Cumulative loss of habitat and long-term decline in the populations of the Lesser Prairie-Chicken (Tympanuchus pallidicinctus) have led to concerns for the species’ viability throughout its range in the southern Great Plains. For more efficient conservation past and present distributions of genetic variation need to be understood. We examined the...
Depleted species of rockfish (Sebastes spp.) from the Northeast Pacific experience high discard mortality due to "barotrauma," induced from the rapid change in pressure during capture. Research suggests rockfish have the potential to survive barotrauma if immediately recompressed, but the potential for long-term recovery is unknown. In this project, we...
The number of endangered species is rapidly increasing while paucity of adequate information and resources delays establishment of conservation actions. The IUCN’s listing system is insufficient to determine conservation priorities and many species lack information even to be evaluated (i.e., “data deficient”). Here I proposed and tested the Rapid Endangered...
Despite evidence that juvenile Chinook salmon (Oncorhynchus tshawytscha) utilize North Pacific estuaries for growth and salinity acclimation, research in the Columbia River estuary has lead to opposing hypotheses about the estuary’s importance as a salmon rearing environment. Many contemporary tagging studies indicate that salmon residency within the estuary is short...
Dietary iodine may play an important role in the nutritional health of freshwater fish larvae. Artemia, commonly used for the culture of larval zebrafish (Danio rerio), contain low concentrations of iodine when compared with wild zooplankton. Water-soluble micronutrients, such as iodine, are difficult to deliver to Artemia due to rapid...
Research conducted on humpback whitefish Coregonus pidschian in the Copper River Delta, Alaska has revealed a complex life history involving seasonal migrations and the occupation of a variety of freshwater and marine habitats including lacustrine, riverine, estuarine, and marine. Forty-five whitefish were tagged with radio transmitters in 2006 and 2007,...
This dissertation focuses on the predator-prey relationship between two species of avian predators, Caspian terns (Hydroprogne caspia) and double-crested cormorants (Phalacrocorax auritus), and one of their important prey types, juvenile salmonids (Oncorhynchus spp.), in the Columbia River estuary of Oregon and Washington states during the period 1998 – 2007. I...
Coastal cutthroat trout (Oncorhynchus clarkii clarkii) and cottids (Cottus spp) commonly co-occur in headwater streams in western Oregon. Little is known about the comparative trophic ecology of these species or how they respond to seasonal scarcity of resources. In this study I evaluated the seasonal variability in diets and consumption...
A topic of recurring interest in ecological research is the degree to which
vegetation structure influences the distribution and abundance of species. Here we test the
applicability of remote sensing, particularly novel use of waveform lidar measurements, for
quantifying the habitat heterogeneity of a contiguous northern hardwoods forest in the...
Over the last decade, the Oregon Department of Fish and Wildlife (ODFW) has documented a precipitous decline in the Crooked River redband trout (Oncorhynchus mykiss) population, prompting this study to address potential factors contributing to the decline. There are two main goals to this project: (1) identify potential factors contributing...
Olive ridley sea turtles (Lepidochelys olivacea) present an interesting case study of the conservation of wildlife species that aggregate in high densities and have served as resources for human consumption. Ridleys exhibit synchronized mass-nesting behavior,
during events called "arribadas," where thousands of females lay eggs together in a small area...
In the Pacific Northwest, several species of rockfishes (Sebastes spp.) are under extreme conservation measures due to low population levels. Although currently at healthy population levels, one species of interest is the black rockfish (S. melanops), which has been shown to utilize estuarine habitat during its early life history stages....
The 100 North Pacific rockfish species in the genus Sebastes are highly diverse. Rockfishes fertilize their eggs internally and release swimming larvae. Complex courting behaviors may allow female rockfish to be selective about their mates and may promote and maintain speciation. In this study, I applied genetic techniques to survey...
We used reverse time capture-mark-recapture models to describe associations between rate of population change (λ) and climate for northern spotted owls (Strix occidentalis caurina) at six long-term study areas in Washington and Oregon, USA. Populations in three of six areas showed strong evidence of declining populations, while populations in two...
