Search

Understanding potential limiting factors affecting population growth of the endangered pallid sturgeon, Scaphirhynchus albus, is important in the upper (UMOR) and lower Missouri River (LMOR) basins. The UMOR is upstream of several reservoirs and generally has more natural habitat features, whereas the LMOR is downstream of these reservoirs and has been channelized to support navigation. In both sections, pallid sturgeon recruitment to age-1 is a concern, but hypothesized for different reasons. One hypothesis in the LMOR centers on food limitation for age-0 fish, which is not considered an issue in the UMOR, but evaluating this hypothesis is challenging given the rarity of age-0 pallid sturgeon. As a result, the related, more abundant shovelnose sturgeon (S. platorhynchus) has been considered as a potential surrogate to assess food-related hypotheses. Thus, the purpose of our study was to compare diets of age-0 sturgeon captured in 2016 from three reaches in the LMOR (Copeland, Langdon, and Lexington) with individuals captured from a reach in the UMOR (Williston) during the same year to provide additional context regarding potential food limitation in the LMOR. Consumption percentage (prey weight in the gut as a percentage of body weight) was similar among all reaches, but diet composition was different for the most downstream reach in the LMOR. Age-0 sturgeon in the UMOR reach as well as the two upstream LMOR reaches primarily consumed Diptera larvae along with Ephemeroptera nymphs. In contrast, age-0 sturgeon in the most downstream LMOR reach (Lexington) almost exclusively consumed Diptera larvae. These results may provide information on relative differences in prey availability between Lexington and the other upstream reaches but the similarity in consumption percentage values across all reaches provide further evidence that age-0 sturgeon are not food limited in the LMOR. Habitat alteration is a factor affecting fishes, including Scaphirhynchus sturgeon, in the Missouri River. The upper portion of this system is fragmented by several dams, yet contains relatively natural riverine habitat features between the reservoirs; the lower portion is heavily altered for barge navigation and bank stabilization. Feeding by age-0 sturgeon in the upper portion has generally been considered adequate for survival, whereas lack of prey has been suggested as limiting survival in the lower portion. We studied age-0 sturgeon prey use in the upper and lower portions of the Missouri River during 2016 and found minimal differences. [ABSTRACT FROM AUTHOR]

While there is substantial support for the river continuum concept (RCC) using aquatic macroinvertebrates, nearly all of this support has come from studies using benthic specimen counts or relative biomass as the basis for comparing sites. We instead assessed the RCC using the ash-free dry mass (AFDM) of winged adult Ephemeroptera, Plecoptera, and Trichoptera (EPT) specimens. Insects were sampled at 13 sites along a 100 km 2nd–4th order reach of the Pine River in northern Lower Michigan using ultraviolet lights. Specimens were identified to the genus level and the AFDM of each functional feeding group (FFG) was calculated. Forty-two environmental and river morphological variables were tested for their ability to predict differences in EPT FFG biomass. A determined environmental gradient relating to increasing river size predicted over 80% of FFG biomass differences. Biomass of each individual FFG increased along the determined gradient, except for scrapers which decreased at the most downstream sites. The number of EPT genera also increased along the gradient. Our results were similar to those of previous studies, except that shredders nearly doubled in importance compared to RCC predictions, suggesting a greater ecological impact of shredders on forested streams than is typically reported. [ABSTRACT FROM AUTHOR]

Nutrient availability in prey items can have important consequences for the growth, reproduction, survival, and recruitment into adulthood of juvenile fish. For young of the year sturgeon, which are highly dependent on macroinvertebrates as prey, knowing the nutritional content across various prey items within their habitats can help managers during habitat restoration. The objective of this study was to test for differences in the macronutrient composition of major invertebrate groups commonly consumed by young of the year sturgeon in the lower Missouri River in the summer, when sturgeon habitat assessments occur. Potential prey vary considerably in size. In addition, there were significant differences in the concentrations of nutrients. The lowest concentration of lipid was found in Odonata (2.36 ± 1.83 mg 100 mg−1; mean ± pooled variance standard error) and the highest was in Diptera (14.49 ± 3.30 mg 100 mg−1). The lowest concentration of protein was found in Ephemeroptera (58.98 ± 1.90 mg 100 mg−1) and the highest concentration was in Trichoptera (70.07 ± 3.26 mg 100 mg−1). Some spatial differences were found in energy derived from protein in Ephemeroptera in the lower Missouri River, but not in energy derived from lipid. Our findings provide useful information that can contribute to adaptive management efforts for sturgeons in the lower Missouri River. [ABSTRACT FROM AUTHOR]

