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At least 901 records · Page 50Linked to original sources
USGS2023

Full-service hotels, convenience stores, or fire escapes? Evaluating the functional role of stopover sites for Neotropical migrants following passage across the Gulf of Mexico in autumn

Nearctic Neotropical migratory songbirds incur the highest mortality during migration. En-route, songbirds rely on a network of stopover sites to rest, refuel, and/or seek refuge during poor weather. Conservation strategies prioritize protection of sites that best meet these needs. However, the specific function of a stopover site is expected to vary in relation to factors, such as geographic location, surrounding landscape, and weather. To identify sites with the highest conservation value for migratory songbirds, a conceptual framework was independently developed to classify sites into three functional categories based on their geographic and landscape features: fire escapes, convenience stores, and full-service hotels. The few attempts to empirically validate this framework have focused on temperate stopover sites. We evaluated the framework by testing the hypothesis that a site’s geographic and landscape characteristics can predict its function. We used capture and radio-tracking data at an island and mainland site in the Yucatan Peninsula, Mexico to quantify mean and variance in daily capture rate, body condition, stopover duration, and departure behavior during autumn, with a focus on four species: Swainson’s Thrush (Catharus ustulatus), Red-eyed Vireo (Vireo olivaceus), Gray Catbird (Dumetella carolinensis), and Prothonotary Warbler (Protonotaria citrea). Our results supported our predictions that the island functions as a fire escape, providing refuge for very high numbers of birds after encountering crosswinds or headwinds over the Gulf of Mexico, and the mainland forest site serves as a full-service hotel. The framework provides valuable insight for strategic conservation planning and management of stopover sites for songbirds. We suggest future studies evaluate the framework’s application to non-forest bird species. Additionally, we encourage collaborative efforts to consolidate and integrate tracking data, capture data from migration banding stations, and radar-based bird density estimates across a broad geography to test the framework’s ability to inform conservation planning across species’ full migratory range.

Avian Conservation and Ecology↗
USGS2023

Network analysis of a northern long-eared bat (Myotis septentrionalis) maternity colony in a suburban forest patch

Many bat species are highly social, forming groups of conspecifics, particularly during the maternity season. In temperate North America, these social groups are typically comprised of closely related individuals or individuals that share some common trait (i.e. reproductive state or shared hibernacula from the previous winter). In the summer, when bats use forests for day-roosts, these social groups often demonstrate nonrandom patterns of periodically associating in common roosts and disassociating using different roosts as a ‘fission–fusion society’. As cave hibernating bat species in North America continue to decline due to the impacts of White-nose Syndrome, opportunities to describe these dynamics are becoming rare. Unfortunately, these patterns often are still poorly documented, yet understanding these behaviors is critical for species-specific habitat conservation and management. In our study, we tracked female northern long-eared bats ( Myotis septentrionalis ) to their day-roosts in a small, suburban forest fragment in coastal New York, USA, in the summers of 2018 and 2019. We confirmed that the bats shared roost sites and, using network analyses, analyzed social dynamics and space use. In contrast to previous research on this imperiled species in large, unfragmented core forests, we found a more dense, connected roost network that concentrated around forest patch edges. Unusual for this species, primary roosts were anthropogenic structures. Our findings suggest that northern long-eared bats can utilize small forest patches and that incorporation of specific types of anthropogenic roosts might be an effective strategy for long-term conservation in more urbanized landscapes where forest management actions to enhance day-roosting conditions a

New York↗
USGS2011

Mortality of Siberian polecats and black-footed ferrets released onto prairie dog colonies

Black-footed ferrets ( Mustela nigripes ) likely were extirpated from the wild in 1985–1986, and their repatriation depends on captive breeding and reintroduction. Postrelease survival of animals can be affected by behavioral changes induced by captivity. We released neutered Siberian polecats ( M. eversmanii ), close relatives of ferrets, in 1989–1990 on black-tailed prairie dog ( Cynomys ludovicianus ) colonies in Colorado and Wyoming initially to test rearing and reintroduction techniques. Captive-born polecats were reared in cages or cages plus outdoor pens, released from elevated cages or into burrows, and supplementally fed or not fed. We also translocated wild-born polecats from China in 1990 and released captive-born, cage-reared black-footed ferrets in 1991, the 1st such reintroduction of black-footed ferrets. We documented mortality for 55 of 92 radiotagged animals in these studies, mostly due to predation (46 cases). Coyotes ( Canis latrans ) killed 31 ferrets and polecats. Supplementally fed polecats survived longer than nonprovisioned polecats. With a model based on deaths per distance moved, survival was highest for wild-born polecats, followed by pen-experienced, then cage-reared groups. Indexes of abundance (from spotlight surveys) for several predators were correlated with mortality rates of polecats and ferrets due to those predators. Released black-footed ferrets had lower survival rates than their ancestral population in Wyoming, and lower survival than wild-born and translocated polecats, emphasizing the influence of captivity. Captive-born polecats lost body mass more rapidly postrelease than did captive-born ferrets. Differences in hunting efficiency and prey selection provide further evidence that these polecats and ferrets are not ecological equivalents in the strict sense.