A number of steelhead (Oncorhynchus mykiss) populations are at risk throughout Oregon, including five populations that are federally listed as threatened or endangered. However, little is known about behavior and survival of these fish as they transition from freshwater to seawater. We investigated whether estuarine survival varies on a temporal...
Tidal marshlands in the upper estuary ecotone provide essential habitat for
juvenile salmonids. In this environment, salmonids grow rapidly and acclimate to
saltwater. Worldwide, tidal marshes have been diked and drained to provide
agricultural and residential land. Tide gates are one-way doors integrated into
dike systems that prevent saltwater flooding...
The Pigeon Guillemot (Cepphus columba) is now the only species of marine bird in Prince William Sound (PWS), Alaska that is listed as "not recovering" on the Exxon Valdez Oil Spill (EVOS) Trustee Council's Injured Resources List and has shown no sign of population recovery. During the 20 years since...
In grasslands, grazing by large ungulates can influence vegetation structure, composition, primary productivity, and ultimately, ecosystem functioning. While grazing represents a complex disturbance, grazing intensity largely determines the effects of
grazing on vegetation. Structural and compositional changes in the plant community caused by grazing could have bottom-up effects on species...
Pacific sardines (Sardinops sagax) are an economically and ecologically important forage fish which transfer energy from planktonic primary producers and secondary consumers to upper trophic predators. Previous genetics studies of Pacific sardine suggested a panmictic population with a shallow genetic structure. However, more than one subpopulation within the Central California...
Severe scouring from splash damming was one of the earliest reported forms of widespread anthropogenic disturbance in streams of the Pacific Northwest, USA. Splash damming was a common method of log transport in western Oregon from the 1880s through the 1950s. Before being released in large freshets to downstream lumber...
Early ocean residence is assumed to be a critical period for juvenile Pacific salmon Oncorhynchus spp. However, the specific mechanisms influencing growth and survival in the ocean have not been identified for most populations. Therefore, three hypotheses regarding the relationship between early marine residence and subsequent survival of mid-upper Columbia...
The Wetland Reserve Program (WRP) is one conservation tool that mitigates national wetland loss and a primary goal for the program includes optimizing wildlife habitat by restoring wetland functions and values. Few studies have evaluated the WRP, which limits our understanding of its impact on wildlife populations. I assessed the...
Fire is an important disturbance mechanism in big sagebrush (Artemisia
tridentata) communities, yet little is known about wildlife population dynamics during
post-fire habitat succession. I estimated the abundance of small mammals and birds in
relation to fire history in mountain big sagebrush (A.t. spp. vaseyana) communities on the
Sheldon National...
The quality and availability of forage fishes and invertebrates can affect the behavior and productivity of predators that rely on these resources. This study measures the proximate composition of forage fishes and invertebrates from the southeastern Bering Sea to estimate prey energy density (quality) using a method that is ecologically...
Native bees play an important role as pollinators of natural vegetation and agricultural
crops. Yet many pollinators, including some native bees, are declining in numbers.
Some of the potential causes of these declines are habitat destruction and degradation
by various human land uses, including urban development and sprawl, construction of...
The use of passive integrated transponder (PIT) tags in ecological studies is increasingly common, but evaluations of their performance and range of application in the field are still emerging. Here, we compare habitat unit–scale abundance estimates of PIT-tagged juvenile coho salmon Oncorhynchus kisutch and steelhead O. mykiss derived from multiple-pass...
As in various freshwater and coastal marine ecosystems worldwide, seasonal bottom water hypoxia is a recurring phenomenon in Lake Erie's central basin. While bottom hypoxia can strongly affect sessile benthic animals, its effects on mobile organisms such as fish are less understood. We evaluated the potential for bottom hypoxia to...
The distribution and geographic range of Greater Sage-Grouse (Centrocercus urophasianus) have been reduced by 56% since European settlement. Although loss and fragmentation of sagebrush (Artemisia spp.) habitats have been cited as the primary causes for the decline of the species, degradation of existing habitat also has been considered an important...
