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The Yellowstone River is the longest unimpounded river in the conterminous United States. It has a relatively natural flow regime, which helps maintain diverse habitats and fish assemblages uncommon in large rivers elsewhere. The lower Yellowstone River was thought to support a diverse nongame fish assemblage including several species of special concern. However, comprehensive data on the small nongame fish assemblage of the lower Yellowstone River is lacking. Therefore, we sampled the Yellowstone River downstream of its confluence with the Clark’s Fork using fyke nets and otter trawls to assess distributions and abundances of small nongame fishes. We captured 42 species (24 native and 18 nonnative) in the lower Yellowstone River with fyke nets. Native species constituted over 99% of the catch. Emerald shiners Notropis atherinoides, western silvery minnows Hybognathus argyritis, flathead chubs Platygobio gracilis, sand shiners Notropis stramineus, and longnose dace Rhinichthys cataractae composed nearly 94% of fyke net catch and were caught in every segment of the study area. We captured 24 species by otter trawling downstream of the Tongue River. Sturgeon chubs Macrhybopsis gelida, channel catfish Ictalurus punctatus, flathead chubs, stonecats Noturus flavus, and sicklefin chubs Macrhybopsis meeki composed 89% of the otter trawl catch. The upstream distributional limit of sturgeon chubs in the Yellowstone River was the Tongue River; few sicklefin chubs were captured above Intake Diversion Dam. This study not only provides biologists with baseline data for future monitoring efforts on the Yellowstone River but serves as a benchmark for management and conservation efforts in large rivers elsewhere as the Yellowstone River represents one of the best references for a naturally functioning Great Plains river.
Pygmy Whitefish (Prosopium coulterii) are a small, glacial relict species with a disjunct distribution in North America and Siberia. In 2013 we collected Pygmy Whitefish at 28 stations from throughout Lake Superior. Total length was recorded for all fish and weight and sex were recorded and scales and otoliths were collected from a subsample. We compared the precision of estimated ages between readers and between scales and otoliths, estimated von Bertalanffy growth parameters for male and female Pygmy Whitefish, and reported the first weight-length relationship for Pygmy Whitefish. Age estimates between scales and otoliths differed significantly with otolith ages significantly greater for most ages after age-3. Maximum otolith age was nine for females and seven for males, which is older than previously reported for Pygmy Whitefish from Lake Superior. Growth was initially fast but slowed considerably after age-3 for males and age-4 for females, falling to 3–4 mm per year at maximum estimated ages. Females were longer than males after age-3. Our results suggest the size, age, and growth of Pygmy Whitefish in Lake Superior have not changed appreciably since 1953.
Interactions among the benthic community are typically overlooked but play an important role in fish community dynamics. We examined the diel feeding ecology of Slimy Sculpin (Cottus cognatus) from Grout Brook, a tributary to Skaneateles Lake. Of the six time periods examined, Slimy Sculpin consumed the least during the nighttime (2400 h and 0400 h). Chironomids were the major prey consumed during all time periods except for 2400 h when ephemeropterans were the major prey consumed. There was a moderate preference by Slimy Sculpin for food from the benthos (0.59 ± 0.06) with Diptera (Chironomids), Ephemeroptera (Baetidae), and Trichoptera (Brachycentridae) representing the major taxa. Slimy Sculpin appear to be opportunistic feeders selecting what is most available in the brook. Index of fullness was variable and averaged 1.15% across the diel cycle. Daily ration was measured as a function of fish dry body weight and ranged from 0.12 to 0.22. Estimates of daily consumption ranged from 0.007% to 4.0% of body weight, which corresponds to reports for other species. These findings have application in gauging the relative importance of Slimy Sculpin in streams where highly valued salmonid species also occur.
River modifications have had detrimental effects on biota that depend on river systems; therefore, information is needed to understand these effects and direct management efforts. Channel catfish (Ictalurus punctatus) are important recreationally, commercially, and ecologically in the Middle Mississippi River (MMR), but few studies have examined their habitat requirements, and food habits have not been evaluated in the MMR. Information about habitat use and food habits could help direct management efforts for channel catfish. To more thoroughly understand the synergistic relation between channel catfish and the associated habitat, we used data from the United States Army Corps of Engineer’s Long-Term Resource Monitoring Program to evaluate channel catfish use of large-scale river features (i.e., macrohabitats) and more fine scale mesohabitats (i.e., substrate type, depth, and velocity). Stomach contents from channel catfish were identified and quantified to determine the relative importance of specific prey items in diets. Channel catfish presence was positively affected by current but negatively affected by depth. Off-channel habitats appeared more suitable for channel catfish. In terms of food habits, Cambaridae, fish, and vegetation were most frequently found in the diet, but a variety of other food items were consumed. Conserving premodification habitat characteristics, such as open side channels, shallow sandbars, and seasonally inundated floodplains, as well as habitats with high forage productivity, should help to sustain a stable population of channel catfish in the MMR. Future studies could examine the tenets of the optimal foraging theory within these habitats to determine the mechanisms regulating channel catfish habitat use and prey selection.
