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Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

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Articles 151 - 167 of 167

Full-Text Articles in Aquaculture and Fisheries

Mixed-Source Reintroductions Lead To Outbreeding Depression In Second-Generation Descendents Of A Native North American Fish, David D. Huff, Loren M. Miller, Christopher J. Chizinski, Bruce Vondracek Jan 2011

Mixed-Source Reintroductions Lead To Outbreeding Depression In Second-Generation Descendents Of A Native North American Fish, David D. Huff, Loren M. Miller, Christopher J. Chizinski, Bruce Vondracek

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Reintroductions are commonly employed to preserve intraspecific biodiversity in fragmented landscapes. However, reintroduced populations are frequently smaller and more geographically isolated than native populations. Mixing genetically, divergent sources are often proposed to attenuate potentially low genetic diversity in reintroduced populations that may result from small effective population sizes. However, a possible negative tradeoff for mixing sources is outbreeding depression in hybrid offspring. We examined the consequences of mixed-source reintroductions on several fitness surrogates at nine slimy sculpin (Cottus cognatus) reintroduction sites in south-east Minnesota. We inferred the relative fitness of each crosstype in the reintroduced populations by comparing …

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Breeding Bird Response To Partially Harvested Riparian Management Zones, Christopher J. Chizinski, Anna Peterson, Joann Hanowski, Charles R. Blinn, Bruce Vondracek, Gerald J. Niemi Jan 2011

Breeding Bird Response To Partially Harvested Riparian Management Zones, Christopher J. Chizinski, Anna Peterson, Joann Hanowski, Charles R. Blinn, Bruce Vondracek, Gerald J. Niemi

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

We compared avian communities among three timber harvesting treatments in 45-m wide even-age riparian management zones (RMZs) placed between upland clearcuts and along one side of first- or second-order streams in northern Minnesota, USA. The RMZs had three treatments: (1) unharvested, (2) intermediate residual basal area (RBA) (targeted goal 11.5m2/ha, realized 16.0m2/ha), and (3) low RBA (targeted goal 5.7m2/ha, realized 8.7m2/ha). Surveys were conducted one year pre-harvest and three consecutive years post-harvest. There was no change in species richness, diversity, or total abundance associated with harvest but there were shifts in the types of …

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The Influence Of Partial Timber Harvesting In Riparian Buffers On Macroinvertebrate And Fish Communities In Small Streams In Minnesota, Usa, Christopher J. Chizinski, Bruce Vondracek, Charles R. Blinn, Raymond M. Newman, Dickson M. Atuke, Keith Fredricks, Nathaniel A. Hemstad, Eric Merten, Nicholas Schlesser Feb 2010

The Influence Of Partial Timber Harvesting In Riparian Buffers On Macroinvertebrate And Fish Communities In Small Streams In Minnesota, Usa, Christopher J. Chizinski, Bruce Vondracek, Charles R. Blinn, Raymond M. Newman, Dickson M. Atuke, Keith Fredricks, Nathaniel A. Hemstad, Eric Merten, Nicholas Schlesser

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Relatively few evaluations of aquatic macroinvertebrate and fish communities have been published in peer-reviewed literature detailing the effect of varying residual basal area (RBA) after timber harvesting in riparian buffers. Our analysis investigated the effects of partial harvesting within riparian buffers on aquatic macroinvertebrate and fish communities in small streams from two experiments in northern Minnesota northern hardwood-aspen forests. Each experiment evaluated partial harvesting within riparian buffers. In both experiments, benthic macroinvertebrates and fish were collected 1 year prior to harvest and in each of 3 years after harvest. We observed interannual variation for the macroinvertebrate abundance, diversity and taxon …

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The Index Of Biological Integrity And The Bootstrap: Can Random Sampling Error Affect Stream Impairment Decisions?, Christine L. Dolph, Aleksey Y. Sheshukov, Christopher J. Chizinski, Bruce Vondracek, Bruce N. Wilson Jan 2010

The Index Of Biological Integrity And The Bootstrap: Can Random Sampling Error Affect Stream Impairment Decisions?, Christine L. Dolph, Aleksey Y. Sheshukov, Christopher J. Chizinski, Bruce Vondracek, Bruce N. Wilson

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Multimetric indices, such as the Index of Biological Integrity (IBI), are increasingly used bymanagement agencies to determine whether surface water quality is impaired. However, important questions about the variability of these indices have not been thoroughly addressed in the scientific literature. In this study, we used a bootstrap approach to quantify variability associated with fish IBIs developed for streams in two Minnesota river basins. We further placed this variability into a management context by comparing it to impairment thresholds currently used in water quality determinations for Minnesota streams. We found that 95% confidence intervals ranged as high as 40 points …

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The Impact Of Rare Taxa On A Fish Index Of Biotic Integrity, Haibo Wan, Christopher J. Chizinski, Christine L. Dolph, Bruce Vondracek, Bruce N. Wilson Jan 2010