Lake trout Salvelinus namaycush in the Laurentian Great Lakes suffer from thiamine deficiency as a result of adult lake trout consuming prey containing thiaminase, a thiamine-degrading enzyme. Sufficiently low egg thiamine concentrations result in direct mortality of or sublethal effects on newly hatched lake trout fry. To determine the prevalence...
Twentieth century commercial whaling drastically reduced the abundance of great whale populations in the Southern Ocean. Exploitation began on the south Atlantic island of South Georgia, where catch records account for over 175,000 whales killed. Modern whaling within the Southern Ocean depleted populations rapidly, and by 1966, hunting blue whales...
Understanding food webs is fundamental in conserving endangered species and maintaining healthy ecosystem function, particularly in desert spring systems. We identified dominant energy sources in the Muddy River Warm Springs area, Clark County, NV using carbon and nitrogen natural abundance stable isotope analyses. We examined isotopic signatures of specific macroinvertebrate...
Pacific rockfish experience high discard mortality when captured owing to a condition called barotrauma,which is caused by the change in pressure during capture. This condition appears to be species specific at the macroscopic level; however, little is known about the microscopic tissue-level effects of barotrauma. Determining whether tissue-level injuries are...
We estimated annual survival rates (S) of 23 radio-marked Northern Spotted Owls (Strix occidentalis caurina) at the Quartz and Timbered Rock burns and adjacent areas in southwest Oregon. We used known-fate models in program MARK to test for differences in survival among three groups (owls dwelling inside of burned areas,...
The majority of the world's breeding population of northern fur seals (Callorhinus ursinus) is found on the Pribilof Islands (St. Paul and St. George) in the Bering Sea, Alaska. Pup production on these islands experienced an irregular but overall decline since the early 1970's. Between 1998 and 2010, pup production...
The energy ratio mapping algorithm (ERMA) was developed to improve the performance of
energy-based detection of odontocete echolocation clicks, especially for application in environments
with limited computational power and energy such as acoustic gliders. ERMA systematically
evaluates many frequency bands for energy ratio-based detection of echolocation clicks produced
by a...
This thesis focuses on the nesting ecology and marine space use of Marbled Murrelets (Brachyramphus marmoratus) during the 2007 and 2008 nesting seasons in and around Port Snettisham, a remote mainland fjord in Southeast Alaska. Marbled Murrelets (murrelets) are a declining species throughout most of their range, and their conservation...
The spatial ecology of a species is a vital component of informed management and restoration plans, yet little is known about how animals use restored or constructed habitat. We assessed home ranges, core areas, and habitat selection of the federally threatened Giant Gartersnake (Thamnophis gigas) using rice agricultural habitat and...
Question: Are there general life-history rules for exploitation-caused extinction of mammal populations?
Mathematical methods: A population of size N faced with the added mortality of human exploitation will deterministically go extinct if its per-capita birth rate can no longer match its per-capita mortality rate as N approaches zero. We develop...
The North Pacific humpback whale (Megaptera novaeangliae) population has been increasing at an average annual rate of ~6% since the early 1990s. In northern Southeast Alaska alone, there are now more whales than estimated for the entire North Pacific several decades ago. An understanding of how this growing population is...
Fire severity is hypothesized as an important driver of bird responses to wildfire. For those species that typically respond negatively to increasing severity, Accessibility of high-severity burned forest may be dependent on the proximity of unburned or low-severity burned forest to meet all of the needs of breeding bird species...
The endemic cyprinids of Lake Lanao, Philippines have been described as a species flock and are thought to be an example of explosive evolution. However, based on historical surveys, 16 of the 18 cyprinid species endemic to Lake Lanao are now believed to be extinct. Furthermore, non-native species have been...
Invasive species are a major threat to global biodiversity. Understanding the mechanisms underlying successful invasions is imperative for developing effective management strategies. Plasticity in physiological, morphological, and behavioral traits could be an indicator of invasion potential in non-native species. The invasive American bullfrog (Lithobates catesbeianus) has recently been observed breeding...
