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At least 955 records · Page 53Linked to original sources
USGS2016

Population-specific life histories contribute to metapopulation viability

Restoration efforts can be improved by understanding how variations in life-history traits occur within populations of the same species living in different environments. This can be done by first understanding the demographic responses of natural occurring populations. Population viability analysis continues to be useful to species management and conservation with sensitivity analysis aiding in the understanding of population dynamics. In this study, using life-table response experiments and elasticity analyses, we investigated how population-specific life-history demographic responses contributed to the metapopulation viability of the Federally threatened Pitcher's thistle ( Cirsium pitcheri ). Specifically, we tested the following hypotheses: (1) Subpopulations occupying different environments within a metapopulation have independent demographic responses and (2) advancing succession results in a shift from a demographic response focused on growth and fecundity to one dominated by stasis. Our results showed that reintroductions had a positive contribution to the metapopulation growth rate as compared to native populations which had a negative contribution. We found no difference in succession on the contribution to metapopulation viability. In addition, we identified distinct population-specific contributions to metapopulation viability and were able to associate specific life-history demographic responses. For example, the positive impact of Miller High Dunes population on the metapopulation growth rate resulted from high growth contributions, whereas increased time of plant in stasis for the State Park Big Blowout population resulted in negative contributions. A greater understanding of how separate populations respond in their corresponding environment may ultimately lead to more effective management strategies aimed at reducing extinction risk. We propose the continued use of sensitivity analyses to evaluate population-specific demographic influences on metapopulation viability. In understanding the underlying causes of the projected extinction probabilities of each population and identifying broad-scale contributions of different populations to the metapopulation, the process of pinpointing target populations is simplified. More detailed analyses can then be applied to the target populations to increase population viability and consequently metapopulation viability. Based on our research, we suggest that the best approach to improve the overall metapopulation viability is to manage the contributions to population growth for each population separately.

Ecosphere↗
USGS2017

Behavioral flexibility as a mechanism for coping with climate change

Of the primary responses to contemporary climate change – “move, adapt, acclimate, or die” – that are available to organisms, “acclimate” may be effectively achieved through behavioral modification. Behavioral flexibility allows animals to rapidly cope with changing environmental conditions, and behavior represents an important component of a species’ adaptive capacity in the face of climate change. However, there is currently a lack of knowledge about the limits or constraints on behavioral responses to changing conditions. Here, we characterize the contexts in which organisms respond to climate variability through behavior. First, we quantify patterns in behavioral responses across taxa with respect to timescales, climatic stimuli, life-history traits, and ecology. Next, we identify existing knowledge gaps, research biases, and other challenges. Finally, we discuss how conservation practitioners and resource managers can incorporate an improved understanding of behavioral flexibility into natural resource management and policy decisions.

Frontiers in Ecology and the Environment↗
USGS2018

Identifying optimal hauling densities for adult Chinook Salmon trap and haul operations

Trap and haul programs are used to conserve fish populations by circumventing high mortality locations or events, and enhancing population abundance by reintroducing fish to historical habitats and mitigating for fish passage limitations. Spring run Chinook Salmon are transported in trucks upstream of barrier dams in Willamette River Tributaries as part of fish conservation efforts. Fish mortalities occurring during hauling minimizes the utility of the effort because natural origin fish are targeted for theses outplanting efforts. The objectives of this study were to develop models predicting hauling mortality and identify optimal hauling densities that minimize mortality risk and effort. We used an information-theoretic approach to evaluate multiple models predicting hauling mortality. Predictors identified varied between the two dams evaluated but were related to operations and annual or in-river conditions. The amount of time loading fish and the density of fish in tank trucks were positively associated with hauling mortality. Instream flows and thermal exposure were also identified as factors predicting with hauling mortality. We used the results of model selection to predict mortality risk and calculate daily hauling effort. Risk and effort were combined into a utility to identify optimal hauling densities for varying numbers of fish to haul and transport truck volume. Optimal hauling densities varied between dams reflecting whether loading time or hauling density was associated with hauling mortality. This analysis provides managers a way to integrate research, monitoring, and management to improve understanding of factors associated with hauling mortality and adjust optimal hauling densities using adaptive management.