The Impact Of Rare Taxa On A Fish Index Of Biotic Integrity, Haibo Wan, Christopher J. Chizinski, Christine L. Dolph, Bruce Vondracek, Bruce N. Wilson

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

The index of biotic integrity (IBI) is a commonly used bioassessment tool that integrates abundance and richness measures to assess water quality. In developing IBIs that are both responsive to human disturbance and resistant to natural variability and sampling error, water managersmust decide how to weigh information about rare and abundant taxa, which in turn requires an understanding of the sensitivity of indices to rare taxa. Herein, we investigated the influence of rare fish taxa (within the lower 5% of rank abundance curves) on IBI metric and total scores for stream sites in two of Minnesota’smajor river basins, the St. …

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Multi-Ideal-Adic Completions Of Noetherian Rings, William J. Heinzer, Christel Rotthaus, Sylvia Wiegand Jan 2008

Multi-Ideal-Adic Completions Of Noetherian Rings, William J. Heinzer, Christel Rotthaus, Sylvia Wiegand

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Let R be a commutative ring with identity. A filtration on R is a decreasing sequence {In}∞ n=0 of ideals of R. Associated to a filtration is a well-defined completion R ∗ = l←i−mn R/In and a canonical homomorphism ψ : R → R ∗ [13, Chap. 9]. If ∞ n=0 In = (0), then ψ is injective and R may be regarded as a subring of R ∗ [13, p. 401]. In the terminology of Northcott, a filtration {In}∞ n=0 is multiplicative if I0 = R and InIm ⊆ In+m for all m ≥ 0 and n ≥ 0 …

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Extensions Of Local Domains With Trivial Generic Fiber, William Heinzer, Christel Rotthaus, Sylvia Wiegand Apr 2007

Extensions Of Local Domains With Trivial Generic Fiber, William Heinzer, Christel Rotthaus, Sylvia Wiegand

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

We consider injective local maps from a local domain R to a local domain S such that the generic fiber of the inclusion map R -> S is trivial, that is P R (0) for every nonzero prime ideal P of S. We present several examples of injective local maps involving power series that have or fail to have this property. For an extension R -> S having this property, we give some results on the dimension of S; in some cases we show dim S = 2 and in some cases dim S = 1.

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Climate-Induced Forest Dieback As An Emergent Global Phenomenon, Craig Allen, David D. Breshears Jan 2007

Climate-Induced Forest Dieback As An Emergent Global Phenomenon, Craig Allen, David D. Breshears

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

An organized oral session at the annual meeting of the Ecological Society of America in San Jose, Calif., posed this question: Is climate-induced drought stress triggering increasing rates and unusual patterns of forest die-off at a global scale? Twenty-nine researchers representing five continents reported on patterns, mechanisms, and projections of forest mortality.

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Maximum Size Of Fish Caught With Standard Gears And Recreational Angling, Kevin L. Pope, Gene R. Wilde, Daryl L. Bauer Oct 2005

Maximum Size Of Fish Caught With Standard Gears And Recreational Angling, Kevin L. Pope, Gene R. Wilde, Daryl L. Bauer

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

We correlated maximum lengths of freshwater fishes captured during 10 years with standard gears (i.e., gill nets, boat electrofishers and trap nets) and angling from Nebraska water bodies to determine which methodology provided better estimates of maximum size of fishes produced within a given water body. In general, maximum length of fishes captured with standard gears was smaller than maximum length of fishes captured with angling. Although significant (based on sequential Bonferroni adjustment) correlation was found in only one of nine sport fishes assessed, all correlations were positive indicating a general trend between maximum size of fishes captured with these …

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The Use Of Discontinuities And Functional Groups To Assess Relative Resilience In Complex Systems, Craig R. Allen, L. Gunderson, A. R. Johnson Jan 2005

The Use Of Discontinuities And Functional Groups To Assess Relative Resilience In Complex Systems, Craig R. Allen, L. Gunderson, A. R. Johnson

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

It is evident when the resilience of a system has been exceeded and the system qualitatively changed. However, it is not clear how to measure resilience in a system prior to the demonstration that the capacity for resilient response has been exceeded. We argue that self-organizing human and natural systems are structured by a relatively small set of processes operating across scales in time and space. These structuring processes should generate a discontinuous distribution of structures and frequencies, where discontinuities mark the transition from one scale to another. Resilience is not driven by the identity of elements of a system, …

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Factors Affecting Regional Variation In Growth Of Channel Catfish, Bart W. Durham, Kevin L. Pope, Gene R. Wilde Jan 2005

Factors Affecting Regional Variation In Growth Of Channel Catfish, Bart W. Durham, Kevin L. Pope, Gene R. Wilde