Understanding the origin and nature of intra specific biodiversity enables us to better conserve and manage animal populations. Biological diversity is seen at different scales and for different traits such as behavior, morphology, physiology, and life history. Behavior is especially important since behavioral changes are believed to precede changes in...
An estimated 99% of native wet prairie has been lost in the Willamette Valley, Oregon, but a large number of seasonal wetlands remain on private lands dedicated to grass seed production within the historical wet prairie landscape. Because agriculture is known to alter physical and chemical wetland conditions, I investigated...
Bycatch, or the incidental capture of non-target species, has been implicated as one of the main factors leading to population declines of many large marine vertebrates, including sea turtles. To effectively manage and conserve these long-lived species, their marine distribution, high use areas, foraging habitats, and regions of highest likelihood...
Effective and sustainable fisheries management not only depends on identifying and defining stocks (fundamental unit of management), but also on having knowledge of factors influencing the abundance, distribution and connectivity of stocks. Population structure of Pacific cod (Gadus macrocephalus) in the southeastern Bering Sea (EBS) remains unresolved although genetic data...
Brooks Island, located in central San Francisco Bay, California, currently supports the largest breeding colony of Caspian terns (Hydroprogne caspia) in the Bay Area, and is one of several proposed relocation sites for some Caspian terns from the world's largest colony in the Columbia River estuary of Oregon. Juvenile salmonids...
Juvenile salmonids display highly variable spatial and temporal movement patterns that are influenced by density dependent (e.g., competition, predation) and density independent (e.g., genetics, stream discharge, physical habitat conditions) factors. The effects of these factors differ with fish life history stage, but will ultimately affect how salmonids utilize freshwater nursery...
Pacific lamprey, Entosphenus tridentatus, have shown recent and rapid declines in abundance. These anadromous fish return to streams where they mature, spawn and die. It has been inferred that Pacific lamprey enter freshwater and reside for ~ 1 year before spawning. This long exposure to the freshwater environment may affect...
Alternative male phenotypes in salmonine fishes arise from individuals that mature as larger and older anadromous marine-migrants or as smaller and younger freshwater residents. To better understand the processes influencing the expression of these phenotypes we examined the influences of growth in length (fork length) and whole body lipid content...
The influence of land use on potential fates of nitrate (NO3-) in stream ecosystems, ranging from denitrification to storage in organic matter, has not been documented extensively. Here, we describe the Pacific Northwest component of Lotic Intersite Nitrogen eXperiment, phase II (LINX II) to examine how land-use setting influences fates...
In 2006–2010, effects of four different cattle stocking rates (0, 14.4, 28.8, and 43.2 animal unit months) were compared, representing 0%, 20%, 32%, and 46% utilization of vegetation by domestic livestock, on vegetation structure (as indexed by visual obstruction), and songbird population and apparent nest density, community composition, and diversity...
Greater Sage-Grouse (Centrocercus urophasianus) depend on sagebrush habitat for food and cover during winter, yet few sage-grouse winter ecology studies have been conducted. During January and February 2007, we monitored 22 radio-collared sage-grouse (7 females and 15 males) in central Oregon to characterize winter habitat use and movement patterns. We...
The extensive reduction in adult Pacific lamprey (Entosphenus tridentatus) counts at many hydroelectric dams in the northwestern USA signals a substantial decline in lamprey numbers across the entire region in the past 40 to 50 years. Among the many potential causes of this decline, obstruction of migration routes has likely...
Collaborative fisheries research provides a mechanism for integrating the unique knowledge, experience, and skills of fishermen and scientists. It is a joint intellectual endeavor that begins with the inception of a project and continues until its final stages, with each group having mutual investment in-and ownership of-the project. Collaborative fisheries...
The distribution and geographic range of Greater Sage-Grouse (Centrocercus urophasianus) have been reduced by 56% since European settlement. Although loss and fragmentation of sagebrush (Artemisia spp.) habitats have been cited as the primary causes for the decline of the species, degradation of existing habitat also has been considered an important...
