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USGS2021

Pelagic forage versus abiotic factors as drivers of walleye growth in northern Wisconsin lakes

Understanding ecological relationships among fishes and their environments are important for informing management policies. We conducted a statewide assessment of cisco (Coregonus artedi) in inland lakes of Wisconsin to better understand the status of this pelagic, coldwater forage fish. We then used long-term (2005–2014), standardized walleye (Sander vitreus) survey data from the Ceded Territory of Wisconsin (CTWI) to test for the influence of cisco (present, extirpated, or never present) and several abiotic factors on walleye growth trajectories described using sex-specific asymptotic lengths (L∞), Brody growth coefficients (K), and time in years required to attain common length limits used to manage harvest of walleye in the recreational fishery (381 and 457 mm). Despite being top predators in many north-temperate waters, walleye growth was highly variable among lakes, suggesting that forage base and abiotic factors may be important drivers. Growth characteristics of 160 CTWI walleye populations revealed that females reached greatest L∞ in lakes with cisco compared to those where cisco were never present or those lakes where cisco have been extirpated; however, differences were not statistically significant. Male walleye L∞ did not differ based on cisco presence. Brody growth coefficients (K) for female walleye were positively correlated with growing degree days and Secchi depth; K for males was positively correlated with Secchi depth. Average time to attain 381 and 457 mm were lowest in lakes where cisco have been extirpated. Our results suggest that cooler water temperatures and lower water clarity may be more important drivers of walleye maximum growth potential in northern Wisconsin lakes than the presence of cisco.

Wisconsin↗

USGSDate not supplied

Sand and gravel resources of Puerto Rico

Many of Puerto Rico's beaches are eroding, and though rates of erosion vary, it is a major concern for the tourism and residential development industries. More than 85 percent of the population lives within 7 kilometers of the coast and they are heavily dependent on tourists that are attracted by the island's beaches and coral reefs. High-quality scientific data are needed to help formulate public policy regarding residential and commercial construction along the coast, beach replenishment, and future use of marine resources. Scientists have long recognized that the causes of coastal land loss are not limited to a relative rise in sea level, but can be manmade as well. For example, sediment supply to beaches especially along the north shore of Puerto Rico has been strongly affected by upstream river channeling, dam construction, various agricultural practices, paving and urbanization, as well as shallow-water oceanographic processes. The response to coastal erosion in Puerto Rico has been mostly crisis based leading to engineered solutions that have a negative effect on the coastal environment.

Puerto Rico↗

USGS2008

Restoring piscivorous fish populations in the Laurentian Great Lakes causes seabird dietary change

Ecosystem change often affects the structure of aquatic communities thereby regulating how much and by what pathways energy and critical nutrients flow through food webs. The availability of energy and essential nutrients to top predators such as seabirds that rely on resources near the water's surface will be affected by changes in pelagic prey abundance. Here, we present results from analysis of a 25-year data set documenting dietary change in a predatory seabird from the Laurentian Great Lakes. We reveal significant declines in trophic position and alterations in energy and nutrient flow over time. Temporal changes in seabird diet tracked decreases in pelagic prey fish abundance. As pelagic prey abundance declined, birds consumed less aquatic prey and more terrestrial food. This pattern was consistent across all five large lake ecosystems. Declines in prey fish abundance may have primarily been the result of predation by stocked piscivorous fishes, but other lake-specific factors were likely also important. Natural resource management activities can have unintended consequences for nontarget ecosystem components. Reductions in pelagic prey abundance have reduced the capacity of the Great Lakes to support the energetic requirements of surface-feeding seabirds. In an environment characterized by increasingly limited pelagic fish resources, they are being offered a Hobsonian choice: switch to less nutritious terrestrial prey or go hungry. ?? 2008 by the Ecological Society of America.