Many outdoor education centers, camps, nature centers, and parks nationwide bring thousands of students to designated stream sites each year. Organizations that repeatedly use the same site for stream ecology classes have the potential to negatively impact the aquatic macroinvertebrate community via frequent rearrangement of stream substrate by students. We placed 15 rocks of three size classes within a riffle subjected to outdoor education stream classes and another set of 15 rocks within an unused riffle and measured rock movement weekly from April 2014 to May 2014 within an agricultural stream in central Ohio. We also documented the number and type of aquatic macroinvertebrates colonizing each rock at the end of the six week study. Upstream rock movement was greater in the class site than the unused site. Total rock movement, vertical movement, and lateral movement were greater in the class site than the unused site only during baseflow conditions. Macroinvertebrate abundance, taxa richness, EPT (Ephemeroptera, Plecoptera, Trichoptera) abundance, and clinger abundance were greater in the unused site than the class site. Our results indicate that outdoor education centers can avoid negatively impacting the aquatic macroinvertebrate community and improve student educational experiences by alternating the stream sites at which stream classes are conducted. [ABSTRACT FROM AUTHOR]

As temperatures rise and precipitation patterns change, approaches are needed for early detection of the effects on ecosystems. Macroinvertebrate data collected from 81 sites with multiple habitat kick sampling were compiled for this study. We used a binary logistic regression model to predict the probability of local extinction or range expansion of aquatic macroinvertebrates with changes in temperature and precipitation in watersheds of Castilla-La Mancha, Spain. Aquatic insect families from the following orders were found to be sensitive to an increase in average spring temperatures: Ephemeroptera, Plecoptera, Megaloptera, Trichoptera, Coleoptera and Diptera. Taxa in Ephemeroptera, Trichoptera, Hemiptera and Coleoptera showed negative relationships with minimum (winter) temperature, maximum spring temperature and/or precipitation. One mayfly,Caenis, exhibited a positive relationship with minimum temperature. These results indicate that these aquatic communities are expected to change significantly in the short-term, with the potential to alter stream ecosystem functioning. Mediterranean ecosystems are considered biodiversity hotspots, and biotic communities in freshwater habitats in these areas may be particularly vulnerable to projected increases in temperature and decreases in precipitation. The ability of taxa to withstand these changes will depend on resistance, resilience and dispersal capabilities of the aquatic macroinvertebrates as well as available habitat. [ABSTRACT FROM AUTHOR]

We examined macroinvertebrate community data from Missouri reference streams collected approximately 12 years apart to evaluate whether substantial changes in community metrics and/or taxonomic composition occurred over that period. We used analysis of variance to test whether metrics differed between years or between other variables and used non-metric multidimensional scaling to examine compositional differences among samples and the environmental variables that were most associated with these differences. Metrics primarily varied on a seasonal basis, largely reflecting life history patterns of dominant groups such as chironomids and the Ephemeroptera, Plecoptera, and Trichoptera orders. Variation between the time periods generally reflected atypically high abundance of chironomids in the spring of 1999/2000, but we did not observe reduced community quality between the earlier and later survey periods. Taxonomic composition was most related to seasonal differences and to the land cover characteristics of the study sites. No long-term compositional changes were evident, but water quality variables did not clearly differ and changes in land cover were slight between the survey periods. Reference stream conditions remained as indicative of high environmental quality in the later samples as in the earlier samples. [ABSTRACT FROM AUTHOR]

