis) and silver carp (H. molitrix)]. Use (residency and passages) of Swan Lake by invasive bigheaded carps was monitored using acoustic telemetry (n = 50 individuals/species) to evaluate the use of a large, restored habitat from 2004 to 2005. Passages (entrances/exits) by bigheaded carps were highest in winter, and residency was highest in the summer. Bighead carp backwater use was associated with the differences in temperature between the main channel and backwater, and passages primarily occurred between 18:00 h and midnight. Silver carp backwater use was positively correlated with water level and main channel discharge, and fewer passages occurred between 12:00 h and 18:00 h than during any other time of day. Harvest occurring during summer or high main channel discharge could reduce backwater abundances while maintenance of low water levels could reduce overall backwater use. Conclusions from this study regarding the timing of bigheaded carps' use of backwater habitats are critical to integrated pest management plans to control invasive species. Copyright © 2017 John Wiley & Sons, Ltd.

Invasive Silver Carp movement patterns in the predominantly free-flowing Wabash River (Indiana, USA)

Many organisms must move among habitats to fulfill life history requirements. Fish movements have been widely studied and tend to be either fine-scale (i.e., routine) and governed by factors such as food availability and cover, or broad-scale and associated with spawning migrations. However, movements of invasive fishes in non-native ecosystems are comparatively poorly understood despite the often critical importance of fish movement and dispersal for invasion success. We examined invasive Silver Carp (Hypophthalmichthys molitrix) movements using acoustic telemetry to monitor the timing, distance, and direction of fish movements and assessed movements in relation to seasonal, annual, environmental, and individual factors in the Wabash River (Indiana, USA), a largely unregulated Midwestern river. Silver Carp exhibited highly variable movements that could be rapid and large in magnitude; however, tagged individuals remained stationary most of the time. Despite high variability, several trends emerged, indicating the importance of backwater habitats, avoidance of small tributaries, and tendencies of tagged fish to exhibit directed spring and fall broad-scale movements. Summer movements were smaller in magnitude, characterized by lower movement rates, and evenly split between upstream and downstream directions, although tagged Silver Carp moved more frequently during summer months. Our results indicate that specific seasons (i.e., spring and early fall) and locations (i.e., backwaters) are likely targets for Silver Carp control in the Wabash River and should also be useful targets for early detection and control in other largely unconstrained rivers over a broad geographic range (e.g., Great Lakes tributaries and upper Mississippi River mainstem and tributaries).