Ecology↗

USGS2000

2nd interface between ecology and land development in California

The 2nd Interface Between Ecology and Land Development Conference was held in association with Earth Day 1997, five years after the first Interface Conference. Rapid population growth in California has intensified the inevitable conflict between land development and preservation of natural ecosystems. Sustainable development requires wise use of diminishing natural resources and, where possible, restoration of damaged landscapes. These Earth Week Celebrations brought together resource managers, scientists, politicians, environmental consultants, and concerned citizens in an effort to improve the communication necessary to maintain our natural biodiversity, ecosystem processes and general quality of life. As discussed by our keynote speaker, Michael Soule, the best predictor of habitat loss is population growth and nowhere is this better illustrated than in California. As urban perimeters expand, the interface between wildlands and urban areas increases. Few problems are more vexing than how to manage the fire prone ecosystems indigenous to California at this urban interface. Today resource managers face increasing challenges of dealing with this problem and the lead-off section of the proceedings considers both the theoretical basis for making decisions related to prescribed burning and the practical application. Habitat fragmentation is an inevitable consequence of development patterns with significant impacts on animal and plant populations. Managers must be increasingly resourceful in dealing with problems of fragmentation and the often inevitable consequences, including susceptibility to invasive oganisms. One approach to dealing with fragmentation problems is through careful landplanning. California is the national leader in the integration of conservation and economics. On Earth Day 1991, Governor Pete Wilson presented an environmental agenda that promised to create between land owners and environmentalists, agreements that would guarantee the protection of -endangered species and out of this grew the pioneering initiative, known as the Natural Communities Conservation Planning (NCCP) program. California's vast expanse of seemingly endless resources has traditionally been viewed as justification for abusive land use practices. The modem day recognition that resources are finite has led to greater concern, not only for conserving what is left, but for restoring abused landscapes. Ecological restoration is a new science devoted to returning disturbed environments to a semblance of their 'pristine' state. Based on principles of 'revegetation,' restoration goes far beyond simple replanting, rather the ambition of ecological restoration is to return landscapes to functioning ecosystems and is the focus of the last section.

Open-File Report↗

USGS2005

Inventory of the mosses, liverworts, and lichens of Olympic National Park, Washington- Species list

The identification of non-vascular cryptogam species (lichens, mosses, liverworts, and hornworts) is especially challenging because of their small size, their often microscopic or chemical distinguishing features, and their enormous diversity. Consequently, they are a poorly known component of Olympic National Park, despite their ecological and aesthetic importance. This project is the first attempt at a systematic, comprehensive survey of non-vascular cryptogams in the Park and presents the current species list with descriptions of the substrate and vascular vegetation type where they were observed. The authors strove to collect from as many park environments as feasible, and distributed collections along important environmental gradients in different regions of the park using vascular vegetation as an environmental indicator. They also collected opportunistically when interesting habitats or microhabitats were encountered. Finally, the authors updated the nomenclature in the Park’s previous collection of nonvascular plants. This study identified approximately 13,200 bryophyte and lichen species, adding approximately 425 new species to the Olympic National Park Herbarium. These data, combined with select literature reports and personal data from Martin and Karen Hutten, added more than 350 species to the previously documented Olympic Peninsula lichen and bryophyte list. The authors discuss the list in a local, regional, and global context of rarity, as well as cryptogam conservation and further work needed in Olympic National Park. The improved inventory of Olympic National Park cryptogams represented by this project enables Olympic National Park to protect populations of rare and sensitive species, assess the damage caused by illegal harvest, and contribute information to the Bureau of Land Management and U.S. Forest Service Sensitive Species Programs.

Scientific Investigations Report↗

USGS2006

Precipitation history and ecosystem response to multidecadal precipitation variability in the Mojave Desert region, 1893-2001

