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At least 991 records · Page 55Linked to original sources
USGS2004

Fort Collins Science Center: Ecosystem Dynamics

Many challenging natural resource management issues require consideration of a web of interactions among ecosystem components. The spatial and temporal complexity of these ecosystem problems demands an interdisciplinary approach integrating biotic and abiotic processes. The goals of the Ecosystem Dynamics Branch are to provide sound science to aid federal resource managers and use long-term, place-focused research and monitoring on federal lands to advance ecosystem science. Current studies fall into five general areas. Herbivore-Ecosystem Interactions examines the efficacy of multiple controls on selected herbivore populations and cascading effects through predator-herbivore-plant-soil linkages. Riparian Ecology is concerned with interactions among streamflow, fluvial geomorphology, and riparian vegetation. Integrated Fire Science focuses on the effects of fire on plant and animal communities at multiple scales, and on the interactions between post-fire plant, runoff, and erosion processes. Reference Ecosystems comprises long-term, place-based studies of ecosystem biogeochemistry. Finally, Integrated Assessments is investigating how to synthesize multiple ecosystem stressors and responses over complex landscapes in ways that are useful for management and planning.

Fact Sheet↗
USGS2009

California's Central Valley Groundwater Study: A Powerful New Tool to Assess Water Resources in California's Central Valley

Competition for water resources is growing throughout California, particularly in the Central Valley. Since 1980, the Central Valley's population has nearly doubled to 3.8 million people. It is expected to increase to 6 million by 2020. Statewide population growth, anticipated reductions in Colorado River water deliveries, drought, and the ecological crisis in the Sacramento-San Joaquin Delta have created an intense demand for water. Tools and information can be used to help manage the Central Valley aquifer system, an important State and national resource.

Fact Sheet↗
USGS2010

Ecological requirements for pallid sturgeon reproduction and recruitment in the Lower Missouri River: Annual report 2009

The Comprehensive Sturgeon Research Project is a multiyear, multiagency collaborative research framework developed to provide information to support pallid sturgeon recovery and Missouri River management decisions. The general Comprehensive Sturgeon Research Project strategy is to integrate field and laboratory studies of sturgeon reproductive ecology, habitat requirements, and physiology to produce a predictive understanding of sturgeon population dynamics. The project scope of work is developed annually with cooperating research partners and in collaboration with the U.S. Army Corps of Engineers, Missouri River Recovery-Integrated Science Program. The research consists of several interdependent and complementary research tasks engaging multiple disciplines that primarily address spawning as a probable limiting factor in reproduction and survival of the pallid sturgeon. The research is multifaceted and is designed to provide information needed for management decisions impacting habitat restoration, flow modification, and pallid sturgeon population augmentation on the Missouri River, and throughout the range of the species. Research activities and progress towards understanding of the species are reported to the U.S. Army Corps of Engineers annually. This annual report details the research effort and progress made by Comprehensive Sturgeon Research Project during 2009.

Open-File Report↗
USGS2015

Climate change and prairie pothole wetlands: mitigating water-level and hydroperiod effects through upland management

Prairie pothole wetlands offer crucial habitat for North America’s waterfowl populations. The wetlands also support an abundance of other species and provide ecological services valued by society. The hydrology of prairie pothole wetlands is dependent on atmospheric interactions. Therefore, changes to the region’s climate can have profound effects on wetland hydrology. The relevant literature related to climate change and upland management effects on prairie pothole wetland water levels and hydroperiods was reviewed. Climate change is widely expected to affect water levels and hydroperiods of prairie pothole wetlands, as well as the biota and ecological services that the wetlands support. In general, hydrologic model projections that incorporate future climate change scenarios forecast lower water levels in prairie pothole wetlands and longer periods spent in a dry condition, despite potential increases in precipitation. However, the extreme natural variability in climate and hydrology of prairie pothole wetlands necessitates caution when interpreting model results. Recent changes in weather patterns throughout much of the Prairie Pothole Region have been in increased precipitation that results in increased water inputs to wetlands above losses associated with warmer temperatures. However, observed precipitation increases are within the range of natural climate variability and therefore, may not persist. Identifying management techniques with the potential to affect water inputs to prairie pothole wetlands would provide increased options for managers when dealing with the uncertainties associated with a changing climate. Several grassland management techniques (for example, grazing and burning) have the potential to affect water levels and hydroperiods of prairie pothole by affecting infiltration, evapotranspiration, and snow deposition.

