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At least 1,189 records · Page 66Linked to original sources

USGS2026

Keeping pace: Migrating sea lampreys adjust swim speed in response to shifting water velocity to maintain a constant ground speed

Upstream migrating fish must balance energetic costs with environmental and ecological constraints. Theoretical models predict that fish can conserve energy by adjusting swim speed in response to changing water velocity, but detailed field tests of these predictions remain rare. We used fine-scale acoustic telemetry and hydrodynamic modeling to track adult sea lamprey (Petromyzon marinus) migrating through a river and evaluated how movement speeds varied with environmental conditions and individual traits. Swim speed increased with faster water velocities, while ground speed remained constant, supporting the hypothesis that lampreys regulate swim effort to maintain a fixed migration pace. The average ground speed aligned with a predicted optimum of ∼1 body length per second. Both swim and ground speeds declined slightly in deeper water, suggesting a trade-off between movement efficiency and predator avoidance. These findings provide field-based support for a theoretical model of energy optimization and underscore how migratory fish adaptively adjust behavior to local hydrodynamic conditions. Our results highlight the value of using high-resolution tracking and environmental modeling to reveal behavioral tactics that underlie efficient migration strategies.

Michigan↗

USGS2024

Tire-derived contaminants 6PPD and 6PPD-Q: Analysis, sample handling, and reconnaissance of United States stream exposures

The environmental ubiquity of tire and road wear particles (TRWP) underscores the need to understand the occurrence, persistence, and environmental effects of tire-related chemicals in aquatic ecosystems. One such chemical is 6PPD-quinone (6PPD-Q), a transformation product of the tire antioxidant 6PPD. In urban stormwater runoff 6PPD-Q can exceed acute toxicity thresholds for several salmonid species and is being implicated in significant coho salmon losses in the Pacific Northwest. There is a critical need to understand the prevalence of 6PPD-Q across watersheds to identify habitats heavily affected by TRWPs. We conducted a reconnaissance of 6PPD and 6PPD-Q in surface waters across the United States from sites (N = 94) with varying land use (urban, agricultural, and forested) and streamflow to better understand stream exposures. A rapid, low-volume direct-inject, liquid chromatography mass spectrometry method was developed for the quantitation of 6PPD-Q and screening for 6PPD. Laboratory holding times, bottle material, headspace, and filter materials were investigated to inform best practices for 6PPD-Q sampling and analysis. Glass bottles with PTFE-lined caps minimized sorption and borosilicate glass fiber filters provided the highest recovery. 6PPD-Q was stable for at least 5 months in pure laboratory solutions and for 75 days at 5 °C with minimal headspace in the investigated surface water and stormwaters. Results also indicated samples can be frozen to extend holding times. 6PPD was not detected in any of the 526 analyzed samples and there were no detections of 6PPD-Q at agricultural or forested sites. 6PPD-Q was frequently detected in stormwater (57%, N = 90) and from urban impacted sites (45%, N = 276) with concentrations ranging from 0.002 to 0.29 μg/L. The highest concentrations, above the lethal level for coho salmon, occurred during stormwater runoff events. This highlights the importance of capturing episodic runoff events in urban areas near ecologically relevant habitat or nursery grounds for sensitive species.

Chemosphere↗

USGS2015

Seasonal dynamics of zooplankton in Columbia–Snake River reservoirs,with special emphasis on the invasive copepod Pseudodiaptomus forbesi

The Asian copepod Pseudodiaptomus forbesi has recently become established in the Columbia River. However, little is known about its ecology and effects on invaded ecosystems. We undertook a 2-year (July 2009 to June 2011) field study of the mesozooplankton in four reservoirs in the Columbia and Snake Rivers, with emphasis on the relation of the seasonal variation in distribution and abundance of P. forbesi to environmental variables. Pseudodiaptomus forbesi was abundant in three reservoirs; the zooplankton community of the fourth reservoir contained no known non-indigenous taxa. The composition and seasonal succession of zooplankton were similar in the three invaded reservoirs: a bloom of rotifers occurred in spring, native cyclopoid and cladoceran species peaked in abundance in summer, and P. forbesi was most abundant in late summer and autumn. In the uninvaded reservoir, total zooplankton abundance was very low year-round. Multivariate ordination indicated that temperature and dissolved oxygen were strongly associated with zooplankton community structure, with P. forbesi appearing to exhibit a single generation per year . The broad distribution and high abundance of P. forbesi in the Columbia–Snake River System could result in ecosystem level effects in areas intensively managed to improve conditions for salmon and other commercially and culturally important fish species.

