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At least 1,117 records · Page 62Linked to original sources

USGS2010

Mercury contamination in fish in midcontinent great rivers of the united states: Importance of species traits and environmental factors

We measured mercury (Hg) concentrations in whole fish from the Upper Mississippi, Missouri, and Ohio Rivers to characterize the extent and magnitude of Hg contamination and to identify environmental factors influencing Hg accumulation. Concentrations were generally lower (80% of values between 20?200 ng g 1 wet weight) than those reported for other regions (e.g., upper Midwest and Northeast U.S.). Mercury exceeded the risk threshold for belted kingfisher (Ceryle alcyon, the most sensitive species considered) in 33?75% of river length and 1?7% of river length for humans. Concentrations were lower in the Missouri than in the Mississippi and Ohio Rivers, consistent with continental-scale patterns in atmospheric Hg deposition. Body size and trophic guild were the best predictors of Hg concentrations, which were highest in large-bodied top predators. Site geochemical and landscape properties were weakly related with fish Hg. Moreover, relationships often ran contrary to conventional wisdom, and the slopes of the relationships (positive or negative) were inconsistent among fish guilds and rivers. For example, sulfate is positively associated with fish Hg concentrations but was negatively correlated with Hg in five of six regression models of tissue concentrations. Variables such as pH, acid neutralizing capacity, and total phosphorus did not occur at levels associated with high fish Hg concentrations, partially explaining the relatively low Hg values we observed. ?? 2010 American Chemical Society.

Environmental Science & Technology↗

USGS2001

An evaluation of selenium concentrations in water, sediment, invertebrates, and fish from the Republican River Basin: 1997-1999

The Republican River Basin of Colorado,Nebraska, and Kansas lies in a valley which contains PierreShale as part of its geological substrata. Selenium is anindigenous constituent in the shale and is readily leached intosurrounding groundwater. The Basin is heavily irrigated throughthe pumping of groundwater, some of which is selenium-contaminated, onto fields in agricultural production. Water,sediment, benthic invertebrates, and/or fish were collected from46 sites in the Basin and were analyzed for selenium to determinethe potential for food-chain bioaccumulation, dietary toxicity,and reproductive effects of selenium in biota. Resultingselenium concentrations were compared to published guidelines orbiological effects thresholds. Water from 38% of the sites (n = 18) contained selenium concentrations exceeding 5 μg L -1 , which is reported to be a high hazard for selenium accumulation into the planktonic food chain. An additional 12 sites (26% of the sites) contained selenium in water between 3–5 μg L -1 , constituting a moderate hazard. Selenium concentrations in sedimentindicated little to no hazard for selenium accumulation fromsediments into the benthic food chain. Ninety-five percent ofbenthic invertebrates collected exhibited selenium concentrationsexceeding 3 μg g -1 , a level reported as potentially lethal to fish and birds that consume them. Seventy-five percent of fish collected in 1997, 90% in 1998, and 64% in 1999 exceeded 4 μg g -1 selenium, indicating a high potential for toxicity andreproductive effects. However, examination of weight profilesof various species of collected individual fish suggestedsuccessful recruitment in spite of selenium concentrations thatexceeded published biological effects thresholds for health andreproductive success. This finding suggested that universalapplication of published guidelines for selenium may beinappropriate or at least may need refinement for systems similarto the Republican River Basin. Additional research is needed todetermine the true impact of selenium on fish and wildliferesources in the Basin.

Environmental Monitoring and Assessment↗

USGS2021

Trophic niches of native and nonnative fishes along a river-reservoir continuum

Instream barriers can constrain dispersal of nonnative fishes, creating opportunities to test their impact on native communities above and below these barriers. Deposition of sediments in a river inflow to Lake Powell, USA resulted in creation of a large waterfall prohibiting upstream movement of fishes from the reservoir allowing us to evaluate the trophic niche of fishes above and below this barrier. We expected niche overlap among native and nonnative species would increase in local assemblages downstream of the barrier where nonnative fish diversity and abundance were higher. Fishes upstream of the barrier had more distinct isotopic niches and species exhibited a wider range in δ 15 N relative to downstream. In the reservoir, species were more constrained in δ 15 N and differed more in δ 13 C, representing a shorter, wider food web. Differences in energetic pathways and resource availability among habitats likely contributed to differences in isotopic niches. Endangered Razorback Sucker ( Xyrauchen texanus ) aggregate at some reservoir inflows in the Colorado River basin, and this is where we found the highest niche overlap among species. Whether isotopic niche overlap among adult native and nonnative species has negative consequences is unclear, because data on resource availability and use are lacking; however, these observations do indicate the potential for competition. Still, the impacts of diet overlap among trophic generalists, such as Razorback Sucker, are likely low, particularly in habitats with diverse and abundant food bases such as river-reservoir inflows.