Journal of Mammalogy↗
USGS2020

After-hatch and hatch year Buff-breasted Sandpipers (Calidris subruficollis) can be sexed accurately using morphometric measures

Determining the sex of birds quickly in the field can help in studies of behavior and distribution, and when selecting particular sexes for deploying tracking devices or collecting samples. However, discerning males from females is difficult in species that are plumage monomorphic and have overlapping sexual-size dimorphism, as in Buff-breasted Sandpipers Calidris subruficollis . We developed three discriminant functions to sex Buff-breasted Sandpipers based on measurements of live birds captured in Brazil whose sex was confirmed with molecular techniques. We validated these discriminant functions using morphometric measures from other independent samples of known-sex live birds from wintering (Brazil), migration (Texas), and breeding (Alaska) sites. Discriminant functions derived from birds captured in Brazil accurately sexed ≥88% of the validation sample from Brazil, Texas, and Alaska. Errors in classification occurred among males on the wintering (0–5%) and breeding (8–12%) grounds, and females during migration (0–11%). Discriminant functions worked well because of the substantial sexual size dimorphism present in the species, with male traits being in general 5.2–10.4% larger than female traits. The size of morphological traits did not vary by age (after controlling for sex) for birds sampled on the wintering grounds and during migration. Our results indicate that discriminant functions can be used to sex after-hatch year (AHY) Buff-breasted Sandpipers throughout their range, and for hatch year (HY) birds during their first southbound migration and winter. Being able to accurately sex both AHY and HY birds using only morphological measurements will improve studies of the ecology and population structure of this species and enhance the application of conservation measures.

Wader Study↗
USGS2026

Small creatures, big challenge: A review of current knowledge and assessment of research needs to inform water withdrawal management for the Duck River's freshwater mussel fauna

The Duck River is a remarkable national resource, boasting outstanding biodiversity (Ahlstedt et al. 2017). It contains 151 fish species, over 60 mussel species, and 22 snail species, many of which are federally listed (Etnier and Starnes 1993; Johnson et al. 2013; Ahlstedt et al. 2017; Womble and Rosenberger 2025a). The Duck River watershed is at a pivotal time in its management and ecological history due to significant growth in human population and economic activity. The consequent increase in surface water demand presents challenges for sustainable water resource management. The Tennessee Department of Environment and Conservation (TDEC) has permitted or proposed to permit eight water utilities to withdraw over 77 million gallons per day (mgd) from the Duck River, representing > 40% increase from previously permitted amounts (USFWS 2025). On November 20, 2024, Tennessee Governor Bill Lee signed Executive Order No 108 to ensure long-term stability of the Duck River watershed through balancing economic growth, water resource management, and environmental conservation. Some primary components of this plan are the creation of a Comprehensive Regional Drought Management Plan, the development of a Habitat Conservation Plan, and the establishment of the Duck River Watershed Planning Partnership (DRWPP). Although the planning partnership is not focused on a sole aspect of the Duck River, but the watershed as a whole, the mussel assemblages of the Duck River have been a particular focus due to their importance in providing ecosystem services, sensitivity to water quality, conservation status, and sensitivity to periodic drought conditions in this system. With multiple state and federal agencies involved in managing the Duck River’s unique water resources, a focused review on how future water management could affect the freshwater mussel communities in the Duck River will contribute to this process. Our objectives of this review are to: 1. Review the effects of changing flow regimes on mussels, with emphasis on the effect of droughts/low flows, highlighting key processes/factors affecting mussels. 2. Highlight critical data gaps that could allow future, evidence-based water management decisions in this system. 3. Propose research topics to address critical data gaps and enable evidence-based water management decisions that consider the needs of freshwater mussels. Freshwater mussels are a critical component of riverine ecosystems, providing ecosystem services including water filtration, nutrient cycling, and habitat provision (Vaughn et al. 2004; Haag 2012) that benefit human communities. Environmental flows, also referred to as ecological or e-flows, refer to the quantity, timing, and quality of water flows necessary to maintain the ecological health of rivers, wetlands, and other aquatic ecosystems (Acreman and Dunbar 2004; Acreman 2016). For freshwater mussels, environmental flows include maintaining a flow regime and associated water quality regimes that are favorable for both juveniles and adults while also seasonally supporting host fish and the survival of settling glochidia (i.e., larval mussels) in suitable environments (Gates et al. 2015). Freshwater mussels are adapted to the natural flow regime of their native streams, including seasonal variability in flows. As sedentary filter feeders, mussels require adequate water flow to provide oxygen and food (Allen and Vaughn 2009); however, they also require periods of low flow to increase access to fish hosts and to ensure juveniles are not displaced (Gates et al 2015). Mussels are sensitive to water quality conditions, including pollutants, sedimentation, and artificial alterations of temperature and pH (Strayer and Malcom 2012). Mussel community characteristics, including presence, abundance, and species richness, generally increase with stream size (e.g., stream order); however, responses to changes in flow conditions are often species-specific, and the magnitude and timing of extreme flow conditions have more predictive power for mussel community response than general changes in flow (Lopez and Vaughn 2021). Complex hydraulic variables, such as relative shear stress and Reynolds number, can be strong predictors of mussel community responses because they combine simple hydraulic variables (e.g., velocity, depth) with stream channel characteristics, such as substrate composition and dynamics. Droughts directly and indirectly affect mussels by influencing their physiology, behavior, reproduction, and ecosystem roles. Mass mussel die-offs during droughts and low water conditions are widely documented (Vaughn et al. 2015; Sousa et al. 2018; Dubose et al. 2019). Droughts can also lead to a shift in mussel community composition, with drought-tolerant species becoming more dominant while more sensitive species experience declines (Galbraith et al, 2010; Lopez et al. 2022; Vaughn and Atkinson 2025). Droughts affect mussels through direct mortality from stranding as well as physiological stress from altered water temperature and quality, reduced habitat and food availability and quality, increased predation and competition, disruption of reproductive cycles, and increased susceptibility to disease and pathogens. Although the effects of droughts, water withdrawals, and low flow conditions on mussels are an increasing area of study, there is a general paucity of data-driven consensus regarding optimal mitigation approaches and strategies (Cushway et al. 2024). Long-term management decisions regarding water withdrawals, particularly during extended or multi-year drought conditions, may consider factors beyond direct mortality such as the sublethal effects of drought and low flow conditions on freshwater mussels for a comprehensive understanding of the effects of prolonged low flows on freshwater mussels and aquatic communities.