Columbia River, Snake River↗

USGS2019

Guadalupe Bass flow-ecology relationships; with emphasis on the impact of flow on recruitment

Guadalupe Bass Micropterus treculii is an economically and ecologically important black bass species endemic to the Edwards Plateau ecoregion and the lower portions of the Colorado River in central Texas. It is considered a fluvial specialist and as such, there are concerns that the increasing demands being placed upon the water resources of central Texas by growing human populations have the potential to negatively impact Guadalupe Bass populations. Therefore, this study assessed the relationship between Guadalupe Bass growth, feeding ecology, and streamflow. Sagittal otoliths were removed from Guadalupe Bass collected from throughout their range during 2015-2017 and used to estimate the age and back-calculate the growth trajectory of each individual. Additionally, young-of-year (YOY) Guadalupe Bass were collected every 10-14 days from two second-order streams, the North Llano River and South Llano River, in the Colorado Basin on the Edwards Plateau. Stomach contents of these individuals were identified and the effect of streamflow on the occurrence of the taxa comprising the stomach contents assessed. Guadalupe Bass growth was greater in the Colorado and Guadalupe River basins, independent of stream order, and tended to increase with increasing stream order within a basin. Growth was higher in higher stream orders and during years with stable and lower spring and summer monthly median flows, lower minimum and maximum flows, slower rise and fall rates, and higher baseflows. Growth was not influenced by years with higher monthly median flows in winter. These results would seem to contradict previous research, but more likely represent a fuller picture of how Guadalupe Bass respond to flow conditions. The disagreement between the current study and past studies seem to be attributable, at least in part, to the fact that previous studies were conducted during a period of extensive drought, while the current study was conducted during relatively wet conditions. Taken together with previous studies, the current study suggests that Guadalupe Bass growth is sensitive to flow conditions and is lower in years with flow conditions that fall outside a basin- and stream order-specific optimal range for the species. A total of 21 unique taxonomic groups were recovered from the stomachs of YOY Guadalupe Bass collected from the North Llano River and South Llano River. Aquatic insects, especially larval mayflies (Ephemeroptera), damselflies (Odanata: Zygoptera), and caddisflies (Trichoptera), were the most frequently encountered taxa. While there was no difference between the two rivers in stomach content composition, there was a strong longitudinal gradient in both systems with aquatic insects predominating at upstream sample sites and fishes being more common at downstream sites. Stream discharge during the 24 hours prior to collection did not have any influence on the probability of a taxa being found in Guadalupe Bass stomachs. The results of this study support efforts to manage Guadalupe Bass populations at a sub-watershed scale and suggests that populations occupying the same stream order within a basin are likely to have similar responses to annual flow conditions. In addition, these results indicate that the lower Colorado River population may inhabit a unique set of conditions that has supported the development of a trophy Guadalupe Bass fishery. Further, this study highlights the need to incorporate a sufficient range of annual flow conditions to ensure that the influence of stream flow on fish growth is adequately assessed. While interannual variation in growth rates seem to be capable of serving as a proxy for recruitment and year-class strength, long-term monitoring of recruitment paired with assessment of growth is necessary to further clarify the relationship between population density, flow regime, recruitment and growth and allow the construction of predictive models.