Periphyton blooms dominated byDidymosphenia geminatahave been reported from hundreds of rivers.D. geminatablooms consist of thick mats that cover kilometers of riverbed. Benthic habitat conditions are altered when large areas of sediment and native periphyton are replaced byD. geminatamats and these habitat changes may lead to changes in the composition and abundance of benthic invertebrates. Mensurative studies have provided circumstantial evidence of changes in invertebrate communities in response toD. geminatablooms. However, those studies may have confounded the effects ofD. geminataand other environmental variables. To identify direct effects ofD. geminataon invertebrate communities, we conducted a paired before–after, control-impact (BACIP) experiment in threeD. geminata-infested rivers. The experimental impact was the removal ofD. geminatamats from 35–50 m2areas of riverbed. We tested for effects ofD. geminataremoval on macroinvertebrate community metrics, including total density, taxon richness, and the prevalence of Ephemeroptera, Plecoptera, and Trichoptera (EPT) and trophic groups. The BACIP analysis indicated thatD. geminataremoval caused a decrease in total density at two rivers, a decrease in the density of dipterans and an increase in % EPT invertebrates at one river, and an increase in % algivorous invertebrates at another river. A multivariate analysis indicated that there was more variation in invertebrate community structure among rivers than between treatments within rivers. The limited effects ofD. geminataremoval on invertebrate communities were probably related to the composition of colonist pools and the relatively small cleared areas; cleared areas were surrounded by large areas ofD. geminata-covered habitat and the colonist pools were dominated by taxa that inhabitD. geminatamats. [ABSTRACT FROM AUTHOR]

Five oxbow lakes of the Łyna River, located in an agricultural area, were studied seasonally in 2005 and 2008. The EPT index (abundance of Ephemeroptera, Plecoptera and Trichoptera larvae), as well as their proportion to Chironomidae indicated that groups sensitive to environmental conditions occurred at low abundance in relation to the different hydrological types of oxbow lakes. The Family Biotic Index, the Biological Monitoring Working Part index adapted to Polish conditions and the Average Score Per Taxon (ASPT) revealed low water quality regardless of the level of hydrological connectivity. In turn, the indices of biodiversity Margalef (d) and probability of interspecific encounters indicated good or satisfactory water quality. The pH correlated positively with the total abundance of aquatic invertebrates, while lower macroinvertebrate abundance was observed in turbid waters of lentic oxbows with a high content of total dissolved solids. Canonical correspondence analysis showed that hydrological connectivity was the main factor responsible for the value of monitoring indices, followed by the physical and chemical parameters of the local environment. Among the indices used, it was ASPT-PL that grouped the studied oxbow lakes according to their hydrological types and seems to be the best index. This study shows that the structure of invertebrate communities inhabiting oxbow lakes reflects physico-chemical conditions of water and can be a valuable source of monitoring data, indispensable to the management and protection of these important aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Large wood has important structural and functional roles in streams but there is little information on large wood dynamics in the southeastern coastal plains, USA. In this study, we surveyed 35 streams in the Choctawhatchee River watershed of southeastern Alabama. These streams were broadly classified into three categories based on land use: urban, forest, and mixed (agriculture plus forest). The number, volume, and functions of large wood were quantified. Pool number, pool spacing, and drainage areas of each stream were measured along with assessment of macroinvertebrate assemblages. Large wood number and volume plus pool number and spacing were used to examine the relationship among large wood characteristics and functions, pool characteristics, drainage area, and attributes of macroinvertebrate assemblages including species richness, Shannon-Wiener diversity (H'), number of Ephemeroptera, Plecoptera, and Trichoptera (EPT) species, and the Invertebrate Community Index (ICI -- a multimetric index that reflects biological integrity of streams). There were significant differences in large wood number and volume among the three different stream categories, with highest large wood number and volume in forest streams. More pools and storage sites for sediment and organic matter were found in forest streams than urban and mixed streams. Large wood appeared to be positively related to macroinvertebrate assemblages, as species richness, H', EPT, and ICI were generally higher in forest streams as compared to those of urban and mixed streams. The outcome of this study suggests that large wood contributes to the physical and biological complexity of streams in the southeastern coastal plain streams of the USA. [ABSTRACT FROM AUTHOR]

Widespread catastrophic flooding struck coldwater streams in southeastern Minnesota in August 2007, drastically scouring and altering stream channels and their biota. Post-flood invertebrate abundances and assemblages in streams in and near Whitewater State Park were compared to data collected from these same streams prior to flooding. Flooding reduced invertebrate densities by 75-95% in some streams. Taxa richness was reduced by 30-70%, and assemblage structure was reduced to poor and very poor levels in first- and second-order streams but not in the larger (fourth-order) system. Ephemeroptera, Plecoptera, and Trichoptera were especially impacted in small streams, and amphipods were virtually eliminated from both large and small streams. Densities of some invertebrate groups recovered within months of the flood, but others were still recovering after nearly two years. Taxa richness and community structure returned to pre-flood levels at most sites within one year, but total densities at many sites remained below long-term averages 22 months post-flood. Invertebrate assemblages were impacted differently by flooding in small versus large streams, resulting in differing patterns and degrees of recovery. [ABSTRACT FROM AUTHOR]