Precipitation varied substantially in the Mojave Desert through the 20th century in a manner broadly similar to the other warm North American deserts. Episodes of drought and prolonged dry conditions (1893-1904, ca. 1942-1975, and 1999-present) alternated with relatively wet periods (1905-ca. 1941 and ca. 1976-1998), probably because of global-scale climate fluctuations. These are the El Nin??o-Southern Oscillation that affects interannual climate and the Pacific Decadal Oscillation that evidently causes decadal-scale variability such as prolonged dry and wet episodes. Studies done in the late 20th century demonstrate that precipitation fluctuations affected populations of perennial vegetation, annuals, and small herbivores. Landscape rephotography reveals that several species, particularly creosote bush, increased in size and density during the ca. 1976-1998 wet period. A brief, intense drought from 1989 to 1991 and the ongoing drought caused widespread mortality of certain species; for example, chenopods and perennial grasses suffered up to 100% mortality. Drought pruning, the shedding of above-ground biomass to reduce carbon allocation, increased substantially during drought. Overall, drought had the greatest influence on the Mojave Desert ecosystem. ?? 2006.

Journal of Arid Environments↗

USGS2021

Livestock grazing, climatic variation, and breeding phenology jointly shape disease dynamics and survival in a wild amphibian

Wildlife responses to infectious disease can be influenced by environmental stressors that alter host-pathogen dynamics. We investigated how livestock grazing, climatic variation, and breeding phenology influence disease prevalence and annual survival in boreal toad ( Anaxyrus boreas boreas ) populations challenged with Batrachochytrium dendrobatidis ( Bd ), a fungal pathogen implicated in global amphibian declines. We conducted a five-year (2015–2019) capture-recapture study of boreal toads ( n = 1301) inhabiting pastures grazed by cattle in western Wyoming, USA. We employed structural equation models to determine whether the effects of climatic variation on Bd prevalence were direct or mediated through effects on breeding phenology and multi-state models to explore the interplay of grazing, weather, and Bd infection on adult survival. Higher winter snowpack was linked with shorter spring breeding seasons, which were associated with lower Bd prevalence. Boreal toads infected with Bd suffered increased mortality, but only at relatively cool temperatures. Although cattle grazing created warmer microclimates, likely by reducing vegetation cover, grazing-induced habitat changes did not scale up to influence adult survival. Our results suggest that boreal toads in cooler environments face increased risk of disease-induced mortality, possibly because infected individuals are not able to elevate body temperature to reduce or clear infection. More generally, we demonstrate that host-pathogen dynamics can be shaped jointly by independent and interactive effects of livestock grazing, breeding season length, and climatic variation. Future investigations of wildlife responses to disease therefore may benefit from considering anthropogenic land use and climatic regimes, including the effect of weather on host phenology.

Wyoming↗

USGS2011

Use of large-scale, multi-species surveys to monitor gyrfalcon and ptarmigan populations

We evaluated the ability of three large-scale, multi-species surveys in the Arctic to provide information on abundance and habitat relationships of Gyrfalcons ( Falco rusticolus ) and ptarmigan. The Program for Regional and International Shorebird Monitoring (PRISM) has surveyed birds widely across the arctic regions of Canada and Alaska since 2001. The Arctic Coastal Plain survey has collected abundance information on the North Slope of Alaska using fixed-wing aircraft since 1992. The Northwest Territories-Nunavut Bird Checklist has collected presence-absence information from little-known locations in northern Canada since 1995. All three surveys provide extensive information on Willow Ptarmigan (Lagopus lagopus) and Rock Ptarmigan (L. muta). For example, they show that ptarmigan are most abundant in western Alaska, next most abundant in northern Alaska and northwest Canada, and least abundant in the Canadian Archipelago. PRISM surveys were less successful in detecting Gyrfalcons, and the Arctic Coastal Plain Survey is largely outside the Gyrfalcon's breeding range. The Checklist Survey, however, reflects the expansive Gyrfalcon range in Canada. We suggest that collaboration by Gyrfalcon and ptarmigan biologists with the organizers of large scale surveys like the ones we investigated provides an opportunity for obtaining useful information on these species and their environment across large areas.

