bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Two PCR-Based Human Papillomavirus Genotyping Methods
Authors: Castle Philip E. , Porras Carolina , Quint Wim G. , Rodriguez Ana Cecilia , Schiffman Mark , Gravitt Patti E. , González Paula , Katki Hormuzd A. , Silva Sandra , Freer Enrique , Van Doorn Leen-Jan , Jiménez Silvia , Herrero Rolando , Hildesheim Allan ,   for the CVT Group
Published: August 2008

We compared two consensus primer PCR human papillomavirus (HPV) genotyping methods for the detection of individual HPV genotypes and carcinogenic HPV genotypes as a group, using a stratified sample of enrollment cervical specimens from sexually active women participating in the NCI/Costa Rica HPV16/18 Vaccine Efficacy Trial. For the SPF
10
method, DNA was extracted from 0.1% of the cervical specimen by using a MagNA Pure LC instrument, a 65-bp region of the HPV L1 gene was targeted for PCR amplification by using SPF
10
primers, and 25 genotypes were detected by reverse-line blot hybridization of the amplicons. For the Linear Array (LA) method, DNA was extracted from 0.5% of the cervical specimen by using an MDx robot, a 450-bp region of the HPV L1 gene was targeted for PCR amplification by using PGMY09/11 L1 primers, and 37 genotypes were detected by reverse-line blot hybridization of the amplicons. Specimens (
n
= 1,427) for testing by the LA method were randomly selected from strata defined on the basis of enrollment test results from the SPF
10
method, cytology, and Hybrid Capture 2. LA results were extrapolated to the trial cohort (
n
= 5,659). The LA and SPF
10
methods detected 21 genotypes in common; HPV16, -18, -31, -33, -35, -39, -45, -51, -52, -56, -58, -59, -66, -68, and -73 were considered the carcinogenic HPV genotypes. There was no difference in the overall results for grouped detection of carcinogenic HPV by the SPF
10
and LA methods (35.3% versus 35.9%, respectively;
P
= 0.5), with a 91.8% overall agreement and a kappa value of 0.82. In comparisons of individual HPV genotypes, the LA method detected significantly more HPV16, HPV18, HPV39, HPV58, HPV59, HPV66, and HPV68/73 and less HPV31 and HPV52 than the SPF
10
method; inclusion of genotype-specific testing for HPV16 and HPV18 for those specimens testing positive for HPV by the SPF
10
method but for which no individual HPV genotype was detected abrogated any differences between the LA and SPF
10
methods. The LA method detected more carcinogenic-HPV-genotype infections per specimen than the SPF
10
method (
P
< 0.001). In conclusion, the LA method and the SPF
10
method with HPV16 and HPV18 genotype-specific detection among ungenotyped HPV-positive specimens were comparable for detection of HPV16 and HPV18, the two HPV genotypes targeted by current prophylactic HPV vaccines. Both approaches are suitable for monitoring the impact of HPV16/18 vaccines in clinical trials.
Haemorrhagic transformation in acute ischaemic stroke following thrombolysis therapy: classification, pathogenesis and risk factors
Authors: Thanvi B R , Treadwell S , Robinson T
Published: August 2008

Haemorrhagic transformation of cerebral infarction is a common and potentially serious occurrence following acute ischaemic stroke. Though often a “natural” evolution, particularly in acute embolic stroke, haemorrhagic transformation is a prime concern with the use of thrombolytic therapy for acute ischaemic stroke. The severity of haemorrhage may range from a few petechiae to a large haematoma with space occupying effect. The pathogenesis of haemorrhagic transformation is not well established, though ischaemia and reperfusion have been proposed to cause disruption of the blood–brain barrier leading to extravasation of blood. At the molecular level, free radicals and proteolotic enzymes (metalloproteinases) may cause tissue injury. Studies have identified a number of clinical, radiological, and biochemical parameters that may serve as potential predictors of increased risk for haemorrhagic transformation. The knowledge of these factors may help in improving patient selection for thrombolytic therapy.
The inter-operator variability in measuring waist circumference and its potential impact on the diagnosis of the metabolic syndrome
Authors: Panoulas V F , Ahmad N , Fazal A A , Kassamali R H , Nightingale P , Kitas G D , Labib M
Published: August 2008

Objective

The International Diabetes Federation (IDF) has proposed ethnicity specific cut-off values for waist circumference, as an essential criterion for the diagnosis of the metabolic syndrome (MetS). However, before introducing waist circumference measurement as part of the clinical examination, or an obligatory criterion for MetS, it is important to ensure that the measurement is reliable and reproducible.

Study design

The inter- and intra-operator variability in measuring waist circumference was assessed in a preliminary study of 10 health professionals and the inter-operator variability in clinical practice was assessed in a study of 102 patients. Repeated measures analysis of variance (ANOVA) was used to assess the significance of the inter- and intra-operator variability.

Results

Intra-operator variability was not found to be significant in the preliminary study (F = 0.15, p = 0.764). However, the inter-operator variability was significant in both studies (preliminary: F = 4.16, p<0.001, clinical practice study: F = 14.06, p<0.001). In clinical practice, this could lead to disagreement among operators regarding the presence of central obesity in 9% of the patients. After giving written instructions on how to measure waist circumference, the coefficient of variation was not significantly altered (p = 0.202) but the inter-operator variability lost significance (F = 2.34, p = 0.11), suggesting a reduction in systematic error.