Tennessee↗
USGS2014

Migrations and swimming capabilities of endangered pallid sturgeon ( Scaphirhynchus albus ) to guide passage designs in the fragmented Yellowstone River

Fragmentation of the Yellowstone River is hypothesized to preclude recruitment of endangered Scaphirhynchus albus (pallid sturgeon) by impeding upstream spawning migrations and access to upstream spawning areas, thereby limiting the length of free-flowing river required for survival of early life stages. Building on this hypothesis, the reach of the Yellowstone River affected by Intake Diversion Dam (IDD) is targeted for modification. Structures including a rock ramp and by-pass channel have been proposed as restoration alternatives to facilitate passage. Limited information on migrations and swimming capabilities of pallid sturgeon is available to guide engineering design specifications for the proposed structures. Migration behavior, pathways (channel routes used during migrations), and swimming capabilities of free-ranging wild adult pallid sturgeon were examined using radiotelemetry, and complemented with hydraulic data obtained along the migration pathways. Migrations of 12–26% of the telemetered pallid sturgeon population persisted to IDD, but upstream passage over the dam was not detected. Observed migration pathways occurred primarily through main channel habitats; however, migrations through side channels up to 3.9 km in length were documented. The majority of pallid sturgeon used depths of 2.2–3.4 m and mean water velocities of 0.89–1.83 m/s while migrating. Results provide inferences on depths, velocities, and habitat heterogeneity of reaches successfully negotiated by pallid sturgeon that may be used to guide designs for structures facilitating passage at IDD. Passage will provide connectivity to potential upstream spawning areas on the Yellowstone River, thereby increasing the likelihood of recruitment for this endangered species.

Montana↗
USGS2019

Sequence analysis and acoustic tracking individual lake sturgeon identifies multiple patterns of river-lake habitat use

Understanding the spatial ecology of sturgeon (Acipenseridae) has proven to be a challenge due to the life history characteristics of these fish, especially their long life span, intermittent spawning, and long‐distance migrations. Within the Huron‐Erie Corridor (HEC) of the Laurentian Great Lakes, habitat use of 247 lake sturgeon ( Acipenser fulvescens ) was monitored over a three‐year period (2015–2017) with acoustic transmitters. Extensive spatial coverage of receivers throughout the St. Clair River, Lake St. Clair, and Detroit River between Lake Huron and Lake Erie (~150 km) allowed for continuous monitoring of the movements of acoustic‐tagged individuals. Sequence analysis of individual detection histories was used to describe lake sturgeon habitat use and to determine (1) whether distinct habitat‐use patterns occurred within the HEC; (2) whether the range of habitats occupied varied across seasons among sturgeon grouped by common patterns; and (3) whether variation identified was related to tagging sites in the two rivers or sex. Lake sturgeon were active throughout the HEC, but five distinct habitat‐use patterns were identified. River residents were not broadly distributed across entire rivers, but rather associated with particular segments (middle Detroit River, St. Clair River delta). Variations in habitat‐use sequences were in part related to three river tagging sites, but not sex, and did not produce groups with sequences that reflected all five habitat‐use patterns derived from cluster analysis. Lake sturgeon distribution was reduced to fewer habitat segments during winter and expanded to the maximum extent during the spring and summer. Conservation planning that incorporates behavioral diversity of habitat use is relatively rare due to a lack of observations on movements of individuals at biologically relevant spatial and temporal scales, but using telemetry and sequence analysis methods may promote the success of conservation and restoration efforts.