We studied the population structure and diet of burbot (Lola Iota) listed as state- endangered and inhabiting small streams near the southern extent of the species' North American range. The size structure was truncated, with a mean total length of 191 mm and range of 84-356 mm. A subsample of individuals (n=32) were euthanized, and age estimates from otoliths revealed surprisingly short lifespans (maximum age of five years). An age-length key was then used to assign ages proportionately to the larger sample, and 80% were estimated to have been age 2 and age 3. Burbot stomach contents were removed with gastric lavage from 120 individuals during summer sampling that occurred at four- hour intervals for 24 h. Burbot specialized on Ephemeroptera, and consumed a variety of other invertebrate prey; surprisingly, fish were only found in three individuals. While similar to other reports of burbot in small streams, (e.g. small body sizes, earlier maturation, short- lifespan, invertebrate-centered diet) the population demographics were considerably different from `typical' burbot populations occurring in lakes, large rivers, and reservoirs. [ABSTRACT FROM AUTHOR]

Mayflies were investigated in a second-order montane stream of the Qingjiang River basin, among which Electrogena sp., Indobaetis sp., Choroterpes sp., and Caenis sp. were the dominant species, contributing 92.4% to the total mayfly standing stock. Electrogena sp., Choroterpes sp., and Caenis sp. all developed two generations per year, and there was little overlap with the two generations in each species. Indobaetis sp. had three generations a year. The average annual production of Electrogena sp., estimated by the size-frequency method, was 15.8 g (dry weight)/m². Indobaetis sp, was 8.8 g/m², Choroterpes sp. was 1.6 g/m², and Caenis sp. was 0.9 g/m². By foregut content analysis, we found that amorphous detritus was the most important food type, accounting for 77.8%-84.4% of their diets and 62.0%-74.7% of their annual ingestion. [ABSTRACT FROM AUTHOR]

Aquatic insects were sampled every ten days from streams and rivers in northwestern Massachusetts between May 22 and October 8, collecting a total of 9,844 specimens that were all identified to the family level. Absolute abundances of insects did not vary throughout the sampling period, although the family composition did. While the total abundance of Ephemeroptera, Plecoptera, and Trichoptera combined was constant throughout the season, trichopterans were more abundant early in the season, and ephemeropterans and plecopterans increased in abundance throughout the season. [ABSTRACT FROM AUTHOR]

We examined the seasonal food habits and diet overlap of juvenile pallid sturgeon (Scaphirhynchus albus) and adult shovelnose sturgeon (S. platorynchus) in the Missouri River downstream of Fort Randall Dam, South Dakota. Seasonal trends were found for both sturgeon species as chironomids were consumed in the greatest numbers and dry weights during early summer, ephemeropterans dominated during late summer, and trichopterans were most abundant in early spring and late fall diets. However, diet overlap between juvenile pallid sturgeon and adult shovelnose sturgeon was low based on a Schoener index value of 0.53 in 2003 and 0.21 in 2004. Juvenile pallid sturgeon consumed a greater proportion of fish in 2003 and Ephemeroptera in 2004 compared to shovelnose sturgeon. Shovelnose sturgeon consumed a greater proportion of Chironomidae in both years compared to juvenile pallid sturgeon. These results illustrate that shovelnose sturgeon is not an acceptable surrogate for the endangered pallid sturgeon based on food habits. [ABSTRACT FROM AUTHOR]

