bluuebunny/crossref_metadata_2025 huggingface dataset:
Prejudiced learning: A connectionist account
Authors: Eiser J. Richard , Stafford Tom , Fazio Russell H.
Published: October 2008

Connectionist simulation was employed to investigate processes that may underlie the relationships between prior expectancies or prejudices and the acquisition of attitudes, under conditions where learners can only discover the valence of attitude objects through directly experiencing them. We compared contexts analogous to learners holding either false negative expectancies (‘prejudices’) about a subclass of objects that were actually good or false positive expectancies about objects that were actually bad. We introduced expectancy‐related bias either by altering the probability of approach, or by varying the rate of learning following experience with good or bad objects. Where feedback was contingent on approach, the false positive expectancies were corrected by experience, but negative prejudices resisted change, since the network avoided objects deemed to be bad, and so received less corrective feedback. These findings are discussed in relation to the effects of intergroup contact and expectancy‐confirmation processes in reducing or sustaining prejudice.
Influence of alcohol on the processing of emotional facial expressions in individuals with social phobia
Authors: Stevens Stephan , Rist Fred , Gerlach Alexander L.
Published: October 2008

Objectives

Individuals with social phobia are at an increased risk to develop alcohol problems. However, the mechanism responsible for this association is unclear. It has been suggested that alcohol reduces anxiety by impairing initial appraisal of threatening stimuli. Information that is especially threatening, however, may be resistant to such an effect of alcohol. We tested the influence of alcohol on the appraisal of five emotional facial expressions.

Methods

40 social phobia patients and 40 controls performed a dot probe task, after drinking either alcohol or orange juice. Stimuli were faces with happy, angry, neutral and also two ambiguous expressions that were formed by blending angry or happy faces and neutral faces. Stimuli were presented for either 175 or 600 ms.

Result

Sober patients showed an attentional bias towards angry faces, indicating preferential processing of threat stimuli. Alcohol significantly reduced this bias. Only in sober participants, this attentional bias correlated with measures of social anxiety. In controls, no biases were observed.

Conclusions

Alcohol seems to attenuate the impact of threatening social stimuli on social phobia patients, which may negatively reinforce the consumption of alcohol and at least partially explain the heightened comorbidity with alcohol related problems known from epidemiological studies. The dot probe task with short stimulus presentation times seems to provide an adequate method to demonstrate alcohol effects on information processing.
Overgeneral autobiographical memory and age of onset of childhood sexual abuse in patients with recurrent suicidal behaviour
Authors: Crane Catherine , Duggan Danielle S.
Published: October 2008

Objective

To explore the association between age of onset of childhood sexual abuse (CSA) and overgeneral memory (OGM) in a clinical sample.

Method

Presence and age of onset of CSA and levels of OGM were assessed in 49 patients attending hospital following a recurrence of suicidal behaviour.

Results

Twenty six participants reported CSA. Earlier age of onset of CSA was associated with greater OGM, indexed by fewer specific and more categoric memories. The association was not accounted for either by elevated levels of depression in those reporting earlier abuse, nor by levels of general verbal fluency.

Conclusions

The findings are consistent with previous work and support the hypothesis that abuse occurring earlier in development results in more pronounced OGM.
Being outperformed in an intergroup context: The relationship between group status and self‐protective strategies
Authors: Redersdorff Sandrine , Martinot Delphine
Published: October 2008

The present study examines the effects of group status on self‐esteem when individuals are outperformed by an in‐group target (Experiments 1 and 2) or an out‐group (Experiment 2). The main aim was to examine different self‐protective mechanisms when the current standing of the in‐group vis‐à‐vis another group is either unfavourable (low status) or favourable (high status). Experiment 1 showed that when outperformed by an in‐group target, the members of a low status group reported higher self‐esteem than members of a high status group. Moreover, this effect was mediated by group identification. Experiment 2 replicated the previous results and gave rise to similar effects on investment in the group. The perceived relevance of the comparison group appeared to protect the self‐esteem of high status group members. This research demonstrates the mediating role of self‐protection mechanisms such as group identification and the perceived relevance of a comparison group.
Dopaminergic Suppression of Brain Deactivation Responses during Sequence Learning
Authors: Argyelan Miklos , Carbon Maren , Ghilardi Maria-Felice , Feigin Andrew , Mattis Paul , Tang Chengke , Dhawan Vijay , Eidelberg David
Published: October 2008

Cognitive processing is associated with deactivation of the default mode network. The presence of dopaminoceptive neurons in proximity to the medial prefrontal node of this network suggests that this neurotransmitter may modulate deactivation in this region. We therefore used positron emission tomography to measure cerebral blood flow in 15 Parkinson's disease (PD) patients while they performed a motor sequence learning task and a simple movement task. Scanning was conducted before and during intravenous levodopa infusion; the pace and extent of movement was controlled across tasks and treatment conditions. In normal and unmedicated PD patients, learning-related deactivation was present in the ventromedial prefrontal cortex (p< 0.001). This response was absent in the treated condition. Treatment-mediated changes in deactivation correlated with baseline performance (p< 0.002) and with theval158metcatechol-O-methyltransferase genotype. Our findings suggest that dopamine can influence prefrontal deactivation during learning, and that these changes are linked to baseline performance and genotype.
Stimulus Similarity-Contingent Neural Adaptation Can Be Time and Cortical Area Dependent
Authors: Verhoef Bram-Ernst , Kayaert Greet , Franko Edit , Vangeneugden Joris , Vogels Rufin
Published: October 2008