Conclusions

Measuring waist circumference is subject to significant inter-operator variability and could potentially lead to misclassifying patients as having the MetS, or not. Better training of health professionals on how to measure waist circumference properly is needed in order to ensure that patients are not misclassified and that international comparisons of the prevalence of the MetS are reliable.
Effect of secondary growth on the conformation and permeability of the endodermis of broad bean (Vicia faba), sunflower (Helianthus annuus), and garden balsam (Impatiens balsamina)
Authors: Weerdenburg Carol Ann , Peterson Carol A.
Published: August 2008

A root undergoing secondary growth exhibits massive girth increases owing to the activity of the vascular cambium. To determine the effects of this growth on endodermal structure and function, cleared cross sections from areas of primary and secondary growth in broad bean, sunflower, and garden balsam roots were examined. Casparian bands were detected by staining the sections with Chelidonium majus root extract and viewing them with ultraviolet (uv) light using an epifluorescence microscope. Endodermal diameter and numbers of endodermal cells increased dramatically in the area of secondary growth. The distance spanned by the Casparian band (i.e., the tangential width of the endodermal cells) between radial walls also increased except in sunflower. The permeability of the endodermis to an apoplastic fluorescent dye in roots undergoing secondary growth was tested by treatment with Calcofluor white M2R. In all species examined, the Casparian band continued to function as an effective apoplastic barrier during early stages of secondary growth despite the increase in endodermal cell size and number. Eventual decortication with concurrent disruption of the endodermis resulted in massive penetration of Calcofluor white M2R into the xylem.
A revision of the genus Trichoderma. I. Section Longibrachiatum sect. nov.
Authors: Bissett J.
Published: August 2008

Variation in strains assignable to the Trichoderma longibrachiatum Rifai and T. pseudokoningii Rifai species aggregates was studied. Morphological similarities allow their assignment to one section in Trichoderma, sect. Longibrachiatum, characterized and differentiated from other species of Trichoderma by the sparsely branched conidiophores having a high proportion of solitary phialides. Cultural characteristics include very rapid growth and the production of characteristic bright yellow-green pigments visible in the colony reverse. Two new species are described in the section: Trichoderma citrinoviride Bissett has ellipsoidal conidia smaller than in the other species and conidiophore branching similar to that in T. pseudokoningii; Trichoderma atroviride Bissett has relatively large, ellipsoidal conidia and a very sparse branching system with curved or sinuous conidiophores, branches, and phialides.
The hydraulic architecture of eastern hemlock (Tsuga canadensis)
Authors: Ewers Frank W. , Zimmermann Martin H.
Published: August 2008

Leaf specific conductivities (LSCs, hydraulic conductivity per gram dry weight of supplied leaves), Huber values (transverse xylem area per gram dry weight of supplied leaves), specific conductivities (hydraulic conductivity per unit transverse xylem area), and tracheid diameters were measured throughout the trunk and erown of 9- to 96-year-old trees of Tsuga canadensis (L.) Carr. By definition, LSC = Huber value × specific conductivity. Specific conductivity is controlled by wood anatomical features, especially tracheid diameter. LSCs, which indicate the relative water supply to different plant parts, decrease acropetally but are higher in the trunk than in branches and are particularly low in second-order branches and at branch insertions. The differential water supply is due to larger Huber values in the leader and to particularly narrow tracheids at branch junctions. In addition, as trunks enlarge they produce wider tracheids, resulting in greater specific conductivity than in supported branches. Based on comparison with results for Abies balsamea, the degree of "hydraulic dominance" in the younger parts of conifers is controlled by the Huber value and may be related to the degree of apical control.
Le phénotype moyen des unités systématiques de la sous-section “Urinaria” du genre Phyllanthus. Les formes adaptatives et la notion d'écotype
Authors: Rossignol L. , Rossignol M. , Haïcour R. , Piquepaille P.
Published: August 2008

In this article, we analyse the results of the study of morphological characteristics observed in various taxons of the urinaria complex regrouped by the authors under the Urinariae subsection of the Linné Urinaria section. By comparing these results with a taxonomic classification based on a previous genetic study, the qualitative analysis has shown that the discriminating characteristics in systematic units of rank equal to or higher than the species mainly belong to the reproductive apparatus. The vegetative apparatus provides only infraspecific characteristics, with the exception of pilosity and the colour of leaves common to the subsection. The quantitative analysis has shown that (i) practically all the information (90–95%) is provided by the plagiotropic branches (their length, the length of their internodes; dimension and number of their leaves) and by the pollen (dimensions); (ii) the various taxons of the subsection exhibit a wide polymorphism but, within the same population, the individuals are rather homogeneous; (iii) there exist "forms" within "lines," characterized by the size of the assimilating leaves, by the relationship between the length of the leaf and the length of the intenode, as well as by the relationship between the length of the plagiotropic branch and the number of leaves on the branch. Taking into account the results of the two preceding studies on P. urinaria from Guyana and the Ivory Coast, these forms appear adapted to climatic factors. They are the expression, at the level of each genotype from the ecodema selected by climate, of the existence (or absence) of regulating systems allowing the adjustment of the forms to abrupt variations (natural or artificial) in external conditions.
Ontogenèse des nodules caulinaires du Sesbania rostrata (légumineuses)
Authors: Duhoux E.
Published: August 2008