Alaska, Northern Canada↗

USGS2023

Attenuation of acid rock drainage by stimulating sulfur-reducing bacteria

Iron-sulfide minerals found in shale formations are stable under anaerobic conditions. However, in the presence of oxygen and water, acid-loving chemolithotrophic bacteria can transform the iron-sulfide minerals into a toxic solution of sulfuric acid and dissolved iron and minerals known as acid rock drainage (ARD). The objective of this study was to disrupt chemolithotrophic bacteria responsible for ARD using chemical treatments and to foster an environment favorable for competing microorganisms to attenuate the biologically induced ARD. Chemical treatments were injected into flow-through microcosms consisting of 501 g of pyrite-rich shale pieces inoculated with ARD bacteria. Three treatments were tested in the microcosms: (1) a sodium hydroxide-bleach mix, (2) a sodium lactate solution, and (3) a sodium lactate-soy infant formula mix. The effectiveness of the treatments was assessed by monitoring pH, dissolved iron, and other geochemical constituents in the discharge waters. The optimal treatment was a sequential injection of 1.5 g sodium hydroxide, followed by 0.75 g lactate and 1.5 g soy formula dissolved in 20 mL water. The pH of the discharge water rose to 6.0 within 10 days, dissolved iron concentrations dropped below 1 mg/L, the median alkalinity increased to 98 mg/L CaCO 3 , and sulfur-reducing and slime-producing bacteria populations were stimulated. The ARD attenuating benefits of this treatment were still evident after 231 days. Other treatments provided a number of ARD attenuating effects but were tempered by problems such as high phosphate concentrations, short longevity, or other shortcomings. The results of these laboratory microcosm experiments were promising for the attenuation of ARD. Additional investigations and careful selection of treatment methods will be needed for field application.

Tennessee↗

USGS2020

Using hair cortisol to assess physiological stress in Alaska polar bears

The concentration of cortisol in hair (HCC) of polar bears (Ursus maritimus) may provide a retrospective view of physiological stress they experience and a link to their response to environmental change. To understand this relationship, we assayed HCC from polar bears captured in the Alaska Beaufort, Bering and Chukchi seas during 1983–1989 and 2004–2016. Cortisol accumulated in hair through summer and autumn and into the subsequent winter. HCC was similar between adult males and adult females. No difference in HCC across regions suggested all bears responded similarly to the environment. HCC in spring was elevated following years with a high winter Arctic Oscillation index and highly variable wind speed. HCC increased non-linearly with increasing duration of the continental shelf summer open water period up to 50 days and then decreased. HCC of spring samples declined with increasing body size, indicating that the stress response was more active in smaller bears or those in poor body condition. HCC of spring samples was greater and more variable in 2004–2006 than during either 1983–1989 or 2008–2016, and significantly so for females with 1st year cubs and subadult females. Elevated HCC in 2004–2006 coincided with years of reduced survival of southern Beaufort Sea polar bears and suggests that unidentified environmental perturbations impacted Alaska polar bears. Because HCC may be obtained by relatively non-invasive means, it has potential use for assessing polar bear populations that are difficult to study by capturing. Hence, information gained from HCC can inform polar bear conservation, especially on the vulnerability of subadult females and adult females with new cubs, and possible future environmental perturbations impacts on bear physiology.

Alaska↗

USGS2026

Determining Volcanic Risk in Auckland (DEVORA) Research Programme—A transdisciplinary approach to address the challenge of distributed volcanism in an urban environment