Repetition of a stimulus results in decreased responses in many cortical areas. This so-called adaptation or repetition suppression has been used in several human functional magnetic resonance imaging studies to deduce the stimulus selectivity of neuronal populations. We tested in macaque monkeys whether the degree of neural adaptation depends on the similarity between the adapter and test stimulus. To manipulate similarity, we varied stimulus size. We recorded the responses of single neurons to different-sized shapes in inferior temporal (IT) and prefrontal cortical (PFC) areas while the animals were engaged in a size or shape discrimination task. The degree of response adaptation in IT decreased with increasing size differences between the adapter and the test stimuli in both tasks, but the dependence of adaptation on the degree of similarity between the adapter and test stimuli was limited mainly to the early phase of the neural response in IT. PFC neurons showed only weak size-contingent repetition effects, despite strong size selectivity observed with the same stimuli. Thus, based on the repetition effects in PFC, one would have erroneously concluded that PFC shows weak or no size selectivity in such tasks. These findings are relevant for the interpretation of functional magnetic resonance adaptation data: they support the conjecture that the degree of adaptation scales with the similarity between adapter and test stimuli. However, they also show that the temporal evolution of adaptation during the course of the response, and differences in the way individual regions react to stimulus repetition, may complicate the inference of neuronal tuning from functional magnetic resonance adaptation.
Activity in the Medial Temporal Lobe Predicts Memory Strength, Whereas Activity in the Prefrontal Cortex Predicts Recollection
Authors: Kirwan C. Brock , Wixted John T. , Squire Larry R.
Published: October 2008

Functional magnetic resonance imaging studies of recognition memory have often been interpreted to mean that the hippocampus supports recollection and that the adjacent perirhinal cortex supports familiarity. Other work points out that these studies have confounded recollection and familiarity with strong and weak memories. In a source memory study, we used two novel approaches to data analysis that allowed item memory strength and source memory strength to be assessed independently. First, we identified regions in both hippocampus and perirhinal cortex in which activity varied as a function of subsequent item memory strength while source memory strength was held constant at chance levels. Second, we identified regions in prefrontal cortex in which activity varied as a function of subsequent source memory strength while item memory strength was held constant. These findings suggest that activity in the medial temporal lobe is predictive of subsequent memory strength, whereas activity in prefrontal cortex is predictive of subsequent recollection.
Charakterisierung von Hohlfasern für kompakte Infrarot-Gasmesszellen Characterization of Hollow Fibres for Compact Infrared Gas Measurement Cells
Authors: Hartwig Susanne , Lambrecht Armin
Published: October 2008

Die Nachweisempfindlichkeit von infrarotoptischen Gassensoren ist von der Wechselwirkungsstrecke zwischen Gas und Strahlung abhängig — d. h. eine Verkleinerung der Absorptionsstrecke bedeutet zugleich eine geringere Nachweisempfindlichkeit. Einer Miniaturisierung sind damit Grenzen gesetzt. Die Verwendung von gasdurchströmten Hohlfasern ist eine Möglichkeit, kompakte Gassensoren mit geringen Gasvolumina bei relativ langer Wegstrecke zu realisieren. Verschiedene Hohlfasertypen wurden charakterisiert und auf ihre Eignung als Gassensor untersucht. Simulation und experimentelle Ergebnisse zur Realisierung eines kompakten Alkoholsensors auf Hohlfaserbasis zeigen sehr gute Übereinstimmung.
Ellipsen- und Kreisdetektion zur Bestimmung der Orientierung von Stahl- und Glasfasern in Beton Detection of Ellipses and Circles to Determine the Orientation of Steel and Glass Fibres in Concrete
Authors: Lange Johannes , Rauscher Sabine , Benning Wilhelm , Hegger Josef
Published: October 2008

Die Detektion von Fasern im Beton wird mittels Bildverarbeitungsmethoden durch Kreis- und Ellipsenerkennung durchgeführt. Eine Herausforderung bei der Auswertung stellen neben der geringen Fasergröße die große Faseranzahl, Überlappungen, Berührungen, Formfehler sowie die Qualität der Bilder dar. Anhand der zufällig verteilten Stahlfasern oder der in Lastrichtung orientierten Glasfasern werden an grundlegend unterschiedlichen, aber ähnlich auszuwertenden Beispielen aus dem Bauwesen Methoden wie die Mathematische Morphologie, die Randomisierte Hough-Transformation und Nachverarbeitungsmethoden erläutert.
Freiheitsgradregularisierte Entfaltung von Messdaten aus AFM-Sondermodi DoF-Restricted Deconvolution of Measured Data from AFM Special Modes
Authors: Nestler Rico , Machleidt Torsten , Franke Karl-Heinz , Sparrer Erik
Published: October 2008

Seit geraumer Zeit werden durch Forschergruppen an verschiedenen Stellen Anstrengungen unternommen, bildhafte Messdaten von Rasterkraftmikroskopen (AFM) mit dem aus der Bildverarbeitung verfügbaren Methodenrepertoire zu verbessern. Im Fall der Potenzialmessung nach der Kelvin-Methode (KFM) bieten sich aufgrund der linearen Zusammenhänge bei der Datenentstehung sehr gute Voraussetzungen, um die prinzipbedingt geringere laterale Auflösung der KFM-Messdaten durch Entfaltung zu erhöhen. Im Beitrag wird in diesem Zusammenhang ein adaptives freiheitsgradbeschränktes Bildmodell zur Verfahrensregularisierung vorgestellt. Derartige Modelle wurden von den Autoren bereits erfolgreich im Bereich der Restauration astronomischer Himmelsüberwachungsaufnahmen eingesetzt.
Bildverarbeitung und Simulation in der statistisch optischen Oberflächenmesstechnik Image Processing and Simulation Methods for Statistic Optical Surface Measuring Techniques
Authors: Patzelt Stefan , Prekel Helmut , Horn Frank , Tausendfreund Andreas , Goch Gert
Published: October 2008