Prairie Pothole Region↗
USGS2022

Counterfactuals to assess effects to species and systems from renewable energy development

Renewable energy production, mostly via wind, solar, and biofuels, is central to goals worldwide to reduce carbon emissions and mitigate anthropogenic climate change (IPCC, 2014; Pörtner et al., 2021). Nevertheless, adverse impacts to natural systems, especially fatalities of wildlife and alteration of habitat, are key challenges for renewable energy production (Allison et al., 2019; Katzner et al., 2019). Because of the magnitude of these challenges, extensive effort has been invested in surveys and science to understand the environmental effects of renewable energy on species and systems. Nevertheless, these impacts have not been formally compared relative to counterfactual conditions (Bull et al., 2021; Coetzee and Gaston, 2021), i.e., those occurring in the absence of renewable energy. As such, cumulative ecological impact assessments required by many regulating agencies typically only consider the adverse impacts of renewables, without evaluating whether mitigative effects of current and planned build-out (e.g., Larson et al., 2020) will offset their adverse impacts to species and natural systems (Allison et al., 2014). Accordingly, these critical decision processes have an insufficient perspective to foster fully informed decisions, and, for some species or systems, renewable energy could lead to more profound impacts than those it is intended to prevent. Furthermore, because of this approach and, despite the well-studied benefits to society of renewable energy development (IPCC, 2014), the ecological value of renewable energy is often premised on the plausible but untested assumption that its negative effects to natural populations and systems are less consequential than the negative effects in alternative scenarios with less renewable energy and greater climate change. A more comprehensive framing of the counterfactual in cumulative ecological impact assessments would evaluate, for each species or system, the incremental effects of renewables over their full life cycle against the incremental effects they provide by mitigating climate change. This framing is important because a given species or system may see net positive or net negative effects from either renewables or climate change. Furthermore, cumulative impact assessments could identify optimized tradeoffs that balance, for each species or system, the effects of both climate change and renewable energy.

Frontiers in Conservation Science↗
USGS2003

Status of Alabama shad and skipjack herring in Gulf of Mexico drainages

Gulf of Mexico drainages are inhabited by two alosine species, the anadromous Alabama shad Alosa alabamae and the skipjack herring A. chrysochloris. Although their distributions are reasonably well documented, the life history and ecology of both species has been incompletely investigated. Infrequent literature references suggest populations of both species have been adversely affected by river management activities throughout parts of their ranges. This purpose of this paper is to summarize available information concerning past and present distributions, population characteristics, spawning and fecundity, age and growth, and population trends of both species as well as threats to the species. Areas of research are suggested to maintain and possibly recover existing populations. ?? 2003 by the American Fisheries Society.