The Determining Volcanic Risk in Auckland (DEVORA) Research Programme was launched in 2008 to address the challenges associated with monogenetic volcanism in an urban setting and to enhance volcanic risk management in Tāmaki Makaurau Auckland in Aotearoa New Zealand. It is a multi-agency, increasingly transdisciplinary (defined here as research that transcends traditional disciplinary boundaries by integrating diverse types of knowledge, perspectives, and methods from academic and non-academic participants to create novel solutions to complex problems), and collaborative research program jointly led by Waipapa Taumata Rau University of Auckland and Earth Sciences New Zealand (ESNZ; formerly GNS Science), with core funding from Natural Hazards Commission Toka Tū Ake (NHC; formerly the Earthquake Commission, EQC) and Te Kaunihera o Tāmaki Makaurau Auckland Council (AC). The primary research focus of DEVORA is to investigate the geologic history, volcanic hazards, and risk posed by the basaltic intraplate Auckland Volcanic Field. Disruption from ash fall and gas from other Aotearoa New Zealand volcanoes is also considered. DEVORA’s work to explore exposure and vulnerability in Tāmaki Makaurau Auckland is also useful for assessing risks from other non-volcanic natural hazards, such as seismic and tsunami hazards. The greater Tāmaki Makaurau Auckland region has an ethnically and socio-economically diverse population of approximately 1.7 million, representing about one-third of the Aotearoa New Zealand population, and hosts critical infrastructure of national significance. The size and nature of the populace, consequential economic base, and important infrastructure within Tāmaki Makaurau Auckland mean that the effects of a volcanic eruption would be felt nationally, including through the disruption of air travel to Aotearoa New Zealand. The hazards from such an eruption could potentially affect hundreds of thousands of people, businesses, and lifelines (critical infrastructure). A considerable challenge for emergency and risk managers is the monogenetic nature of the volcanic field. It is not known where or when the next eruption will occur, how much warning we may get before an eruption, nor how an eruption and its effects might unfold. In this contribution, we highlight the concept and collaborative intent of the DEVORA Programme and show how it has evolved over the 16 years since its inception. We describe how DEVORA has unified more than 100 researchers (including more than 50 graduate students) and numerous stakeholders to address key issues facing Tāmaki Makaurau Auckland and describe how research findings are being implemented into policy and communicated to stakeholder agencies and the public. We also illustrate the broader influence of the DEVORA Programme and provide some learnings that might benefit others embarking on similar integrated projects, especially those focused on distributed volcanism in and near populated areas.

Auckland↗

USGS2005

Drainage ditches facilitate frog movements in a hostile landscape

Ditches are common in landscapes influenced by agricultural, forestry, and peat mining activities, and their value as corridors remains unassessed. Pond-breeding amphibians can encounter hostile environments when moving between breeding, summering, or hibernation sites, and are likely to benefit from the presence of ditches in the landscape. Within a system consisting of ditch networks in bogs mined for peat in eastern New Brunswick, Canada, I quantified the breeding, survival, and movements of green frogs (Rana clamitans melanota) in drainage ditches and also surveyed peat fields. Frogs rarely ventured on peat fields and most individuals frequented drainage ditches containing water, particularly in late summer. Though frogs did not breed in ditches, their survival rate in ditches was high (88%). Ditches did not hinder frog movements, as frogs moved independently of the current. Results indicate that drainage ditches containing water enable some movements between habitats isolated by peat mining, in contrast to peat surfaces, and suggest they function as amphibian movement corridors. Thus, such drainage ditches may mitigate the effects of peat extraction on amphibian populations. At the very least, these structures provide an alternative to hostile peat surfaces. This study highlights that small-scale corridors are potentially valuable in population dynamics. ?? Springer 2005.

Landscape Ecology↗

USGS2021

Distribution, abundance, and genomic diversity of the endangered antioch dunes evening primrose (Oenothera deltoides subsp. howellii) surveyed in 2019