Size-structured spatial patterns in larvae of 2 sucker and 3 minnow species are described from fixed-site
sampling in Upper Klamath Lake, Oregon, and are used to demonstrate patterns of size-based losses downstream and
retention in the lake. The smallest larvae of shortnose suckers (Chasmistes brevirostris), Lost River suckers (Deltistes
luxatus),...
In the Pacific Northwest ecoregion of North America, sculpins represent a major constituent of freshwater assemblages in coastal rivers. Based on their prevalence and abundance, sculpins are likely important ecologically, yet little is known of their interactions with co-occurring species, such as widely studied salmon and trout (salmonines). In this...
The Kittlitz's murrelet (Brachyramphus brevirostris) is a species of conservation concern over the entirety of its known range, which spans coastal Alaska and northeastern Russia. Concerns about the status of the species have been raised due to evidence of population declines in key breeding areas, low reproductive output, and perceived...
The United States Pacific Northwest is well known for its shellfish farming. Historically, commercial harvests were dominated by the native Olympia oyster, Ostrea lurida, but over-exploitation, habitat degradation, and competition and predation by non-native species has drastically depleted their densities and extirpated many local populations. As a result, shellfish aquaculture...
We recovered passive integrated transponder (PIT) tags from nine piscivorous waterbird colonies in the Columbia River basin to evaluate avian predation on Endangered Species Act (ESA)-listed salmonid Oncorhynchus spp. populations during 2007–2010. Avian predation rates were calculated based on the percentage of PIT-tagged juvenile salmonids that were detected as passing...
Marine provinces, founded on contrasting floras or faunas, have been recognized for more than 150 years but were not consistently defined by endemism until 1974. At that time, provinces were based on at least a 10% endemism and nested within biogeographic regions that covered large geographic areas with contrasting biotic...
Vocalizations of Indo-Pacific humpback dolphins (Sousa chinensis) in west Hong Kong waters were described from 12 recordings in 2010. A broadband hydrophone system recorded sounds. Vocalizations were characterized as broadband click trains, burst pulses, and narrowband frequency modulated sounds, including whistles generally similar to those of some other delphinid cetaceans....
Nassau grouper Epinephelus striatus are a large bodied, top level predator that is ecologically important throughout
the Caribbean. Although typically solitary, Nassau grouper form large annual spawning aggregations at predictable times in specific
locations. In 2003, The Cayman Islands Marine Conservation Board established protection for a newly rediscovered Nassau
grouper...
Hatchery supplementation of anadromous salmon is extensive across the Pacific Northwest region with millions of juvenile salmon stocked annually. The influence of hatchery-origin fish as prey items in recipient ecosystems has been explored, but influences of these fish on broader stream nutrient dynamics has not been well-studied. Salmon-derived nutrients (SDN)...
Morphologically divergent ecotypes arise in fish populations on postglacial time scales, and resource polymorphisms
are often invoked to explain their origin. However, genetic recombination can constrain the ability of divergent selection to produce
reproductive isolation in sympatry. Recombination breaks up favorable combinations of traits (”adaptive suites”) if individual
traits are...
Mesoscale physical oceanographic features, such as jets and eddies, can influence the structure of marine ecosystems. We used trophically transmitted parasite communities of pelagic fishes in the northern California Current to examine effects of physical oceanographic features on pelagic ecosystem structure. We tested the hypotheses that (1) oceanographic features associated...
Caspian terns (Hydroprogne caspia) and double-crested cormorants
(Phalacrocorax auritus) nest in large colonies on East Sand Island in the Columbia
River estuary, the largest known colonies for the two species in the world. Both
species of piscivorous colonial waterbirds have been identified as predators with a
significant impact on the...
Mesozooplankton (>200 μm) collected in August and September of 2010 from the northern Gulf of Mexico show evidence of exposure to polycyclic aromatic hydrocarbons (PAHs). Multivariate statistical analysis revealed that distributions of PAHs extracted from mesozooplankton were related to the oil released from the ruptured British Petroleum Macondo-1 (M-1) well...