American Fisheries Society Symposium↗
USGS2012

Fire in Mediterranean climate ecosystems-A comparative overview

Four regions of the world share a similar climate and structurally similar plant communities with the Mediterranean Basin. These five areas, known collectively as "mediterranean-type climate (MTC) regions", are dominated by evergreen sclerophyllous-leaved shrublands, semi-deciduous scrub, and woodlands, all of which are prone to widespread crown fires. Summer droughts produce an annual fire hazard that contributes to a highly predictable fire regime. Fire has been an important factor driving the convergence of these systems and is reflected in plant traits such as lignotubers in resprouting shrubs and delayed reproduction that restricts recruitment to a postfire pulse of seedlings. On fertile soils where postfire resprouting is very rapid, opportunities for postfire seedling recruitment are limited and thus these woody taxa have not opted for delaying reproduction. Such fire-independent recruitment is widespread in the floras of MTC regions of the Mediterranean Basin and California and postfire seeding tends to dominate at the more arid end of the gradient. Due to very different geological histories in South Africa and Western Australia, substrates are nutrient poor and thus postfire resprouters do not pose a similar competitive challenge to seedlings and thus postfire seeding is very widespread in these floras. Although circumstantial evidence suggests that the MTC region of Chile had fire-prone landscapes in the Tertiary, these were lost with the late Miocene completion of the Andean uplift, which now blocks summer lightning storms from moving into the region. Today these five regions pose a significant fire management challenge due to the annual fire hazard and metropolitan centers juxtaposed with highly flammable vegetation. This challenge varies across the five MTC landscapes as a function of differences in regional fuel loads and population density.

Israel Journal of Ecology and Evolution↗
USGS2011

Diet and population metrics of the introduced blue catfish population in the Altamaha, River, GA

Blue catfish (Ictalurus furcatus) were first detected in the Altamaha River, Georgia, during an access creel survey in 2005 and subsequently in 2006 during annual ictalurid sampling. Introduction of this species in the Altamaha River is believed to have occurred via escape from normal upstream reservoir releases from Lake Sinclair and Lake Oconee. Relative abundance, as indexed by electrofishing catch rate (fish per hour), has increased from 2.9±1.0 SE in 2006 to 38.8±8.2 SE in 2011. The size of blue catfish captured ranged from 56 to 820 mm total length and 0.001 to 7.7 kg. Using otoliths obtained in 2010 (n=214), age of fish ranged from 0 to 6 yrs, which indicated a relatively young population. The catch-curve analysis resulted in an instantaneous mortality rate (Z) of 0.75. Despite concerns of blue catfish predation on native fishes and mussels, a diet analysis of blue catfish (n=257) obtained in 2010 revealed that diets of fish in all size groups were dominated by the introduced Asiatic clam (Corbicula fluminea). This study describes a recently introduced blue catfish population in an Atlantic coastal plain river and provides insight on possible ecological effects during the early phases of establishment. These results offer an early status assessment of the invasion dynamics before the system has had time to reach a new equilibrium state.

Conference Paper↗
USGS2017

Characterization of microsatellite loci for the Gulf Coast waterdog (Necturus beyeri) using paired-end Illumina shotgun sequencing and cross-amplification in other Necturus

Amphibians are one of the most threatened groups of vertebrates (Stuart et al. 2004; Wake and Vredenburg 2008), and the application of molecular techniques to amphibian ecology and genetics has dramatically improved our ability to conserve species and populations (see Shaffer et al. [2015] for review). Microsatellites, tandem repeats of two to six nucleotides in the nuclear genome, are highly variable molecular markers that can be used to describe gene flow and genetic diversity, each of which is positively correlated with population persistence (Allendorf and Luikart 2007; Allentoft and O’Brien 2010; Avise 2004; Selkoe and Toonen 2006). Microsatellite loci have frequently been applied to studies involving terrestrial and pond breeding amphibians (Emel and Storfer 2012), but fewer studies have focused on taxa inhabiting lotic systems (Emel and Storfer 2012). For example, studies characterizing microsatellite loci are completely lacking for a group of permanently aquatic salamanders, the waterdogs and mudpuppies (Family Proteidae, Genus Necturus ) (Rafinesque 1819). The genus Necturus consists of several species of perennibranch salamanders that can be found throughout many freshwater streams, rivers, and lakes in North America (Petranka 1998). Some authorities recognize five species (Crother 2012; Petranka 1998), including the Mudpuppy ( Necturus maculosus ) (Rafinesque 1819), Gulf Coast Waterdog ( N. beyeri ) (Viosca 1937), Black Warrior Waterdog ( N. alabamensis ) (Viosca 1937), Neuse River Waterdog ( N. lewisi ) (Brimley 1924), and Dwarf Waterdog ( N. punctatus ) (Gibbes 1850). This taxonomy also recognizes two subspecies within N. maculosus , including the Common Mudpuppy ( N. m. maculosus ) and the Red River Waterdog ( N. m. louisianensis ) (Crother 2012; Petranka 1998; Schmidt 1953). Other authorities suggest that there are six or seven species within Necturus (Collins 1990; Frost 2016; Powell et al. 2016). These more diverse schemes recognize each of the aforementioned five species while also elevating the Red River Waterdog ( N. louisianensis ) (Collins 1990; Frost 2016; Powell et al. 2016; Viosca 1938) and Löding’s Waterdog ( N. lödingi or N. cf. beyeri ) (Bart et al. 1997; Guyer 2005a; Viosca 1938). Allozyme work by Guttman et al. (1990) suggests that there is at least one cryptic species of Necturus in drainages east of the Mobile Basin and south of the Alabama River, and both Bart et al. (1997) and Guyer (2005a) advise that these populations should be referred to as N. cf. beyeri . However, until range wide studies incorporating genetic and other data are published, we will follow the five species taxonomy outlined by Crother (2012) while acknowledging that certain taxa, such as N. maculosus and N. beyeri , may require systematic revision.