Stem nodules of the legume Sesbania rostrata are ovoids, contain chlorophyll and have determinate growth. They possess a large central mass of infected cells. Stem mamillae are regularly arranged in vertical files along the stem and develop into nodules when they are infected by a specific Rhizobium. Each nodule arises from the development of an infected region of the incipient root cortex. The infection in S. rostrata has been shown to proceed in four sequential stages. Some of them have never been shown to occur in other legumes: (i) bacterial penetration takes place in degenerated (dead) cortical cells; (ii) proliferation of the bacteria occurs in the intercellular cavities and initiates a meristematic nodule; (iii) protusion of infection threads at first occurs intercellularly and then intracellularly from the cavities; (iv) finally there is an intracellular release of Rhizobia by an endocytotic process.
A cline and other patterns of genetic variation in Cochliobolus carbonum isolates pathogenic to corn in North Carolina
Authors: Lodge Deborah J. , Leonard Kurt J.
Published: August 2008

Patterns of genetic variation were studied in natural populations of Cochliobolus carbonum Nelson (anamorph Helminthosporium carbonum Ullstrup), a haploid asexually reproducing fungus. Two virulence races (2 and 3) are common on corn in North Carolina. Race 3 has occurred in the Appalachian mountains for at least 25 years, but has recently expanded its range eastward. The expanded range of race 3 cannot be explained by adaptation through parasexual recombination between races or mutation alone. Five polymorphic traits in addition to virulence were compared in races 2 and 3 to evaluate possible recombination between races. If sexual recombination occurred between races, it was rare and was not detected in this study. The simplest explanation for the expansion of race 3 involves historical factors such as increased corn production and changes in weather which aided gene flow. A steep cline was found on the Appalachian escarpment, where the proportion of race 3 isolates dropped from 100% at high elevations to 30% at low elevations over a distance of 7–20 km. No barriers to gene flow were found on the escarpment, suggesting that the environment and possibly cultural practices may restrict race 3 at low elevations and race 2 at high elevations. Race 3 may adapt to conditions in eastern North Carolina only slowly via mutation unless recombination occurs and has gone undetected.
Periphyton biomass and species composition in 21 British Columbia lakes: seasonal abundance and response to whole-lake nutrient additions
Authors: Shortreed K. S. , Costella A. C. , Stockner J. G.
Published: August 2008

Periphyton communities on artificial substrates in 21 oligotrophic British Columbia lakes were sampled from 1978 to 1980. Periphyton biomass (ash-free dry weight (AFDW) and total chlorophyll (Chl)) and accumulation rates (milligrams AFDW per square metre per day) were among the lowest recorded from temperate oligotrophic lakes, averaging from 0.01 to 5.69 mg Chl∙m−2, 0.04 to 2.86 g AFDW∙m−2, and 1 to 47 mg AFDW∙m−2∙day−1. Diatoms were the dominant group in most lakes at most times, comprising over 70% of total periphyton biomass. Achnanthes minutissima and Tabellaria flocculosa were the most ubiquitous species in the study, and Eunotia spp. were common only in acidic humic-stained lakes. Of the physical and chemical factors measured in this study, pH appeared to be most important in regulating diatom species composition. In those lakes fertilized with nitrogen and phosphorus, periphyton biomass showed marked increases over untreated years, but the community species composition in most lakes remained similar between treated and untreated years. Comparisons between artificial and natural substrates showed that the same species were common on both substrates, although relative abundances varied. The littoral zone of most study lakes is small relative to the pelagic, and it is estimated that periphyton comprised < 1% of average total algal biomass (as chlorophyll) and also represented < 1% of estimated total annual carbon metabolism.
A comparative study of Pyrola minor × Pyrola asarifolia (Ericaceae) and its parental species in North America
Authors: Haber Erich
Published: August 2008

This study is the first documented account of the occurrence of the hybrid Pyrola minor × Pyrola asarifolia in North America. Seventeen localities have been verified with 15 of these occurring in the Cordillera from Colorado to the Aleutian Islands. In the east, one locality has been found in Ontario and one in Quebec. The hybrid is intermediate in morphology in 10 of 12 quantitative characters analyzed. Eight character means were significantly distinct for all three taxa (flower number, lengths of bracts, sepals, petals, anthers, petioles, styles and blade width). The hybrid differs from the parents in having campanulate flowers with distinctly exserted styles and anthers of intermediate form that are frequently malformed and have relatively large pores. Pollen fertility is low as judged by the high incidence of collapsed tetrads.
Compartmental analysis of phosphate in roots of intact barley seedlings
Authors: Lefebvre Daniel D. , Clarkson David T.
Published: August 2008

Elution profiles of 32P-labelled inorganic phosphate (Pi) from roots of intact barley plants were observed and were found to conform to the pattern theoretically derived for three compartments in series. An allowance was made for the movement of labelled phosphate from the cytoplasm into the root xylem. Transformations of labelled phosphate within metabolically labile organic pools seem to be invisible kinetically because their rate constants are generally higher than that for Pi efflux across the plasmalemma and tonoplast. It is concluded that compartmentation of phosphate between cytoplasm and vacuole can be explored usefully by this technique especially if used in conjunction with other methods which can measure the size of cytoplasmic organic phosphate pools.
Optimal Assay Conditions for Serum and Liver Glutamate Oxaloacetate Transaminase, Glutamate Pyruvate Transaminase, and Sorbitol Dehydrogenase from the Rainbow Trout, Salmo gairdneri
Authors: d'Apollonia S. , Anderson P. D.
Published: August 2008