Oregon↗
USGS2025

Principles of riverscape health

Riverscapes are the integration of terrestrial and aquatic systems from headwaters to estuaries that provide habitat and ecosystem benefits when in good health. However, current riverscape degradation is pervasive, impairing the function and resulting benefits of these systems. Healthy riverscapes are adaptive and some can ‘heal’ after disturbance with minimal to no human assistance. As riverscape health is threatened, a need exists to address current degradation and understand the potential for riverscape restoration—concisely communicating what comprises healthy riverscapes is essential to direct limited resources and increase efficacy of restoration and conservation efforts. Healthy riverscapes have (i) space to interact within their valley bottom; (ii) natural flow, sediment, and vegetation regimes appropriate to the biophysical setting and river type; and (iii) structural forcing to support diversity and that creates varied residence times for water, sediment, and vegetation. These three principles are grounded in interdisciplinary science and lessons from riverscape scientists and restoration practitioners across the world. Understanding the context, anthropogenic influences, boundary conditions, and legacy effects influencing riverscapes is essential for the appropriate application of these principles in pursuit of achieving riverscape health. Emphasizing a holistic, biogeomorphic view of riverscapes through these principles can guide policies, restoration actions, and monitoring frameworks that ensure that riverscapes remain capable of accommodating and adjusting to disturbances while continuing to support biodiversity and human benefits.

WIREsWATER (Wiley Interdisciplinary Reviews Primer↗
USGS2017

Identifying small depressional wetlands and using a topographic position index to infer hydroperiod regimes for pond-breeding amphibians

Small, seasonal pools and temporary ponds (<4.0 ha) are the most numerous and biologically diverse wetlands in many natural landscapes. Thus, accurate determination of their numbers and spatial characteristics is beneficial for conservation and management of biodiversity associated with these freshwater systems. We examined the utility of a topographic position index (TPI) landscape classification to identify and classify depressional wetlands. We also assessed relationships between topographic characteristics and ponded duration of known wetlands to allow hydrological characteristics to be extended to non-monitored locations in similar landscapes. Our results indicate that this approach was successful at identifying wetlands, but did have higher errors of commission (10%) than omission (5%). Additionally, the TPI procedure provided a reasonable means to correlate general ponded duration characteristics (long/short) with wetland topography. Although results varied by hydrologic class, permanent/long ponded duration wetlands were more often classified correctly (80%) than were short ponded duration wetlands (67%). However, classification results were improved to 100 and 75% for permanent/long and short ponded duration wetlands, respectively, by removing wetlands occurring on an abrupt marine terrace that erroneously inflated pond topographic characteristics. Our study presents an approach for evaluating wetland suitability for species or guilds that are associated with key habitat characteristics, such as hydroperiod.

Wetlands↗
USGS2018

Toward a resilience-based conservation strategy for wetlands in Puerto Rico: Meeting challenges posed by environmental change

Designing conservation strategies in human-dominated landscapes is challenging, owing to complex human-natural systems and evolving societal values. To meet this challenge, a robust, adaptive strategy should have a process for flexible implementation of incremental actions. We describe a hypothetical example for the Rio Grande de Arecibo watershed and coastal wetlands in Puerto Rico to address the first component. The process begins by identifying shared stakeholder objectives. This process benefits from a review of foundational research and knowledge base that includes global forcings and vulnerability of resources of interest. Forcings include climate change and pervasive urban sprawl. We focus on two taxonomic groups with differing life histories but strong dependence on water resource dynamics, another resource valued by humans. We stipulate objectives and multiple actions, but focus on those pertaining to hydro-management as the common thread in our example. We advanced two decision contexts of contrasting complexity, illustrated links between objectives and actions, and highlighted trade-offs triggered by varying resource valuation. Our focus was to highlight various components necessary to frame a resilience-based strategy, but we cannot overemphasize the importance of accommodating institutional and stakeholder changing priorities and values to ensure its successful implementation.

