bluuebunny/crossref_metadata_2025 huggingface dataset:
Ontogenetic Diet Shift in Lake Erie Age-0 Yellow Perch (Perca flavescens): A Size-Related Response to Zooplankton Density
Authors: Wu Lin , Culver David A.
Published: June 2008

Through field studies, we demonstrated that age-0 yellow perch (Perca flavescens) in western Lake Erie underwent an ontogenetic diet shift from exclusively zooplankton to mainly benthic prey during June through August. This shift coincided with a decline in zooplankton populations in the lake. Further, laboratory experiments on feeding ontogeny suggest that the diet shift was related to fish size. Yellow perch less than 30 mm total length did not consume benthic prey either during the feeding experiments or in the field studies, while fish greater than 50 mm did at low zooplankton densities. Interactions between fish size and zooplankton density, therefore, likely determine the ontogenetic diet shift in young-of-the-year yellow perch. Growth of yellow perch declined following the zooplankton decline. Reduced growth during this life stage may extend the period of vulnerability of yellow perch to its predators, thus reducing survival and, ultimately, recruitment.
Morphological Differentiation of Lake Sturgeon (Acipenser fulvescens) from the St. Lawrence River and Lac des Deux Montagnes (Quebec, Canada)
Authors: Guénette Sylvie , Rassart Eric , Fortin Réjean
Published: June 2008

We investigated the degree of morphological differentiation of lake sturgeon (Acipenser fulvescens) from the St. Lawrence River (Lacs Saint-Pierre and Saint-Louis and the river itself downstream from Lac Saint-Pierre) and from Lac des Deux Montagnes. Forty-one morphometric characters (traditional and truss network) and two meristic traits were used on 200 sturgeon (890–1010 mm total length) from five sites. The study of the meristic characters showed a difference of 1.5 gill rakers between Lac Saint-Louis sturgeon and those from Lac Saint-Pierre and Lac des Deux Montagnes although the range was identical in all groups. Principal components and discriminant analyses performed on morphometric characters showed that Lac des Deux Montagnes sturgeon differ markedly from the St. Lawrence River fish by their proportionally higher and longer head (correct reclassification 89%). The more discriminant descriptors show a difference ranging from 4 to 16 mm between Lac des Deux Montagnes fish and those from the St. Lawrence River. The multivariate analyses also revealed significant morphometric differences between fish in different sectors of the St. Lawrence River. However, the absolute differences are rather tenuous and are not adequate to designate separate stocks based solely on morphology.
Introduction to the Northwest Ontario Lake Size Series (NOLSS)
Authors: Fee E. J. , Hecky R. E.
Published: June 2008

The rationale, design, and limitations of the Northwest Ontario Lake Size Series (NOLSS) research program are described. The primary purpose of NOLSS is to discover how lake size per se influences limnological and fisheries phenomena, so that conclusions drawn from studies of particular lakes can be rigorously scaled and applied to lakes of other sizes. NOLSS consists of six lakes located in a remote wilderness region of Northwest Ontario. These lakes were chosen for their geological, hydrological, and morphological similarity (Canadian Shield geology; water renewal time> 5 yr; fully stratified in summer), but they form an exponential gradient in surface area (from 89 to 34 700 ha.) Associated with this gradient of lake size are gradients of physical properties (turbulent energy, mixing depth, thermal behaviour) to which biological communities must adapt. NOLSS fills the conspicuous gap in size that separates two well-studied groups of lakes in Northwest Ontario: the Experimental Lakes Area (ELA), where whole-lake manipulation experiments are performed, and the Laurentian Great Lakes (Nipigon, Superior), where these experiments find some of their most important applications.
Effects of Lake Size on Phytoplankton Photosynthesis
Authors: Fee E. J. , Shearer J. A. , DeBruyn E. R. , Schindler E. U.
Published: June 2008

Phytoplankton photosynthesis (PP) was measured for 6 yr in seven remote Canadian Shield lakes that stratify fully during the summer and have water renewal times > 5 yr but vary from 29 to 34 700 ha; Lakes Nipigon and Superior were also studied in two years. Chlorophyll and PP at optimum light were low in the smallest and largest lakes and increased systematically to values nearly five times higher in midsized lakes (~103 ha). Daily PP per square metre of lake surface and annual PP per cubic metre of the mixed layer also varied in this manner, but annual PP per square metre was high in large lakes (despite their low density rates) because of their long growing seasons. Additional data are needed to determine whether the photosynthesis maximum in midsized lakes is inherently size related or an accidental statistical result. Intraannually, chlorophyll-based photosynthesis parameters ([Formula: see text], αB) were similar in all lake sizes, but interannually they varied by two to three times; this interannual variation was significantly correlated with total rainfall during May and June. Implications for extrapolating experimental results from small to large lakes, selecting lakes for interregional comparison studies and predicting how climatic warming would affect phytoplankton photosynthesis are discussed.
Morphometry and Gonad Maturity of Male Snow Crab, Chionoecetes opilio
Authors: Comeau Michel , Conan Gérard Y.
Published: June 2008

