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At least 199 records · Page 11Linked to original sources
USGS2025

Disturbance is the primary determinant of food chain length when the top predator is constant

Food chain length (FCL) is a primary determinant of food web structure and is hypothesized to be influenced by habitat size, productivity, and disturbance. Understanding the environmental characteristics that determine food chain length can assist in understanding how food webs may be impacted due to changes in habitats and environmental characteristics. This study examines the impact of hydrologic disturbance on stream food webs when the top predator is constant. We analyzed FCL in less disturbed groundwater flashy streams and more disturbed runoff flashy streams using stable isotopes. Despite no difference in species richness or fish density, food chains in more disturbed streams had a lower FCL compared to food chains in more stable streams. Assemblage analysis showed that flow regime and drainage area significantly impacted individual species abundances. The more disturbed runoff flashy streams had higher proportions of primary consumer fish, such as the algivorous Campostoma sp. (Stonerollers), which likely drives the reduced FCL. Drainage area and land cover had non-significant relationships with FCL. Shifting community structure due to hydrologic variability likely leads to differences in diet of Micropterus dolomieu (Smallmouth Bass), and thus a difference in FCL.

Arkansas, Missouri, Oklahoma↗
USGS2026

Variation in diet and lipid content of age-0 sturgeon (Scaphirhynchus sp.) in the lower Missouri River basin

Shovelnose sturgeon ( Scaphirhynchus platorynchus ) and related endangered pallid sturgeon ( S. albus ) are species of interest in the highly modified Missouri River. Scaphirhynchus sturgeon require long distances of riverine habitat for the development of drifting free embryos along with suitable foraging habitat during the subsequent transition to exogenous feeding. Working with specimens collected by the US Army Corps of Engineers and Nebraska Game and Parks Commission, we examined diet composition of age-0 (<12 cm) sturgeon at four reaches in the lower Missouri River to examine the potential role of prey acquisition at this vulnerable life stage. In general, Ephemeroptera were more represented at reaches further upstream in the lower Missouri River, whereas Diptera larvae were the dominant prey item in reaches downstream. Body condition, as measured by total lipid content and length‒weight regressions, exhibited spatial differences in 2016 but not in 2017. Even with differences in prey frequencies and numbers consumed, percent consumption regardless of prey type remained consistent among reaches within years, but was overall higher in 2016 when river discharge was greater. Although temporal and spatial differences were observed in condition, comparisons using previous data from 2014 and 2015 suggest that these condition results were not driven by the longitudinal variability in prey composition as the reaches below Kansas city yielded relatively high and low lipid values despite the limited consumption of ephemeropteran prey relative to upstream reaches. Although it is unknown if any of the observed differences affected survival, our results, coupled with previous work, suggest that age-0 sturgeon can opportunistically forage in the lower Missouri River.

Missouri River↗
USGS2026

Rain interacts with directional wind to cause nest failures within breeding colonies of Western and Clark's Grebes

Western Grebe ( Aechmophorus occidentalis ) and Clark's Grebe ( Aechmophorus clarkii ) populations have declined across their range, and they are species of high conservation concern. Cascade Reservoir in central Idaho supports one of the largest breeding colonies of Aechmophorus grebes in North America (and the largest in Idaho), but few offspring are produced from the colony in most years. Low fecundity and little natal recruitment may be the proximate cause of Aechmophorus grebe population declines, but the ultimate cause of low recruitment is not known. One hypothesis for the low fecundity at Cascade Reservoir (and at other grebe colonies in the region) is that waves on freshwater breeding lakes inundate nests and cause pairs to abandon their nests. We tested that hypothesis by examining whether nest survival was negatively associated with changes in daily water level, daily peak wind speed and daily peak wind direction (i.e. winds that push water into the breeding colony). We also included daily mean temperature and daily total precipitation to evaluate a more general hypothesis that weather events caused nest failures. We used aerial imagery obtained from repeated drone flights to create encounter histories for 3888 Aechmophorus grebe nests to then estimate daily nest survival and evaluate whether daily water level, daily peak wind speed and daily peak wind direction (as predicted by the wind-driven wave hypothesis) were important causes of nest failure relative to other factors that commonly affect daily nest survival in birds. Nesting success was alarmingly low and we found some support for the wave inundation hypothesis; the results suggest that nesting attempts are more likely to fail on days with precipitation combined with winds blowing into the colony. Our results are the first to show that wind and precipitation affect the nest fate of Aechmophorus grebes.