Puerto Rico↗
USGS2001

Solute transport along preferential flow paths in unsaturated fractures

Laboratory experiments were conducted to study solute transport along preferential flow paths in unsaturated, inclined fractures. Qualitative aspects of solute transport were identified in a miscible dye tracer experiment conducted in a transparent replica of a natural granite fracture. Additional experiments were conducted to measure the breakthrough curves of a conservative tracer introduced into an established preferential flow path in two different fracture replicas and a rock‐replica combination. The influence of gravity was investigated by varying fracture inclination. The relationship between the travel times of the solute and the relative influence of gravity was substantially affected by two modes of intermittent flow that occurred: the snapping rivulet and the pulsating blob modes. The measured travel times of the solute were evaluated with three transfer function models: the axial dispersion, the reactors‐in‐series, and the lognormal models. The three models described the solute travel times nearly equally well. A mechanistic model was also formulated to describe transport when the pulsating blob mode occurred which assumed blobs of water containing solute mixed with residual pools of water along the flow path.

Water Resources Research↗
USGS2020

The historical context of contemporary climatic adaptation: A case study in the climatically dynamic and environmentally complex southwestern United States

The process of adaptation can be highly dependent upon historical and contemporary factors, especially in environmentally and topographically complex regions affected by Pleistocene glaciations. Here, we investigate Hilaria jamesii (Poaceae), a dryland C 4 graminoid, to test how patterns of adaptive genetic variation are linked to its glacial and post‐glacial history. We show that the species persisted in a single, southern refugium during the last glacial period and subsequently migrated throughout its current distribution concurrent with post‐glacial warming. The species’ putative adaptive genetic variation correlates with climatic gradients (e.g. monsoon precipitation and mean diurnal temperature range) that covary with the species’ probable route of demographic expansion. The short timescale and multiple climatic dimensions of adaptation imply that natural selection acted primarily upon standing genetic variation. These findings suggest that restoration and conservation practices should prioritize the maintenance of standing genetic variation to ensure that species have the capacity to respond to future environmental changes.

Arizona, California Colorado, Nevada, New Mexico, ↗
USGS2007

Mangrove forest distributions and dynamics (1975–2005) of the tsunami-affected region of Asia

Aim We aimed to estimate the present extent of tsunami-affected mangrove forests and determine the rates and causes of deforestation from 1975 to 2005. Location Our study region covers the tsunami-affected coastal areas of Indonesia, Malaysia, Thailand, Burma (Myanmar), Bangladesh, India and Sri Lanka in Asia. Methods We interpreted time-series Landsat data using a hybrid supervised and unsupervised classification approach. Landsat data were geometrically corrected to an accuracy of plus-or-minus half a pixel, an accuracy necessary for change analysis. Each image was normalized for solar irradiance by converting digital number values to the top-of-the atmosphere reflectance. Ground truth data and existing maps and data bases were used to select training samples and also for iterative labelling. We used a post-classification change detection approach. Results were validated with the help of local experts and/or high-resolution commercial satellite data. Results The region lost 12% of its mangrove forests from 1975 to 2005, to a present extent of c . 1,670,000 ha. Rates and causes of deforestation varied both spatially and temporally. Annual deforestation was highest in Burma ( c . 1%) and lowest in Sri Lanka (0.1%). In contrast, mangrove forests in India and Bangladesh remained unchanged or gained a small percentage. Net deforestation peaked at 137,000 ha during 1990–2000, increasing from 97,000 ha during 1975–90, and declining to 14,000 ha during 2000–05. The major causes of deforestation were agricultural expansion (81%), aquaculture (12%) and urban development (2%). Main conclusions We assessed and monitored mangrove forests in the tsunami-affected region of Asia using the historical archive of Landsat data. We also measured the rates of change and determined possible causes. The results of our study can be used to better understand the role of mangrove forests in saving lives and property from natural disasters such as the Indian Ocean tsunami, and to identify possible areas for conservation, restoration and rehabilitation.

Journal of Biogeography↗
USGS1983

Mineral surveys by the Geological Survey and the Bureau of Mines of Bureau of Land Management Wilderness Study Areas

The Federal Land Policy and Management Act of 1976 instructed the Bureau of Land Management (BLM) to review all public lands under its jurisdiction and to determine their suitability or nonsuitability for wilderness designation. As part of this process, the Geological Survey and the Bureau of Mines conduct mineral surveys of areas for which a preliminary determination of wilderness suitability has been made. The BLM has completed its wilderness inventory phase and has found that 23.2 million acres deserve further study for wilderness consideration. These 23.2 million acres of wilderness study areas include 1 million acres of natural and primitive areas (Instant Study Areas), 5.7 million acres in the California Desert Conservation Area, and 16.5 million acres in other wilderness study areas. Mineral surveys on all areas recommended for wilderness will be completed by 1990.