St. Clair River, Lake St. Clair, Detroit River↗
USGS2019

Growth, condition, and trophic relations of stocked trout in southern Appalachian mountain streams

Stream trout fisheries are among the most popular and valuable in the United States, but many are dependent on hatcheries to sustain fishing and harvest. Thus, understanding the ecology of hatchery‐reared trout stocked in natural environments is fundamental to management. We evaluated the growth, condition, and trophic relations of Brook Trout Salvelinus fontinalis , Brown Trout Salmo trutta , and Rainbow Trout Oncorhynchus mykiss that were stocked in southern Appalachian Mountain streams in western North Carolina. Stocked and wild (naturalized) trout were sampled over time (monthly; September 2012–June 2013) to compare condition and diet composition and to evaluate temporal dynamics of trophic position with stable isotope analysis. Relative weights ( W r ) of stocked trout were inversely associated with their stream residence time but were consistently higher than those of wild trout. Weight loss of harvested stocked trout was similar among species and sizes, but fish stocked earlier lost more weight. Overall, 40% of 141 stomachs from stocked trout were empty compared to 15% of wild trout stomachs ( N = 26). We identified a much higher rate of piscivory in wild trout (18 times that of stocked trout), and wild trout were 4.3 times more likely to consume gastropods relative to stocked trout. Hatchery‐reared trout were isotopically similar to co‐occurring wild fish for both δ 13 C and δ 15 N values but were less variable than wild trout. Differences in sulfur isotope ratios (δ 34 S) between wild and hatchery‐reared trout indicated that the diets of wild fish were enriched in δ 34 S relative to the diets of hatchery‐reared fish. Although hatchery‐reared trout consumed prey items similar to those of wild fish, differences in consumption or behavior (e.g., reduced feeding) may have resulted in lower condition and negative growth. These findings provide critical insight on the trophic dynamics of stocked trout and may assist in developing and enhancing stream trout fisheries.

North Carolina↗
USGS2010

Hydrology and Ecology of Freshwater Wetlands in Central Florida - A Primer

Freshwater wetlands are an integral part of central Florida, where thousands are distributed across the landscape. However, their relatively small size and vast numbers challenge efforts to characterize them collectively as a statewide water resource. Wetlands are a dominant landscape feature in Florida; in 1996, an estimated 11.4 million acres of wetlands occupied 29 percent of the area of the State. Wetlands represent a greater percentage of the land surface in Florida than in any other state in the conterminous United States. Statewide, 90 percent of the total wetland area is freshwater wetlands and 10 percent is coastal wetlands. About 55 percent of the freshwater wetlands in Florida are forested, 25 percent are marshes and emergent wetlands, 18 percent are scrub-shrub wetlands, and the remaining 2 percent are freshwater ponds. Freshwater wetlands are distributed differently in central Florida than in other parts of the State. In the panhandle and in northern Florida, there are fewer isolated wetlands than in the central and southern parts of the State, and few of those wetlands are affected by activities such as groundwater withdrawals. In southern Florida, the vast wetlands of the Everglades and the Big Cypress Swamp blanket the landscape and form contiguous shallow expanses of water, which often exhibit slow but continuous flow toward the southwestern coast. In contrast, the wetlands of central Florida are relatively small, numerous, mostly isolated, and widely distributed. In many places, wetlands are flanked by uplands, generating a mosaic of contrasting environments-unique wildlife habitat often adjacent to dense human development. As the population of central Florida increases, the number of residents living near wetlands also increases. Living in close proximity to wetlands provides many Floridians with an increased awareness of nature and an opportunity to examine the relationship between people and wetlands. Specifically, these residents can observe how wetlands are affected by human activities. Freshwater wetlands are unique and complex ecosystems defined by characteristic properties. Wetlands usually have standing water during at least part of the year, although water depths can vary from a few inches to as much as several feet from one wetland to another. The hydrologic behavior of wetlands is influenced by drainage basin characteristics, as well as by natural variations in climate. Wetlands in central Florida (especially forested wetlands) often have acidic waters that are darkly stained from organic substances released by decomposing leaves and other plant material. Wetlands are characterized by biogeochemical cycles in which vital elements such as carbon, nitrogen, phosphorus, and others are transformed as they move between wetland soils and sediments, the open water, and the atmosphere. Wetlands are populated with plants that can thrive under conditions of saturated soils and low dissolved-oxygen concentrations. The bottoms of many wetlands, especially marshes, are covered with decayed plant material that can accumulate over time to form brown peat or black muck soils. Wetlands are inhabited by animals that need standing water to complete some or all of their life cycles, and they also provide periodic food, water, and shelter for many other animals that spend most of their lives on dry land. The complex and interrelated components of wetlands directly affect one another and there are numerous feedback mechanisms.