The endangered western stock of the Steller sea lion (Eumetopias jubatus) - the largest of the eared seals - has declined by 80% from population levels encountered four decades ago. Current overall trends from the Gulf of Alaska to the Aleutian Islands appear neutral with strong regional heterogeneities. A published...
The dynamic watershed acid-base chemistry model of acidification of groundwater in catchments (MAGIC) was used to calculate target loads (TLs) of atmospheric sulfur and nitrogen deposition expected to be protective of aquatic health in lakes in the Adirondack ecoregion of New York. The TLs were calculated for two future dates...
Studies examining the effects of human disturbance on avian parental behavior and reproductive
success are fundamental to bird conservation. However, many such studies fail to also consider the influence of
natural threats, a variable environment, and parental roles. Our work examines interactive relationships of cyclical
(time of day, tide, temperature,...
Vegetation structure is important in structuring avian communities. In the sagebrush biome, where continued habitat loss is thought to threaten shrusteppe-obligate birds, both remotely sensed and field-acquired measures of big sagebrush (Artemisia tridentata) cover have proven valuable in understanding avian abundance. Differences in structure between the exotic annual cheatgrass (Bromus...
We describe the migration distances and timing of the adult Pacific lamprey, Entosphenus tridentatus, in the Willamette River Basin (Oregon, U.S.A.). We conducted aerial surveys to track radio-tagged fish upstream of a major waterfall and hydropower complex en route to spawning areas. We detected 24 out of the 43 fish...
Non-breeding sooty shearwaters are the most abundant seabird in the California Current Large Marine Ecosystem (CCLME) during boreal spring and summer months. This, combined with relatively great energy demands, reliance on patchy, shoaling prey (krill, squid, and forage fishes), and unconstrained mobility free from central-place-foraging demands-make shearwaters useful indicators of...
Pacific lamprey (Entosphenus tridentatus) are experiencing population declines throughout their range. Xenobiotics could be an important risk factor for lamprey populations. Our goal was to establish if common herbicides, as used in forest management, could affect reproductive fitness. We determined that atrazine was a likely compound of greatest concern to...
In the US Pacific Northwest, rockfishes Sebastes spp. have recently become a focus for increased management efforts; several species are currently managed under extreme conservation measures due to low population levels and intense fishing pressure. Rockfish recruitment is extremely variable, and a better understanding of the factors influencing recruitment and...
Management strategies to prevent overfishing while achieving optimum yield vary according to the available data and life history of the fished stock. I evaluated two sets of management strategies for Pacific coast rockfish: strategies to set harvest limits for data-poor stocks, and strategies intended to protect the age structure of...
Habitat loss and fragmentation is a crisis affecting wildlife worldwide. In Tanzania, East Africa, a dramatic and recent (<80 years) expansion in human settlement and agriculture threatens to reduce gene flow among protected areas for many species of large mammals. Wildlife linkages can mitigate population isolation, but linkage designs lacking...
Small, low-head diversion dams are capable of withdrawing much of the flow of a river, often resulting in elevated water temperatures. Accelerated growth and development of aquatic invertebrates has been demonstrated in warmer temperatures, suggesting that the timing of insect emergence and adult body size may be significantly altered by...
Colony size, nesting ecology and diet of Caspian Terns (Hydroprogne caspia) were investigated in the San Francisco Bay area (SFBA) during 2003-2009 to assess the potential for conservation of the tern breeding population and possible negative effects of predation on survival of juvenile salmonids (Oncorhynchus spp.). Numbers of breeding Caspian...
Despite the importance of Pacific cod in Bering Sea fisheries and foodwebs, little is known about the habitat use and the distribution of early life stages. We analysed 6 years of catch data for 0-group Pacific cod in fishery-independent surveys of the Bering Sea shelf. Juvenile cod were most commonly...
Current bioassessment efforts are focused on small wadeable streams, at least partly because assessing ecological conditions in non-wadeable large rivers poses many additional challenges. In this study, we sampled 20 sites in each of seven large rivers in the Pacific Northwest, USA, to characterize variation of benthic diatom assemblages among...