Herpetological Review↗
USGS2010

The transboundary nature of seabird ecology

The term ‘seabird’ is generally applied to avian species that forage in the marine environment over open water. Seabirds typically nest in colonies and are long-lived species with low annual reproductive rates. Seabird breeding sites typically occur on islands or along coasts and as such are often at the boundaries of ecological or political zones. During the breeding season, seabirds cross a very distinct terrestrial/marine ecological boundary on a regular basis to forage. Even relatively ‘local’ species cross multiple jurisdictions within a day (e.g., state lands and waters, and federal waters) while pelagic species may transit through international waters on a daily, weekly, or monthly time-frame. Seabird life-histories expose individuals and populations to environmental conditions affecting both terrestrial and marine habitats. The wide-ranging and transboundary nature of seabird ecology also exposes these species to various environmental and anthropogenic forces such as contamination, commercial fisheries and climate forcing that also are transboundary in nature. Therefore, wherever conservation of seabirds or the management of their populations is the goal, consideration must be given to ecosystem dynamics on land and at sea. Because the jurisdiction of agencies does not cross the land-sea boundary in the same manner as the seabirds they are managing, these efforts are facilitated by multi-agency communication and collaboration. By their very nature and by the nature of the systems that they must function within, seabirds embody the complexity of wildlife ecology and conservation in the twenty-first century.

Book chapter↗
USGS2021

Fisheries research and monitoring activities of the Lake Erie Biological Station, 2021

A comprehensive understanding of fish populations and their interactions is the cornerstone of modern fishery management and the basis for Lake Erie’s Fish Community Goals and Objectives (FCOs) developed in 2020 (Francis et al. 2020). The 2021 USGS Lake Erie Biological Station annual report is responsive to these FCOs and the U.S. Geological Survey (USGS) obligations via a Memorandum of Understanding (MOU) in 2004 with the GLFC Council of Lake Committees (CLC) to provide scientific information in support of fishery management. Goals for the USGS Great Lakes Deepwater Fish Assessment and Ecological Studies were to monitor long-term changes in the fish community and population dynamics of key fishes of interest to management agencies (MOU 2004). Specific to Lake Erie, expectations of the MOU were sustained investigations of native percids, forage (prey) fish populations, and Lake Trout. Additionally, this work was conducted under the authority of the Great Lakes Fishery Research Authorization Act of 2019.