The fountain darter Etheostoma fonticola is a federally endangered species that is associated with primarily clear, spring-fed systems, suggesting even minor changes in turbidity have the potential to affect behavior. We examined the effects of turbidity [control: <1 Nephelometric Turbidity Unit (NTU), minimal turbidity: mean = 8.7 NTU, moderate turbidity: mean = 23.2 NTU, and high turbidity: mean = 74.6 NTU] on the total number of prey items consumed, time to initiate foraging, total prey consumed out of the time left to forage, and number of strikes made per prey items (prey capture success). Our results indicate elevated turbidity significantly affects the number of prey consumed, time to initiate foraging, and total prey consumed out of the time left to forage. Turbidity does not appear to affect prey capture success. These data suggest even a slight elevation in turbidity (≥8.7 NTU) can significantly impair foraging behavior in E. fonticola.
Barred tiger salamanders [Ambystoma mavortium (Baird, 1850)] exhibit two trophic morphologies; a typical and a cannibalistic morph. Cannibalistic morphs, distinguished by enlarged vomerine teeth, wide heads, slender bodies, and cannibalistic tendencies, are often found where conspecifics occur at high density. During 2012 and 2013, 162 North Dakota wetlands and lakes were sampled for salamanders. Fifty-one contained A. mavortium populations; four of these contained cannibalistic morph individuals. Two populations with cannibalistic morphs occurred at sites with high abundances of conspecifics. However, the other two populations occurred at sites with unexpectedly low conspecific but high fathead minnow [Pimephales promelas (Rafinesque, 1820)] abundances. Further, no typical morphs were observed in either of these later two populations, contrasting with earlier research suggesting cannibalistic morphs only occur at low frequencies in salamander populations. Another anomaly of all four populations was the occurrence of cannibalistic morphs in permanent water sites, suggesting their presence was due to factors other than faster growth allowing them to occupy ephemeral habitats. Therefore, our findings suggest environmental factors inducing the cannibalistic morphism may be more complex than previously thought.
Plastic responses by amphibian larvae to various pond hydroperiods have received much theoretical and empirical attention. In contrast few studies examined maternal plasticity in oviposition in response to different hydroperiods. Using the Eastern Newts as a model, we tested a hypothesis that mothers respond to water reduction of aquatic habitats and alter life history traits such as timing of oviposition, clutch size, and egg size. Alternatively, females may entirely forgo oviposition if aquatic habitats are unsuited for larval survival, in which case we predicted greater body-mass gain of females that forgo oviposition. We daily monitored oviposition of 20 females for 38 d, 10 in constant water treatment and 10 in water reduction treatment. Six females deposited a total of 265 eggs in the constant water treatment whereas only one female deposited 17 eggs in the water reduction treatment, suggesting females facultatively altered oviposition behavior in response to water reduction. Contrary to the prediction, oviposited females gained significantly more body mass, suggesting those females that skipped oviposition stopped vitellogenesis during the experiment; whereas, oviposited females still contained yolk-laden ova at the end of the experiment. We could not test maternal plasticity in timing of oviposition, egg size, and clutch size because only one female from the water reduction treatment deposited eggs. The present study demonstrates that the Eastern Newt is a potentially useful model to further explore maternal plasticity in amphibians.
Early successional habitats are declining in eastern North America while at the same time remaining habitats are being invaded by a suite of nonnative shrub species. While the significance of these transitional habitats to breeding birds is well known, increasing evidence suggests they are important during the postfledging/premigratory and migratory periods, not only for shrub-nesting species but also for many species that breed in late-successional habitats. Additionally a number of studies suggest exotic species have the potential to alter habitat quality, in turn affecting the fitness of migratory landbirds. The purpose of this study was to evaluate fitness correlates associated with migrant use of shrubland habitat dominated by nonnative honeysuckle (Lonicera spp.) in order to gauge habitat quality for spring migrants using an inland stopover site in northeastern Pennsylvania. We used estimates of mass change as our fitness indicator, with positive mass change indicating quality habitat. Our results suggest most birds gain mass while using honeysuckle-dominated habitat and many species, including species that characteristically breed in forested habitats, accrue fitness advantages from using shrubland habitat during spring stopover in northeastern Pennsylvania. However, we emphasize the need to examine the cumulative effects of exotic vegetation through multiple stages of the avian annual cycle to better understand the fitness consequences of nonnative vegetation on migratory landbirds.