A technique often used to minitor sublethal impairment of physiological functions in fish is clinical serum enzyme analysis. However, the assay conditions used in such studies in fish systems are often those derived from mammalian studies. For some enzymes (e.g. sorbitol dehydrogenase) mammalian assay conditions are applicable to fish serum; however, for glutamate oxaloacetate transaminase and glutamate pyruvate transaminase, assay conditions must be modified for fish systems. This paper thus reports pH and substrate optima for rainbow trout SDH, GOT, and GPT. Using these optimal assay conditions, liver GOT, GPT, and SDH activities were determined to be 187, 152, and 26.6 mU/mg protein, respectively. The equivalent serum GOT, GPT, and SDH activities were 255, 17, and 17.5 mU/mL serum, respectively.Key words: rainbow trout, serum enzyme analysis, glutamate dehydrogenase, glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, sorbitol dehydrogenase, liver, biochemistry
Distribution of Fatty Acids in Lipids of the Common Atlantic Sea Urchin Strongylocentrotus droebachiensis
Authors: Takagi T. , Eaton C. A. , Ackman R. G.
Published: August 2008

Lipid classes and fatty acid details of sea urchins Strongylocentrotus droebachiensis harvested in subtidal water near Halifax, and in deep water in St. Margaret's Bay, were compared. All samples contained an eicosenoic acid with 5,6-ethylenic unsaturation and two non-methylene-interrupted eicosadienoic acids (NMID) with the one 5,6 bond and a second in either the 11,12 or 13,14 positions. Structures were identified by combinations of ozonolysis, partial hydrazine reduction and argentation-TLC and by mass spectra of pyrrolidine derivatives. No 3,11-eicosadienoic acid was observed and elongation of C20 materials with few ethylenic bonds to C22 homologues was confined to 11–20:1 and to the minor 5,13–20:2 NMID and did not include either the relatively important 5–20:1. monoene or the 5,11–20:2 NMID. Individual animals showed considerable variation in total lipid and lipid classes, but the consistent distribution of the fatty acids with 5,6 unsaturation, irrespective of the nutritional status of the animal, suggests a basic role in membrane function.Key words: Strongylocentrotus droebachiensis, sea urchin lipids, sea urchin fatty acids, non-methylene-interrupted fatty acids, eicosadienoic fatty acids
Growth of Underyearling Sockeye Salmon (Oncorhynchus nerka) under Constant and Cyclic Temperatures in Relation to Live Zooplankton Ration Size
Authors: Biette R. M. , Geen G. H.
Published: August 2008

Growth rates of Babine Lake underyearling sockeye salmon (Oncorhynchus nerka) fed rations of zooplankton of 14–84 cal/kcal sockeye∙d−1 (1 cal = 4.1868 J; 1.3–7.8% of dry body wt) were determined at constant temperatures of 6.2, 11.3, 15.3, and 15.9 °C, and under a cyclic temperature regime similar to that encountered during their diel vertical migrations. Growth of fish fed rations of 43–76 cal/kcal∙d−1 (4.0–6.9% of dry body wt) was equal or greater under cyclic temperatures than constant temperatures. At the lowest and highest rations growth was greater, respectively, under the constant low temperature and the constant high temperature than under cyclic temperatures. Gross growth efficiency, ranging from < 1 to 31%, was affected by temperature and ration in much the same way as growth. Young sockeye ingesting moderate rations comparable to those probably available in the relatively warm surface layers of Babine Lake, and undergoing diel migrations from deep cold waters to the surface, and return, are likely to grow more rapidly and efficiently than fish maintained at constant temperatures. The selective value of vertical migrations in thermally stratified waters may have an energetic basis as suggested by some other workers.Key words: sockeye salmon, growth rate, conversion efficiency, diel vertical migration, temperature, zooplankton ration, diel cyclic temperature
Correlation and Prediction of Metal Toxicity to Aquatic Biota
Authors: Kaiser Klaus L. E.
Published: August 2008

Published data on the toxicity of metal ions to aquatic biota, in particular Daphnia magna, were analyzed for their correlation with ion specific physico-chemical parameters. Significant correlations were obtained for three groups of ions with similar electron configurations in the outer orbitals. Group I ions include Na (I), Be (II), Ba (II), Al (III), and Cr (VI) with inert gas-like electron configurations; group II ions include Cr (III), Mn (II), Fe (III), Co (II), Ni (II), Cu (II), Zn (II), As (V), Cd (II), Pt (IV), Au (III), and Hg (II) with partially or completely filled d electron orbitals; group III ions include Sn (II), As (III), Se (IV), and Pb (II), with filled d and s, but unfilled p electron orbitals. The toxicity of an ion within a group can be calculated from the general equation[Formula: see text]where pT is the negative logarithm of a metal ion concentration with a certain toxicity in mol∙L−1; AN is the metal's atomic number; ΔIP is the difference between the ion's ionization potential with the oxidation number (OX) and the ionization potential of the next lower oxidation number (OX − 1) in electron volts (eV); and ΔE0 is the absolute value of the electrochemical potential between the ion and the first stable reduced state. The values for the constants a0, a1, and a2 depend on the group of ions, the biota, and the particular toxic effect determined. The equation is applied to predict the toxicities of other ions under similar test conditions.Key words: toxicity, metals, ions, correlations, Daphnia magna, aquatic tests
Role of a Unionid Clam Population in the Calcium Budget of a Small Arctic Lake
Authors: Green Roger H.
Published: August 2008