Lake Erie↗
USGS2020

Estimation of vital population rates to assess the relative health of mussel assemblages in the Upper Mississippi River

Native freshwater mussels are a guild of benthic, filter feeding invertebrates that perform important ecological functions in rivers. Because of their long lifespans (30–50 years or longer), mussels are slow to respond to human‐induced alterations. Thus, development of sensitive indicators of mussel population responses to river conditions and management would be beneficial. Compared to marine species, estimation of vital rates (e.g. survival, growth) in freshwater mussels has received little attention. We placed passively integrated transponder tags on 578 mussels of four species ( Amblema plicata , Cyclonaias pustulosa , Obliquaria reflexa , and Pleurobema sintoxia ) in a well‐studied mussel assemblage in a side channel of the upper Mississippi River. Growth and survival of tagged mussels were assessed annually for 4 years across core (high density) and peripheral (low density) areas of the assemblage. Overall survival was highly variable, ranging from c . 15 to 90%, and was related to life history, habitat quality, and hydrologic events. Survival, which varied significantly among species and over time, was consistently higher in the dense and species‐rich core of the mussel assemblage, relative to the periphery because substrates were consistently more stable in the core of the mussel bed relative to the periphery. Substrate movement during low flows was an order of magnitude lower in the core relative to the periphery, and survival was inversely related to stability of river substrates. Patterns in habitat‐specific survival indicate source–sink population dynamics such that mussels in the core habitat provide recruitment to the periphery, but mussels in the periphery are subject to unsustainably low survival; additional studies to track the source of recruitment in the periphery are needed to test this hypothesis. Growth rate did not vary significantly between core and peripheral areas but did vary by species. Growth rate (proportional change per year) declined with age, and was similar at mean age for A. plicata (0.016 per year), P. sintoxia (0.015 per year), and C. pustulosa (0.013 per year), but much lower for O. reflexa (0.008 per year). Effective management decisions for mussels requires a better understanding of how vital rates govern populations and how they vary across a suite of physical and biological factors. Information on how population vital rates vary among species and over time gives managers another tool to understand how mussels may respond to management actions such as habitat restoration projects. Given the importance of substrate stability inferred from this study, management actions that maintain or increase substrate stability are likely to result in high quality mussel assemblages and may restore a valuable component of ecosystem function in this region.

Minnesota, Wisconsin↗
USGS2016

Bayesian analysis of Jolly-Seber type models

We propose the use of finite mixtures of continuous distributions in modelling the process by which new individuals, that arrive in groups, become part of a wildlife population. We demonstrate this approach using a data set of migrating semipalmated sandpipers ( Calidris pussila ) for which we extend existing stopover models to allow for individuals to have different behaviour in terms of their stopover duration at the site. We demonstrate the use of reversible jump MCMC methods to derive posterior distributions for the model parameters and the models, simultaneously. The algorithm moves between models with different numbers of arrival groups as well as between models with different numbers of behavioural groups. The approach is shown to provide new ecological insights about the stopover behaviour of semipalmated sandpipers but is generally applicable to any population in which animals arrive in groups and potentially exhibit heterogeneity in terms of one or more other processes.

Environmental and Ecological Statistics↗
USGS2012

A horizon scanning assessment of current and potential future threats to migratory shorebirds

We review the conservation issues facing migratory shorebird populations that breed in temperate regions and use wetlands in the non-breeding season. Shorebirds are excellent model organisms for understanding ecological, behavioural and evolutionary processes and are often used as indicators of wetland health. A global team of experienced shorebird researchers identified 45 issues facing these shorebird populations, and divided them into three categories (natural, current anthropogenic and future issues). The natural issues included megatsunamis, volcanoes and regional climate changes, while current anthropogenic threats encompassed agricultural intensification, conversion of tidal flats and coastal wetlands by human infrastructure developments and eutrophication of coastal systems. Possible future threats to shorebirds include microplastics, new means of recreation and infectious diseases. We suggest that this review process be broadened to other taxa to aid the identification and ranking of current and future conservation actions.