Streulichtbasierte Oberflächenmessverfahren eignen sich aufgrund der schnellen und berührungslosen Messdatenerfassung für den Einsatz in laufenden Fertigungsprozessen (in-prozess). Der Beitrag beschreibt verschiedene Streulicht-Messeffekte (Speckle-Elongation, Speckle-Intensitätsmodulation, Speckle-Bewegung) und deren Modellierung. Die resultierenden Laserstreulicht-Bilder werden digital verarbeitet und ausgewertet, um quantitative Informationen über das Werkstück (Position, Identifikation) oder die Oberflächenrauheit zu erhalten.
General Tilney's Timely Approach to the Improvement of the Estate in Jane Austen's Northanger Abbey
Authors: Kickel Katherine
Published: October 2008

Improvement practices and their critique are core features of the Austen milieu. In this essay, though, I argue that in Austen's Northanger Abbey (1818), General Tilney's reliance on clock time to manage his estate's operations indicates a relatively unexamined aspect of the debate. Thus Austen contrasts the leisure of Bath to the labor of Northanger in order to highlight the new economic challenges that the landed gentry face. General Tilney's time-discipline management style suggests his anxiety about his home's declining value and his insistence on regulating his family's emotional lives. It reflects his effort to recoup some of his diminishing economic and patriarchal authority. Ultimately redefining the very notion of gentry leisure, Northanger Abbey functions as a site where domestic labor, leisure, and etiquette are all subordinate to the same rigid, time-discipline decorum that the General uses to regulate his home's marketable operations (e.g., its pinery, hot-houses, and timber). Viewing the General's chronometric improvements as both inhospitable and oppressive, Catherine Moreland's preference for the relaxed but modest Woodston at the novel's end is, in part, a reaction to the General's timekeeping dictums and, finally, an important register of the emotional toll that the General's improvement practices have wrought.
Sanctify Our Suffering World with Tears: Transamerican Sentimentalism in Joaquín Murieta
Authors: Windell Maria A.
Published: October 2008

This essay explores the often-overlooked affective discourse that emerges from a close reading of the Mexican and European American women in the first Native American novel, John Rollin Ridge's sensational dime novel The Life and Adventures of Joaquín Murieta, the Celebrated California Bandit (1854). Through their investment in sentimental tropes such as the tearful scene, the angelic figure, and the untimely fainting fit, these women enact what I term a transamerican sentimental diplomacy that counters the attempt of the novel's men to define the United States via a nationalistic violence (the legacy of the U.S.-Mexican War). Through their tears, pleas, and actions, the women test the cultural and political milieu of the newly minted state of California. While the women's promotion of a peaceful paradigm for borderland interaction ultimately falls short, its undeniable presence is an important counterweight to the sensational violence in Joaquín Murieta that has thus far captivated critics.
Racial Duties: Toward a Pragmatist Ethic of Race in W. D. Howells's An Imperative Duty
Authors: Petrie Paul R.
Published: October 2008

William Dean Howells's 1891 novel of interracial marriage, An Imperative Duty, has recently received increasing critical attention because of its saturation with the language of contemporary scientific racism and its complex and apparently inconsistent approach to questions of race and identity. The novel's other major conceptual concern with questions of moral duty, clearly announced in its title, has generally been neglected in this discussion. This essay examines the crucial interplay between questions of race and ethics, arguing that Howells's novel undertakes an ethical critique of late-nineteenth-century scientific racism from a specifically Pragmatist philosophical perspective. Reasoning according to Pragmatist principles, and pursuing an inherently Pragmatist narrative form, the novel implicitly asks its readers to understand the “facts” of race in terms of their intersections with personal and social morality rather than in strict accord with the essentialist claims of ascendant nineteenth-century race theory. In its refusal of ontological absolutism and its embrace of an ethically pluralist and instrumentalist approach to questions of race, Howells's novel offers a Pragmatist challenge to the interlocking absolutisms of traditional ethics and contemporary scientific racism.
yellow and ebony Are the Responsible Genes for the Larval Color Mutants of the Silkworm Bombyx mori
Authors: Futahashi Ryo , Sato Jotaro , Meng Yan , Okamoto Shun , Daimon Takaaki , Yamamoto Kimiko , Suetsugu Yoshitaka , Narukawa Junko , Takahashi Hirokazu , Banno Yutaka , Katsuma Susumu , Shimada Toru , Mita Kazuei , Fujiwara Haruhiko
Published: October 2008

Many larval color mutants have been obtained in the silkworm Bombyx mori. Mapping of melanin-synthesis genes on the Bombyx linkage map revealed that yellow and ebony genes were located near the chocolate (ch) and sooty (so) loci, respectively. In the ch mutants, body color of neonate larvae and the body markings of elder instar larvae are reddish brown instead of normal black. Mutations at the so locus produce smoky larvae and black pupae. F2 linkage analyses showed that sequence polymorphisms of yellow and ebony genes perfectly cosegregated with the ch and so mutant phenotypes, respectively. Both yellow and ebony were expressed in the epidermis during the molting period when cuticular pigmentation occurred. The spatial expression pattern of yellow transcripts coincided with the larval black markings. In the ch mutants, nonsense mutations of the yellow gene were detected, whereas large deletions of the ebony ORF were detected in the so mutants. These results indicate that yellow and ebony are the responsible genes for the ch and so loci, respectively. Our findings suggest that Yellow promotes melanization, whereas Ebony inhibits melanization in Lepidoptera and that melanin-synthesis enzymes play a critical role in the lepidopteran larval color pattern.
Utilization of a Rapid DNA-Based Assay for Molecular Verification of Channel Catfish, Blue Catfish, F1 Hybrids, and Backcross Offspring at Several Life Stages
Authors: Waldbieser Geoffrey C , Bosworth Brian G
Published: October 2008