Circular↗
USGS2017

The influence of local- and landscape-level factors on wetland breeding birds in the Prairie Pothole Region of North and South Dakota

We examined the relationship between local- (wetland) and landscape-level factors and breeding bird abundances on 1,190 depressional wetlands in the Prairie Pothole Region of North and South Dakota during the breeding seasons in 1995–97. The surveyed wetlands were selected from five wetland classes (alkali, permanent, semipermanent, seasonal, or temporary), two wetland types (natural or restored), and two landowner groups (private or Federal). We recorded 133 species of birds in the surveyed wetlands during the 3 years. We analyzed the nine most common (or focal) species (that is, species that were present in 25 percent or more of the 1,190 wetlands): the Red-winged Blackbird ( Agelaius phoeniceus ), Blue-winged Teal ( Anas discors ), Mallard (Anas platyrhynchos ), American Coot ( Fulica americana ), Gadwall ( Anas strepera ), Common Yellowthroat ( Geothlypis trichas ), Yellow-headed Blackbird ( Xanthocephalus xanthocephalus ), Northern Shoveler ( Anas clypeata ), and Savannah Sparrow ( Passerculus sandwichensis ). Our results emphasize the ecological value of all wetland classes, natural and restored wetlands, and publicly and privately owned wetlands in this region, including wetlands that are generally smaller and shallower (that is, temporary and seasonal wetlands) and thus most vulnerable to drainage. Blue-winged Teal, Northern Shoveler, Gadwall, Common Yellowthroat, and Red-winged Blackbird had higher abundances on Federal than on private wetlands. Abundances differed among wetland classes for seven of the nine focal species: Blue-winged Teal, Northern Shoveler, Mallard, American Coot, Common Yellowthroat, Yellow-headed Blackbird, Red-winged Blackbird. American Coot had higher abundances on restored wetlands than on natural wetlands overall, and Gadwall and Common Yellowthroat had higher abundances on private restored wetlands than on private natural wetlands. The Common Yellowthroat was the only species that had higher abundances on restored private wetlands than on restored Federal wetlands. After adjusting for wetland size and the date and location of the surveys, our results demonstrated that incorporating wetland- and landscape-level factors in models can improve our ability to predict abundances of wetland birds in this region. The top model for eight of the nine focal species included wetland- and landscape-level factors, whereas the best model for Blue-winged Teal included only wetland-level attributes. Although local factors (for example, percent open water or emergent vegetation) in individual wetlands are important factors for some wetland breeding birds, it is important that natural resource managers consider landscape-level factors beyond the local factors in their conservation plans for wetland birds.

North Dakota, South Dakota↗
USGS2004

Hydrogeology and ground-water-flow simulation in the former airfield area of Naval Support Activity Mid-South, Millington, Tennessee

Naval Support Activity Mid-South is a Department of the Navy base located in Millington, Tennessee. The facility was home to the Naval Aviation Technical Training Center from 1943 until 1996. As part of the Base Closure and Realignment Act of 1990, the primary training mission of the facility was realigned and most of the northern part of the base, referred to as the Northside and consisting primarily of an airfield, was transferred to the city of Millington in January 2000. During environmental investigations at the base, plumes of dissolved chlorinated solvents resulting from past aircraft maintenance and training operations were identified in shallow ground water beneath the airfield area. The airfield area containing the plumes has been designated as Area of Concern (AOC) A. Chlorinated solvents, primarily trichloroethene (TCE), are the principal contaminants in ground water at AOC A, with TCE identified in concentrations as high as 4,400 micrograms per liter. The nature and extent of these plumes at AOC A were addressed during a Resource Conservation and Recovery Act Facility Investigation, and selected options for remediation currently are being implemented under a corrective action program. As part of these efforts, the U.S. Geological Survey (USGS) is working with the Navy and its consultants to study the hydrogeologic framework of the base and surrounding area, with a focus on AOC A. Since 1997, investigations at and near the facility have produced data prompting revisions and additions to information published that year in two USGS reports. The updates are presented in this report and consist primarily of (1) refinements to selected hydrogeologic maps presented in the 1997 reports, on the basis of data collected from new wells at on- and off-base locations, (2) additional hydraulic-conductivity data collected for the alluvial-fluvial deposits aquifer at AOC A, and (3) construction of a potentiometric-surface map of the shallow aquifer for the former part of the Naval Support Activity Mid-South Northside and adjacent off-base locations for February and March 2000 water-level conditions. Additionally, a numerical ground-water-flow model of AOC A was developed and calibrated to the February and March 2000 potentiometric-surface data, the results of which also are presented in this report. Particle-tracking simulations were used with the model to simulate ground-water-flow paths from two sites suspected of being contaminant source areas at AOC A. The flow paths indicated by the particle tracking simulations agree reasonably well with maps of the interpreted extents of TCE plumes. The time-of-travel plots show that advective travel times from the two suspected source areas to the model boundary are controlled by relative proximities of the source areas to a part of AOC A identified from investigations and simulated with the model as having the highest horizontal hydraulic conductivity.