Sand dune ecosystems are highly dynamic landforms found along coastlines and riverine deltas where a supply of sand-sized material is available to be delivered by aquatic and wind environments. These unique ecosystems provide habitat for a variety of endemic and rare plant and animal species. Sand dunes have been affected by human development, sand mining, and shoreline stabilization from invasive weeds. This report provides a summary of a comprehensive literature review, field survey, and genomic analysis for the Antioch Dunes evening primrose ( Oenothera deltoides subsp. howellii , hereafter howellii ), an endemic species to the San Francisco Bay-Delta, California, which was listed as a federally endangered subspecies in 1978. Howellii is found on a historic dune sheet (the Antioch sand sheet) near the confluence of the Sacramento and San Joaquin Rivers. The Antioch sand sheet has been greatly altered by sand mining and land conversion into agriculture and urban development. In chapter A, we describe results of the literature review and field survey. We found howellii at eight locations with over 90 percent of the adult population and nearly 99 percent of juveniles observed on the Antioch Dunes National Wildlife Refuge. We measured a negative relationship between howellii numbers and invasive weed cover, illustrating the importance of mobilized open sand for this species. In chapter B, we describe the genomic study results. We surveyed genomic diversity by using double-digest restriction-site associated sequencing to estimate population genetic structure and levels of diversity across all surveyed occurrences. The genomic analyses included outgroup samples of the closely related Oenothera deltoides subsp. cognata and three occurrences of an unknown taxon with intermediate morphology to cognata and howellii , which also occurs on the Antioch sand sheet, east of the Antioch Dunes National Wildlife Refuge. These three morphologically distinctive groups formed genetically distinctive clusters and well-supported monophyletic clades in clustering and phylogenetic analyses, respectively. There was no indication of recent hybridization among any of the groups. Among howellii occurrences, the Antioch Dunes National Wildlife Refuge contained the greatest genetic diversity. Our approach, which combined field surveys, habitat assessments, and genetic analyses, can provide useful information for the conservation and management of rare and at-risk plant species and highlights the uniqueness of the Antioch sand sheet floral diversity through the discovery of a putative new taxon within the bird-cage evening primrose species complex.

California↗

USGS2023

Discovery of a rare pillar coral (Dendrogyra cylindrus) death assemblage off southeast Florida reveals multi-century persistence during the late Holocene

In recent years, coral populations in the western Atlantic have undergone widespread declines from climate change, anthropogenic stressors, and infectious disease outbreaks. The pillar coral, Dendrogyra cylindrus , has been one of the most affected species, prompting its listing as threatened under the United States Endangered Species Act in 2014 and critically endangered under the IUCN Red List in 2022. However, due to its natural rarity, it is particularly difficult to study using conventional long-term monitoring studies or less common paleontological investigations. Here, we document for the first time, the multi-century persistence of D. cylindrus on high-latitude nearshore reefs off southeast Florida during the late Holocene. Using high-precision uranium–thorium (U-Th) dating, we constrain the ages of well-preserved subfossil D. cylindrus colonies recovered from newly described coral death assemblages. We also describe specific morphological characteristics and taphonomic indicators reflecting their unique depositional environment. Our findings demonstrate long-term persistence of D. cylindrus in southeast Florida, despite geographical isolation and historical rarity in the region.

Coral Reefs↗

USGS2025

Characterization of the long-distance dispersal kernel of white-tailed deer and evaluating its impact on chronic wasting disease spread in Wisconsin

Chronic wasting disease (CWD) is a fatal neurodegenerative disease infecting cervids. It is highly contagious and caused by misfolded prions that propagate via templated conformational conversion of the cervid’s normal prion protein. Prevalence of CWD in free-ranging deer in North America is mostly low, but in some regions local prevalence has reached 80%. CWD prions can be transmitted via direct contact with infected individuals or indirectly through the environment. Infected individuals shed prions through feces, urine, saliva or carcasses, and prions have long environmental persistence. Long-distance dispersal of infected deer poses a significant risk for CWD spread. We propose an integrodifference equation (IDE) model to capture CWD dynamics and the consequences of long-distance dispersal behavior in white-tailed deer (WTD, Odocoileus virginianus ). A diffusion-settling model characterizes long-distance dispersal kernels, accommodating hypothetical dispersal behaviors through time-dependent settling rate functions. Three new closed-form dispersal kernels are approximated using Laplace’s method and parameterized with GPS location data collected from WTD in Wisconsin, USA. Settling rates reflecting ongoing sensitivity to stimuli which prompt deer to disperse from their natal home range give the most supported long-distance dispersal kernel. Impact of long-distance dispersal on CWD spread is quantified using the IDE model. At high population densities, long-distance dispersal can magnify CWD spread by a factor of four. At lower population densities single infected individuals cannot initiate an outbreak, but CWD may still spread due to the accumulation of environmental hazard from prions behind the wave of invasion, possibly presenting substantial management challenges.