Texas↗

USGS2012

USGS Zebra Mussel Monitoring Program for north Texas

The U.S. Geological Survey (USGS) Zebra Mussel Monitoring Program for north Texas provides early detection and monitoring of zebra mussels ( Dreissena polymorpha ) by using a holistic suite of detection methods. The program is designed to assess zebra mussel occurrence, distribution, and densities in north Texas waters by using four approaches: (1) SCUBA diving, (2) water-sample collection with plankton tow nets (followed by laboratory analyses), (3) artificial substrates, and (4) water-quality sampling. Data collected during this type of monitoring can assist rapid response efforts and can be used to quantify the economic and ecological effects of zebra mussels in the north Texas area. Monitoring under this program began in April 2010. The presence of large zebra mussel populations often causes undesirable economic and ecological effects, including damage to water-processing infrastructure and hydroelectric powerplants (with an estimated 10-year cost of $3.1 billion), displacement of native mussels, increases in concentrations of certain species of cyanobacteria, and increases in concentrations of geosmin (an organic compound that results in taste and odor issues in water). Since no large-scale, environmentally safe eradication method has been developed for zebra mussels, it is difficult to remove established populations. Broad physicochemical adaptability, prolific reproductive capacity, and rapid dispersal methods have enabled zebra mussels, within a period of about 20 years, to establish populations under differing environmental conditions across much of the eastern part of the United States. In Texas, the presence of zebra mussels was first confirmed in April 2009 in Lake Texoma in the Red River Basin along the Texas-Oklahoma border. They were most likely introduced into Lake Texoma through overland transport from an infested water body. Since then, the presence of zebra mussels has been reported in both the Red River and Washita River arms of Lake Texoma, in Sister Grove Creek, and in Ray Roberts Lake. Water managers tasked with supplying the 6.6 million residents of the Dallas-Fort Worth metropolitan area must ensure that the area receives a continuous supply of water that meets both the needs of the current (2012) and the projected (doubling in number by 2050) populations. This metropolitan area depends on surface water captured in area reservoirs, including those in the Trinity River Basin, for the primary source of drinking water. The presence of an established zebra mussel population in a reservoir in the Trinity River Basin could result in increased operations and maintenance costs for water resource managers and could potentially serve as a source population leading to further expansion of this aquatic nuisance species.

Oklahoma County, Texas County↗

USGS2021

Merging empirical and mechanistic approaches to modeling aquatic visual foraging using a generalizable visual reaction distance model

Visual encounter distance models are important tools for predicting how light and water clarity mediate visual predator-prey interactions that affect the structure and function of aquatic ecosystems at multiple spatial, temporal, and organizational scales. The two main varieties of visual encounter distance models, mechanistic and empirical, are used for similar purposes but take fundamentally different approaches to model development and have different strengths and weaknesses in terms of predictive accuracy, physical and biological interpretability of parameters, ability to incorporate outside information, and utility for knowledge transfer. To overcome weaknesses of existing mechanistic and empirical models and bridge the gap between approaches, we developed a generalized visual reaction distance model that relaxes assumptions of a widely-used mechanistic model that are violated in real predator-prey interactions. We compared the performance of the generalized visual reaction distance model to a widely used mechanistic model and an empirical visual encounter distance model by fitting models to data from four predator-prey experiments. The generalized visual reaction distance model substantially outperformed the other models in all cases based on fit to reaction distance data and presents an attractive alternative to prior models based on comparatively high predictive accuracy, use of interpretable parameters, and ability to incorporate outside information—characteristics that facilitate knowledge transfer.

Ecological Modelling↗

USGS2017

Novel application of explicit dynamics occupancy models to ongoing aquatic invasions

Identification of suitable habitats, where invasive species can establish, is an important step towards controlling their spread. Accurate identification is difficult for new or slow invaders because unoccupied habitats may be suitable, given enough time for dispersal, while occupied habitats may prove to be unsuitable for establishment. To identify the suitable habitat of a recent invader, I used an explicit dynamics occupancy modelling framework to evaluate habitat covariates related to successful and failed establishments of American bullfrogs ( Lithobates catesbeianus ) within the Yellowstone River floodplain of Montana, USA from 2012-2016. During this five-year period, bullfrogs failed to establish at most sites they colonized. Bullfrog establishment was most likely to occur and least likely to fail at sites closest to human-modified ponds and lakes and those with emergent vegetation. These habitat covariates were generally associated with the presence of permanent water. Suitable habitat for bullfrog establishment is abundant in the Yellowstone River floodplain, though many sites with suitable habitat remain uncolonized. Thus, the maximum distribution of bullfrogs is much greater than their current distribution. Synthesis and applications. Focused control efforts on habitats with or proximate to permanent waters are most likely to reduce the potential for invasive bullfrog establishment and spread in the Yellowstone River. The novel application of explicit dynamics occupancy models is a useful and widely applicable tool for guiding management efforts towards those habitats where new or slow invaders are most likely to establish and persist.