Tennessee↗
USGS2004

Direction of ground-water flow in the surficial aquifer in the vicinity of impact areas G-10 and K-2, Camp Lejeune Marine Corps Base, North Carolina, 2004

Marine Corps Base Camp Lejeune is located in Onslow County in the North Carolina Coastal Plain. In support of North Carolina Department of Environment and Natural Resource requirements, Camp Lejeune is developing a site closure plan for two Resource Conservation and Recovery Act (RCRA) regulated open burn/open detonation (OB/OD) facilities located within Impact Area K-2 and Impact Area G-10, respectively. Both Impact Areas are used for training activities involving live artillery fire. The two OB/OD facilities are used to treat RCRA regulated waste munitions. To provide Base officials with information needed for assessing the quality of ground water at these sites, hydrologic data were used to characterize groundwater flow directions and hydraulic gradients in the surficial aquifer underlying the Impact Areas. Water-level data in the unconfined surficial aquifer and potentiometric head data in the underlying Castle Hayne aquifer were compiled from existing and newly drilled wells. Water-table contour maps were developed for Impact Areas K-2 and G-10 to examine the direction of ground-water flow in the surficial aquifer. The primary directions of ground-water flow beneath K-2 are southward and eastward toward discharge zones along the New River and its tributaries. Beneath interior areas of G-10, water in the surficial aquifer flows outward in all directions toward discharge zones along local streams that drain westward to the New River or to streams that drain southward and eastward to the Intracoastal Waterway and the Atlantic Ocean. Long-term water-level data for the period October 1994 through September 2004 at selected Camp Lejeune well sites were used to examine trends in ground-water levels and vertical hydraulic gradients between the surficial and Castle Hayne aquifers. Evaluation of water-level data for three wells in the surficial aquifer indicated no significant trends for this period of record. The apparent water-level declines in two of the three Castle Hayne wells examined are likely the result of local pumping of the Castle Hayne aquifer. Vertical hydraulic gradients determined for two well cluster sites indicate a downward flow of water from the surficial aquifer into the underlying Castle Hayne aquifer.

Scientific Investigations Report↗
USGS2022

Assessing the spawning movement and habitat needs of riverine Neosho Smallmouth Bass