Ibis↗
USGS2012

Spatial ecology of refuge selection by an herbivore under risk of predation

Prey species use structures such as burrows to minimize predation risk. The spatial arrangement of these resources can have important implications for individual and population fitness. For example, there is evidence that clustered resources can benefit individuals by reducing predation risk and increasing foraging opportunity concurrently, which leads to higher population density. However, the scale of clustering that is important in these processes has been ignored during theoretical and empirical development of resource models. Ecological understanding of refuge exploitation by prey can be improved by spatial analysis of refuge use and availability that incorporates the effect of scale. We measured the spatial distribution of pygmy rabbit (Brachylagus idahoensis) refugia (burrows) through censuses in four 6-ha sites. Point pattern analyses were used to evaluate burrow selection by comparing the spatial distribution of used and available burrows. The presence of food resources and additional overstory cover resources was further examined using logistic regression. Burrows were spatially clustered at scales up to approximately 25 m, and then regularly spaced at distances beyond ~40 m. Pygmy rabbit exploitation of burrows did not match availability. Burrows used by pygmy rabbits were likely to be located in areas with high overall burrow density (resource clusters) and high overstory cover, which together minimized predation risk. However, in some cases we observed an interaction between either overstory cover (safety) or understory cover (forage) and burrow density. The interactions show that pygmy rabbits will use burrows in areas with low relative burrow density (high relative predation risk) if understory food resources are high. This points to a potential trade-off whereby rabbits must sacrifice some safety afforded by additional nearby burrows to obtain ample forage resources. Observed patterns of clustered burrows and non-random burrow use improve understanding of the importance of spatial distribution of refugia for burrowing herbivores. The analyses used allowed for the estimation of the spatial scale where subtle trade-offs between predation avoidance and foraging opportunity are likely to occur in a natural system.

Ecosphere↗
USGS2018

Barred owl research needs and prioritization in California

Barred owls (Strix varia) have reached high densities within the range of the northern spotted owl (S. occidentalis caurina) and are rapidly increasing in number within the range of the California spotted owl (S. o. occidentalis). Encroaching populations of barred owls pose a significant competitive threat to the viability of both spotted owl subspecies in California. In response, the Director of the California Department of Fish and Wildlife (CDFW) convened the California Barred Owl Science Team (BOST) to identify and address the threat posed by barred owls to spotted owls in California. BOST is composed of subject matter scientists with a goal to provide objective scientific review and recommendations to CDFW to promote the recovery and conservation of spotted owls in California. In this document, BOST identifies, describes, and prioritizes key research needs for barred owls that have the potential to benefit the conservation of spotted owls in California. Key research needs were identified from multiple in-person and remote meetings of BOST, with considerable input from attending representatives from state and federal natural resource agencies. BOST and liaisons recognize that periodic updates of this document will likely be required as more is learned about the ecology of barred owls in California and research needs and priorities evolve. Research that BOST deemed the most likely to provide a rigorous scientific basis for reducing barred owl populations included experimental removals, along with ecological studies expected to generate information that would provide avenues for the effective management of barred owls. Other high priority research needs include research using biological samples obtained during experimental removals to better understand the ecology of barred owls and the threats they pose to spotted owls and associated wildlife. We conclude the document with a discussion of how projects are related to the State Wildlife Action Plan. In Appendix I, we discuss considerations for maximizing the success of proposed removal experiments and ecological research on barred owls.

Report↗
USGS1958

Distribution and ecology of whistling swans in the Chesapeake Bay region

The Whistling Swan, Olor columbianus , is of particular significance in the Chesapeake Bay region, since major wintering and transient populations occur here regularly, constituting in some years more than half the total population of the species. Some of these concentrations are so large that they attract many bird-watchers, who often travel long distances to see them. Whistling Swans are also of concern to the local shell-fish gatherers, who claim that depredations by these birds cause considerable damage to the supply of commercially valuable long ("soft-shelled") clams. During recent years, there has been an increasing demand from some sources for an open hunting season. It has been suggested that the swan populations may be of sufficient numerical size, to withstand a limited harvest. Because of these considerations, a special effort was made to obtain more information concerning the local distribution, numerical status and ecology of Whistling Swans throughout the Chesapeake Bay region.