Circular↗
USGS2003

Evolution of CAM and C 4 carbon-concentrating mechanisms

Mechanisms for concentrating carbon around the Rubisco enzyme, which drives the carbon-reducing steps in photosynthesis, are widespread in plants; in vascular plants they are known as crassulacean acid metabolism (CAM) and C 4 photosynthesis. CAM is common in desert succulents, tropical epiphytes, and aquatic plants and is characterized by nighttime fixation of CO2. The proximal selective factor driving the evolution of this CO2-concentrating pathway is low daytime CO2, which results from the unusual reverse stomatal behavior of terrestrial CAM species or from patterns of ambient CO2 availability for aquatic CAM species. In terrestrials the ultimate selective factor is water stress that has selected for increased water use efficiency. In aquatics the ultimate selective factor is diel fluctuations in CO2 availability for palustrine species and extreme oligotrophic conditions for lacustrine species. C4 photosynthesis is based on similar biochemistry but carboxylation steps are spatially separated in the leaf rather than temporally as in CAM. This biochemical pathway is most commonly associated with a specialized leaf anatomy known as Kranz anatomy; however, there are exceptions. The ultimate selective factor driving the evolution of this pathway is excessively high photorespiration that inhibits normal C3 photosynthesis under high light and high temperature in both terrestrial and aquatic habitats. CAM is an ancient pathway that likely has been present since the Paleozoic era in aquatic species from shallow-water palustrine habitats. While atmospheric CO2 levels have undoubtedly affected the evolution of terrestrial plant carbon-concentrating mechanisms, there is reason to believe that past atmospheric changes have not played as important a selective role in the aquatic milieu since palustrine habitats today are not generally carbon sinks, and the selective factors driving aquatic CAM are autogenic. Terrestrial CAM, in contrast, is of increasing selective value under extreme water deficits, and undoubtedly, high Mesozoic CO2 levels reduced the amount of landscape perceived by plants as water limited. Late Tertiary and Quaternary reductions in atmospheric CO2, coupled with increasing seasonality, were probably times of substantial species radiation and ecological expansion for CAM plants. C4 photosynthesis occurs in only about half as many families as CAM, and three-fourths of C4 species are either grasses or sedges. Molecular phylogenies indicate C4 is a more recent innovation than CAM and that it originated in the mid-Tertiary, 20–30 Ma, although some data support an earlier origin. While the timing of the origin of C4 remains controversial, the nearly explosive increase in C4 species is clearly documented in the late Miocene, 4–7 Ma. Increasing seasonality has been widely suggested as an important climatic stimulus for this C4 expansion. Alternatively, based on models of photosynthetic quantum yield at different temperatures and CO2 concentration, it has been hypothesized that the late Miocene C4 expansion resulted from declining atmospheric CO2 levels. This model is most appropriate for explaining the transition from C3 grasslands to C4 grasslands but by itself may not be sufficient to explain the more likely scenario of a late Miocene transition from C3 woodland/ savanna to C4 grasslands. A largely unexplored hypothesis is that climatic changes in late Miocene altered disturbance regimes, in particular the incidence of fires, which today are often associated with maintenance of C4 grasslands. Oceanic charcoal sediments that appear to represent Aeolian deposits from continental wildfires follow a strikingly similar pattern of explosive increase in late Miocene. Climate, CO2, and disturbance are not mutually exclusive explanations and probably all acted in concert to promote the expansion of C4 grasslands. More recently, late Quaternary changes in CO2 may have been responsible for driving major changes in the landscape distribution of C4 species. The theory is sound; however, many of the studies cited in support of this model are open to alternative interpretations, and none has eliminated climatic factors as important selective agents. CAM and C4 evolution required coupling of biochemical pathways with structural changes in photosynthetic tissues, succulence in CAM and Kranz in C4. This was apparently accomplished by piecemeal evolution beginning with mechanisms for recapturing respiratory CO2, although this need not have been so in aquatic CAM species. It has been proposed that the extreme rarity of both pathways in the same plant results from biochemical and structural incompatibilities (Sage 2002). Equally important is the fact that the selective environments are quite different, with CAM evolution thriving on stressful sites inhospitable to C3 species whereas C4 evolution has selected for rapid growth capable of outcompeting associated C3 plants.

International Journal of Plant Sciences↗
USGS2009

Fire treatment effects on vegetation structure, fuels, and potential fire severity in western U.S. forests

Abstract. Forest structure and species composition in many western U.S. coniferous forests have been altered through fire exclusion, past and ongoing harvesting practices, and livestock grazing over the 20th century. The effects of these activities have been most pronounced in seasonally dry, low and mid-elevation coniferous forests that once experienced frequent, low to moderate intensity, fire regimes. In this paper, we report the effects of Fire and Fire Surrogate (FFS) forest stand treatments on fuel load profiles, potential fire behavior, and fire severity under three weather scenarios from six western U.S. FFS sites. This replicated, multisite experiment provides a framework for drawing broad generalizations about the effectiveness of prescribed fire and mechanical treatments on surface fuel loads, forest structure, and potential fire severity. Mechanical treatments without fire resulted in combined 1-, 10-, and 100-hour surface fuel loads that were significantly greater than controls at three of five FFS sites. Canopy cover was significantly lower than controls at three of five FFS sites with mechanical-only treatments and at all five FFS sites with the mechanical plus burning treatment; fire-only treatments reduced canopy cover at only one site. For the combined treatment of mechanical plus fire, all five FFS sites with this treatment had a substantially lower likelihood of passive crown fire as indicated by the very high torching indices. FFS sites that experienced significant increases in 1-, 10-, and 100-hour combined surface fuel loads utilized harvest systems that left all activity fuels within experimental units. When mechanical treatments were followed by prescribed burning or pile burning, they were the most effective treatment for reducing crown fire potential and predicted tree mortality because of low surface fuel loads and increased vertical and horizontal canopy separation. Results indicate that mechanical plus fire, fire-only, and mechanical-only treatments using whole-tree harvest systems were all effective at reducing potential fire severity under severe fire weather conditions. Retaining the largest trees within stands also increased fire resistance. ?? 2009 by the Ecological Society of America.