Stream fishes are vulnerable to a variety of natural and anthropogenic stressors. Information on fish movements and habitat use is essential to conserve and manage populations, particularly at the edges of distributions and novel habitats. The Neosho Smallmouth Bass Micropterus dolomieu velox is endemic to the southwestern Ozark Highlands ecoregion, where the riverscape is highly dissected by impoundments. Our study objectives were to determine the pre-spawn, spawn, and post-spawn movements of adult, radio-tagged Neosho Smallmouth Bass, and identify the habitat factors at multiple spatial scales related to suitable spawning habitat. Movements by tagged fish in the Elk River of Oklahoma and Missouri and two Oklahoma tributaries draining to lower Elk River and Grand Lake O’ the Cherokee were greatest during the spring spawning period and were positively related to discharge and fish size; however, we observed considerable individual and stream-specific variability. Temperature and fish movement rate in the Elk River were positively related in all seasons except for winter, although temperature was less important for Smallmouth Bass movement in the smaller streams. Tagged fish were never detected using active or passive telemetry in the reservoir or reservoir-river interface except during periods of lotic character (i.e., the reservoir was not pooled above the Buffalo Creek-Elk River confluence). Nests were typically located at intermediate depths (mean = 0.8 m; SD = 0.3) and in low velocity habitats (0.0–0.2 m/s). Most of the nests examined comprised gravel substrates; however, 2.5% of the nests observed were located on full or partial bedrock substrate. We also documented nest clustering behavior by Neosho Smallmouth Bass (i.e., adjacent nests within 2 m of each other); 66 nest clusters were identified across 22 stream reaches. Cluster presence was more prevalent in warmer stream reaches with wide, shallow channels, and less likely in groundwater-gaining reaches, whereas overall nest abundance was greater in warmer streams and reaches with deeper pools. We showed the importance of both warmer streams and deep pools of small streams for Smallmouth Bass rearing (i.e., young-of-year abundance). We found negative relationships between floods and first-year juvenile survival and show the importance of stream network position (i.e., adjacency to larger streams) for mitigating the negative effects of July floods. Our analyses of both nesting and young-of-year habitat use suggest small streams, typically not considered important to many fisheries, are responsible for a proportion of Neosho Smallmouth Bass production. Further, consideration of management actions restricting take during the early spawning season may be warranted due to the unique nesting behavior (i.e., clustering) exhibited by this subspecies.

Arkansas, Missouri, Kansas, Oklahoma↗
USGS1956

Land use and sediment yield

When the vegetal cover is removed from a land surface, the rate of removal of the soil material, at least initially, increases rapidly. So well known is this principle that it hardly needs restatement. If attention is focused on any individual drainage basin in its natural state, large or small, and inquiry is made as to the rate of denudation, a quantitative answer is not easily obtained. The possible error in any computation of rate of sediment production from any given drainage basin is considerable. Significant variations are found in sediment yields from closely adjacent watersheds which appear to be generally similar. To make a quantitative evaluation of the change in the rate of denudation when the natural vegetation is disturbed is, therefore, even more difficult. Considering the fact that "soil conservation" has been promoted to the status of a science, our lack of ability to answer what is apparently so simple a question may seem surprising. Let us look at some of the reasons.

Conference Paper↗
USGS2015

Application and utility of a low-cost unmanned aerial system to manage and conserve aquatic resources in four Texas rivers

Low-cost unmanned aerial systems (UAS) have recently gained increasing attention in natural resources management due to their versatility and demonstrated utility in collection of high-resolution, temporally-specific geospatial data. This study applied low-cost UAS to support the geospatial data needs of aquatic resources management projects in four Texas rivers. Specifically, a UAS was used to (1) map invasive salt cedar (multiple species in the genus Tamarix) that have degraded instream habitat conditions in the Pease River, (2) map instream meso-habitats and structural habitat features (e.g., boulders, woody debris) in the South Llano River as a baseline prior to watershed-scale habitat improvements, (3) map enduring pools in the Blanco River during drought conditions to guide smallmouth bass removal efforts, and (4) quantify river use by anglers in the Guadalupe River. These four case studies represent an initial step toward assessing the full range of UAS applications in aquatic resources management, including their ability to offer potential cost savings, time efficiencies, and higher quality data over traditional survey methods.