Utah↗

USGS2022

Effects of shady environments on fish collective behavior

Despite significant efforts devoted to understanding the underlying complexity and emergence of collective movement in animal groups, the role of different external settings on this type of movement remains largely unexplored. Here, by combining time series analysis and complex network tools, we present an extensive investigation of the effects of shady environments on the behavior of a fish species (Silver Carp Hypophthalmichthys molitrix ) within earthen ponds. We find that shade encourages fish residence during daylight hours, but the degree of preference for shade varies substantially among trials and ponds. Silver Carp are much slower and exhibit lower persistence in their speeds when under shade than out of it during daytime and nighttime, with fish displaying the highest persistence degree and speeds at night. Furthermore, our research shows that shade affects fish schooling behavior by reducing their polarization, number of interactions among individuals, and the stability among local neighbors; however, fish keep a higher local degree of order when under shade compared to nighttime positions.

Scientific Reports↗

USGS2023

Whole-lake acoustic telemetry to evaluate survival of stocked juvenile fish

Estimates of juvenile survival are critical for informing population dynamics and the ecology of fish, yet these demographic parameters are difficult to measure. Here, we demonstrate that advances in animal tracking technology provide opportunities to evaluate survival of juvenile tagged fish. We implemented a whole-lake telemetry array in conjunction with small acoustic tags (including tags < 1.0 g) to track the fate of stocked juvenile cisco ( Coregonus artedi ) as part of a native species restoration effort in the Finger Lakes region of New York, USA. We used time-to-event modeling to characterize the survival function of stocked fish, where we infer mortality as the cessation of tag detections. Survival estimates revealed distinct stages of juvenile cisco mortality including high immediate post-release mortality, followed by a period of elevated mortality during an acclimation period. By characterizing mortality over time, the whole-lake biotelemetry effort provided information useful for adapting stocking practices that may improve survival of stocked fish, and ultimately the success of the species reintroduction effort. The combination of acoustic technology and time-to-event modeling to inform fish survival may have wide applicability across waterbodies where receiver arrays can be deployed at scale and where basic assumptions about population closure can be satisfied.

New York↗

USGS2002

Predation on exotic zebra mussels by native fishes: Effects on predator and prey

1. Exotic zebra mussels, Dreissena polymorpha, occur in southern U.S. waterways in high densities, but little is known about the interaction between native fish predators and zebra mussels. Previous studies have suggested that exotic zebra mussels are low profitability prey items and native vertebrate predators are unlikely to reduce zebra mussel densities. We tested these hypotheses by observing prey use of fishes, determining energy content of primary prey species of fishes, and conducting predator exclusion experiments in Lake Dardanelle, Arkansas. 2. Zebra mussels were the primary prey eaten by 52.9% of blue catfish, Ictalurus furcatus; 48.2% of freshwater drum, Aplodinotus grunniens; and 100% of adult redear sunfish, Lepomis microlophus. Blue catfish showed distinct seasonal prey shifts, feeding on zebra mussels in summer and shad, Dorosoma spp., during winter. Energy content (joules g-1) of blue catfish prey (threadfin shad, Dorosoma petenense; gizzard shad, D. cepedianum; zebra mussels; and asiatic clams, Corbicula fluminea) showed a significant species by season interaction, but shad were always significantly greater in energy content than bivalves examined as either ash-free dry mass or whole organism dry mass. Fish predators significantly reduced densities of large zebra mussels (>5 mm length) colonising clay tiles in the summers of 1997 and 1998, but predation effects on small zebra mussels (???5 mm length) were less clear. 3. Freshwater drum and redear sunfish process bivalve prey by crushing shells and obtain low amounts of higher-energy food (only the flesh), whereas blue catfish lack a shell-crushing apparatus and ingest large amounts of low-energy food per unit time (bivalves with their shells). Blue catfish appeared to select the abundant zebra mussel over the more energetically rich shad during summer, then shifted to shad during winter when shad experienced temperature-dependent stress and mortality. Native fish predators can suppress adult zebra mussel colonisation, but are ultimately unlikely to limit population density because of zebra mussel reproductive potential.