Ecological Applications↗
USGS1995

Assimilation of trace elements ingested by the mussel Mytilus edulis: Effects of algal food abundance

Pulse-chase feeding and multi-labeled radiotracer techniques were employed to measure the assimilation of 6 trace elements ( 110m Ag, 241 Am, 109 Cd, 57 Co, 75 Se and 65 Zn) from ingested diatoms in the mussel Mytilus edulis feeding at different rates (0.1, 0.49 and 1.5 mg dry wt h -1 ). Uniformly radiolabeled diatoms Thalassiosira pseudonana were fed to mussels for 0.5 h, and the behavior of the radiotracers in individual mussels was followed for 96 h in a depuration seawater system. Assimilation efficiency (AE) of each element declined with increasing ingestion rate and increased with gut passage time. The importance of extracellular digestion relative to intracellular digestion increased with ingestion activity, which, when coupled with a decline in AE, suggested that extracellular digestion is less efficient in metal absorption. Zn assimilation was most affected by ingestion rate, suggesting that AE may play a role in the physiological regulation of this metal in M. edulis . In an experiment to simulate the effects of an acidic gut, lowered pH (5.5) enhanced the release of elements from intact diatom cells, especially at low particle concentration. These results indicate that both feeding components of the mussel (i.e. gut passage time, digestive partitioning) and metal chemistry (i.e. metal release at lowered pH within the bivalve gut) are responsible for the difference in the assimilation of trace metals at different food quantities observed in mussels.

Marine Ecology Progress Series↗
USGS2007

Cross-shelf transport of pink shrimp larvae: Interactions of tidal currents, larval vertical migrations and internal tides

Transport and behavior of pink shrimp Farfantepenaeu s duorarum larvae were investigated on the southwestern Florida (SWF) shelf of the Gulf of Mexico between the Dry Tortugas spawning grounds and Florida Bay nursery grounds. Stratified plankton samples and hydrographic data were collected at 2 h intervals at 3 stations located on a cross-shelf transect. At the Marquesas station, midway between Dry Tortugas and Florida Bay, internal tides were recognized by anomalously cool water, a shallow thermocline with strong density gradients, strong current shear, and a high concentration of pink shrimp larvae at the shallow thermocline. Low Richardson numbers occurred at the pycnocline depth, indicating vertical shear instability and possible turbulent transport from the lower to the upper layer where myses and postlarvae were concentrated. Analysis of vertically stratified plankton suggested that larvae perform vertical migrations and the specific behavior changes ontogenetically; protozoeae were found deeper than myses, and myses deeper than postlarvae. Relative concentrations of protozoea in the upper, middle and bottom layers were consistent with a diel vertical migration, whereas that of postlarvae and myses were consistent with the semidiurnal tides in phase with the flood tide. Postlarvae, the shallowest dwellers that migrate with a semidiurnal periodicity, experienced the largest net onshore flux and larval concentrations were highly correlated with the cross-shelf current. These results provide the first evidence of an onshore tidal transport (a type of selective tidal stream transport, STST), in decapod larvae migrating in continental shelf waters offshore, ca. 100 km from the coast and at a depth of 20 m, while approaching the coastal nursery grounds. Longer time series would be necessary to establish whether internal tides play any role in the larval onshore transport of this species and determine if the STST is the dominant onshore transport mechanism.

Florida↗
USGS2022

Pathways of productivity and influences on top consumers in forested streams

Forested stream ecosystems involve complex physical and biotic pathways that can influence fish in numerous ways. Consequently, the responses of fish communities to disturbance can be difficult to understand. In this study, we employed a food web model that links biotic (e.g., physiology, predator–prey interactions) and abiotic (e.g., temperature, sunlight) attributes to address fish responses to changes in stream-riparian ecosystems. We modeled responses to food web dynamics in four streams, using scenarios that included responses to riparian disturbance, climate change, and shifts in top consumers. The two consumers we focused on were coastal cutthroat trout ( Oncorhynchus clarkii clarkii ) and sculpin ( Cottus spp., collectively treated as a functional group) . We found the responses to environmental changes varied by fish species and among streams, and that responses were not independent due to exploitative interspecific competition. Simulations based on long-term data indicated that coastal cutthroat trout were responsive to changes in allochthonous resources including terrestrial detritus and invertebrates, whereas sculpin were more responsive to changes to autochthonous resources that included, periphyton and aquatic invertebrates. These results may be, in part, a consequence of species-specific foraging behavior. Trout have a higher propensity to drift feed and therefore receive a substantial subsidy from terrestrial invertebrates, whereas sculpin feed mostly on aquatic insects on the streambed. Simulations of changes in summer temperature and stream discharge suggest decreased biomass of both fish species because of physiological constraints on invertebrate prey which reduce fish foraging opportunities. Exploitative competition also may be important in fish responses: when one fish taxon was removed, the other showed increased biomass. Although the pattern of simulation results was consistent across the four streams, the magnitude of change varied among streams. Streams with food webs fueled by multiple energy sources may be more resilient to changes to riparian forests and climate. Through application of a systems model, we gained insights into pathways of productivity for fish in forested stream ecosystems that provide understanding of processes that influence fish and streams, as well as implications for management of both.