Species distributed across diverse climate and thermal conditions represent opportune systems for studying tolerance of low temperature stress. We examined variation in cold acclimation capacity and freezing tolerance among three natural populations (Texas, Kansas, and Manitoba) of the perennial sunflower species Helianthus maximiliani, originally collected across 2134 km in central North America. Tolerance to low temperatures was evaluated through leaf electrolyte leakage assays that quantify loss of cellular electrolytes into an aqueous medium due to plasma membrane damage. Freezing tolerance was highest for plants from the northernmost latitude (Manitoba population) under both non cold- acclimated and cold- acclimated experimental conditions. Individuals from Kansas and Texas populations exhibited lower freezing tolerance compared to Manitoba but did not differ from one another. Plants from all populations retain the ability to increase freezing tolerance through the process of cold acclimation. Freezing tolerance of Manitoba × Texas F1 hybrids was statistically indistinguishable from plants from the Texas population and possible explanations for these observations are discussed. Analysis of flowering specimens from herbaria records of corresponding regional locations indicates considerable variation in flowering phenology whereby flowering occurs progressively earlier with increasing latitude. This phenological variation may provide an additional mechanism of coping with low temperature stress through temporal avoidance.
This study examines the role mycorrhizae may play in protecting host plants from a soil fungal pathogen. Asexual propagules of three Allium vineale genotypes were grown in the presence and absence of mycorrhizae and the pathogen, Sclerotium cepivorum (white rot), with some plants encountering the mycorrhizal fungi first and others encountering the pathogen first. A significant three-way interaction indicates plant genotypes vary in response to the combined effects of mycorrhizae and the pathogen, with the A. vineale genotype most resistant to the pathogen deriving the least growth benefit from mycorrhizae and the genotype most susceptible to the pathogen receiving the highest relative growth benefit from mycorrhizae, despite there being no difference in the level of mycorrhizal colonization among the plant genotypes. No evidence was found that the presence of mycorrhizae reduced the impact of the pathogen for the most susceptible plant genotype (B). These findings support the hypothesis the primary function of mycorrhizae for A. vineale is nutrient acquisition and indicate genetic diversity within plant species is an important component in plant-mycorrhizae-pathogen interactions.
Eastern redcedar (Juniperus virginiana) is a fire-intolerant tree species that has encroached into grassland ecosystems throughout central and eastern North America. Many land managers are interested in removing eastern redcedar to restore native grasslands. We surveyed small mammals using mark-recapture methods in eastern redcedar forest, warm-season grassland, and oldfield habitats in the Ozark region of northwest Arkansas. We conducted over 3300 trap-nights and captured 176 individuals belonging to eight small mammal species, primarily Peromyscus spp. and Reithrodonotmys fulvescens. While species diversity did not vary among habitats, small mammal species composition in eastern redcedar forest differed from that of warm-season grassland and oldfield habitats. The small mammal community of eastern redcedar forest is as diverse as the warm-season grasslands and oldfields it succeeds but replaces grassland associated small mammal species with forest associated species.
Yegua Creek, a tributary of the Brazos River, Texas has yet to be comprehensively surveyed for freshwater mussels, despite previous studies documenting high mussel abundance and richness and the occurrence of Quadrula houstonensis, a federal candidate species under the U.S. Endangered Species Act. We qualitatively sampled mussels at 52 sites in lower Yegua Creek to assess the status of mussel populations and provide a baseline for future monitoring efforts. In total 10,010 mussels representing 16 species were observed, including Q. houstonensis and Truncilla macrodon, which is also a federal candidate species. Mussel species richness and abundance increased with distance downstream from Lake Somerville, which corresponded with changes in assemblage structure. Recruitment was lowest near Lake Somerville and highest in reaches located in the middle sections of the study area. Taken together these results indicate that Lake Somerville may be negatively impacting the mussel fauna in Yegua Creek. Despite these impacts, mussel abundance and diversity is high in reaches located at intermediate distances from the reservoir and represents some of the largest known populations in central Texas.
Up to date research on the historical and current distribution of the least darter (Etheostoma microperca) in Ohio is not available, despite its status as a Species of Concern. Using a dataset of 229 recorded occurrences, we compared 20th and 21st century presence/ absence of least darter in Ohio to detect changes in distribution and evaluate the need for conservation measures. We added 11 recent surveys for streams that lacked 21st century data. Before 2000 the least darter was known from 44 streams in 18 counties across the glaciated portion of Ohio. This decreased to 37 streams in 14 counties in surveys from 2000 to 2013 considering only temporally spaced collections (e.g., at least two collections per location – one from the 20th and one from the 21st century). Two streams added E. microperca populations since 2000. However, in spite of continued monitoring, nine streams lost populations including the disappearance from counties in its Northeastern Ohio range. Farm ditches with ample vegetation were common locations where least darters were encountered. Because least darters are associated with vegetated habitat throughout their life history, such ditches may serve as important habitat for this species if plant communities are maintained. E. microperca remains vulnerable in Ohio, and we recommend continued monitoring.
Predation on reptiles and amphibians by whooping cranes (Grus americanus) is widely reported, but all published data are anecdotal or based on singular observations, and mostly refer to isolated predation events. Some observers consider reptiles and amphibians to only be occasional prey items of whooping cranes. I report observations that show reptiles and amphibians to be an important food source for reintroduced whooping cranes in Louisiana, particularly in spring months, in that they might become a significant source of high-value food during the cranes’ nesting season.