The multiple habitat sampling protocol (MHSP) is a bioassment method designed to assess the ecological health of South Carolina streams on the basis of macroinvertebrate samples collected from natural substrates. The MHSP is computed by averaging the EPT (numbers of Ephemeroptera, Plecoptera, Trichoptera taxa) and BI (a biotic index that reflects the pollution tolerances of individual taxa) to produce a bioclassification score. The MHSP produced low bioclassification scores that could falsely indicate environmental degradation in some undisturbed, high quality streams in the Sandhills ecoregion. This problem had two causes. The metrics (especially EPT) were significantly related to stream size, which potentially confounded stream size effects with environmental impacts, and the scoring criteria for EPT were too high for some Sandhills streams. We corrected these problems by developing new scoring criteria for Sandhills streams that utilized residuals from regressions of the metrics on stream width to normalize for stream size. The MHSP and related protocols are effective methods for assessing environmental quality, but allowances must be made for the effects of stream size and the potential ecological heterogeneity that naturally exists among streams in some ecoregions. [ABSTRACT FROM AUTHOR]

The diel and seasonal food habits of young-of-year (YOY) and post-young-of-year (PYOY) Atlantic salmon (Salmo salar) parr were assayed over the course of 11 months in the West Brook, Massachusetts USA. Gut fullness of YOY salmon did not vary significantly among months. PYOY salmon exhibited significant seasonal differences in gut fullness, with peak fullness occurring in the spring and late fall. Significant diel differences in PYOY gut fullness occurred in June and April, with peak fullness always occurring at dawn. Prey composition varied substantially among months. Dominant prey items of PYOY salmon were baetid mayflies in June, July, and August, limnephilid caddisflies in October and November, and ephemerellid mayflies in February and April. Few differences in prey composition between PYOY and YOY salmon were observed. Fish growth was unrelated to prey availability, but gut fullness explained up to 97% of growth variation across seasons. Results suggest that spring and tall are critical periods of feeding for PYOY salmon and that diel feeding intensity shifts seasonally. [ABSTRACT FROM AUTHOR]

In a second-order montane stream of the Hanjiang River basin, Leptophlebia sp. and Ephemera sp. appeared to develop two generations per year, and there was little overlap with the two generations in either species. Leptophlebia sp. pupated in autumn and winter, while Ephemera sp. did so in summer and winter. Annual production of Leptophlebia sp., estimated by the size-frequency method, was 7.23 g (dry weight)/m². The annual production of Ephemera sp. was 14.45 g/m². The principal food type and major contributor to this production in both mayflies was amorphous detritus (59.2%), while diatoms contributed 36.4% to the production. [ABSTRACT FROM AUTHOR]

We studied the temporal pattern of the aquatic insect assemblage of an Ozark stream by sampling riffle areas every two weeks from early February through late July, 2002. Total richness of the assemblage, for the entire study, was 138 taxa, including 57 from the dipteran family Chironomidae. Richness levels, per sampling period, ranged from the low 40s to the high 50s and were highest in late March through mid-April. Assemblage composition shifted from one dominated by chironomids in the winter and spring to one dominated by mayflies in the late spring and early summer and by caddisflies in summer. EPT richness levels, diversity, biotic index values, and relative abundances of functional feeding groups varied substantially during the study, occasionally even between two-week sampling periods. The data suggested that, for this type of stream, winter and summer are the times of year that the insect assemblage is least dynamic. These periods, despite lower overall community richness, may therefore be more appropriate to compare samples from different locations or years. [ABSTRACT FROM AUTHOR]

Surveys of macroinvertebrates were carried out in the Xiangxi River system during July of 2001. Among the 121 taxa collected, Ephemeroptera, Trichoptera, and Diptera dominated (41.7, 26.0, and 24.5% of the total relative abundance, respectively). Two-way indictor species analysis and detrended correspondence analysis divided the 49 sites into four groups based on species composition and relative abundance. Canonical correspondence analysis indicated that elevation, SiO2, pH, conductivity, hardness, and NO2-N were significant environmental factors affecting the distribution of macroinvertebrates. [ABSTRACT FROM AUTHOR]

Hexagenia bilineata, a large-bodied mayfly, provided a convenient model for the study of the physiological ecology of the Ephemeroptera. The thorax temperature (Tth) of free-flying H. bilineata was significantly different from ambient temperature (Ta), but the gradient between them was only about 1~C, which is probably not biologically significant. H. bilineata is clearly ectothermic, and low wing loading may explain the low Tth. H. bilineata emerges during warm and stable weather, when endothermy would provide little advantage. H. bilineata hada very high ratio of flight muscle mass to body mass, which is expected to result from selection pressure on flight performance, yet H. bilineata is a poor flyer. This effect may be a result of freedom fromweight constraints. [ABSTRACT FROM AUTHOR]