Montana↗

USGS2011

Natural-channel-design restorations that changed geomorphology have little effect on macroinvertebrate communities in headwater streams

Stream restorations that increase geomorphic stability can improve habitat quality, which should benefit selected species and local aquatic ecosystems. This assumption is often used to define primary restoration goals; yet, biological responses to restoration are rarely monitored or evaluated methodically. Macroinvertebrate communities were inventoried at 6 study reaches within 5 Catskill Mountain streams between 2002 and 2006 to characterize their responses to natural-channel-design (NCD) restoration. Although bank stability increased significantly at most restored reaches, analyses of variation showed that NCD restorations had no significant effect on 15 of 16 macroinvertebrate community metrics. Multidimensional scaling ordination indicated that communities from all reach types within a stream were much more similar to each other within any given year than they were in the same reaches across years or within any type of reach across streams. These findings indicate that source populations and watershed-scale factors were more important to macroinvertebrate community characteristics than were changes in channel geomorphology associated with NCD restoration. Furthermore, the response of macroinvertebrates to restoration cannot always be used to infer the response of other stream biota to restoration. Thus, a broad perspective is needed to characterize and evaluate the full range of effects that restoration can have on stream ecosystems.

Catskill Mountains↗

USGS2020

Chronic and episodic acidification of streams along the Appalachian Trail corridor, eastern United States

Acidic atmospheric deposition has adversely affected aquatic ecosystems globally. As emissions and deposition of sulfur (S) and nitrogen (N) have declined in recent decades across North America and Europe, ecosystem recovery is evident in many surface waters. However, persistent chronic and episodic acidification remain important concerns in vulnerable regions. We evaluated acidification in 269 headwater streams during 2010–2012 along the Appalachian Trail (AT) that transits several ecoregions and is located downwind of high levels of S and N emission sources. Discharge was estimated by matching sampled streams to those of a nearby gaged stream and assuming equivalent daily mean flow percentiles. Charge balance acid‐neutralizing capacity (ANC) values were adjusted to the 15th (Q15) and 85th flow percentiles (Q85) by applying the ANC/discharge slope among sample pairs collected at each stream. A site‐based approach was applied to streams sampled twice or more and a second regression‐based approach to streams sampled once to estimate episodic acidification magnitudes as the ANC difference from Q15 to Q85. Streams with ANC <0 μeq/L doubled from 16% to 32% as discharge increased from Q15 to Q85 according to the site‐based approach. The proportion of streams with ANC <0 μeq/L at low flow and high flow decreased from north to south. Base cation dilution explained the greatest amount of episodic acidification among streams and variation in sulfate (SO 4 2− ) concentrations was a secondary explanatory variable. Episodic SO 4 2− patterns varied geographically with dilution dominant in northern streams underlain by soils developed in glacial sediment and increased concentrations dominant in southern streams with older, highly weathered soils. Episodic acidification increased as low‐flow ANC increased, exceeding 90 μeq/L in 25% of streams. Episodic increases in ANC were the dominant pattern in streams with low‐flow ANC values <30 μeq/L. Chronic and episodic acidification remain an ecological concern among AT streams. The approach developed here could be applied to estimate the magnitude and extent of chronic and episodic acidification in other regions recovering from decreasing levels of atmospheric S and N deposition.