The Auk↗
USGS2011

Development of a bioenergetics model for age-0 American shad

Bioenergetics modeling can be used as a tool to investigate the impact of non-native age-0 American shad ( Alosa sapidissima ) on reservoir and estuary food webs. The model can increase our understanding of how these fish influence lower trophic levels as well as predatory fish populations that feed on juvenile salmonids. Bioenergetics modeling can be used to investigate ecological processes, evaluate alternative research hypotheses, provide decision support, and quantitative prediction. Bioenergetics modeling has proven to be extremely useful in fisheries research (Ney et al. 1993,Chips and Wahl 2008, Petersen et al. 2008). If growth and diet parameters are known, the bioenergetics model can be used to quantify the relative amount of zooplankton or insects consumed by age-0 American shad. When linked with spatial and temporal information on fish abundance, model output can guide inferential hypothesis development to demonstrate where the greatest impacts of age-0 American shad might occur. Bioenergetics modeling is particularly useful when research questions involve multiple species and trophic levels (e.g. plankton communities). Bioenergetics models are mass-balance equations where the energy acquired from food is partitioned between maintenance costs, waste products, and growth (Winberg 1956). Specifically, the Wisconsin bioenergetics model (Hanson et al. 1997) is widely used in fisheries science. Researchers have extensively tested, reviewed, and improved on this modeling approach for over 30 years (Petersen et al. 2008). Development of a bioenergetics model for any species requires three key components: 1) determine physiological parameters for the model through laboratory experiments or incorporate data from a closely related species, 2) corroboration of the model with growth and consumption estimates from independent research, and 3) error analysis of model parameters. Wisconsin bioenergetics models have been parameterized for many of the salmonids and predatory fishes encountered in the lower Columbia River (Petersen and Ward 1999). The Wisconsin bioenergetics model has not been developed for American shad, however Limburg (1996) parameterized a simplified bioenergetics growth model for this species. A common application for the Wisconsin bioenergetics model is to estimate the consumption or growth of a fish population under different temperature and feeding scenarios (Ney 1993). One advantage of the bioenergetics approach is that consumption can be estimated without direct field measurements of predation rate (prey·predator -1 · day -1 ; Petersen and Ward 1999). Field estimates of fish consumption are time consuming and costly to determine, and estimates may show wide variance due to environmental and sampling variability. However, the consumption parameters used in a newly developed bioenergetics model must be verified with field and laboratory estimates of consumption (Ney 1993). The objective of this research was to parameterize a Wisconsin bioenergetics model for age-0 American shad using published physiological data on American shad and closely related alosine species. The American shad bioenergetics model will be used as a tool to explore various hypotheses about how age-0 American shad directly and indirectly affect Columbia River salmon through ecological interactions in lower Columbia River food webs. One over-arching focus of the larger research project was to identify potential interactions between age-0 American shad and juvenile salmonids, addressing potential outcomes through bioenergetics modeling scenarios. This report contains two bioenergetics modeling applications to demonstrate how these models can be used to address management questions and direct research effort. The first modeling application uses the American shad bioenergetics model described in this report to explore prey consumption by age-0 American shad (Chapter 1, this report). Dietary data on age-0 American shad and previously published reports on the diet of juvenile fall Chinook salmon (Rondorf et al. 1990, USGS unpublished data) suggested there might be considerable dietary overlap between these species in the lower Columbia River. The U.S. Geological Survey (USGS) was interested in using the American shad bioenergetics model to explore hypotheses concerning dietary overlap between age-0 American shad and emigrating fall Chinook salmon. The second modeling application uses the fall Chinook salmon bioenergetics model (Koehler et al. 2006) to explore the growth potential of juvenile fall Chinook salmon predating on age-0 American shad in the lower Columbia River. This modeling was based dietary information on a small number of age-0 fall Chinook salmon (n = 13) collected in John Day Reservoir in 1994 - 1996 (unpublished USGS data). Analysis of this dietary data found that these salmonids were feeding primarily on age-0 American shad (> 75% by weight).

Oregon↗