Growth rate and morphometric parameters were estimated for the Anodonta grandis (Pelecypoda, Unionidae) population in Shell Lake, N.W.T. (68°N), based on sampling during the summer of 1972. Variation in density and size of Anodonta within the lake as a function of varying depth and slope of bottom was estimated by SCUBA during the summer of 1973. Predictive models based on these data estimate total calcium in shells of the Anodonta population to be 10.1 Mg, which is approximately half the amount of calcium dissolved in Shell Lake water. The youngest four or five year-classes are missing from the estimated age distribution, and recent pollution may be a factor. Independent estimates of calcium used for shell growth, and of calcium released by death of individuals and subsequent shell dissolution, approximate 50% (of the calcium in the Anodonta population) per year. This implies a mean residence time in the Anodonta population of approximately 2 yr.Key words: calcium, clam, unionid, lake, arctic
Effect of Individual Variability on the von Bertalanffy Growth Equation
Authors: Sainsbury K. J.
Published: August 2008

The growth in length of a group of animals is examined. Each animal is assumed to grow according to the von Bertalanffy model with fixed parameters, but these parameters are allowed to differ between individuals. Equations governing the mean and variance of length at given age and growth increment at given length are provided, and their implications discussed. Results indicate that the traditional growth equation is likely to result in an underestimate of the mean value of K when either length at age or growth increment data are analyzed. This problem does not appear serious when using length at age data. However, the problems of interpretation are more serious in the case of growth increment data where serious overestimates of the reconstructed mean length at age can result. A thorough analysis of growth cannot be made for a population exhibiting individual variability in L∞ and K from growth increment data alone. In particular a nonlinear relationship between growth increment and initial length does not necessarily imply that the von Bertalanffy model is inappropriate to the species in question. A topic urgently in need of examination is the form of the joint distribution of K and L∞ in animal populations.Key words: von Bertalanffy, growth models
Growth and Recruitment in Experimentally Exploited Lake Whitefish (Coregonus clupeaformis) Populations
Authors: Healey M. C.
Published: August 2008

From 1971 to 1978 I conducted an exploitation experiment on lake whitefish (Coregonus clupeaformis) in four Northwest Territories lakes. The objective was to test the hypotheses that, when exploited, growth and recruitment would increase in the populations, and that the degree of increase would be proportional to the intensity of exploitation. Significant increases in size-at-age were recorded in the exploited lakes, and the degree and persistence of the increase were proportional to the intensity of exploitation. Good recruitment was stimulated in the heavily exploited lake, and to a lesser degree in the moderately exploited lake. The hypotheses were, therefore, corroborated. Analyses of growth and year-class strength in the unexploited control lake and the lightly exploited lake indicated that natural variation in growth and recruitment, on a similar scale to that stimulated by exploitation, had occurred in the past. The compensatory responses of lake whitefish populations to exploitation appear to be a logical consequence of the natural population regulating mechanisms for the species. The results of my experiment indicate that in unexploited lakes, recruitment and growth of young fish is regulated by the established population of mature fish.Key words: lake whitefish, growth, recruitment, exploitation, population regulation
Confidence Intervals for Optimal Effort Estimates from the Schaefer Production Model
Authors: McGaw Richard L.
Published: August 2008

The Schaefer production model uses ratios of estimated parameters to determine maximum sustainable yield and the associated level of effort. By using the Fieller method, whereby confidence intervals can be determined for ratios of linear combinations of estimated parameters, the error component of the estimate of effort at maximum sustainable yield can be determined. The information needed to make the calculations is available from standard output of most regression programs. An example is given for the Georges Bank scallop fishery.Key words: Fieller method, Schaefer production model, confidence interval, fisheries management
Presence-Absence Sampling for Fisheries Management
Authors: Mangel Marc , Smith Paul E.
Published: August 2008

It is often important to estimate the abundance of a fish stock when the stock is somewhat depleted. For pelagic species this presents great operational difficulties, because adult surveys may be prohibitively expensive and time consuming. Here we introduce a method for estimating the spawning biomass of a stock by means of egg or larval surveys. In particular, we develop a series of models for presence-absence sampling of eggs or larvae and show how presence-absence data can be used to estimate adult spawning biomass. The models are based on an underlying probabilistic description of the aggregation of eggs or larvae, a search process, and a description of habitat structure. Methodologies are given for estimating the distribution of the size of the spawning biomass from presence-absence data. A case study of sardine is used to justify a number of the assumptions. The methods are applied to a 1985 survey for sardine eggs and are compared to an alternative method based on egg production.
Larval Herring (Clupea harengus) Dispersion, Growth, and Survival in the St, Lawrence Estuary: Match/Mismatch or Membership/Vagrancy?
Authors: Fortier Louis , Gagné Jacques A.
Published: August 2008