Texas↗
USGS2017

Assessing the risk of non-native marine species in the Bering Sea

Invasive species are one of the leading global conservation concerns, which can have strong, negative impacts on ecosystems, vulnerable species, and valuable natural resources. Arctic regions have experienced a relatively low number of biological introductions to date. Their geographical remoteness, cold waters, and presence of sea ice present challenging conditions for both non-native organisms and the vessels that transport them, presumably leading to low rates of introduction and establishment. However, observed increases in water temperatures reductions in sea ice, and projected increases in shipping traffic are expected to render arctic marine regions more susceptible to the arrival and colonization of marine invasives. Risk assessments for these Arctic regions are important to inform management and monitoring priorities by determining which species pose the greatest risk. To this end, we developed a ranking system for non-native marine species and used this system to assess the risk of non-native species to the Bering Sea. Using species’ published physiological tolerances, we mapped habitat suitability under current and future climate scenarios to identify geographic areas of current and future concern. In addition, we described shipping traffic from commercial and fishing vessels to identify ports of entry for non-native species. Collectively, these analyses identify which marine species have the greatest risk for invasion, where in the Bering Sea invasion risk and species establishment is greatest, and which ports are most likely to serve as an entry point for marine invasives into Alaska’s Bering Sea. The ranking system we developed for non-native marine species consists of 33 questions grouped into five categories. The first four categories evaluate a species’ ability to arrive and establish in the Bering Sea, its reliance on humans for introductions, its biology, and its impacts on ecological and human systems. The fifth category is not included in the total ranking score, but provides information on management considerations. The ranking system has methods to account for data deficiencies and calculates these deficiencies to allow readers to weigh the lack of knowledge with the ranking score. We prioritized non-native species for ranking based on their geographic proximity to the Bering Sea. We evaluated 46 species and ranking scores ranged from 29.1 to 74.3 (out of a possible 100), with highest scores indicating greatest risk. Taxonomy at the level of phylum did not explain variation in ranking values, likely due to the substantial biological variation relative to our ranking criteria among members of the same phylum. To investigate where non-native species may survive and persist in the Bering Sea, we compared species’ temperature and salinity thresholds to environmental conditions of the Bering Sea. Environmental conditions were obtained from three Regional Ocean Modeling Systems (ROMS) and investigated under two time periods: current (2003-2012) and mid-century (2030-2039). We identified potential habitat for survival for 42 species, and potential habitat for reproduction for 29 species. Under current conditions, all species had temperature and salinity thresholds that would allow survival in the Bering Sea for at least part of the year, and most species (79% to 83%) had thresholds that would allow for survival year-round. For species with temperature and salinity thresholds unsuitable for survival in the Bering Sea, winter temperatures appear to be the limiting factor. Most species had six to nine weeks of suitable conditions for reproduction. Future increases in water temperatures are expected to open more habitat for marine invasives. Two of the three ROMs project an increase in the number of non-native species that would be able to survive year-round by mid-century. Moreover, models project between 37% and 60% of the Bering Sea shelf habitat to become more suitable under mid-century climate condition.

Alaska↗
USGS2018

Modelling effects of invasive species and drought on crayfish extinction risk and population dynamics

Hydrological alteration, which may be exacerbated by climate change, is known to facilitate aquatic species invasion. Altered hydrology, invasive species, and the additive effects of these stressors pose a threat to aquatic biodiversity. Understanding extinction risk in the context of these stressors is crucial for prioritizing conservation efforts. As case studies, three narrow‐ranged endemic crayfish species of conservation concern ( Faxonius marchandi , Faxonius roberti , and Cambarus hubbsi ) in the Ozark Highlands of Arkansas and Missouri, USA, were used to examine the effects of invasive species and drought on crayfish population dynamics. The objectives of this study were to model the population dynamics of these imperilled species, assess how these populations may be affected under increased invasion effects and intensified drought, determine potential refuge effects, and examine the sensitivity of quasi‐extinction to model parameters. ramas‐metapop was used to construct stage‐based demographic models. Terminal extinction risk, median time to quasi‐extinction, and metapopulation occupancy were used to assess population viability under different scenarios. Cambarus hubbsi appears to be highly susceptible to decline if survival rates are reduced by simulated drought, as they have low reproductive potential and mature slowly. Models indicated that potential refuges allow F. roberti and C. hubbsi to persist, even when invasion and drought effects were extreme. Conversely, barriers to dispersal for F. marchandi led to reduced quasi‐extinction times and the greatest extinction risk under most invasion scenarios. Quasi‐extinction was most sensitive to changes in juvenile survival for all species examined, which indicates that improved estimates of stage‐specific demographic parameters for crayfish will improve model predictions. An increased understanding of the mechanisms of displacement of native crayfish by invasive crayfish is needed for most crayfish species. Limiting the spread of invasive species, maintaining natural habitat and hydrological regimes, and gaining insight into life histories and demographic parameters will increase the ability to conserve endemic and imperilled crayfish.

Arkansas, Missouri↗