Freshwater Biology↗

USGS2012

Mineralization, watershed geochemistry, and metals in fish from a Subarctic River, Alaska

We report on the levels of trace metals and metalloids in Arctic grayling (Thymallus arcticus), an important freshwater sport and subsistence fish in the Fortymile River, east-central Alaska. Functional biogeochemical baseline values and (or) ranges are presented for 38 major- and trace-elements in the muscle (fillet) and liver of 34 fish collected from 11 sampling sites in the watershed. In addition, we present N-, C-, and S-isotopic data for muscle samples. These data are the first to be reported for Arctic grayling in this region of Alaska. Geometric means for total Hg in muscle and liver tissue are 0.069 and 0.062 ppm, respectively. These levels are more than an order of magnitude below the FDA permissible value for methylmercury in fish fillets. In general, we noted little variation in the elemental concentrations in muscle tissue among samples at each of the 11 fish-sampling sites. No definitive link could be attributed between biogeochemical patterns and regional lithology. Stomach-content chemistry varied widely (relative muscle tissue or liver) and generally reflected sediment chemistry - a component of the ingested material. Stomach-content material was examined for the occurrence and frequency of macroinvertebrates and their chemical composition in three fish. Results showed considerable diversity, with 9 to 15 invertebrate taxa of which both aquatic and terrestrial individuals were found. The N-isotopic compositions of muscle fillet samples are homogeneous (??15N = 7.6 - 9.7 permil), reflecting a restricted, low trophic (primary predator) position for the grayling. C and S isotopic compositions (??13C and ??34S) of fillet samples range from -33.1 to -25.8 permil and -8.4 to 8.2 permil, respectively, suggesting heterogeneity of food sources (both aquatic and terrestrial). Copyright ASCE 2005.

Conference Paper↗

USGS2016

Seasonal and diel effects on acoustic fish biomass estimates: application to a shallow reservoir with untargeted common carp ( Cyprinus carpio )

The aim of the present study was to understand how seasonal fish distributions affect acoustically derived fish biomass estimates in a shallow reservoir in a semi-arid country (Tunisia). To that end, sampling events were performed during four seasons (spring (June), summer (September), autumn (December) and winter (March)) that included day and night surveys. A Simrad EK60 echosounder, equipped with two 120-kHz split-beam transducers for simultaneous horizontal and vertical beaming, was used to sample the entire water column. Surveys during spring and summer and daytime hours of winter were deemed unusable owing to high methane flux from the sediment, and during the day survey of autumn, fish were close to the reservoir bottom leading to low detectability. It follows that acoustic surveys should be conducted only at night during the cold season (December–March) for shallow reservoirs having carp Cyprinus carpio (L.) as the dominant species. Further, night-time biomass estimates during the cold season declined significantly ( P < 0.001) from autumn to winter. Based on our autumn night-time survey, overall fish biomass in the Bir-Mcherga Reservoir was high (mean (± s.d.) 185 ± 98 tonnes (Mg)), but annual fishery exploitation is low (19.3–24.1 Mg) because the fish biomass is likely dominated by invasive carp not targeted by fishers. The results suggest that controlling carp would help improve the fishery.

Marine and Freshwater Research↗

USGS2016

Climate warming reduces fish production and benthic habitat in Lake Tanganyika, one of the most biodiverse freshwater ecosystems

Warming climates are rapidly transforming lake ecosystems worldwide, but the breadth of changes in tropical lakes is poorly documented. Sustainable management of freshwater fisheries and biodiversity requires accounting for historical and ongoing stressors such as climate change and harvest intensity. This is problematic in tropical Africa, where records of ecosystem change are limited and local populations rely heavily on lakes for nutrition. Here, using a &sim;1,500-y paleoecological record, we show that declines in fishery species and endemic molluscs began well before commercial fishing in Lake Tanganyika, Africa’s deepest and oldest lake. Paleoclimate and instrumental records demonstrate sustained warming in this lake during the last &sim;150 y, which affects biota by strengthening and shallowing stratification of the water column. Reductions in lake mixing have depressed algal production and shrunk the oxygenated benthic habitat by 38% in our study areas, yielding fish and mollusc declines. Late-20th century fish fossil abundances at two of three sites were lower than at any other time in the last millennium and fell in concert with reduced diatom abundance and warming water. A negative correlation between lake temperature and fish and mollusc fossils over the last &sim;500 y indicates that climate warming and intensifying stratification have almost certainly reduced potential fishery production, helping to explain ongoing declines in fish catches. Long-term declines of both benthic and pelagic species underscore the urgency of strategic efforts to sustain Lake Tanganyika’s extraordinary biodiversity and ecosystem services.