The relationship between chela height (CH) and carapace width (CW) of male snow crab, Chionoecetes opilio, goes through three allometric stages. The "immature stage" (mostly < 34 mm CW) evolves into a "juvenile stage" (34–120 mm CW) through a "juvenile molt" defining a change in allometry marked by an angular point around 34 mm CW. Fifty percent of males reach gonad maturity, defined by the presence of spermatophores inside the vasa deferentia, at an estimated size of 34 mm CW) The third allometric stage, "morphometrically mature," is separated from the juvenile stage by a "molt to morphometric maturity" at sizes ranging from 50 to 120 mm CW. Juvenile males have smaller claws than morphometrically mature males of the same size. This secondary sexual character is justified by a specific behavior of the males holding the pereipods of the female in one chela during precopulatory embrace. Male snow crab efficiently mate in nature with intermolt multiparous females only after reaching morphometric maturity. Therefore, the presence of spermatophores is not the sole determinant factor necessary for male copulation. Juvenile males larger than the minimum legal size of 95 mm CW are harvestable before, they may efficiently mate.
Metabolic Stores of Yellow Perch (Perca flavescens): Comparison of Populations from an Acidic, Dystrophic Lake and Circumneutral, Mesotrophic Lakes
Authors: Nelson Jay A. , Magnuson John J.
Published: June 2008

Little is known about the animals that occupy naturally acidic habitats. To better understand the physiological state of animals from temperate, naturally acidic systems, we compared metabolite stores and meristics of two yellow perch (Perca flavescens) populations in northern Wisconsin. One population originated from a naturally acidic, dystrophic lake (Acid-Lake-Perch, ALP) and had previously been shown to have enhanced tolerance to low pH. The second population came from two nearby interconnected circumneutral, mesotrophic lakes (Neutral-Lake-Perch, NLP). Perch were collected throughout the year to account for seasonal effects and to discern whether patterns of metabolite utilization differed between populations. ALP had smaller livers containing less glycogen and greater muscle glycogen content than NLP. The ALP also had significantly greater liver and visceral lipid contents, and females from this population committed a greater fraction of their body mass to egg production. We interpret these results as indicative of physiological divergence at the population level in yellow perch. These results are discussed as possible products of H+ -driven changes in metabolism and as possible products of different life history strategies between populations. Our results also show that perch living in acidic, dystrophic Wharton Lake are not acid stressed.
Water Flow and Clay Retention in Submerged Macrophyte Beds
Authors: Petticrew Ellen L. , Kalff Jacob
Published: June 2008

The effect of aboveground plant structure on near-bottom water flow and surficial sediment composition was evaluated in Lake Memphremagog (Quebec–Vermont) at 34 nearshore sites within three mixed-species macrophyte beds. Plant surface area accounted for 70% of the variance in flow reduction when the effect of changing water depth was removed. Relationships between plant surface area and surficial sediment clay content were evident within each of the three multispecies beds. The equations predicting within-bed clay concentrations were not significantly different from a general among-bed model (r2 = 0.74) developed at 25 sites of high biomass from other nearshore locations in Lake Memphremagog. The study provides quantitative evidence for the importance of macrophytes as sites of sedimentation of fine particles and their associated nutrients and contaminants.
Nutrient Regeneration by Sockeye Salmon (Oncorhynchus nerka) Fry and Subsequent Effects on Zooplankton and Phytoplankton
Authors: Schindler Daniel E.
Published: June 2008

Planktivorous fish can affect phytoplankton indirectly by control of herbivore communities, and directly by excretion of soluble nutrients. A field mesocosm study showed that nutrient regeneration by sockeye salmon (Oncorhynchus nerka) fry substantially increased biomass of zooplankton and phytoplankton relative to fishless controls. Plankton communities in enclosures treated with only fish-regenerated nutrients but not fish predation responded differently to two densities of fish. Enclosures with low fish densities exhibited significant increases in zooplankton biomass and small increases in phytoplankton biomass. Nutrients resulting from high fish densities stimulated blooms of ungrazable Dinobryon, and extremely low zooplankton biomass when compared with fishless controls. Phosphorus excretion rates by zooplankton and fish explained 55% of the variance in total plankton biomass in predation-free enclosures and 95% of the variance in chlorophyll a concentrations for enclosures with predators and fish-regenerated nutrients. The results of this experiment suggest that algal production is greatly enhanced by excretion of nutrients by fish, while grazer control is less important.
Acidification Effects on the Algal–Zooplankton Interface
Authors: Havens Karl E.
Published: June 2008

An in situ mesocosm experiment was done to assess the impacts of acidification on algal and zooplankton biomass and C assimilation, and on the efficiency of energy transfer in the grazing food chain. Triplicate mesocosms were left untreated (pH 8.5), or were acidified to pH 6.5, 5.5, or 4.5 with H2SO4 over 9 d. Algal biomass was reduced at pH 6.5 and lower, but showed no further decline across the gradient of pH 6.5–4.5. Algal C assimilation rates consistently declined with decreasing pH, reflecting a shift in dominance to larger, less productive cells at pH 5.5 and 4.5. Zooplankton biomass and productivity also declined with decreasing pH, as nearly all crustacean herbivores became extinct. In the low-pH treatments, only cyclopoids and rotifers persisted. Overall, there were significant reductions in the ratios of zooplankton/algal biomass and zooplankton/algal C assimilation (ecological transfer efficiency) with declining pH. The latter was a result of reduced grazer biomass, rather than reduced grazing efficiency; the mean zooplankton P/B ratio at pH 4.5 exceeded that measured in the higher pH treatments.
Mitochondrial DNA Differentiation in Western North Atlantic Populations of Haddock (Melanogrammus aeglefinus)
Authors: Zwanenburg K. C. T. , Bentzen P. , Wright J. M.
Published: June 2008