The relative success of the 1985 spring and fall cohorts of Atlantic herring (Clupea harengus) in the St. Lawrence estuary was studied in relation to food availability (match/mismatch hypothesis) and hydrography (member/vagrant hypothesis). The development of the spring cohort (early June) matched remarkably well the development of suitable prey and larval abundance within the estuary decreased slowly (7.8%∙d−1). The fall cohort (mid-September) hatched in a period of low food availability and dwindled rapidly (28.9%∙d−1). The initial growth of both cohorts appeared limited by food. The stratification front limiting seaward drift was strong in the spring (0–80 j∙m−3) and weak in the fall (0–20 J∙m−3), suggesting that advection out of the estuary could also have contributed to the observed differences in the fate of the two cohorts. We conclude from this case study that spawning times and locations may have evolved to favor the initial cohesion of larval fish cohorts by limiting dispersion and that both transport and energetic processes can influence the success of a population at colonizing its dispersion area. The relative contribution of initial vagrancy and subsequent trophic interactions in determining final recruitment remains to be assessed.
Meiobenthic Copepods: Tracers of Where Juvenile Leiostomus xanthurus (Pisces) Feed?
Authors: Feller Robert J. , Coull Bruce C. , Hentschel Brian T.
Published: August 2008

Simultaneous collections of meiobenthic copepods with cores at three sites along a saltmarsh tidal elevation gradient (subtidal, intertidal, marsh) and of juvenile Leiostumus xanthurus (spot) in an adjacent tidal creek were made every 2 h for 24 h in May 1986 and again in May 1988. Certain copepod species were restricted to specific habitats along the gradient. By comparing the species composition of copepod prey in the spots' foreguts as it changed through time with the distribution of copepod species along the gradient, some copepod species served as markers of where the fish had fed. Species that occupied the high intertidal occurred in fish guts primarily at high tide while subtidal prey species were eaten only at low tide. The most abundant copepod species collected with core samplers, Stenhelia (D.) bifidia, lives too deep in the sediment for the fish to catch and was not eaten in proportion to its abundance. When predators are highly motile and their prey have a restricted areal distribution, it is possible to infer where fish have fed by identifying prey to the species level in both fish stomach contents and the local environment.
Influence of Water Chemistry on Size Structure of Zooplankton Assemblages
Authors: Tessier Alan J. , Horwitz Richard J.
Published: August 2008

A stratified-random selection of all lakes in the northeastern United States was sampled for zooplankton composition, and physical and chemical characteristics during midsummer 1986. In all, 146 lakes were sampled from five geographic subregions and three categories of water alkalinity. There was no significant variation in total zooplankton abundance among regions or alkalinity categories; however, the body-size structure of assemblages was dependent on both alkalinity and geographic subregion. The largest change in size structure occurred at alkalinity levels > 150 μeq∙L−1and pH > 7.0, and appeared less related to change in pH than to variation in water hardness. This shift of size structure was caused by a loss of large-bodied zooplankton and an increase in small rotifers with decreasing water hardness. Exploratory analysis revealed that lake stratification also explained significant variation in zooplankton size structure, but was largely independent of the effects of water chemistry. We hypothesize that the association of large zooplankton with hard water is casual; large-bodied cladocerans may require high calcium levels.
Behavioral Ecology of Podding Red King Crab, Paralithodes camtschatica
Authors: Dew C. Braxton
Published: August 2008

Diel activity cycles and foraging dynamics for two pods of 500–800 juvenile red king crab, Paralithodes camtschatica, were monitored for 196 d. (Nov. 1987–June 1988) and 148 d. (Oct. 1988–Feb. 1989) in Womans Bay, Kodiak, Alaska, using SCUBA. Nocturnal foraging and homing behavior of podding red king crab were documented for the first time. Variation in time of pod dispersal into a nightly foraging aggregation was explained (R2 = 0.72) by changes in water temperature, crab weight, and time of sunset. A trend of increased foraging time and movement to deeper, cooler water was apparent after mid-April, as water temperatures reached 4 °C and began a sustained summer increase. Molting occurred only at night, and seasonal variations in molting rate were estimated using molting probability models based on length-frequency distributions. Average pod movement was counter to the direction of strongest water currents, and homing behavior suggested some affinity for a low-light environment in man-made niches. Items most frequently eaten were sea stars (Evasterias troschelii) and macrophytes (Laminaria sp. and Ulva sp.). I discuss the inception of podding as a discontinuity in behavior, perhaps reflecting a break in the fractal continuum of niche availability within red king crab habitat.
Bacterial Production in the Bottom Surface of Sea Ice in the Canadian Subarctic
Authors: Bunch J. N. , Harland R. C.
Published: August 2008