The F1 hybrid offspring of female channel catfish Ictalurus punctatus × male blue catfish I. furcatus contain many desirable traits for commercial production, such as enhanced growth and increased survivability. Hybrids can be produced through pond spawning (although at a low efficiency), but hybrid catfish cannot always be readily distinguished from channel catfish, especially at early life stages. The present research was designed to produce a rapid DNA-based test for the identification of hybrid catfish. Channel catfish and blue catfish genomic regions were amplified by polymerase chain reaction (PCR)using common primers for the follistatin (Fst) and hepcidin antimicrobial protein (Hamp) genes, and fragment length polymorphisms between the two species caused by ancestral insertions and deletions were resolved by agarose electrophoresis. The Fst amplicons were 348 and 399 base pairs (bp), while the Hamp amplicons were 222 and 262 bp from channel catfish and blue catfish, respectively. The mitochondrial cytochrome c oxidase 1 (Mtco1) gene was also differentially amplified from each species by using species-specific primers to enable determination of the maternal parent species. The DNA preparation technique provided sufficient genomic DNA to test several life stages. The PCR products were successfully amplified from genomic DNA isolated from embryos at 1, 2, or 5 d after fertilization; from fry 2 d after hatching; from the blood and barbels of juveniles and adults; and from fresh, frozen, and cooked fillet samples. The results from this assay were available as soon as 24 h after receipt of sample. This assay will be useful for management of hybrid populations and postharvest detection of hybrid catfish products.
Farm-Level Economic Impacts of Bolbophorus Infections of Channel Catfish
Authors: Wise David J , Hanson Terrill R , Tucker Craig S
Published: October 2008

The prevalence of infections by trematodes Bolbophorus sp. in populations of pond-raised channel catfish Ictalurus punctatus was determined by sampling 64 ponds on a farm in northwestern Mississippi. Of the 40 food fish ponds sampled, 23 (58%) contained trematode-infected fish; 7 pond populations were categorized as having light infections (1–33% infection rates), 5 as having moderate infections (34–66% infection rates), and 11 as having severe infections (≥67% infection rates). Only 3 of the 24 fingerling ponds contained fish infected with Bolbophorus trematodes, and the infection rates were light. Feed consumption and estimated fish production in food fish ponds differed significantly among the four categories of within-population infection rate, and feed consumption and fish production decreased as infection rates increased. Relative to the production in uninfected populations, estimated fish production was reduced by 14, 35, and 40% in populations with light, moderate, and severe infections, respectively. Estimated catfish receipts and actual feed costs were used in a generalized enterprise budget format to calculate income above variable costs and net returns for each infection-rate category. The estimated net return to land for uninfected food fish populations was US$1,526/ha. Lower fish production in infected populations resulted in decreased incomes. The net return to land was $592/ha for the light-infection-rate category, a 61% reduction from that achieved in uninfected populations. Production receipts from food fish ponds in the moderate- and severe-infection-rate categories did not cover the costs of production, and the net returns to land were −$781/ha for moderately infected populations and −$1,123/ha for severely infected populations. This study shows that trematode infections reduce fish production and farm economic returns and that the impacts increase as infection rates increase. However, even light and moderate infections—which may go unnoticed by farmers—can seriously affect farm profitability.
Production Responses of Channel Catfish to Minimum Daily Dissolved Oxygen Concentrations in Earthen Ponds
Authors: Torrans Eugene L
Published: October 2008

This study determined the effects of the minimum daily dissolved oxygen (DO) concentration on the production parameters of channel catfish Ictalurus punctatus in earthen ponds. Fifteen 1-acre ponds (five ponds per treatment) were managed as high-oxygen (minimum DO concentrations averaging 4.37 ppm or 54% air saturation from June through September), medium-oxygen (minimum DO concentrations averaging 2.68 ppm or 33.2% air saturation), or low-oxygen treatments (minimum DO concentrations averaging 2.32 ppm or 28.7% air saturation) using one 5-hp electric paddlewheel aerator per pond. Fish in the high-, medium-, and low-oxygen treatment ponds were fed a mean total of 14,008, 13,212, and 12,607 lb/acre of 28%-protein floating feed, respectively. Net production paralleled the total amount of feed fed, averaging 5,772, 5,278, and 5,113 lb/acre in the high-, medium-, and low-oxygen treatments, respectively. Individual fish weight at harvest also showed a similar trend, averaging 1.37, 1.33, and 1.30 lb in the high-, medium-, and low-oxygen treatments, respectively. No visible stress responses were observed in any ponds during this study. Total aeration averaged 5,245, 2,518, and 1,337 hp-h/acre in the high-, medium-, and low-oxygen treatments, respectively. Treatments with higher minimum DO concentrations had significantly higher nitrite-nitrogen, suspended solids, chlorophyll a, and pH and lower Secchi disk visibility, alkalinity, and hardness; however, no water quality parameters exceeded the normal acceptable range for channel catfish. While the cost of electricity must be considered, maintaining a minimum daily DO concentration of 2.3–2.5 ppm is suggested as a compromise between maximizing both the amount of feed fed and fish production while minimizing aeration costs.
Harvesting and Processing Zooplankton for Use as Supplemental Channel Catfish Fry Feed
Authors: Mischke Charles C , Wise David J
Published: October 2008