Mitochondrial DNA polymorphism was examined in haddock (Melanogrammus aeglefinus) from five offshore banks in the western North Atlantic. A total of 21 genotypes were observed in an initial survey of 54 haddock with 12 restriction endonucleases. Five enzymes that revealed most of the genetic variation were used in an expanded survey from which we observed 22 genotypes among 133 haddock. Both the 12- and 5-enzyme results showed that haddock from each of the five banks comprised a mixture of divergent genotypes that could each be assigned to one of at least four groups of related genotypes differing by mean estimated divergences of 0.6–0.8%. These divergent genotypes may have arisen in past haddock populations that were more isolated than those of the present. Although genotype frequencies did not differ significantly in most pairwise comparisons of banks, two measures of genetic (dis)similarity were significantly correlated with geographic distance as well as with the presence and relative size of deepwater (> 180 m) channels separating the banks. One of the genotype groups also exhibited a geographic cline in frequency of occurrence. These features indicate that gene flow among populations is restricted, and hence support the existence of discrete stocks of haddock.
Hooded Seal (Cystophora cristata) Pup Production in the Gulf of St. Lawrence
Authors: Hammill M. O. , Stenson G. B. , Myers R. A.
Published: June 2008

Systematic visual aerial surveys were flown in the southern Gulf of St. Lawrence during March 1990 and 1991 to estimate hooded seal (Cystophora cristata) pup production. In 1990, the main whelping patch, occupying an area of 264 km2, was located near Cape Breton Island. One hundred and five pups were counted on 17 transects, resulting in a mean density of 1.74 pups∙kim−2 and an estimated pup production of 1638 (SE = 466). In 1991, a large whelping patch was located to the west of the Magdalen Islands, a second off the coast of Prince Edward Island, and a small patch was later found south of the Magdalen Islands. The two major patches were surveyed, resulting in a pup production estimate of 1564 (SE = 101). During the 1991 surveys, an estimated 71–93% of the pups were on the ice. Correcting for the distribution of births results in a minimum 1991 pup production estimate of 2006 (SE = 190) for the Gulf of St. Lawrence.
Population Genetics of the Hard Clam,Mercenaria mercenaria, at the Northern Limit of Its Range
Authors: Dillon Jr. Robert T. , Manzi John J.
Published: June 2008

Canadian populations of Mercenaria deserve recognition as stocks distinct from the larger population of the U.S. Atlantic coast. Although the hard clam occupies a virtually continuous range from Florida to Massachusetts, its distribution north of Cape Cod becomes disjunct. Here, we use protein electrophoresis to determine gene frequencies a seven polymorphic enzyme loci in clam populations from Maine, USA, and New Brunswick and Prince Edward Island, Canada, and compare our results with previously published data from Massachusetts. The fit to the Hardy–Weinberg expectation within populations was very good. The Maine population showed small but statistically significant divergence from its putative source population to the south at most loci, with an apparent loss of two rare alleles. Both Canadian populations showed larger levels of divergence, with the loss of 6–12 alleles and significant reductions in overall heterozygosity. The recognition of a St. Lawrence stock of hard clams at Prince Edward Island may have important implications for the fishery.
Survival of Northern Atlantic Cod (Gadus morhua) Eggs and Larvae when Exposed to Ice and Low Temperature
Authors: Valerio Paul F. , Goddard Sally V. , Kao Ming H. , Fletcher Garth L.
Published: June 2008

Freeze resistance of eggs and larvae of Atlantic cod (Gadus morhua) from the northern cod stock was investigated to determine whether ice contact could affect survival during the spring spawning season off Newfoundland. Egg and larval homogenates did not appear to contain antifreeze proteins (mean freezing points −0.78 and −0.88 °C, respectively). However, cod eggs did not freeze at −1.8 °C in icy aerated seawater, could be undercooled to −4.0 °C in ice, and froze at temperatures between −4.1 and −1 7 °C; freeze resistance depended on the integrity of the chorion. Larvae withstood undercooling to −1.8 °C, provided they were not brought into direct contact with ice crystals, if directly touched with ice, larvae froze at −1.36 °C (feeding stage) or −1.34 °C (yolk-sac), approximately 0.5 °C lower than would be expected from the freezing temperatures of their body fluids. The nature of their external epithelium and delayed development of sensitive gill structures below 0 °C may contribute to larval freeze resistance. Cod eggs and larvae are found in spring off Newfoundland and Labrador, when sea temperatures can be as low as −1.8 °C and ice cover extensive. While cod eggs are remarkably freeze resistant, such environmental conditions may cause freezing mortalities in larval cod.
Sigmoid Relationships between Phosphorus, Algal Biomass, and Algal Community Structure
Authors: Watson Susan , McCauley Edward , Downing John A.
Published: June 2008