Forest Ecology and Management↗
USGS2026

Mesophotic octocoral larval settlement preferences and behaviors

Introduction Lab-based coral reproduction is advancing restoration efforts to support coral populations injured by the 2010 Deepwater Horizon oil spill. Objectives This study aimed to answer foundational questions concerning coral spawning and larval settlement that need to be resolved for these mesophotic and deep-sea coral species before restoration efforts can be scaled up. Methods From 2021 to 2023, fragments of the mesophotic octocorals Swiftia exserta and Thesea nivea were collected from the continental shelf offshore from Texas to Florida and transported to a federal facility in Florida. Multiyear spawning allowed for in-depth analysis of spawning periodicity, egg development, larval behavior, settlement rate, and substrate preference. In addition, we determined the likelihood of successful development and survival during early stages of development. Results Fertilization rates remained high throughout spawning periods of both species, with S. exserta spawning during a 1-month period and T. nivea continuing to spawn year-round. Larvae from both corals significantly preferred tiles seeded with crustose coralline algae, and there were species-specific preferences in substrate material. Additionally, larval survival or mortality was typically evident within a few days when in the presence of settlement substrates. In the absence of substrates, we observed larvae surviving for up to 2 months without settling. Conclusions This work answers critical questions to inform the long-term logistical planning for eventual out-planting of these species. Further, it highlights avenues that could accelerate future restoration-based reproduction efforts into unexplored mesophotic and deep species.

Alabama, Louisiana, Mississippi, Texas↗
USGS2013

Simulating mechanisms for dispersal, production and stranding of small forage fish in temporary wetland habitats

Movement strategies of small forage fish (<8 cm total length) between temporary and permanent wetland habitats affect their overall population growth and biomass concentrations, i.e., availability to predators. These fish are often the key energy link between primary producers and top predators, such as wading birds, which require high concentrations of stranded fish in accessible depths. Expansion and contraction of seasonal wetlands induce a sequential alternation between rapid biomass growth and concentration, creating the conditions for local stranding of small fish as they move in response to varying water levels. To better understand how landscape topography, hydrology, and fish behavior interact to create high densities of stranded fish, we first simulated population dynamics of small fish, within a dynamic food web, with different traits for movement strategy and growth rate, across an artificial, spatially explicit, heterogeneous, two-dimensional marsh slough landscape, using hydrologic variability as the driver for movement. Model output showed that fish with the highest tendency to invade newly flooded marsh areas built up the largest populations over long time periods with stable hydrologic patterns. A higher probability to become stranded had negative effects on long-term population size, and offset the contribution of that species to stranded biomass. The model was next applied to the topography of a 10 km × 10 km area of Everglades landscape. The details of the topography were highly important in channeling fish movements and creating spatiotemporal patterns of fish movement and stranding. This output provides data that can be compared in the future with observed locations of fish biomass concentrations, or such surrogates as phosphorus ‘hotspots’ in the marsh.

Ecological Modelling↗
USGS2016

Scale-dependent habitat selection and size-based dominance in adult male American alligators

Habitat selection is an active behavioral process that may vary across spatial and temporal scales. Animals choose an area of primary utilization (i.e., home range) then make decisions focused on resource needs within patches. Dominance may affect the spatial distribution of conspecifics and concomitant habitat selection. Size-dependent social dominance hierarchies have been documented in captive alligators, but evidence is lacking from wild populations. We studied habitat selection for adult male American alligators ( Alligator mississippiensis ; n = 17) on the Pearl River in central Mississippi, USA, to test whether habitat selection was scale-dependent and individual resource selectivity was a function of conspecific body size. We used K-select analysis to quantify selection at the home range scale and patches within the home range to determine selection congruency and important habitat variables. In addition, we used linear models to determine if body size was related to selection patterns and strengths. Our results indicated habitat selection of adult male alligators was a scale-dependent process. Alligators demonstrated greater overall selection for habitat variables at the patch level and less at the home range level, suggesting resources may not be limited when selecting a home range for animals in our study area. Further, diurnal habitat selection patterns may depend on thermoregulatory needs. There was no relationship between resource selection or home range size and body size, suggesting size-dependent dominance hierarchies may not have influenced alligator resource selection or space use in our sample. Though apparent habitat suitability and low alligator density did not manifest in an observed dominance hierarchy, we hypothesize that a change in either could increase intraspecific interactions, facilitating a dominance hierarchy. Due to the broad and diverse ecological roles of alligators, understanding the factors that influence their social dominance and space use can provide great insight into their functional role in the ecosystem.