Standing stocks of bacteria in the bottom of first-year sea ice at Frobisher Bay, N.W.T., increased fivefold between March and May (1985 and 1986) and constituted up to 5% of particulate organic carbon (POC). Autoradiography demonstrated that approximately one-third of the bacterial assemblage incorporated radioactive thymidine. The mean volume of cells was six times larger than that in the underlying water, and the assemblage was dominated by rod-shaped cells rather than the coccus-shaped cells prevalent in the water column. Bacterial carbon production by 3H-thymidine incorporation amounted to 0.04 mg carbon m−2∙h−1, or a doubling time of about 22 h, in the bottom ice surface and 0.01 mg carbon m−3∙h−1 in the underlying water. The concentration of dissolved organic carbon (DOC) was generally much higher in the bottom ice surface than in the underlying water, and was closely related to rate of cell production. A model of bacterial dependancy on DOC derived from primary production suggests that bacteria are important in the localized production of POC in the bottom of arctic sea ice, and contribute to an early source of nutrition for higher trophic levels before summer production in open water.
Benthos Response to Disturbance in Western Lake Erie: Regional Faunal Surveys
Authors: McCall Peter L. , Soster Frederick M.
Published: August 2008

Infauna at six stations in western Lake Erie was sampled on four occasions during 1981–1982 to determine if natural patterns of distribution and abundance reflected the response to disturbance that was revealed previously in tray colonization experiments. The distribution of opportunist species was patchy and positively associated with a gradient of bottom disturbance due to prevailing southwest winds. Distribution of late colonizers was more even and either unrelated to the gradient or more abundant in lower stress regions. Except to the extent that it covaried with bottom stress gradients, sediment grain size was not a significant predictor of benthos distribution. Small, shallow-dwelling, early colonizers appeared to suffer higher mortality during an unusually windy period (October 1981–April 1982) than the larger, deeper-dwelling, late colonizers. We suggest that a portion of the spatial and temporal variability of benthos in large, shallow lakes is probably the result of differential adaptation to a variety of bottom disturbances.
Threshold Management Policies for Exploited Populations
Authors: Quinn II Terrance J. , Fagen Robert , Zheng Jie
Published: August 2008

Under a threshold management policy, harvesting occurs at a constant rate but ceases when a population drops below a threshold. A simulation model of an age-structured population with stochastic recruitment was constructed with such a harvest policy with several threshold levels. Other factors were fishing mortality, recruitment, and initial biomass. The objective function was a weighted function of average yield and standard deviation over a planning horizon. First, we determined the optimal threshold given fishing mortality. Secondly, we determined optimal threshold and fishing mortality, simultaneously. In application to eastern Bering Sea pollock, a threshold management policy always increased average yield over a non-threshold policy. For the first problem, optimal threshold levels ranged from 20 to 30% of pristine biomass. For the second problem, each scenario had a unique threshold and fishing mortality, with fishing mortality slightly above the maximum sustainable yield (MSY) level and a threshold range of 25–50%. These results were robust in regard to other factors. Benefits of the threshold policy were greater with a Ricker spawner-recruit model and with higher fishing mortality. The success of the threshold management policy is due to the relatively rapid rebuilding of a population to levels producing MSY.
Position Choice by Drift-Feeding Salmonids: Model and Test for Arctic Grayling (Thymallus arcticus) in Subarctic Mountain Streams, Interior Alaska
Authors: Hughes Nicholas F. , Dill Lawrence M.
Published: August 2008

We develop a model to predict position choice of drift-feeding stream salmonids, assuming a fish chooses the position that maximizes its net energy intake rate. The fish's habitat is represented as a series of stream cross-profiles, each divided into vertical strips characterized by water depth and velocity. The fish may select a focal point in any of these strips, and include several neighbouring strips in its foraging area. The number of prey the fish encounters depends on its reaction distance to prey, water depth, and water velocity; the proportion of detected prey the fish is able to capture declines with water velocity. The fish's net energy intake rate is its gross energy intake rate from feeding minus the swimming cost calculated by using water velocity at the fish's focal point. There was a close match between the positions predicted by this model and those chosen by solitary Arctic grayling (Thymallus arcticus) in the pools of a mountain stream in Alaska.
Prey Retention and Sieve Adjustment in Filter-Feeding Bream (Abramis brama) (Cyprinidae)
Authors: Hoogenboezem Wim , Lammens Eddy H. R. R. , MacGillavry Peter J. , Sibbing Ferdinand A.
Published: August 2008

The hypothesis that the variability in prey-size selection of filter-feeding bream (Abramis brama) is related to sieve adjustment was tested by feeding bream of approximately 20 and 30 cm standard length with daphnids. The size-selective feeding observed in experiments was compared with predicted selectivity curves derived from the channel width of branchial sieves, total filtered volume, and the retention probability of prey in the reduced or unreduced channels. The relationship between mesh size and retention probability of Daphnia of known length was determined empirically in sieving experiments using commercial sieves. The results with 20-cm fish demonstrated that the variability in prey selection of bream can be explained by the adjustment of its filter in two distinct mesh sizes. The relationship between filter adjustment and zooplankton availability was not always clear. The retention ability of large bream (>30 cm) was in close accordance with the model prediction for filter-feeding with reduced channels.
Importance of Mucus in Filter-Feeding of Bream (Abramis brama)
Authors: Hoogenboezem Wim , Boogaart Jos G. M. van den
Published: August 2008