It has long been recognized that there is a positive relationship between total phytoplankton biomass and eutrophication. Recent independent studies demonstrated that algal biomass (chlorophyll) actually responds in a nonlinear, sigmoidal fashion with increasing phosphorus levels among lakes. Chlorophyll has been considered (by some authors) as an inconsistent estimate of algal biomass. Using a wide range of published data, we first demonstrate that the sigmoidal nature of the phosphorus–biomass relationship is quite robust, and not simply generated by a systematic variation in the relationship between algal chlorophyll to cell volume ratio and nutrient levels. We show that the sigmoid relationship with total phosphorus persists whether algal biomass is measured by chlorophyll or biovolume. We hypothesize that this nonlinearity actually reflects an underlying systematic variation in one or more of the components of total phytoplankton biomass. In this paper, we examine two functional size groups and show that the large inedible fraction exhibits a strong, nonlinear response to increasing nutrient levels, while the small edible algae do not vary systematically with phosphorus. We hypothesize that this discontinuous shift in the ratio of edible to inedible phytoplankton should be accompanied by concomitant shifts in the structure of the herbivore community.
Relationship between Diurnal Activity Patterns, Cryptic Coloration, and Subsequent Avoidance of Predaceous Fish by Perlid Stoneflies
Authors: Feltmate Blair W. , Williams D. Dudley , Montgomerie Adriane
Published: June 2008

We demonstrate that prey (stoneflies), which are either solidly coloured or patterned, coordinate intervals of maximum daytime activity with periods when visually foraging predators (rainbow trout, Oncorhynchus mykiss) are least able to detect them. In this study, rainbow trout attacked solidly coloured stonefly nymphs (Paragnetina media) more frequently under conditions of low illumination (simulated dawn and dusk) than high illumination (simulated midday) whereas the frequency of attacks on patterned stonefly nymphs (Agnetina capitata) was reversed. Consequently, in both the presence and absence of trout, the activity (i.e. frequency of crawling) of P. media and A. capitata was highest under conditions of high and low illumination, respectively. The number of attacks by trout on all nymphs was significantly less when nymphs were on dark-brown, rather than mottled, substrates. When given a choice between dark-brown and mottled substrate, both species selected dark substrate. Suggestions that the visual acuity of predators varies as a function of light intensity and the coloration, patterning, and daytime activity of prey are corroborated for the first time.
Reproductive Tactics of Walleye (Stizostedion vitreum) in Lake Erie
Authors: Henderson Bryan A. , Nepszy Stephen J.
Published: June 2008

The average age of mature female walleye (Stizostedion vitreum) (5 yr) assessed in October or November is about 1 yr younger than the average age of spawners (6 yr) collected in April of the next year. To determine why there was a delay in the age at first reproduction, walleye were collected in western Lake Erie and the Thames River. Energy stored in the form of fat increased exponentially with body weight. Gonad size increased linearly with body size, the ovary constituting a relatively constant 18–22% of total body weight over all body sizes. Although allometric relations constrain energy acquistion and allocation, ecological conditions (water temperature and prey availability) affect variability within those bounds. Surplus energy (stored energy minus energy allocated to gonads and metabolism) was increasingly available for females greater than 2 kg, corresponding to females older than 5 yr. Thus, age at first reproduction is influenced by the physiological constraints on acquiring and allocating energy and by the energetic demands of spawning. Energetic condition of the spawning stock was associated with year-class strength. The strong 1991 year-class was produced by females with greater surplus energy than the spawners of the weak 1992 year-class.
Mixed-Species Yield-per-Recruit Simulations of the Effect of Seasonal Closure on a Central Queensland Coastal Prawn Trawling Ground
Authors: Gribble N. , Dredge M.
Published: June 2008

An assessment of the effect of seasonal closure on the central Queensland coastal prawn trawling grounds was carried out by mixed-species yield-per-recruit simulations of the fishery based on parameters determined from field studies and analysis of logbook data. Under a conventional scenario of constant fishing mortality, simulations suggest little positive effect on yield to be achieved from closures of up to 15 wk in duration. Economic gain would have to be made via reduced costs during the closure, rather than through increased value of the postclosure yield. Logbook data clearly showed that the fishery underwent a heavy pulse of effort, immediately after the fishing season opened. Nonlocal boats had entered the fishery to take advantage of the prawns available. Using this more realistic regime of fishing mortality, simulations suggest a significant increase in yield and value of catch. The increase was caused by boosted exploitation rates of the stocks and was determined by the magnitude of the effort pulse rather than as a direct benefit of the closure.
Comparative Survival and Growth of Two Strains of Atlantic Cod (Gadus morhua) through the Early Life Stages in a Marine Pond
Authors: Blom Geir , Svåsand Terje , Jørstad Knut E. , Otterå Håkon , Paulsen Ole I. , Holm Jens C.
Published: June 2008

Survival and growth of two strains of Atlantic cod (Gadus morhua) were compared through the larval and juvenile stages in a marine pond in western Norway in 1990 and 1991. Strain A was homozygous for the genetic marker allele GPI-1*30 at the glucose phosphate isomerase (GPI) locus expressed in white muscle, and Strain B possessed other GPI-1* genotypes, in 1990 the frequency of Strain B increased significantly from the larval to the juvenile stage; however, in 1991 the frequency of Strain A increased slightly but not significantly from the larval to the juvenile phase. Larval mortality did not differ significantly between strains any year, but juvenile mortality was significantly lower in Strain B in 1990 and Strain A in 1991. Average growth rates in length estimated from regressions were not significantly different between strains during the larval and juvenile period any year, but initial length was significantly larger in Strain B in 1990 and Strain A in 1991. Our results indicated that food limitation during the early juvenile stage induced differential size-selective mortality among the strains due to small differences in body size and actual age between strains. Body size did not become important for survival until the food-limited regime had occurred.
Effects of the Bacterial Insecticide Bacillus thuringiensis var. kurstaki (Btk) on a Stream Benthic Community
Authors: Richardson John S. , Perrin Chris J.
Published: June 2008