We present the methods that we used to capture and dry large zooplankton from ponds to feed to channel catfish Ictalurus punctatus fry. Using a submersible pump and canister filter, we were able to capture about 1.0 kg (wet weight; 200 g in terms of dry weight) of zooplankton from well-fertilized ponds over 24-h trapping periods. This was a practical method for obtaining the large zooplankton that catfish fry prefer. Fish culturists may be able to use this method to harvest zooplankton throughout the year and store dried zooplankton for the hatchery season. The drying process may also be useful for processing and storing small zooplankton for the culture of other species of fish. The cost was about US$200 for the submersible pump, $200 for the canister and filter, and $40 for the food dehydrator.
Salmonid Fry Stranding Mortality Associated with Daily Water Level Fluctuations in Trail Bridge Reservoir, Oregon
Authors: Bell Ethan , Kramer Sharon , Zajanc David , Aspittle Jennifer
Published: October 2008

Little information exists on how reservoir fluctuations affect stranding risk for early life stages of salmonids. This study focuses on the effects of hydroelectric-related water level fluctuations in Trail Bridge Reservoir, Oregon, where salmonids, including the bull trout Salvelinus confluentus and spring Chinook salmon Oncorhynchus tshawytscha, which are listed under the U.S. Endangered Species Act, commonly occur. A distance-from-line sampling design was employed using permanently established transects to estimate the magnitude of stranding of juvenile salmonids during 30 surveys over 3 months in spring 2006. All stranded fish observed during field surveys were mapped onto spatially rectified, low-elevation aerial photographs to assess the patterns in stranding. Most fish were stranded in habitats with a slope of less than 6%, typically in interstitial spaces among cobbles, and in “potholes.” Fish were stranded in similar numbers following small or large fluctuations, and no relationship was apparent between the range in fluctuation and the number of stranded fish or between the average rate of water surface decline and the number of stranded fish. Based on extrapolation, we estimated that 808 spring Chinook salmon fry and 444 brook trout S. fontinalis fry were stranded in Trail Bridge Reservoir during spring 2006. One dead bull trout was observed, but based on the abrasions, open wounds, and signs of infection that we observed, it died prior to the decline in reservoir elevation. Our findings suggest that stranding in this reservoir could be reduced (while retaining the hydroelectric function of the reservoir) by restricting fluctuations to specific elevations during vulnerable fish migration periods, increasing the slope of areas identified as having a high stranding risk, or both.
Age, Growth, and Maturity of Chub Mackerel off Korea
Authors: Hwang Sun-Do , Kim Jin-Yeong , Lee Tae-Won
Published: October 2008

The age, growth, and maturity of chub mackerel Scomber japonicus were determined by otolith analysis and gonad observation. Fish were subsampled monthly from Korean offshore commercial catches between September 1994 and August 1995. Gonad observations suggest that chub mackerel spawned mainly in May. The size at 50% maturity was calculated to be 28.8 cm fork length at an age of 1.01 years. Annuli in otoliths can be distinguished from false annuli because the true annuli were formed continuously all around the sagittal plane as distinct dark marks. They were mainly formed in May, coinciding with the main spawning season. Chub mackerel grew to over 20 cm by December and attained up to 28 cm in 1 year. Thereafter, the growth rate slowed down. The age composition was 40.2, 42.5, 15.4, 1.7, and 0.1% for age-groups 0–4, respectively. Using three different approaches, the von Bertalanffy growth parameter was estimated to be between 1.51 and 2.19 and the maximum length between 34.1 and 34.6 cm. The growth coefficient was higher than that in previous studies because of differences in aging technique and the inclusion of juvenile data in one of the approaches. Over 40% of the immature fish of age 0 were included in the current harvest owing to the catch of juveniles in summer and strong fishing intensity in autumn. We recommend regulating catch size during the fast-growing stage to allow the juveniles to grow and reducing the fishing efforts during autumn to conserve the spawning biomass.
Hybridization between Spring- and Fall-Run Chinook Salmon Returning to the Trinity River, California
Authors: Kinziger Andrew P. , Loudenslager Eric J. , Hankin David G. , Anderson Eric C. , Garza John Carlos
Published: October 2008

It is believed that spring- and fall-run Chinook salmon Oncorhynchus tshawytscha returning to the Trinity River, California, were once reproductively isolated such that spring-run fish spawned upstream in early fall, whereas fall-run fish spawned further downstream in late fall. However, construction of Lewiston Dam and the Trinity River Hatchery (TRH) in 1964 resulted in extensive compression of spawning habitat and the potential for inadvertent interbreeding of the two runs. In this study, we used genetic methods and developed a simulation procedure to assess the degree to which spring- and fall-run Chinook salmon returning to TRH were genetically distinct and to determine the extent of hybridization between the runs. Approximately 40 adults/week were sampled throughout the 1992 spawning season, and all individuals were genotyped at 29 polymorphic loci. Analysis with the program STRUCTURE (Pritchard et al. 2000) supported the hypothesis that the data represented two subpopulations. Individual assignments using STRUCTURE indicated that the spring- and fall-run proportions among fish sampled at TRH gradually shifted through time; weekly samples taken earlier in the spawning season had a higher proportion of presumptive spring run, and those taken later in the season had a higher proportion of presumptive fall run. Comparison of observed results with simulated data suggested the occurrence of hybridization between spring- and fall-run Chinook salmon returning to TRH, particularly during the transition or overlap period between fish from the two phenotypic groups. The extent to which hybridization was caused by hatchery operations or occurred prior to Lewiston Dam construction was unclear. Additional hybridization analyses of samples collected prior to dam and hatchery construction would be needed to evaluate the impacts of these facilities on hybridization. Further, studies of contemporary populations are needed to determine whether two runs currently exist despite the marked hybridization that was documented herein for the 1992 return year.
Assessment of Stocking Success of Walleye in the Eleven Point River, Arkansas
Authors: Henry Sam D. , Barkley Sam W. , Koppelman Jeffrey B. , Johnson Ronald L.
Published: October 2008