Wisconsin↗

USGS2020

Dermal denticle assemblages in coral reef sediments correlate with conventional shark surveys

1. It is challenging to assess long-term trends in mobile, long-lived, and relatively rare species such as sharks. Despite ongoing declines in many coastal shark populations, conventional surveys might be too fleeting and too recent to describe population trends over decades to millennia. Placing recent shark declines into historical context should improve management efforts as well as our understanding of past ecosystem dynamics. 2. A new paleoecological approach for surveying shark abundance on coral reefs is to quantify dermal denticle assemblages preserved in sediments. This approach assumes that denticle accumulation rates correlate with shark abundances. Here, we test this assumption by comparing the denticle record in surface sediments to three conventional shark survey methods at Palmyra Atoll, Line Islands, central Pacific Ocean, where shark density is high and spatially heterogeneous. 3. We generally found a significant positive correlation between denticle accumulation rates and shark abundances derived from underwater visual census, baited remote underwater video, and hook and line surveys. 4. Denticle accumulation rates reflected shark abundances, suggesting that denticle assemblages can preserve a signal of time-averaged shark abundance in low-energy coral reef environments. We offer suggestions for applying this tool to measure shark abundance over long timescales in other contexts.

Methods in Ecology and Evolution↗

USGS2014

Migratory behavior of Chinook salmon microjacks reared in artificial and natural environments

Emigration was evaluated for hatchery Chinook salmon ( Oncorhynchus tshawytscha ) microjacks (age-1 mature males) and immature parr (age-1 juveniles, both sexes) released from both a hatchery and a natural stream (fish released as fry). In the hatchery, volitional releases (&sim;14 to 15 months post-fertilization) to an adjacent river occurred during October–November. The hatchery release was monitored by using an experimental volitional release that diverted fish to a neighboring raceway. Fish captured during the experimental release (range 361–4,321 volitional migrants) were made up of microjacks and immature parr. Microjacks were found only in the migrant samples, averaged 18% (range 0–52%) of all migrants, and were rarely found in non-migrant samples. In comparison, immature parr were common in both the migrant and non-migrant samples. Microjacks were significantly longer (9%), heavier (36%), and had a greater condition factor (16%) than migrant immature parr (P<0.01). In addition, they differed significantly (P<0.01) from non-migrant immature parr; 10% longer, 44% heavier and 14% greater condition factor. In natural streams, microjacks were captured significantly earlier (P<0.01) than immature parr during the late-summer/fall migration and comprised 9–89% of all fish captured. Microjacks have the potential to contribute to natural spawning populations but can also represent a loss of productivity to hatchery programs or create negative effects by introducing non-native genes to wild populations and should be monitored by fishery managers.

Journal of Fish and Wildlife Management↗

USGS2004

Habitat use and spatial structure of a barking frog (Eleutherodactylus augusti) population in southeastern Arizona

Barking Frogs ( Eleutherodactylus augusti ) are the northernmost ranging member of the large tropical family Leptodactylidae. We investigated the ecology of this saxicolous species at the northern edge of its range in a canyon in southern Arizona. We captured 54 frogs on discontinuous rock outcrops; eight of nine females and 39 of 45 males were on limestone outcrops. The remaining frogs were closer to limestone outcrops by more than 200 m than would be expected if they were distributed randomly with respect to limestone formations. Seven of 10 frogs radio-tracked had core home ranges (50% fixed kernel) from 94 to 100% on limestone; the other three frogs did not have any part of their home range on limestone outcrops. During five years of mark-recapture efforts, no frogs were found on a different outcrop from the one where they were originally captured; no radio-tracked frogs moved between outcrops during the breeding season. We estimated that four to 20 Barking Frogs occupied each outcrop; these groups probably are connected primarily by juvenile dispersal. As an organism living at the edge of its range, Barking Frogs in Arizona may rely heavily on extensive underground areas such as those found in limestone to protect them from a physiologically challenging environment. To manage for the persistence of Barking Frogs in southern Arizona, we must identify and protect habitat patches and movement pathways among them.

Arizona↗