Commercial formulations of the insecticidal bacterium Bacillus thuringiensis var. kurstaki (Btk) are frequently sprayed over bodies of water. The hypothesis that Btk poses a threat to stream communities was tested using streamside, flow-through mesocosms which received water and invertebrate colonists from a second-order stream in southwestern British Columbia; low (50 BIU/ha) and high (≥ 5000 BIU/ha) treatment levels were contrasted with controls. There were no significant differences in the density or composition of benthos sampled 7 d after Btk application. The densities were highest in the high-dose mesocosms. There were no significant differences in emergence rate of adults due to treatment. During the 2.5-h treatment, there were marginally elevated drift rates of the mayfly Baetis when exposed to the solution, but these differences were negated during the remainder of the 24-h period. Leaf packs lost significantly more mass in controls than in high-dose mesocosms, but there were no significant differences in the numbers of macro-invertebrates on those leaf packs. There was no evidence that addition of Btk to stream mesocosms created adverse effects for this benthic community, even at > 100 times expected exposure rates.
Statistical Properties of an Index of Biological Integrity Used to Evaluate Water Resources
Authors: Fore Leska S. , Karr James W. , Conquest Loveday L.
Published: June 2008

We determined the statistical properties of the index of biotic integrity (IBI) from electrofishing samples collected from Ohio streams. Although IBI is widely used to evaluate the condition of water resources by biologists and resource managers, expanding its role as a regulatory tool depends on statistical validation of its precision and power. We addressed these issues by constructing an additive variance model for IBI and testing the assumptions of that model directly with a bootstrap resampling algorithm and simulations using field data. Statistical properties of IBI supported the use of standard analysis techniques such as ANOVA for hypothesis testing. We determined with power analysis that IBI can distinguish between five and six nonoverlapping categories of biotic integrity based on a model that includes the effects of measurement error, variability of fish assemblages through time, and statistical interaction of location and time. We conclude that IBI is an effective monitoring tool that can be used to communicate qualitative assessments to the public and policy makers or to provide quantitative assessments for a legal or regulatory context based on confidence intervals or hypothesis testing procedures.
Use of a Stereo-video System to Estimate the Energy Expenditure of Free-swimming Fish
Authors: Krohn Martha M. , Boisdair Daniel
Published: June 2008

We tested the ability of a stereo-video method to provide estimates of the metabolic costs of spontaneous swimming by simultaneously video taping free-swimming fish and measuring their oxygen consumption. Three swimming characteristics (speed, turning rate, and acceleration) obtained from image analysis of video recordings explained, on average, 80% of the variability in spontaneous swimming costs. Colinearity among the swimming characteristics prevented us from estimating their relative importance. We converted the swimming speeds recorded by the stereo-video system to metabolic costs using relationships from the literature between oxygen consumption and speed during forced swimming (swimming with constant speed and direction). Spontaneous swimming costs, measured directly by respirometry, were, on average, six times higher than the costs predicted by the forced swim relationships for the same speeds. This difference suggests that the metabolic costs of turning and acceleration can be substantial. Relationships used to convert movements obtained with the stereo-video method into energy expenditure should therefore be developed using spontaneously swimming fish and should include turning rate and acceleration as well as speed.
Effects of Experimental and Cultural Lake Acidification on Littoral Benthic Macroinvertebrate Assemblages
Authors: Stephenson Malcolm , Mierle Gregory , Reid Ronald A. , Mackie Gerald L.
Published: June 2008

A simple method for the assessment of littoral benthic macroinvertebrate (BMI) assemblages in lakes was developed at the Experimental Lakes Area (ELA) in northwestern Ontario and applied to 64 lakes in central Ontario. The presence (1) or absence (0) of BMI taxa was established at five sites on each lake, using a kick-and-sweep net technique. Summing presence/absence scores across sites ranked the importance of each taxon in each lake on a scale of 0 to 5. Relationships between the BMI assemblages were assessed using nonmetric multidimensional scaling (NMDS), based upon the Kendall's τ correlation matrix. Correlations between NMDS dimension 1 and 2 scores and environmental variables identified factors that may structure BMI assemblages. The BMI assemblages of three experimentally acidified and seven reference lakes at the ELA were correlated strongly with lake pH. The BMI assemblage structure of central Ontario lakes was predicted by lake area and sensitivity to acidification (NMDS dimension 1) and by lake elevation (NMDS dimension 2). The BMI assemblages of small or Ca-poor and acidic lakes include fewer oligochaetes, mayflies, and Cryptochironomus and Stictochironomus (chironomids) and more Odonata, Trichoptera, Chironomus, Conchapelopia, Microtendipes, and Procladius (chironomids), and Crangonyx (Amphipoda) than other central Ontario lakes.
A Possible Relict Population of Mesodesma deauratum (Turton):Bivalvia (Mesodesmatidae) from the Southeast Shoal, Grand Banks of Newfoundland
Authors: Hutcheson Michael S. , Stewart Patrick L.
Published: June 2008