Idaho↗
USGS2026

Seasonal and longitudinal variability of benthic macroinvertebrates collected from a series of dam impoundments in a cold-water tailrace

Natural lotic systems follow longitudinal, biophysical gradients as described by the river continuum concept; however, anthropogenic structures such as dams fragment these gradients and alter downstream communities, i.e. the serial discontinuity concept. We investigated the effects of successive impoundments on benthic macroinvertebrate assemblages in the Lower Mountain Fork River (LMFR), a 19-km cold tailwater reach in southeastern Oklahoma fragmented by four dams. Cold releases from Broken Bow Dam maintain year-round trout habitat but substantially modify thermal regimes and flow patterns relative to natural warmwater systems. From June 2016 through May 2017, we sampled 12 sites monthly, which were divided into three zones with 4 sites per zone: below the spillway, below the powerhouse discharge and Old Park dam, and below the re-regulation dam. We quantified abundance, taxa richness, percent Ephemeroptera-Plecoptera-Trichoptera (%EPT), diversity indices (e.g. Shannon and Simpson), functional feeding groups, and community structure using nMDS, ANOSIM, and SIMPER analyses. We collected 19,194 individuals representing 51 taxa. Assemblages were dominated by Trichoptera, Diptera, Isopoda, and Ephemeroptera, with collector/filterers comprising the most abundant functional group. Community structure differed significantly among dam-influenced reaches (ANOSIM global R = 0.521, p < 0.01). Sites nearest the spillway were characterized by high abundance but reduced diversity and low %EPT, driven by dominance of cold-tolerant taxa, including Simulium , Isopoda, and Amphipoda. In contrast, downstream sites exhibited greater taxa richness, higher diversity, and increased %EPT values, suggesting partial recovery along the longitudinal gradient. Seasonal variation was evident, with highest abundance in winter and peak diversity in spring. Our findings support the serial discontinuity concept, demonstrating that hypolimnetic releases and successive impoundments create spatially structured assemblages dominated by cold-tolerant taxa near dams, with gradual biophysical adjustment downstream. Despite substantial alteration, macroinvertebrate communities exhibited resilience and partial convergence toward regional warmwater assemblages at increasing distances from cold-water discharge.

Oklahoma↗
USGS2015

Decision support system for optimally managing water resources to meet multiple objectives in the Savannah River Basin

Managers of large river basins face conflicting demands for water resources such as wildlife habitat, water supply, wastewater assimilative capacity, flood control, hydroelectricity, and recreation. The Savannah River Basin, for example, has experienced three major droughts since 2000 that resulted in record low water levels in its reservoirs, impacting dependent economies for years. The Savannah River estuary contains two municipal water intakes and the ecologically sensitive freshwater tidal marshes of the Savannah National Wildlife Refuge. The Port of Savannah is the fourth busiest in the United States, and modifications to the harbor to expand ship traffic since the 1970s have caused saltwater to migrate upstream, reducing the freshwater marsh’s acreage more than 50 percent. A planned deepening of the harbor includes flow-alteration features to minimize further migration of salinity, whose effectiveness will only be known after all construction is completed. One of the challenges of large basin management is the optimization of water use through ongoing regional economic development, droughts, and climate change. This paper describes a model of the Savannah River Basin designed to continuously optimize regulated flow to meet prioritized objectives set by resource managers and stakeholders. The model was developed from historical data using machine learning, making it more accurate and adaptable to changing conditions than traditional models. The model is coupled to an optimization routine that computes the daily flow needed to most efficiently meet the water-resource management objectives. The model and optimization routine are packaged in a decision support system that makes it easy for managers and stakeholders to use. Simulation results show that flow can be regulated to substantially reduce salinity intrusions in the Savannah National Wildlife Refuge, while conserving more water in the reservoirs. A method for using the model to assess the effectiveness of the flow-alteration features after the deepening also is demonstrated.