Connecticut, Georgia, Maine, Massachusetts, Maryla↗

USGS2009

Hepatic pathologies in the brackish water catfish (Chrysichthys nigrodigitatus) from contaminated locations of the Lagos lagoon complex

Several toxicological studies into the effects of aquatic pollutants on the liver of teleost fish exist in literature. The focus on the liver in these studies is predicated on its central nature in the scheme of biotransformation and excretion of xenobiotics following exposure in polluted water bodies. As a consequence of the latter primary role of the liver in these processes it is regarded as a predilective site for the sub lethal effects of xenobiotics on the organism usually detectable at histological level. Hepatic histopathology recorded in livers from feral populations of the brackish water catfish Chrysichthys nigrodigitatus from locations on the Lagos lagoon complex with significant anthropogenic inputs from denizen populations and industries are presented. Liver sections from sixty specimens from two locations on the Lagos lagoon complex (Badagry lagoon: 6°24'N, 2°56'E; and Lagos lagoon: 6°29'N, 3°22'E) were analysed. Observed pathologies included hydropic degeneration (58%), portal / sinusoidal congestion (33%), hepatic necrosis (26%), hemosiderosis (12%) and foci of cellular alterations (FCA's). No obvious oncologic features were observed; the presence of the hydropic Vacuolation lesion was taken as prelude to the development of neoplasms and discussed as such.

Badagry Lagoon, Lagos Lagoon↗

USGS2012

Biomedical health assessments of the Florida manatee in Crystal River - providing opportunities for training during the capture, handling, and processing of this endangered aquatic mammal

Federal and state researchers have been involved in manatee (Trichechus manatus) biomedical health assessment programs for a couple of decades. These benchmark studies have provided a foundation for the development of consistent capture, handling, and processing techniques and protocols. Biologists have implemented training and encouraged multi-agency participation whenever possible to ensure reliable data acquisition, recording, sample collection, publication integrity, and meeting rigorous archival standards. Under a U.S. Fish and Wildlife Service wildlife research permit granted to the U.S. Geological Survey (USGS) Sirenia Project, federal biologists and collaborators are allowed to conduct research studies on wild and captive manatees detailing various aspects of their biology. Therefore, researchers with the project have been collaborating on numerous studies over the last several years. One extensive study, initiated in 2006 has focused on health and fitness of the winter manatee population located in Crystal River, Florida. During those health assessments, capture, handling, and work-up training has been afforded to many of the participants. That study has successfully captured and handled 123 manatees. The data gathered have provided baseline information on manatee health, reproductive status, and nutritional condition. This research initiative addresses concerns and priorities outlined in the Florida Manatee Recovery Plan. The assessment teams strive to continue this collaborative effort to help advance our understanding of health-related issues confronting manatees throughout their range and interlacing these findings with surrogate species concepts.

Florida↗

USGS2024

Spatial patterns as long transients in submersed-floating plant competition with biocontrol

A cellular automata model was developed and parameterized to test the effectiveness of application of biological control insects to water hyacinth ( Pontederia crassipes ), which is an invasive floating plant species in many parts of the world and outcompetes many submersed native aquatic species in southern Florida. In the model, P. crassipes was allowed to compete with Nuttall’s waterweed ( Elodea nuttallii ). In the absence of biocontrol acting on the P. crassipes , E. nuttallii excluded P. crassipes at low concentrations of the limiting nutrient (nitrogen), and the reverse occurred at high nutrient concentrations. At intermediate values, alternative stable states could occur; either P. crassipes alone or a mixture of the two species. When the biocontrol agent, the weevil Neochetina eichhorniae , was applied in the model, there was initially a rapid reduction of the P. crassipes , however, over time a regular striped pattern of moving spatially alternating stripes of P. crassipes and E. nuttallii emerged. -This pattern of moving stripes emerged and persisted over thousands of days but could quickly transform into an irregular pattern at some apparently random time, when either external stochasticity (added adult weevils) or only the weak internal stochasticity of weevil movements occurred. The cause of the end of the long transient can be traced to a single slightly irregular pixel within the striped pattern. Model parameters were varied to study effects of plant growth rate, nutrient concentration and nutrient diffusion rate on the dynamics of the system.