Extremely dense, localized concentrations of Turton's wedge clam Mesodesma deauratum (Turton) were found in quantitative grab samples on poorly sorted, medium to fine, low organic content sands (total organic carbon < 0.05%) at depths of 44–51 m at a single location on eastern Southeast Shoal of the Grand Banks of Newfoundland. Mean densities ranged from 24 to 5890 individuals∙m−2 and wet weight standing crop from 0 to 21.4 kg∙m−2. A peak standing crop of 69.4 kg∙m−2 was observed in one grab. There was a strong bimodal size distribution (17–27 and 34–56 mm shell length) at the site, but the two size groups never occurred together. Based on external growth checks, the smaller individuals were 4–5 yr old and the larger ones 10 to more than 15 yr. This population is suggested to be a relict of shallow littoral populations which probably existed in the area in the late Wisconsinan glacial period.
Responses of Plankton, Turbidity, and Macrophytes to Biomanipulation in a Shallow Prairie Lake
Authors: Hanson Mark A. , Butler Malcolm G.
Published: June 2008

We evaluated effects of complete fish kill in a large, shallow, eutrophic lake in Minnesota. Low densitites of Bosmina and Chydorus (< 100∙L−1) were replaced in the early spring/early summer by high densities of larger Daphnia galeata and D. pulex (> 100∙L−1) during the first year after the fish kill (1988). During peak daphnid abundance (May–June), chlorophyll a concentrations and edible phytoplankton were reduced, water transparency increased, and submerged macrophytes expanded. Orthophosphate and ammonia were detectable during clear-water phases, indicating that phytoplankton were not severely nutrient limited. Increased water transparency in subsequent years (1989–90) apparently was related to decreased sediment resuspension and lower algal biomass owing to the expansion of submerged plants. The fish kill invoked a strong initial response that transmitted to the phytoplankton level and increased water clarity. Higher transparency persisted during subsequent years because submerged macrophytes both responded to improved water clarity and subsequently prolonged it. These results support the contention that removal of fish from shallow lakes may invoke "cascading impacts" that enhance water clarity, stimulate macrophytes, and establish a new steady state.
Comparative Pharmacokinetics and Bioavailability of Oxolinic Acid in Channel Catfish (Ictalurus punctatus) and Rainbow Trout (Oncorhynchus mykiss)
Authors: Kleinow Kevin M. , Jarboe Herman H. , Shoemaker Kathy E. , Greenless Kevin J.
Published: June 2008

The pharmacokinetics, bioavailability, and disposition of oxolinic acid (OA), a quinolone antibacterial drug, were examined in a warmwater (channel catfish (Ictalurus punctatus)) and coldwater fish species (rainbow trout (Oncorhynchus mykiss)). Studies were performed at 24 and 14 °C for catfish and at 14 °C for trout to compare temperature- and species-related differences. Analysis of OA pharmacokinetics when determined by HPLC provided elimination half-life [Formula: see text], volume of distribution (Vss), and clearance (Clb) estimates for 24 °C catfish, 14 °C catfish, and 14 °C trout of 40.9, 69.3, and 81.3 h, 939, 880, and 1817 mL/kg, and 16.3, 8.9, and 16.9 mL∙kg∙h−1, respectively. Following oral administration, OA plasma concentrations peaked between 8 and 24 h for all treatments; however, 14 °C trout and 14 °C catfish sustained peak concentrations for a longer duration than 24 °C catfish. Oral OA bioavailabilities were 56.0, 91.8, and 90.7% for 24 °C catfish, 14 °C catfish, and 14 °C trout, respectively. OA distribution data for muscle of 14 °C catfish demonstrated an inordinately high peak concentration and delayed time to peak relative to other treatments. Elimination half-lives of OA in muscle were 33.1, 54.3, and 141 h for 24 °C catfish, 14 °C catfish, and 14 °C trout, respectively.
Estimation of crown form for six conifer species of northern California
Authors: Biging Greg S. , Wensel Lee C.
Published: June 2008

Geometric models are presented for the prediction of crown volume and width at any height in the crown of six conifer species in the Sierra Nevada. Crown volume is defined as the geometric space occupied by the crown and is allometrically related to the diameter, height, and crown ratio of individual trees. Crown diameter is derived from crown volume, tree height, and crown ratio. The crown volumes and associated measures can be used to compute indices of individual tree competition such as those used in the CACTOS (California Conifer Timber Output Simulator) system or to compute other measures such as wildlife habitat suitability or insect damage potential. Estimation equations are developed by regression using data collected on crowns of 593 felled trees. The equations use dbh, total height, and crown ratio to estimate total crown volume, crown volume above a specified height, and cumulative crown cross sectional area at a specified height.
Site-specific growth and nutrition of planted Piceamariana in the Ontario Clay Belt. III. Biomass and nutrient allocation
Authors: Munson Alison D. , Timmer V. R.
Published: June 2008