Georgia, North Carolina, South Carolina↗
USGS2013

Newly documented host fishes for the eastern elliptio mussel (Elliptio complanata)

The eastern elliptio Elliptio complanata is a common, abundant, and ecologically important freshwater mussel that occurs throughout the Atlantic Slope drainage in the United States and Canada. Previous research has shown E. complanata glochidia to be host fish generalists, parasitizing yellow perch Perca flavescens , banded killifish Fundulus diaphanus , banded sculpin Cottus carolinae , and seven centrarchid species. Past laboratory studies have been conducted in the Midwest; however, glochidia used in these studies were obtained from adult mussels in the Great Lakes or St. Lawrence River basins, or glochidia sources were not reported. The objective of this study was to identify host fishes for E. complanata from streams in the Mid-Atlantic region. We used artificial laboratory infections to test host suitability of 38 fish and 2 amphibian species with E. complanata glochidia from the Chesapeake Bay drainage. Glochidia successfully metamorphosed into juvenile mussels on five fish species: American eel Anguilla rostrata , brook trout Salvelinus fontinalis , lake trout Salvelinus namaycush , mottled sculpin Cottus bairdii , and slimy sculpin Cottus cognatus . American eel was the most effective host, yielding the highest overall metamorphosis success (percentage of attached glochidia that transformed into juvenile mussels; ≥0.90) and producing 13.2 juveniles per fish overall. No juvenile E. complanata metamorphosed on other fish or amphibian species tested, including many previously identified host fishes that appear in the literature. Reasons for discrepancies in published host fish could include geographic variation in host use across the species' range, differences in host use between lentic and lotic populations, or poorly resolved taxonomy within the genus Elliptio .

Journal of Fish and Wildlife Management↗
USGS1992

Morphology of ruffe (Gymnocephalus cernuus) protolarvae from the St. Louis River, Lake Superior

We describe hatching and the morphological and meristic characteristics of 2.5-5.6 mm long ruffe protolarvae (Gymnocephalus cernuus). Eggs and sperm from St. Louis River ruffe were mixed, producing fertilized eggs that were 0.9-1.2 mm in diameter. Newly hatched protolarvae were 2.5-3.2 mm long. They had 14-15 preanal and 23-24 postanal myomeres, a continuous finfold of even width, unpigmented eyes, and a large anterior oil globule in the yolk sac, and the head deflected over the yolk sac. Pectoral fin buds appeared on the dorsal side of the yolk sac 5 hours after hatching. Two-day-old protolarvae had fully pigmented eyes, and the head was free from the yolk sac. Three-day-old protolarvae were 3.9-4.3 mm long and possessed opercula, gills, pectoral fins, and a functional jaw. Feeding and swimming began about one week after hatching when the yolk sac was almost completely absorbed. Protolarvae grew rapidly at 20-22 degrees C and were 4.9-5.6 mm long after 13 days. Newly hatched ruffe protolarvae are distinguished from other Lake Superior percids by having the fewest preanal myomeres (14-15), the head deflected over the yolk sac, continuous finfold of even width, and a total length of less than 4.0 mm.

Journal of Freshwater Ecology↗
USGS1985

Distribution and food habits of young-of-the-year fishes in a backwater lake of the upper Mississippi River

The distribution patterns and food habits of young-of-the-year (YOY) fishes in a lentic area adjacent to the main channel of Pool 7 of the upper Mississippi River were studied. Habitats sampled grouped distinctly based on percent composition and abundance of YOY fishes with those having submergent vegetation dominated by a number of important sport species. In late spring, the grouping of stations depended on the presence or absence of newly transformed northern pike (Esox lucius). In early summer, stations did not differ as distinctly in composition, but in total abundance of young. Those stations with submergent vegetation had total catches which were more than double those elsewhere. By late summer, submergent and mixed vegetation stations formed a distinct assemblage influenced by the preponderance of three species of sunfishes. (DBO).