Theoretical Ecology↗

USGS2005

Ecology of the Lake Huron fish community, 1970-1999

We review the status of the Lake Huron fish community between 1970 and 1999 and explore the effects of key stressors. Offshore waters changed little in terms of nutrient enrichment, while phosphorus levels declined in inner Saginaw Bay. Introduced mussels ( Dreissena spp.) proliferated and may have caused a decline in Diporeia spp. This introduction could have caused a decline in lake whitefish ( Coregonus clupeaformis ) growth and condition, with serious repercussions for commercial fisheries. Bythotrephes , an exotic predatory cladoceran, and other new exotics may be influencing the fish community. Sea lampreys ( Petromyzon marinus ) remained prevalent, but intensive control efforts on the St. Mary's River may reduce their predation on salmonines. Overfishing was less of a problem than in the past, although fishing continued to reduce the amount of lake trout ( Salvelinus namaycush ) spawning biomass resulting from hatchery-reared fish planted to rehabilitate this species. Massive stocking programs have increased the abundance of top predators, but lake trout were rehabilitated in only one area. Successful lake trout rehabilitation may require lower densities of introduced pelagic prey fish than were seen in the 1990s, along with continued stocking of hatchery-reared lake trout and control of sea lamprey. Such reductions in prey fish could limit Pacific salmon ( Oncorhynchus spp.) fisheries.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS2023

Genetic analysis of North American Phragmites australis guides management approaches

Phragmites australis subsp. australis is an invasive and ecologically detrimental plant in multiple regions of North America. Its co-occurrence with the native subspecies, and multiple instances of hybridization, has created the need to differentiate Phragmites subspecies or haplotypes so that management can be appropriately targeted to the invader. We compiled a review of current genetic discrimination methods among the three Phragmites subspecies inhabiting the United States and Canada, and discussed how each method can contribute to control of the introduced subspecies while preserving the two endemic subspecies. We also discussed various control tools and the implications of Phragmites genetics for implementation. The Phragmites subspecies endemic to North America have environmental or infrastructure significance (e.g., habitat sustainability, biodiversity, storm surge and erosion protection). Thus, faster and more accurate differentiation among the endemic and introduced subspecies is needed. Additionally, more in-depth genetic information on Phragmites subspecies could support better management decisions, as well as the development of improved control treatments. This review highlights technologies and approaches currently available for genetic identification, recently collected genomic, transcriptomic and proteomic information, and implications for biological control and herbicide treatments.

Aquatic Botany↗

USGS2022

Lake trout (Salvelinus namaycush) otoliths indicate effects of climate and lake morphology on growth patterns in Arctic lakes

Climate change is occurring rapidly in the Arctic, and an improved understanding of the response of aquatic biota and ecosystems will be important for this data-limited region. Here, we applied biochronology techniques and mixed-effects modelling to assess relationships among growth increments found on lake trout ( Salvelinus namaycush ) otoliths ( N = 49) captured from 13 lakes on the Arctic Coastal Plain of northern Alaska, observed and modelled climate patterns, and individual-level fish and lake characteristics. We found that annual growth varied by year, fish growth slowed significantly as individuals aged, and females grew faster than males. Lake trout had higher growth in flow-through lakes relative to lakes that were perennially or seasonally connected. Annual growth was positively correlated with observed air temperature measurements from a local weather station for the period 1998–2014, but no clear warming trend was evident for this period. Modelled August air temperatures from 1978–2014 predicted lake trout annual growth (root mean squared error = 0.045 mm) and indicated increasing temperatures and annual lake trout growth over the period 1950–2014. This study demonstrated that biochronology techniques can reconstruct recent climate patterns and provide a better understanding of trends in Arctic lake ecosystems under a changing climate.

Alaska↗

USGS2010

Relationship between fibropapillomatosis and environmental quality: A case study with Chelonia mydas off Brazil

We documented the presence of fibropapillomatosis (FP), a debilitating tumor-forming disease, in marine turtles in Espírito Santo Bay (Brazil) from March 2007 to April 2008, and assessed the value of a specific environmental index for predicting the prevalence of FP. Turtles were captured monthly with entanglement nets and scored for presence and severity of FP. For the assessment of habitat quality, we used the ecological evaluation index (EEI) based on benthic macrophytes. The FPfree control area was classified as good quality (EEI = 8) and the study area, with high FP prevalence, was classified as bad quality (EEI = 2). Prevalence of FP in the study area was 58.3% with an average of 40 tumors per individual, and prevalence varied positively with curved carapace length (CCL). No FP was seen in the control area. The number of turtles heavily afflicted (tumor score category 3) was 10 times larger than those lightly affected (tumor score category 1). Most tumors were found on or near the front and rear flippers; no oral tumors or internal tumors were found. At recapture, 41% of formerly tumor-free turtles revealed FP, often increasing in severity with time, and very few turtles showed signs of disease regression. From the results of this study we concluded that FP is particularly severe in Espírito Santo Bay. Future studies should focus on evaluating how widespread FP is in Brazil, whether prevalence is increasing or decreasing, and elucidating the pathology and pathogenesis of FP in sea turtles in Brazil.