The federally threatened northern spotted owl (Strix occidentalis caurina) is the focus of intensive conservation efforts that have led to much forested land being reserved as habitat for the owl and associated wildlife species throughout the Pacific Northwest of the United States. Recently, however, a relatively new threat to spotted...
The Antarctic blue whale (Balaenoptera musculus intermedia) was hunted to near extinction between 1904 and 1972, declining from an estimated initial abundance of more than 250,000 to fewer than 400. Here, we describe mtDNA control region diversity and geographic differentiation in the surviving population of the Antarctic blue whale, using...
The biodiversity of most marine communities is more or less dependent on continuous invasions from sources with greater richness. These ongoing, natural invasions have become greatly augmented by ship traffic in numerous estuaries and harbors where the native biota has been diminished or lost due to habitat destruction and pollution....
Understanding the movement behavior and foraging strategies of individuals across multiple spatial and temporal scales is essential not only for understanding the biological requirements of individuals but also for linking individual strategies to population level effects. Glacial fjords scattered throughout south-central and southeastern Alaska host some of the largest seasonal...
Cyphocharax biocellatus, a species of curimatid characiform apparently endemic to the Marowijne River/Fleuve Maroni system in Suriname and French Guiana, and the Maim River basin in French Guiana is described as new. The new species is diagnosed from congeners based on meristic and morphometric features and details of pigmentation of...
Diversité et distribution des poissons anostomoides (Teleostei, Characiformes) dans les Guyanes.
Cinquante-six espèces, soit approximativement 20% des Characiformes de la superfamille des Anostomidea (familles
des Anostomidae, Chilodontidae, Curimatidae et Prochilodontidae), fréquentent les eaux douces de la Guyane française, du
Guyana et du Suriname bien que ces régions ne recouvrent qu’environ...
Overfished species of rockfish, Sebastes spp., from the Northeast Pacific experience high bycatch mortality because of ‘barotrauma’, a condition induced from the rapid change in pressure during capture. Field experiments show that it may be possible for rockfish to recover from barotrauma if quickly recompressed; however, no work has followed...
Despite the importance of habitat in determining species distribution and persistence, habitat dynamics are rarely modeled in studies of metapopulations. We used an integrated habitat-occupancy model to simultaneously quantify habitat change, site fidelity, and local colonization and extinction rates for larvae of a suite of Great Plains stream fishes in...
Many highly exploited ecosystems are managed on the basis of single-species demographic information. This management approach can exacerbate tensions among stakeholders with competing interests who in turn rely on data with notoriously high variance. In this case study, an application of diet and dive survey data was used to describe...
We described and predicted spatial variation in marine migration (anadromy) of female Oncorhynchus mykiss in the John Day River watershed, Oregon. We collected 149 juvenile O. mykiss across 72 sites and identified locations used by anadromous females by assigning maternal origin (anadromous versus non-anadromous) to each juvenile. These assignments used...
Early ocean residence is considered a critical period for juvenile salmon although specific survival mechanisms are often unidentified and may vary by species or life stage. Columbia River spring-run Chinook salmon Oncorhynchus tshawytscha abundance has declined dramatically since the early 1900s. To elucidate mechanisms of early marine survival, we tested...
Agricultural practices, including tillage, fertilization, and residue management, can affect surface runoff, soil erosion, and nutrient cycling. These processes, in turn, may adversely affect (1) quality of aquatic resources as habitat for amphibians, fish, and invertebrates, (2) costs of treating surface and ground water to meet drinking water standards, and...
OBJECTIVE. Hospital readmissions are a current target of initiatives to reduce healthcare costs. This study quantified the association between having a clinical culture positive for 1 of 3 prevalent hospital-associated organisms and time to hospital readmission.
DESIGN. Retrospective cohort study.
PATIENTS AND SETTING. Adults admitted to an academic, tertiary care...
The number of sites sampled must be considered when determining the effort necessary for adequately assessing taxa richness in an ecosystem for bioassessment purposes; however, there have been few studies concerning the number of sites necessary for bioassessment of large rivers. We evaluated the effect of sample size (i.e., number...