Journal of Freshwater Ecology↗
USGS1992

Heavy metals in the threeridge mussel Amblema plicata plicata (Say, 1817) in the upper Mississippi River

Concentrations of mercury and zinc in the threeridge mussel Amblema plicata plicata, sampled in 1987 from Pools 3 and 10 in the upper Mississippi River, were comparable to concentrations in mussels from moderately contaminated systems, while copper concentrations were similar to concentrations in mussels from more polluted waters. Cadmium concentrations in mussels were significantly less at a lightly contaminated site (Pool 10, range 0.53 to 0.92 mu g/g dry weight) than at a site where metal abundances were strongly influenced by industrial and domestic inputs (Pool 3, range 0.80 to 1.25 mu g/g dry weight). Yet, cadmium concentrations in Pool 3 were an order of magnitude less than values reported for mussels from more metal-polluted systems. In contrast, concentrations of copper, mercury, and zinc did not differ between sites. Cadmium and zinc concentrations generally increased with size of the mussel, copper concentrations decreased with size, and mercury concentrations were unrelated to size.a

Journal of Freshwater Ecology↗
USGS2004

Cannibalism and predation by western toad (Bufo boreas boreas) larvae in Oregon, USA

Larval amphibians have been widely used as model organisms in studies of community ecology of freshwater systems (Morin 1983, Alford 1999). Much of this work has assumed that trophic effects of larval anurans are focused on periphyton and planktonic algae (Dickman 1968, Seale 1980, Duellman and Trueb 1986), a view that has recently been questioned. Recent experiments suggest that anuran larvae can occupy broader trophic roles than previously believed and may function as important predators in some pond communities (Petranka et al. 1994, Petranka and Kennedy 1999)

Oregon↗
USGS2008

The effect of fixative on total length of small-bodied stream fishes

Longnose dace (Rhinichthys cataractae), red shiner (Cyprinella lutrensis), and green sunfish (Lepomis cyanellus) were fixed in 5% and 10% formalin and 70% and 95% ethyl alcohol to determine fixative effects on total length (TL). Total length reduced over the first 24h for all species (P<0.0001) but then stabilized. Longnose dace and green sunfish TL reduction was less for 5% formalin than for either 70% or 95% ethanol (both P<0.0001), whereas the fixative solution had no effect on red shiner TL (P=0.347). A greater percentage of change in TL was observed in green sunfish and red shiner than in longnose dace, suggesting that body form (compressiform vs. fusiform) may affect shrinkage rate among adult stream fishes.

Journal of Freshwater Ecology↗
USGS2008

Habitat features affect bluehead sucker, flannelmouth sucker, and roundtail chub across a headwater tributary system in the Colorado River Basin

We assessed the distributions of three species of conservation concern, bluehead sucker (Catostomus discobolus), flannelmouth sucker (Catostomus latipinnis), and roundtail chub (Gila robusta), relative to habitat features across a headwater tributary system of the Colorado River basin in Wyoming. We studied the upper Muddy Creek watershed, Carbon County, portions of which experience intermittent flows during late summer and early fall. Fish and habitat were sampled from 57 randomly-selected, 200-m reaches and 416 habitat units (i.e., pools, glides, or runs) during the summer and fall of 2003 and 2004. Among reaches, the occurrences of adults and juveniles of all three species were positively related to mean wetted width and the surface area of pool habitat, and the occurrences of adult bluehead sucker and roundtail chub were also positively related to the abundance of rock substrate. Only juvenile bluehead sucker appeared to be negatively influenced by the proportion of a reach that was dry at the time of sampling. Within individual pools, glides, and runs, the occurrences of adults and juveniles of all three species were positively related to surface area and maximum depth, and occurrences of bluehead sucker and flannelmouth sucker juveniles were more probable in pools than in glides or runs.

Journal of Freshwater Ecology↗
USGS1997

Late summer and fall use of stream margins by young-of year brown trout in a high-elevation stream

We determined the relative abundance of young-of-year (YOY) brown trout (Salmo trutta) from late summer to fall during day and night in stream margin habitats of Douglas Creek, Wyoming. No significant differences in relative abundance were observed from August 14 through October 26. Few YOY brown trout were observed during the day over the entire sampling period, but significantly greater numbers were seen at night. Within stream margins, YOY brown trout of 36-75 mm total length primarily resided in concealment cover among interstices of cobbie during the day and emerged at night. Because no significant change in relative abundance was observed throughout the study period, we conclude that a shift to winter habitat did not occur up until three days prior to ice formation when the diurnal range in water temperature was 2.5-7.5??C.