First and second-season morphological responses of outplanted Piceamariana (Mill.) B.S.P. (black spruce) seedlings to site conditions of three cutover boreal ecosystems were analysed in terms of biomass and nutrient allocation to structural components (current shoots, previous year's shoots, stem, and roots). Improved N nutrition on an upland Feathermoss site had the greatest positive effect on biomass and nutrient allocation to current shoots, while allocation to other components was reduced. Seedlings on lowland Alnus – Herb poor and Ledum sites responded to site nutrient stress by allocating more biomass to the stem and roots. Multivariate procedures indicated that the overall pattern of biomass and nutrient allocation was significantly affected by site, and also differed depending on the individual element considered (N, P, K, Ca, Mg). Changes in nutrient-use efficiency with site were also investigated. With decreased seedling N uptake on the two lowland sites, biomass production per unit N increased, but specific absorption rate of roots decreased. Under N limitation, evidence for nutrient retranslocation was noted by decreases in nutrient content in the same component over 2 years and by lower concentrations in older shoots than in current growth. The alternative allocation of biomass and nutrients to seedling components with changes in site nutrition has implications for tree development on specific sites, and also for management of site nutrient regime to improve early seedling performance.
Invitro regeneration of plantlets of Canary Island pine (Pinuscanariensis)
Authors: Pulido Carolina Martinez , Harry Indra S. , Thorpe Trevor A.
Published: June 2008

A protocol is described for plantlet formation in juvenile tissues of Pinuscanariensis Sweet ex K. Spreng. (Canary Island pine). Adventitious buds were induced on 3-day-old cotyledonary explants cultured on Bornman's MCM medium supplemented with cytokinin. The concentration of benzylaminopurine, the use of other cytokinins alone or in combination with benzylaminopurine, and the concentration of mineral salts strongly affected the bud forming capacity of the cotyledonary explants. Also, the age of the explants significantly influenced the frequency of adventitious bud formation. Bud development was enhanced by the elimination of phytohormones, a reduction of mineral salts and sucrose, and the inclusion of activated charcoal in the medium. The conditions used during the induction phase strongly affected the ability of the induced buds to develop into vigorous rootable shoots. Vitrification problems were eliminated by transferring the shoots to the elongation medium solidified with Gelrite, and shoot remultiplication was enhanced by removing the apical bud. Maximum rooting was obtained by pulsing shoots with a high concentration of indolebutyric acid and by using peat–vermiculite or peat–vermiculite–perlite as substrates. Roots developed within 6–8 weeks, and the regenerated plantlets were transferred to soil under nonsterile conditions, where further development occurred.
Extending the range of applicability of an individual tree mortality model
Authors: Hamilton Jr. David A.
Published: June 2008

Limits are frequently encountered in the range of values of independent variables included in data sets used to develop individual tree mortality models. If the resulting model is to be utilized, its ability to extrapolate to conditions outside these limits must be evaluated. This paper describes the development and evaluation of six assumptions required to extend the range of applicability of an individual tree mortality model previously described. The assumptions deal with mortality in very dense stands, mortality for very small trees, mortality on habitat types and regions poorly represented in the data, and mortality for species poorly represented in the data.
Cellulose decomposition in southeast Alaskan forests: effects of pit and mound microrelief and burial depth
Authors: McClellan Michael H. , Bormann Bernard T. , Cromack Jr. Kermit
Published: June 2008

In southeast Alaska, where wildfires are rare, uprooting is the predominant disturbance influencing stand development in Tsugaheterophylla (Raf.) Sarg. – Piceasitchensis (Bong.) Carr. forests. We compared 1-year decomposition of confined cellulose filter paper placed in the organic horizon and at the organic–mineral interface on both tree-throw mounds and adjacent pits. Decomposition rates were not significantly different between pits and mounds, but filter papers within the organic layer lost 33.7% of their original dry mass, and packs within the mineral layer lost 14.5% of their mass. This effect was highly significant (p < 0.01). We concluded that the greater organic accumulations observed in pits are largely due to litter redistribution.
Jack pine budworm populations and staminate flowers
Authors: Nealis V. G.
Published: June 2008

The relationship between jack pine budworm (Choristoneurapinuspinus Free.) and staminate flowers of its principal host, jack pine (Pinusbanksiana Lamb.), is reviewed. Data from jack pine budworm outbreaks in northern Ontario are used to examine the relationship between the relative frequency of staminate shoots and the mortality of early-and late-larval jack pine budworm. Although there was some indication that early-instar budworm may be more successful at establishing feeding sites when flowers are abundant, there was no evidence that larval survival during the active feeding stages of the budworm was enhanced by the presence of staminate flowers. The assumption that staminate flowers greatly influence jack pine budworm population dynamics is questioned.
THE CONJUGACY CLASSES OF A SUBGROUP $S_{n}^{m} : C_{m}$ OF Smn, prime m
Authors: ZIMBA KENNETH , RABOSHAKGA MERIAM
Published: June 2008

The conjugacy classes of any group are important since they reflect some aspects of the structure of the group. The construction of the conjugacy classes of finite groups has been a subject of research for several authors. Let n,m be positive integers and [Formula: see text] be the direct product of m copies of the symmetric group Sn of degree n. Then [Formula: see text] is a subgroup of the symmetric group Smn of degree m × n. Let g∈Smn, of type [mn] where each m-cycle contains one symbol from each set of symbols in that order on which the copies of Sn act. Then g permutes the elements of the copies of Sn in [Formula: see text] and generates a cyclic group Cm = 〈g〉 of order m. The wreath product of Sn with Cm is a split extension or semi-direct product of [Formula: see text] by Cm, denoted by [Formula: see text]. It is clear that [Formula: see text] is a subgroup of the symmetric group Smn. In this paper we give a method similar to coset analysis for constructing the conjugacy classes of [Formula: see text], where m is prime. Apart from the fact that this is an alternative method for constructing the conjugacy classes of the group [Formula: see text], this method is useful in the construction of Fischer–Clifford matrices of the group [Formula: see text]. These Fischer–Clifford matrices are useful in the construction of the character table of [Formula: see text].
ASSERTIONALLY EQUIVALENT QUASIVARIETIES
Authors: BLOK W. J. , RAFTERY J. G.
Published: June 2008