Few studies have evaluated stocking programs for walleye Sander vitreus in the southern United States; this may be the first such study for a southern river. The Eleven Point River, located in southeastern Missouri and northeastern Arkansas, has been supplementally stocked by the Arkansas Game and Fish Commission (AGFC) and the Missouri Department of Conservation (MDC) for many years. Our goals were (1) to assess the contribution of walleye fingerlings in the Arkansas section (∼60 km) of the Eleven Point River using the recapture rates of marked walleyes and (2) to assess the reproductive contribution of stocked walleyes using genetic tracking of mitochondrial DNA markers. All of the walleyes stocked by the AGFC during 1999–2002 were freeze-branded; these fish possess the A haplotype, which is the most common one rangewide. Wild fish and those stocked by the MDC in the Missouri portion of the Eleven Point River possess the native C haplotype of the Black River system, which includes the Eleven Point River. Electrofishing samples revealed that the stocked fish captured in Arkansas from 2002 to 2004 were almost evenly divided by cohort; 52% possessed the A marker and 43% the C marker. Forty-three percent of the walleyes older than age 3 (and therefore present in the river before the release of the freeze-branded fish) had the A marker. Walleyes originating from the AGFC-source fish had significantly greater relative weights than did native-spawned walleyes and fish released in Missouri. In addition, haplotype-A walleyes had significantly greater relative weights than haplotype-C walleyes. The high relative weights of the sampled fish throughout the study suggests a lack of intraspecific competition as a result of stocking.
A Proposed Standard Weight Equation for Blue Suckers
Authors: Neely Ben C. , Hamel Martin J. , Steffensen Kirk D.
Published: October 2008

Length and weight data were obtained from 46 populations of blue suckers Cycleptus elongatus (N = 8,811 fish) across the species' geographic distribution to develop a standard weight (Ws) equation. The Ws equation was derived using the empirical percentile technique applied to fish between 240 and 809 mm total length (TL). We calculated a quadratic model and a linear model to derive Ws. The proposed 75th-percentile quadratic equation (metric units) is log10  Ws = −2.980 + 0.977 log10TL + 0.461(log10TL)2, where Ws is expressed in grams and TL is expressed in millimeters. The proposed English-equivalent 75th-percentile quadratic equation is log10  Ws = −3.354 + 2.273 log10TL + 0.461(log10TL)2, where Ws is expressed in pounds and TL is expressed in inches. The 75th-percentile linear equation (metric units) is log10  Ws = −6.301 + 3.456 log10TL, and the proposed English equivalent is log10  Ws = −4.104 + 3.456 log10TL.
Harvest Efficiency of Bloodworms on Maine Mudflats
Authors: Sypitkowski Eben , Ambrose William G. , Bohlen Curtis , Warren Joseph
Published: October 2008

Efficiency of diggers of varying experience levels in harvesting bloodworms Glycera dibranchiata was documented during multiple tides on several intertidal flats in midcoast Maine. Individually coded-wire-tagged bloodworms were seeded in 20-m2 plots and harvested by professional diggers after allowing ample time for bloodworms to burrow. To ensure that bloodworms reached depths similar to those of naturally occurring individuals, we measured the depths at which tagged and naturally occurring bloodworms were found in preliminary experiments. Using the same methods but without measuring bloodworm depths, we performed efficiency experiments. The rate of tag loss was also determined. Measured efficiency of diggers ranged from 26% to 75% and averaged about 45%. Retrieved bloodworms were marginally larger than seeded bloodworms. Diggers generally dug deeper than bloodworms burrowed, and all seeded bloodworms reached depths similar to those of naturally occurring bloodworms within 1 h. The relatively low observed harvest efficiency and the bias towards larger individuals may contribute to the long-term sustainability of the bloodworm fishery.
Use of Parentage Analysis to Determine Reproductive Success of Hatchery-Origin Spring Chinook Salmon Outplanted into Shitike Creek, Oregon
Authors: Baumsteiger Jason , Hand David M. , Olson Douglas E. , Spateholts Robert , FitzGerald Geoff , Ardren William R.
Published: October 2008