Lake Tanganyika, Mahale Mountains National Park↗

USGS2021

Convergence of undulatory swimming kinematics across a diversity of fishes

Fishes exhibit an astounding diversity of locomotor behaviors from classic swimming with their body and fins to jumping, flying, walking, and burrowing. Fishes that use their body and caudal fin (BCF) during undulatory swimming have been traditionally divided into modes based on the length of the propulsive body wave and the ratio of head:tail oscillation amplitude: anguilliform, subcarangiform, carangiform, and thunniform. This classification was first proposed based on key morphological traits, such as body stiffness and elongation, to group fishes based on their expected swimming mechanics. Here, we present a comparative study of 44 diverse species quantifying the kinematics and morphology of BCF-swimming fishes. Our results reveal that most species we studied share similar oscillation amplitude during steady locomotion that can be modeled using a second-degree order polynomial. The length of the propulsive body wave was shorter for species classified as anguilliform and longer for those classified as thunniform, although substantial variability existed both within and among species. Moreover, there was no decrease in head:tail amplitude from the anguilliform to thunniform mode of locomotion as we expected from the traditional classification. While the expected swimming modes correlated with morphological traits, they did not accurately represent the kinematics of BCF locomotion. These results indicate that even fish species differing as substantially in morphology as tuna and eel exhibit statistically similar two-dimensional midline kinematics and point toward unifying locomotor hydrodynamic mechanisms that can serve as the basis for understanding aquatic locomotion and controlling biomimetic aquatic robots.

Proceedings of the National Academy of Sciences↗

USGS2011

Comparison of fish assemblages in two disjoined segments of an oxbow lake in relation to connectivity

Disconnection between adjacent habitat patches is one of the most notable factors contributing to the decreased biotic integrity of global ecosystems. Connectivity is especially threatened in river–floodplain ecosystems in which channel modifications have disrupted the lateral links between the main river channel and floodplain lakes. In this study, we examined the interaction between the interconnectedness of floodplain lakes and main river channels and fish assemblage descriptors. Fish assemblages in two segments of an oxbow lake, one connected to and the other isolated from the Yazoo River, Mississippi, were estimated with daytime boat electrofishing during 2007–2010. The frequency of connection for the connected segment ranged from zero to seven individual events per year (mean, &sim;2). The timing of most connection events reflected regional precipitation patterns. Greater species richness, diversity, and evenness were observed in the connected segment. Additionally, the connected segment had a greater abundance of piscivores and periodic life history strategists. All fishes collected solely in the connected segment were typically riverine in nature, whereas fishes collected only in the disconnected segment were more lacustrine adapted. These results suggest that periodic connection and the associated habitat heterogeneity that it provides are important for maintaining fish species richness and diversity in large-river floodplain lakes. We suggest that maintenance or restoration of connection be an integral part of fluvial ecosystem management plans.

Mississippi↗

USGS2014

Development of a multimetric index for fish assemblages in a cold tailwater in Tennessee

Tailwaters downstream of hypolimnetic-release hydropeaking dams exhibit a unique combination of stressors that affects the structure and function of resident fish assemblages. We developed a statistically and biologically defensible multimetric index of fish assemblages for the Caney Fork River below Center Hill Dam, Tennessee. Fish assemblages were sampled at five sites using boat-mounted and backpack electrofishing gear from fall 2009 through summer 2011. A multivariate statistical approach was used to select metrics that best reflected the downstream gradients in abiotic variables. Five metrics derived from boat electrofishing samples and four metrics derived from backpack electrofishing samples were selected for incorporation into the index based on their high correlation with environmental data. The nine metrics demonstrated predictable patterns of increase or decrease with increasing distance downstream of the dam. The multimetric index generally exhibited a pattern of increasing scores with increasing distance from the dam, indicating a downstream recovery gradient in fish assemblage composition. The index can be used to monitor anticipated changes in the fish communities of the Caney Fork River when repairs to Center Hill Dam are completed later this decade, resulting in altered dam operations.