A translation in an algebraic signature is a finite conjunction of equations in one variable. On a quasivariety K, a translation τ naturally induces a deductive system, called the τ-assertional logic of K. Two quasivarieties are τ-assertionally equivalent if they have the same τ-assertional logic. This paper is a study of assertional equivalence. It characterizes the quasivarieties equivalent to ones with various desirable properties, such as τ-regularity (a general form of point regularity). Special attention is paid to structural properties of quasivarieties that are assertionally equivalent to their varietal closures under an indicated translation.
SEMI-SUPERVISED CLASSIFICATION USING BRIDGING
Authors: CHAN JASON , KOPRINSKA IRENA , POON JOSIAH
Published: June 2008

Traditional supervised classification algorithms require a large number of labelled examples to perform accurately. Semi-supervised classification algorithms attempt to overcome this major limitation by also using unlabelled examples. Unlabelled examples have also been used to improve nearest neighbour text classification in a method called bridging. In this paper, we propose the use of bridging in a semi-supervised setting. We introduce a new bridging algorithm that can be used as a base classifier in most semi-supervised approaches. We empirically show that the classification performance of two semi-supervised algorithms, self-learning and co-training, improves with the use of our new bridging algorithm in comparison to using the standard classifier, JRipper. We propose a similarity metric for short texts and also study the performance of self-learning with a number of instance selection heuristics.
THE DIMENSION OF ECOCs FOR MULTICLASS CLASSIFICATION PROBLEMS
Authors: PIMENTA EDGAR , GAMA JOÃO , CARVALHO ANDRÉ
Published: June 2008

Several classification problems involve more than two classes. These problems are known as multiclass classification problems. One of the approaches to deal with multiclass problems is their decomposition into a set of binary problems. Recent work shows important advantages related with this approach. Several strategies have been proposed for this decomposition. The strategies most frequently used are All-vs-All, One-vs-All and Error Correction Output Codes (ECOC). ECOCs are based on binary words (codewords) and have been adapted to deal with multiclass problems. For such, they must comply with a number of specific constraints. Different dimensions may be adopted for the codewords for each number of classes in the problem. These dimensions grow exponentially with the number of classes present in a dataset. Two methods to choose the dimension of a ECOC, which assure a good trade-off between redundancy and error correction capacity, are proposed in this paper. The proposed methods are evaluated in a set of benchmark classification problems. Experimental results show that they are competitive with other multiclass decomposition methods.
LARGE SCALE EXPERIMENTS WITH NAIVE BAYES AND DECISION TREES FOR FUNCTION TAGGING
Authors: LINTEAN MIHAI , RUS VASILE
Published: June 2008

This paper describes the use of two machine learning techniques, naive Bayes and decision trees, to address the task of assigning function tags to nodes in a syntactic parse tree. Function tags are extra functional information, such as logical subject or predicate, that can be added to certain nodes in syntactic parse trees. We model the function tags assignment problem as a classification problem. Each function tag is regarded as a class and the task is to find what class/tag a given node in a parse tree belongs to from a set of predefined classes/tags. The paper offers the first systematic comparison of the two techniques, naive Bayes and decision trees, for the task of function tags assignment. The comparison is based on a standardized data set, the Penn Treebank, a collection of sentences annotated with syntactic information including function tags. We found out that decision trees generally outperform naive Bayes for the task of function tagging. Furthermore, this is the first large scale evaluation of decision trees based solutions to the task of functional tagging.
LOW-EFFORT LABELING OF NETWORK EVENTS FOR INTRUSION DETECTION IN WLANS
Authors: KHOSHGOFTAAR TAGHI M. , SELIYA NAEEM , SEIFFERT CHRIS
Published: June 2008

A typical data mining approach to network intrusion detection mandates a training dataset of network events labeled as either normal or a particular attack category. Such a training dataset is usually very large since there are many events to track. This is particularly the case in a WLAN where the number of devices communicating with the WLAN can be large and with adhoc connectivity. The large size of the unlabeled training dataset creates a problem for the domain expert who is asked to label the records toward creating a training dataset. We present an effective approach by which the number of network records the expert has to examine is a relatively small proportion of the given training dataset. A clustering algorithm is used to form relatively coherent groups which the expert examines as an entity to label records as one of four classes: Red (definite intrusion), Yellow (possibly intrusion), Blue (probably normal), and Green (definite normal). Subsequently, an ensemble classifier-based data cleansing approach is used to detect records that were likely mislabeled by the expert. The proposed approach is investigated with a case study of a large real-world WLAN. In addition, ensemble classifier-based intrusion detection models built using the labeled training dataset demonstrate the effectiveness of the labeling process with good generalization accuracy over multiple test datasets.