Removal of fish passage barriers provides Pacific salmon Oncorhynchus spp. and steelhead O. mykiss the opportunity to recolonize previously accessible habitat, though the time scale of natural recolonization may not be sufficient for management or conservation goals. One strategy for accelerating recolonization is to outplant hatchery-origin adults into newly restored habitats. In this paper, we describe how genetic parentage analysis was used to determine the reproductive success of adult stream-type spring Chinook salmon O. tshawytscha taken from two localized hatchery stocks and outplanted into a stream. We defined reproductive success as the production of migratory juveniles. In 2002 and 2003, 83 and 265 adult hatchery salmon, respectively, were outplanted into Shitike Creek, Oregon, a tributary to the Deschutes River. Using 11 microsatellite markers, 799 and 827 migratory juveniles from the two brood years were genotyped and matched back to potential outplanted parents using genetic parentage analyses. Successful spawning of outplant–outplant, outplant–wild, and wild–wild fish occurred in Shitike Creek in both years. Adults outplanted in 2002 showed far fewer matches (18%) to sampled juveniles than those from 2003 (88%). Additionally, only 1% of juveniles had both parents identified as outplants in 2002, compared with almost 61% in 2003. Differences in the number of females outplanted each year appeared to account for the differential productivity. The number of offspring attributed to an individual outplant was variable, ranging from 1 to more than 10. Multiple outplant × outplant matings were identified for each sex as males mated with up to seven females and females mated with up to four males. This study shows that, under the right conditions, outplanted adult hatchery fish taken from localized hatchery stocks can contribute to the overall juvenile production in a natural stream.
Using Conventional Analysis in Parallel with Geographical Information Systems Techniques to Examine the Distribution of Brown Shrimp in the Mississippi Sound
Authors: Riedel Ralf , Perry Harriet , Warren James , Criss Alan , Devender Thomas
Published: October 2008

A geographical information systems technique for visualizing spatial data was used in conjunction with standard analytical procedures to examine the size-specific distribution of brown shrimp Farfantepenaeus aztecus in nearshore nursery areas and open waters of the Mississippi Sound. Brown shrimp abundance was assessed during 2000, 2001, and 2002 by means of an otter trawl along 10 transects consisting of three stations each. The number of brown shrimp, together with the dissolved oxygen, temperature, and salinity values, were collected at each sampling station. A decreasing trend in salinity was observed from east to west. The highest salinities were measured in 2000. No temporal patterns in dissolved oxygen or temperature were apparent. Brown shrimp showed the highest abundances in western Mississippi Sound, an area adjoining the extensive marshes of St. Tammany and St. Bernard parishes in Louisiana. The average size of the brown shrimp in the western sound was smaller than that of the brown shrimp in other areas, indicating continued recruitment in the former area.
Variabilidade e correlação espacial de propriedades físicas de solo sob plantio direto e preparo convencional
Authors: Schaffrath Valter Roberto , Tormena Cássio Antônio , Fidalski Jonez , Gonçalves Antônio Carlos Andrade
Published: October 2008

Os sistemas de manejo do solo influenciam a distribuição espacial das propriedades físicas do solo. Os objetivos deste estudo foram verificar a dependência e a correlação espacial de algumas propriedades físicas do solo por meio do ajuste de dados aos semivariogramas simples e cruzados num Latossolo Vermelho distroférrico, sob plantio direto e preparo convencional, no município de Campo Mourão, Estado do Paraná. Em abril de 2004, realizou-se a amostragem de solo e retiraram-se 128 amostras de solo indeformadas, em malha de 3,0 x 5,0 m, no terço médio da camada de 0-0,15 m de profundidade. Foram determinadas as seguintes propriedades físicas do solo: densidade do solo, macroporosidade, microporosidade, porosidade total, e o conteúdo de água do solo na tensão de 100 hPa ou equivalente à capacidade de campo. Essas propriedades físicas do solo apresentaram semivariogramas simples com maior variabilidade espacial e menor alcance no plantio direto do que no preparo convencional. Contrariamente, os semivariogramas cruzados entre a densidade do solo com a porosidade total ou a capacidade de campo mostraram correlação espacial com menor variabilidade espacial e maior alcance no plantio direto, comparado ao preparo convencional. Os semivariogramas cruzados evidenciaram que a densidade do solo determinou as correlações espaciais com as outras propriedades físicas nos dois sistemas de manejo do solo.
Crescimento de milheto e guandu, desempenho de plantas cítricas e propriedades físicas do solo escarificado em um pomar
Authors: Bordin Ivan , Neves Carmen Silvia Vieira Janeiro , Francio Filho Pedro , Preti Edilene Aparecida , Cardoso Carina
Published: October 2008

Escarificação do solo e plantas de cobertura em pomares podem ser utilizados para melhorar as condições físicas do solo. Este trabalho teve como objetivo avaliar a influência da escarificação no crescimento de adubos verdes, no desempenho das árvores e em propriedades físicas de um Latossolo Vermelho distroférrico, num pomar cítrico com histórico de compactação. Foi realizada uma escarificação à profundidade de 0,30 m, seguida por três tipos de plantas de cobertura: vegetação espontânea, guandu (Cajanus cajan) e milheto (Pennisetum americanum). O delineamento experimental utilizado foi o inteiramente aleatorizado, num fatorial 2 x 3 (escarificado e não-escarificado e três plantas de cobertura do solo). Para as coberturas do solo, foi avaliada a fitomassa da parte aérea e abertas trincheiras para avaliação do crescimento das raízes. As plantas cítricas foram avaliadas com relação a seu crescimento e produção. Os atributos físicos do solo foram determinados em três locais (copa, rodado e entrelinha) e quatro profundidades (0-0,1; 0,1-0,2; 0,2-0,3; e 0,3-0,4 m). A fitomassa da parte aérea do guandu e a do milheto aumentaram com a escarificação do solo. O crescimento do sistema radicular do milheto foi maior do que o do guandu no manejo escarificado e igual ao deste no manejo não-escarificado. O crescimento e a produção das plantas cítricas não foram influenciados pelos tratamentos. Houve aumento da macroporosidade do solo e redução da densidade e da resistência do solo à penetração com a escarificação do solo.
Dispersão de amostras de latossolo vermelho eutroférrico influenciadas por pré-tratamento para oxidação da matéria orgânica e pelo tipo de agitação mecânica
Authors: Tavares-Filho João , Magalhães Francis Stefano de
Published: October 2008