Mucus boluses, found in the oropharyngeal cavity of a large number of freshly caught bream (Abramis brama), appear to play an important role in the aggregation and transport of food particles from the branchial sieve to the esophagus. Mucus boluses, some containing up to 900 zooplankters, were isolated from the oropharyngeal cavity of bream, and from these the filtering rate and retention ability of the filtering system were calculated. Using light microscopy and special staining methods, we identified different types of mucus cells in the oropharyngeal wall of bream that increase in number from anterior to posterior. Based on these data and on our knowledge of branchial sieving, we have hypothesized the role of mucus in the filter feeding mechanism of bream. Initially, small particles are retained mechanically in the branchial sieve, eventually becoming coated with mucus. They then act as "sticky" particles with respect to other mucus-coated particles. During recollection from the branchial sieve following closed protrusion of the mouth, the sticky particles adhere to one another forming a mucus bolus that is stored at the posterior end of the branchial chamber. After several of these cycles over a period of several minutes the bolus is swallowed.
Breakdown and Invertebrate Colonization of Leaf Litter in Two Contrasting Streams, Significance of Oligochaetes in a Large River
Authors: Chauvet E. , Giani N. , Gessner M. O.
Published: August 2008

The breakdown of willow (Salix alba) and beech (Fagus silvatica) leaves and their colonization by invertebrates were studied in a third-order mountain stream (breakdown rate k = 0.0147 and 0.0052∙d−1, respectively) and a seventh-order lowland river (k = 0.0094 and 0.0027∙d−1). Willow leaves broke down three times faster than beech leaves; this difference was twice that between streams. Total invertebrate densities and biomass and the proportion of shredders were higher in the large river; therefore, differences in breakdown capacities between streams cannot be attributed to differences in invertebrate community structure. Instead, microbial processing and abiotic fragmentation are suggested as factors controlling breakdown rates. Owing to the abundance of naidids, up to 2000 invertebrates per leaf bag were recorded in the large river. These oligochaetes appeared to use litter accumulations as a microhabitat that provided shelter and a rich supply of food in the form of fine particulate organic matter. Tubificid oligochaetes accounted for 55% of total biomass on partly degraded leaves at this site. Their abundance and regular occurrence inside willow leaves suggest that tubificids enhance leaf fragmentation and possibly mediate the incorporation of organic matter in river sediments once the plant tissue is sufficiently macerated.
Mercury in Macroinvertebrates from Swedish Forest Lakes: Influence of Lake Type, Habitat, Life Cycle, and Food Quality
Authors: Parkman Helena , Meili Markus
Published: August 2008

Mercury concentrations in lacustrine macroinvertebrates were concurrently studied in eight remote Swedish forest lakes of differing dystrophy, acidity, and eutrophy. The aim was to assess the influence of ecological factors (taxon, habitat, and feeding habits), chemical factors (characterizing different types of lakes), and regional and climatic factors (Hg deposition and mean temperature) on the accumulation of Hg. Concentrations varied from <50 to >5000 ng Hg∙g dry weight−1. A large part of this high variability could be ascribed to differences in water and sediment chemistry, ecological niches, and species-specific seasonalities. Both taxonomic composition and Hg concentrations were highly dependent on the type of lake. Concentrations were highest in acidic dystrophic lakes and lowest in oligotrophic lakes. Mean Hg concentrations in the examined taxa within a lake differed 100-fold. Contrary to widely held views on biomagnification, the lowest concentrations among profundal chironomids were found in predators whereas the highest concentrations occurred in detritivores. Seasonal variations were negligible in some taxa but considerable in others and appeared in some taxa to be related to the life cycle. We conclude that Hg accumulation in macroinvertebrates is largely determined by feeding behaviour and food quality.
Localisation cytologique du cuivre et de quelques autres métaux dans la glande digestive de la seiche, Sepia officinalis L (Mollusque Céphalopode)
Authors: Martoja Micheline , Marcaillou Christiane
Published: August 2008

The cuttlefish, Sepia officinalis L., liver was investigated by histochemical and microanalytical methods. The greater part of the accumulated Cu is concentrated in spherulae which are elaborated by the basal cells. Cu is associated with both Ag and Zn. Fe is also found but the digestive cells are the most important site of Fe storage. Our data show that the spherulae are made of metallothionein-like proteins. The occurrence of these metal-binding proteins has ecological effects. The metals are easily assimilable and can be transferred to higher levels of the food chain.
Spatial and Parent-Age Analysis of Stock–Recruitment in the Georges Bank Sea Scallop (Placopecten magellanicus) Population
Authors: McGarvey Richard , Serchuk Fredric M. , McLaren Ian A.
Published: August 2008

Reproductive interaction between and within subpopulations on Georges Bank was investigated employing annual sampling surveys of sea scallop (Placopecten magellanicus) abundance available from 1977 to 1988. Time series of recruitment and, together with size-specific fecundity, total yearly egg production were constructed for Georges Bank and all subregions to generate a spatial stock–recruitment analysis. Recruitment is correlated with egg production within the population on the Northern Edge and Northeast Peak which may imply that it is reproductively self-sustaining. Stock–recruitment correlations increased when the eggs of scallops age 3 and 4 were excluded from the stock measure of total egg production. This increase in correlation occurred in every subregion where there was evidence of a positive relationship between eggs and recruits, most strongly for the Northern Edge and Northeast Peak. This is consistent with the hypothesis that older scallops (ages 5 +) are the principle contributors to recruitment. Presently, the fishery begins removing large numbers at age 3.25. Previous yield per recruit analyses have predicted higher yields if age of first capture were raised. These correlations may suggest that the same policy could also result in higher recruitment.