Diseases of Aquatic Organisms↗

USGS2010

The influence of partial timber harvesting in riparian buffers on macroinvertebrate and fish communities in small streams in Minnesota, USA

Relatively few evaluations of aquatic macroinvertebrate and fish communities have been published in peer-reviewed literature detailing the effect of varying residual basal area (RBA) after timber harvesting in riparian buffers. Our analysis investigated the effects of partial harvesting within riparian buffers on aquatic macroinvertebrate and fish communities in small streams from two experiments in northern Minnesota northern hardwood-aspen forests. Each experiment evaluated partial harvesting within riparian buffers. In both experiments, benthic macroinvertebrates and fish were collected 1 year prior to harvest and in each of 3 years after harvest. We observed interannual variation for the macroinvertebrate abundance, diversity and taxon richness in the single-basin study and abundance and diversity in the multiple-basin study, but few effects related to harvest treatments in either study. However, interannual variation was not evident in the fish communities and we detected no significant changes in the stream fish communities associated with partially harvested riparian buffers in either study. This would suggest that timber harvesting in riparian management zones along reaches ≤200 m in length on both sides of the stream that retains RBA ≥ 12.4 ± 1.3 m 2 ha −1 or on a single side of the stream that retains RBA ≥ 8.7 ± 1.6 m 2 ha −1 may be adequate to protect macroinvertebrate and fish communities in our Minnesota study systems given these specific timber harvesting techniques.

Minnesota↗

USGS2026

Integrating climate data and river modeling to reveal Chinook salmon habitat conditions in subarctic river basins

Climatic extremes can impact the productivity of aquatic species, affecting ecosystems and fishery-dependent communities. Advances in climate products, such as gridded datasets and downscaled projections, may be useful for quantifying freshwater habitat conditions and predicting climate change effects on fish. However, limited guidance exists for selecting climate products to develop indicators of freshwater habitat conditions that influence fish population dynamics. Here, we develop an approach for identifying streamflow and stream temperature models to address this need. We evaluated skill in predicted versus observed streamflow and stream temperature, with predictions depending on different models and gridded climate data as inputs. The best performing models were used in a case study exploring habitat conditions influencing Chinook salmon in the Yukon and Kuskokwim River basins, two remote high-latitude watersheds with few in situ habitat observations and recent salmon declines. Three modeled streamflow datasets had variable performance (median Nash–Sutcliffe efficiencies from 0.39 to 0.70). Three gridded temperature products differed in their ability to explain variation in weekly stream temperatures (median r 2 from 0.42 to 0.76). We selected a single gridded air temperature dataset to compare two novel predictive stream temperature models, both of which had good accuracy (root mean squared error [RMSE] of 1.19 and 0.95°C). Stream temperature indicators calculated from modeled daily data, maximum temperatures during adult migration and cumulative temperatures during juvenile rearing, had high spatial correlation across tributaries within the Yukon and Kuskokwim River basins and showed significant warming over the past 40 years. Streamflow indicators calculated from modeled daily data, maximum flow during spawning and median flow during rearing, had few trends and were largely uncorrelated within the Yukon River basin and moderately correlated within the Kuskokwim River basin. Overall, we found that generic measures of model performance varied considerably, and it was important to consider the models best suited to our case study. For both streamflow and stream temperature, multiple high-performing models allowed estimation of ecologically relevant conditions affecting Chinook salmon. The approach we used to estimate local-scale habitat conditions has value to identify synchronous conditions that may influence multiple salmon populations under a changing subarctic climate.

Alaska↗