A dispersão de amostras de Latossolos oxídicos pode ser mais difícil devido a microagregados de alta estabilidade, que nem sempre são totalmente desfeitos pela dispersão química e mecânica. A combinação de métodos químicos e mecânicos associados ao pré-tratamento da amostra é importante para se obter completa dispersão das partículas do solo e mantê-la estável durante toda a marcha analítica. Diante do exposto, objetivou-se avaliar a eficiência da dispersão mecânica (agitação lenta com agitador orbital de mesa - 30 rpm por 16 h, na presença de abrasivo, e agitação rápida com agitadores do tipo coqueteleira - 1.200 rpm por 20 min) e química com NaOH 1N, associada ao pré-tratamento para eliminação da matéria orgânica, independentemente de seu teor na amostra de solo na realização da análise granulométrica utilizada como método de rotina. Para as análises, foram coletadas com trado holandês, em uma área de Latossolo Vermelho eutroférrico, 50 amostras de forma inteiramente casualizada, nas profundidades de 0-0,20 e de 1,15-1,25 m; cada amostra representou uma repetição. Foi possível concluir que: sempre ocorreu maior dispersão das amostras analisadas quando se fez o pré-tratamento para oxidação da MO; o processo de agitação lenta, em relação ao de agitação rápida, é sempre mais eficiente na dispersão das amostras de solo; e o tratamento que utilizou pré-tratamento para eliminação da MO e dispersão mecânica com agitação lenta por 16 h e 30 g de areia grossa como abrasivo foi mais eficiente na dispersão das amostras estudadas, tanto para as amostras coletadas entre 0 e 0,20 m como para as coletadas na profundidade de 1,15-1,25 m.
Fracionamento químico e físico do carbono orgânico total em um solo de mata submetido a diferentes usos
Authors: Barreto Arlete Côrtes , Freire Maria Betania Galvão dos Santos , Nacif Paulo Gabriel Soledade , Araújo Quintino Reis , Freire Fernando José , Inácio Euzelina dos Santos Borges
Published: October 2008

A matéria orgânica é um importante indicador da qualidade do solo, pois está relacionada com diversas propriedades químicas, físicas e biológicas, sendo importante o conhecimento do teor de C orgânico total (COT), bem como de suas frações. Com base nisso, realizou-se esta pesquisa objetivando caracterizar e quantificar os estoques de COT e suas frações como indicadores da qualidade de um solo, submetido a diferentes usos: (1) Mata Atlântica, (2) Cacau (Theobroma cacao) e (3) Pastagem (Brachiaria decumbens), em uma microbacia no sul da Bahia. Para cada uso, coletaram-se amostras nas profundidades de 0-10 e 10-20 cm e procedeu-se à caracterização química e física do solo, à determinação do COT e ao seu fracionamento químico e físico. O teor de COT não diferiu entre os diferentes usos do solo nas duas profundidades estudadas. A percentagem de C humificado e nas frações de ácidos fúlvicos e humina foi maior na pastagem, na camada de 0-10 cm. Houve menor percentagem de C não-humificado nos sistemas cacau e pastagem, e maior relação C:N no sistema pastagem na camada de 10-20 cm. O sistema cacau promoveu aumento na quantidade de C orgânico na fração leve na camada de 10-20 cm. A substituição da mata pelo cultivo do cacau no sistema cabruca (sub-bosque) ou pela pastagem não alterou os teores de COT e de suas frações na área estudada.
Produtividade e acúmulo de potássio na soja em função da antecipação da adubação potássica no sistema plantio direto
Authors: Foloni José Salvador Simoneti , Rosolem Ciro Antonio
Published: October 2008

A aplicação antecipada de fertilizante potássico no cultivo de espécies de cobertura no sistema plantio direto (SPD) pode ser vantajosa para a lavoura comercial. O objetivo deste trabalho foi avaliar a produtividade de grãos e a acumulação de K na soja em função da aplicação antecipada de fertilizante potássico na instalação do milheto em relação com o K aplicado na semeadura da soja subseqüente no SPD. O experimento foi realizado na FCA-Unesp em Botucatu-SP, nas safras 2000/2001, 2001/2002 e 2002/2003. Utilizou-se um Latossolo Vermelho distroférrico de textura média, que estava sendo cultivado com soja e aveia-preta no SPD, por dois anos antes da instalação do experimento. O milheto (Pennisetum glaucum) foi semeado em setembro sobre a palhada de aveia-preta (Avena strigosa), e a soja (Glycine max) na primeira quinzena de dezembro, nos três anos agrícolas. Utilizou-se o delineamento experimental em blocos ao acaso no esquema fatorial 4 x 4, com quatro repetições, com 0, 30, 60 e 90 kg ha-1 de K2O no milheto, combinados com 0, 30, 60 e 90 kg ha-1 de K2O na soja. Coletaram-se plantas de soja aos 25, 50, 75 e 100 dias após a emergência, e os grãos no final do ciclo, para a determinação do acúmulo de K e da produtividade. A antecipação de 60 a 90 kg ha-1 de K2O na semeadura do milheto não comprometeu o acúmulo de K na lavoura de soja. As máximas produtividades de soja foram alcançadas no primeiro e segundo ano com doses de 85 a 90 kg ha-1 de K2O, que poderiam ser antecipadas totalmente na semeadura da gramínea de cobertura. A aplicação antecipada de KCl na semeadura do milheto minimizou a exportação de K pela colheita de grãos de soja.