Tennessee↗

USGS2014

High diet overlap between native small-bodied fishes and nonnative fathead minnow in the Colorado River, Grand Canyon, Arizona

River regulation may mediate the interactions among native and nonnative species, potentially favoring nonnative species and contributing to the decline of native populations. We examined food resource use and diet overlap among small-bodied fishes in the Grand Canyon section of the Colorado River as a first step in evaluating potential resource competition. We compared the diets of the predominant small-bodied fishes (native Speckled Dace Rhinichthys osculus , juvenile Flannelmouth Sucker Catostomus latipinnis , and juvenile Bluehead Sucker C. discobolus , and nonnative Fathead Minnow Pimephales promelas ) across seasons at four sites downstream of Glen Canyon Dam using nonmetric multidimensional scaling and Schoener's similarity index. The diets of these fishes included diatoms, amorphous detritus, aquatic invertebrates (especially simuliid and chironomid larvae), terrestrial invertebrates, and terrestrial vegetation. Diets varied with season and were affected by high turbidity. Fish consumed more amorphous detritus and terrestrial vegetation during the summer monsoon season (July–September), when turbidity was higher. The diets of all species overlapped, but there was large variation in the degree of overlap. The diets of juvenile suckers and Fathead Minnows were most similar, while Speckled Dace had relatively distinct diets. The differences took the form of higher proportions of diatoms and amorphous detritus in the diets of Bluehead Suckers and Fathead Minnows and higher proportions of simuliids and chironomids in those of Speckled Dace. If food resources are or become limiting, diet overlap suggests that competition may occur among native and nonnative species, which could have implications for the population dynamics of these fishes and for the management of the Colorado River ecosystem in Grand Canyon.

Arizona↗

USGS2014

Fish assemblages, connectivity, and habitat rehabilitation in a diked Great Lakes coastal wetland complex

Fish and plant assemblages in the highly modified Crane Creek coastal wetland complex of Lake Erie were sampled to characterize their spatial and seasonal patterns and to examine the implications of the hydrologic connection of diked wetland units to Lake Erie. Fyke netting captured 52 species and an abundance of fish in the Lake Erie–connected wetlands, but fewer than half of those species and much lower numbers and total masses of fish were captured in diked wetland units. Although all wetland units were immediately adjacent to Lake Erie, there were also pronounced differences in water quality and wetland vegetation between the hydrologically isolated and lake-connected wetlands. Large seasonal variations in fish assemblage composition and biomass were observed in connected wetland units but not in disconnected units. Reestablishment of hydrologic connectivity in diked wetland units would allow coastal Lake Erie fish to use these vegetated habitats seasonally, although connectivity does appear to pose some risks, such as the expansion of invasive plants and localized reductions in water quality. Periodic isolation and drawdown of the diked units could still be used to mimic intermediate levels of disturbance and manage invasive wetland vegetation.

Transactions of the American Fisheries Society↗

USGS2015

Patterns of fish assemblage structure and habitat use among main- and side-channel environments in the lower Kootenai River, Idaho

The lower Kootenai River, Idaho, was sampled during the summers of 2012 and 2013 to evaluate its fish assemblage structure at seven sites within main- and side-channel habitats where large-scale habitat rehabilitation was undertaken. Understanding the current patterns of fish assemblage structure and their relationships with habitat is important for evaluating the effects of past and future rehabilitation projects on the river. Species-specific habitat associations were modeled, and the variables that best explained the occurrence and relative abundance of fish were identified in order to guide future habitat rehabilitation so that it benefits native species. The results indicated that the side-channel habitats supported higher species richness than the main-channel habitats and that nonnative fishes were closely associated with newly rehabilitated habitats. This research provides valuable insight on the current fish assemblages in the Kootenai River and the assemblage-level responses that may occur as a result of future rehabilitation activities.