Mississippi↗
USGS1985

Effects of flood control alternatives on fish and wildlife resources of the Malheur-Harney lakes basin

Malheur Lake is the largest freshwater marsh in the western contiguous United States and is one of the main management units of the Malheur National Wildlife Refuge in southeastern Oregon. The marsh provides excellent waterfowl production habitat as well as vital migration habitats for birds in the Pacific flyway. Water shortages have typically been a problem in this semiarid area; however, record snowfalls and cool summers have recently caused Malheur Lake to rise to its highest level in recorded history. This has resulted in the loss of approximately 57,000 acres of important wildlife habitat as well as extensive flooding of local ranches, roads, and railroad lines. Because of the importance of the Refuge, any water management plan for the Malheur-Harney Lakes Basin needs to consider the impact of management alternatives on the hydrology of Malheur Lake. The facilitated modeling workshop described in this report was conducted January 14-18, 1985, under the joint sponsorship of the Portland Ecological Services Field Office and the Malheur National Wildlife Refuge, Region 1, U.S. Fish and Wildlife Service (FWS). The Portland Field Office is responsible for FWS reporting requirements on Federal water resource projects while the Refuge staff has management responsibility for much of the land affected by high water levels in the Malheur-Harney Lakes Basin. The primary objective of the workshop was to begin gathering and analyzing information concerning potential fish and wildlife impacts, needs, and opportunities associated with proposed U.S. Army Corps of Engineers (COE) flood control alternatives for Malheur Lake. The workshop was structured around the formulation of a computer model that would simulate the hydrologic effects of the various alternatives and any concommitant changes in vegetation communities and wildlife use patterns. The simulation model is composed of three connected submodels. The Hydrology submodel calculates changes in lake volume, elevation, and surface area, as well as changes in water quality, that result from the proposed water management projects (upstream storage, upstream diversions, drainage canals) and the no action alternative. The Vegetation submodel determines associated changes in the areal extent of wetland and upland vegetation communities. Finally, the Wildlife submodel calculates indices of abundance or habitat suitability for colonial nesting birds (great egret, double-crested cormorant, white-faced ibis), greater sandhill crane, diving ducks, tundra swan, dabbling ducks, and Canada goose based on hydrologic and vegetation conditions. The model represents the Malheur-Harney Lakes Basin, but provides water quantity and quality indicators associated with additional flows that might occur in the Malheur River Basin. Several management scenarios, representing various flood control alternatives and assumptions concerning future runoff, were run to analyze model behavior. Scenario results are not intended as an analysis of all potential management actions or assumptions concerning future runoff. Rather, they demonstrate the type of analysis that could be conducted if the model was sufficiently refined and tested. Early in a model development project, the process of building the model is usually of greater benefit than the model itself. The model building process stimulates interaction among agencies, assists in integrating existing information, and helps identify research needs. These benefits usually accrue even in the absence of real predictive power in the resulting model. This workshop initiated interaction among the primary State and Federal resource and development agencies in a nonadversarial forum. The exchange of information and expertise among agencies provided the FWS with the best information currently available for use in the Planning Aid Letter it will develop at the Reconnaissance state of the COE study. If the COE subsequently initiates a Feasability Study, this information will be refined further and will aid the FWS in preparing its Coordination Act Report on any flood control alternative proposed by the COE. The model building and testing process also helped identify model limitations and more general information needs that should be evaluated for further study prior to preparation of an FWS Coordination Act Report. Major needs associated with the Hydrology submodel include a more detailed representation of hydrologic units (separately consider Harney Lake, Mud Lake, and Malheur Lake or the three hydrological units within Malheur Lake, rather than a combined lake system) and explicitly representation of groundwater storage and discharge in water budget calculations. A better representation of the hydrological units will require more detailed topographic data for the basin, capacity-elevation and elevation-surface area curves for each unit, and better water flow data between the units. Additional water quality parameters and constraints on proposed canal operation due to conditions in the Malheur River might also be added. Key Vegetation submodel needs include fine-tuning existing vegetation relationships in the model and adding relationships to address the influence of historical conditions on vegetation development, effects of very rapid changes in lake level, effects of wildlife populations (e.g., carp, muskrat), responses of vegetation to habitat management actions (e.g, haying, grazing, burning), and better representation of sago pondweed dynamics. A complementary geographic information system might also be developed for spatial analyses. Major needs that should be evaluated for the Wildlife submodel include addition of other wildlife species that have important effects on habitat on the Refuge (e.g., carp, muskrat) and consideration of additional life-cycle requisites and controlling variable for species presently in the model. Some of these limitations could perhaps be overcome if historical data on habitat conditions were developed to use with historical data on wildlife populations.

Oregon↗