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

We related the length at age of channel catfish Ictalurus punctatus, an indirect measure of growth, to three climatic and five morphoedaphic variables in 144 Texas reservoirs. Growth of channel catfish ages 3 through 6 was negatively related to longitude, a factor that explained as much as 34% of the variation in length at age. Channel catfish length at age was not significantly related to latitude, conductivity, morphoedaphic index, mean depth, and maximum depth in all age-classes. Among age-7 channel catfish, length at age was positively related to reservoir area, which explained 35% of the variation in growth. A …

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Intermediate Rings Between A Local Domain And Its Completion, Ii, William Heinzer, Christel Rotthaus, Sylvia Wiegand Oct 2001

Intermediate Rings Between A Local Domain And Its Completion, Ii, William Heinzer, Christel Rotthaus, Sylvia Wiegand

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

We present results connecting flatness of extension rings to the Noetherian property for certain intermediate rings between an excellent normal local domain and its completion. We consider conditions for these rings to have Cohen-Macaulay formal fibers. We also present several examples illustrating these results.

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Yellow Jackets (Vespula Spp.) Disperse Trillium (Spp.) Seeds In Eastern North America, Jennifer A. Zettler, Timonthy P. Spira, Craig R. Allen Jan 2001

Yellow Jackets (Vespula Spp.) Disperse Trillium (Spp.) Seeds In Eastern North America, Jennifer A. Zettler, Timonthy P. Spira, Craig R. Allen

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Approximately 70 plant families worldwide have ant-dispersed seeds (myrmecochory). In this putative ant-plant mutualism, ants are attracted to and disperse seeds that have a lipid-rich elaiosome. We observed yellow jackets (Vespula spp.) dispersing seeds of three elaiosome-bearing species-Trillium cuneatum, T. undulatum and T catesbaei-in the Blue Ridge Mountains of North Carolina and South Carolina. Moreover, we estimated the mean distance yellow jackets dispersed seeds of T. cuneatum by placing intact fruits on index cards and recovering dispersed seeds on sheets placed on the ground surface. Of the seeds presented, 41% were recovered and the average dispersal distance …

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Intermediate Rings Between A Local Domain And Its Completion, William Heinzer, Christel Rotthaus, Sylvia Wiegand Apr 1999

Intermediate Rings Between A Local Domain And Its Completion, William Heinzer, Christel Rotthaus, Sylvia Wiegand

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

We consider the structure of certain intermediate domains between a local Noetherian domain Rand an ideal-adic completion R* of R that arise as the intersection of R* with a field containing R. In the case where the intersection domain A can be expressed as a directed union of localized polynomial extension rings of R, the computation of A is easier. We examine conditions for this to happen. We also present examples to motivate and illustrate the concepts considered.

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Drought-Induced Shift Of A Forest–Woodland Ecotone: Rapid Landscape Response To Climate Variation, Craig Allen, David D. Breshears Jan 1998

Drought-Induced Shift Of A Forest–Woodland Ecotone: Rapid Landscape Response To Climate Variation, Craig Allen, David D. Breshears

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

In coming decades, global climate changes are expected to produce large shifts in vegetation distributions at unprecedented rates. These shifts are expected to be most rapid and extreme at ecotones, the boundaries between ecosystems, particularly those in semiarid landscapes. However, current models do not adequately provide for such rapid effects—particularly those caused by mortality—largely because of the lack of data from field studies. Here we report the most rapid landscape-scale shift of a woody ecotone ever documented: in northern New Mexico in the 1950s, the ecotone between semiarid ponderosa pine forest and pinon– juniper woodland shifted extensively (2 km or …

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Idealwise Algebraic Independence For Elements Of The Completion Of A Local Domain, William Heinzer, Christel Rotthaus, Sylvia Wiegand Jul 1997

Idealwise Algebraic Independence For Elements Of The Completion Of A Local Domain, William Heinzer, Christel Rotthaus, Sylvia Wiegand

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Over the past forty years many examples in commutative algebra have been constructed using the following principle: Let k be a field, let S k[xl Xn]x,xn) be a localized polynomial ring over k, and let a be an ideal in the completion S of S such that the associated prims of a are in the generic formal fiber of S; that is, p N S (0) for each p Ass(S/a):. Then S embeds in S/a, the fraction field Q(S) of S embeds in the fraction ring of S/a, and for certain choices of a, the intersection D Q(S) f3 (S/a) …

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Finitely Generated Modules Over Bezout [email protected], Roger Wiegand, Sylvia Wiegand Apr 1974

Finitely Generated Modules Over Bezout [email protected], Roger Wiegand, Sylvia Wiegand

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Let R be a Bezout ring (a commutative ring in which all finitely generated ideals are principal), and let M be a finitely generated R -module. We will study questions of the following sort: (A) If every localization of M can be generated by n elements, can M itself be generated by n elements? (B) If M 0 R m = Rn for some m, n, is Af necessarily free? (C) If every localization of M has an element with zero annihilator, does M itself have such an element? We will answer these and related questions for various familiar classes …

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