Idaho↗

USGS2003

Aquatic invertebrate assemblages in shallow prairie lakes: Fish and environmental influences

We sampled zooplankton and benthic macroinvertebrate assemblages in 30 shallow natural lakes to determine the effects of the environment (i.e., habitat and fish abundance) on invertebrates. Zooplankters were identified to genus, and up to 120 individuals per genus were measured. Macroinvertebrates were identified to order, class, or family. Fish communities were also sampled. Relative abundances of zooplankton and macroinvertebrates were low at increased chlorophyll a concentrations, although mean zooplankton length increased with total phosphorus, possibly because of an increased proportion of microzooplankton (rotifers and copepod nauplii) at higher phosphorus levels. Canonical correspondence analysis revealed that zooplankton and macroinvertebrate abundance was influenced by submersed vegetation coverage, whereas zooplankton abundance and size structure were also related to productivity (i.e., chlorophyll a and total phosphorus). However, relative abundance of fish species or fish feeding guilds was not strongly correlated with zooplankton or macroinvertebrate abundance or zooplankton size structure. Physical habitat (e.g., vegetation coverage) may exert substantial influences on invertebrate assemblages in these lakes , possibly providing a refuge from fish predation.

Journal of Freshwater Ecology↗

USGS2013

Effects of depletion sampling by standard three-pass pulsed DC electrofishing on blood chemistry parameters of fishes from Appalachian streams

Adverse effects on fishes captured by electrofishing techniques have long been recognized, although the extent of associated physical injury and behavioral alterations are highly variable and dependent on a number of factors. We examined the effects of three-pass pulsed DC (PDC) electrofishing on two salmonid species (Rainbow Trout Oncorhynchus mykiss and Brook Trout Salvelinus fontinalis) and five other genera (Green Sunfish Lepomis cyanellus, Potomac Sculpin Cottus girardi, Fathead Minnow Pimephales promelas, Largemouth Bass Micropterus salmoides, and Channel Catfish Ictalurus punctatus) common to Appalachian streams. We examined the corresponding effects of PDC electroshock on the following physiological indicators of stress and trauma: blood glucose and serum lactate, as well as on other blood chemistry, namely, enzymes, electrolytes, minerals, and proteins. All species demonstrated physiological responses to PDC electroshock, indicated by the biochemical differences in blood parameters in unshocked and shocked groups of fish with or without gross evidence of hemorrhagic trauma. Serum lactate was the most consistent indicator of these effects. Significant differences in whole blood glucose levels were also noted in treatment groups in all species except Green Sunfish, although the patterns observed were not as consistent as for serum lactate. Elevations in the serum enzymes, aspartate aminotransferase and creatine kinase, in the electroshocked fish occurred only in the two salmonid species. In many instances, although blood parameters were elevated in electroshocked fish compared with the unshocked controls for a given species, there were no differences in those levels in electroshocked fish based on the presence of gross hemorrhagic trauma to axial musculature. While some of the blood parameters examined correlated with both the occurrence of electroshock and the resultant tissue injury, there was no apparent link between the altered blood chemistry and increased mortality 30 d after electrofishing.

Appalachian Mountains↗

USGS2014

Assessing distribution of migratory fishes and connectivity following complete and partial dam removals in a North Carolina River

Fish, especially migratory species, are assumed to benefit from dam removals that restore connectivity and access to upstream habitat, but few studies have evaluated this assumption. Therefore, we assessed the movement of migratory fishes in the springs of 2008 through 2010 and surveyed available habitat in the Little River, North Carolina, a tributary to the Neuse River, after three complete dam removals and one partial (notched) dam removal. We tagged migratory fishes with PIT tags at a resistance-board weir located at a dam removal site (river kilometer [rkm] 3.7) and followed their movements with an array of PIT antennas. The river-wide distribution of fish following removals varied by species. For example, 24–31% of anadromous American Shad Alosa sapidissima , 45–49% of resident Gizzard Shad Dorosoma cepedianum , and 4–11% of nonnative Flathead Catfish Pylodictis olivaris passed the dam removal site at rkm 56 in 2009 and 2010. No preremoval data were available for comparison, but reach connectivity appeared to increase as tagged individuals passed former dam sites and certain individuals moved extensively both upstream and downstream. However, 17–28% did not pass the partially removed dam at rkm 7.9, while 20–39% of those that passed remained downstream for more than a day before migrating upstream. Gizzard Shad required the deepest water to pass this notched structure, followed by American Shad then Flathead Catfish. Fish that passed the notched dam accessed more complex habitat (e.g., available substrate size-classes) in the middle and upper reaches. The results provide strong support for efforts to restore currently inaccessible habitat through complete removal of derelict dams.

North Carolina↗