Journal of Freshwater Ecology↗
USGS1998

Foraging characteristics of larval bluegill sunfish and larval longear sunfish in the Kanawha River, West Virginia

We determined spatial and temporal foraging characteristics of larval bluegill sunfish (Lepomis macrochirus) and longear sunfish (Lepomis megalotis) in the upper Kanawha River, West Virginia during the summer of 1989. Stomach contents were examined among habitat types (i.e., main channel, main-channel border, and shoreline habitats) and depth (surface, middle, and bottom). Diet of larval bluegill sunfish was dominated by Chironomidae, temporally and spatially. Chironomidae dominated larval longear sunfish diet in main channel and main-channel border collections from all three depths. However, along the shoreline, larval longear sunfish diet was dominated by Cladocera.

Journal of Freshwater Ecology↗
USGS2006

Relative persistence and dispersal of age-0 and age-1 largemouth bass stocked into two Ohio River embayments

In October of 1998 the West Virginia Division of Natural Resources stocked age-0 [mean total length (MTL) = 178 mm] and age-1 (MTL = 273 mm) hatchery-reared largemouth bass into two embayments of the Ohio River. Stocked fish were fitted with both an anchor tag and a visible implant elastomer mark. A multifaceted sampling approach was undertaken to (1) evaluate the persistence of stocked largemouth bass, (2) estimate fidelity of stocked largemouth bass to release sites, and (3) compare return rates of the two age classes. Although stocked largemouth bass comprised the majority (81%) of all bass captured in electrofishing surveys of the stocked embayments during fall 1998, catches declined rapidly during winter 1998, and by spring and summer 1999 stocked largemouth bass were virtually absent from electrofishing surveys. Creel surveys indicated no catch of stocked largemouth bass in the release sites after winter 1998. Electrofishing surveys, creel surveys, and angler call-ins all suggested stocked fish did not persist and either moved out of the stocked embayments or died. The results suggest that stocking advanced-size largemouth bass into these embayments only provided a limited and short-term enhancement of the fishery in those areas.

Journal of Freshwater Ecology↗
USGS2008

Use of an annular chamber for testing thermal preference of westslope cutthroat trout and rainbow trout

Remaining populations of westslope cutthroat trout (Oncorhynchus clarkii lewisi) in western North America are primarily confined to cold headwaters whereas nonnative rainbow trout (Oncorhynchus mykiss) predominate in warmer, lower elevation stream sections historically occupied by westslope cutthroat trout. We tested whether differing thermal preferences could account for the spatial segregation observed in the field. Thermal preferences of age-1 westslope cutthroat trout and rainbow trout (125 to 150 mm total length) were assessed in the laboratory using a modified annular preference chamber at acclimation temperatures of 10, 12, 14, and 16??C Final preferred temperature of westslope cutthroat trout (14.9??C) was similar to that of rainbow trout (14.8??C) when tested in a thermal gradient of 11-17??C The high degree of overlap in thermal preference indicates the two species have similar thermal niches and a high potential for competition. We suggest several modifications to the annular preference chamber to improve performance in future studies.

Journal of Freshwater Ecology↗
USGS2009

Influence of diet of double-crested cormorants on thiamine, lead, and mineral contents of their eggs

Throughout much of the Great Lakes basin, reproduction of several fish species is impaired by deficiency of thiamine in their eggs, an effect attributed to consumption of thiaminase-containing forage species, primarily alewife ( Alosa pseudoharengus ). Because the double-crested cormorant ( Phalacrocorax auritus ) nesting on islands in Lake Ontario is known to consume considerable amounts of alewife, we examined cormorant food habits and measured thiamine content in eggs collected in 1999 from six separate nests of cormorants from colonies near Lake Ontario and contrasted them with food habits and eggs of cormorants from Oneida Lake where the alewife is rare. Thiamine concentrations in eggs varied between 4.31 and 11.24 nmoles/g with no significant ( P >0.18) difference between mean concentrations for Lake Ontario and Oneida Lake (8.08 vs 8.36 nmoles/g) even though alewife comprised approximately 65 vs 0 % of their diets, respectively. Consumption of other thiaminase-containing species was minor in both lakes. Therefore, consumption of alewife and other thiaminase containing fishes by cormorants on Lake Ontario did not appear to significantly impair the levels of thiamine in their eggs. However, we found that the concentration of thiamine in eggs (T; nmoles/g) was inversely related ( P <0.02) to lead (Pb) concentration (µg/g) according to the equation: T = -3.142 Pb + 16.25. This relationship may reflect the known ability of thiamine to chelate lead and increase its excretion.

Journal of Freshwater Ecology↗