bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Coded Wire Tag Returns from Commercial Catches
Authors: Cormack R. M. , Skalski J. R.
Published: June 2008

Three alternative but equivalent approaches to the analysis of coded wire tag (CWT) data using log-linear models are presented. All three use iteratively weighted least squares to estimate treatment effects in hatchery releases under the assumption that the variance of a count is proportional to its expected value. The commonly made assumption of normal distributions with constant variance for recovery rates is inefficient. Analysis of tag recovery at the most disaggregated level (i.e. the level at which the sample fraction f is measured) is found necessary for valid inferences. Failure to include zero counts in analyses of recovery data is also shown to induce or mask interactions among CWT recoveries. Recoveries of CWT from coho salmon (Oncorhynchus kisutch) are used to illustrate the method of analysis. Coordinated CWT releases to facilitate mixing of stocks is recommended in the design of hatchery studies.
Feeding, Reconditioning, and Rematuration Responses of Captive Atlantic Salmon (Salmo salar) Kelt
Authors: Crim L. W. , Wilson C. E. , So Y. P. , Idler D. R. , Johnston C. E.
Published: June 2008

Wild Atlantic salmon (Salmo salar) kelt were reconditioned in the laboratory by initiating their feeding during the winter on freshly thawed Atlantic silverside (Menidia menidia) supplemented with vitamins and trace minerals. Some kelt improved in condition by April, and by June the majority were reconditioned. Some females skipped a year of reproductive activity with most rematuring a second time the following year. One group of females rematured and was spawned a third time without skipping another reproductive cycle. Plasma levels of vitellogenin, estradiol, and testosterone remained low in reproductively inactive female kelt; in contrast, these substances increased and peaked just prior to spawning in late October in maturing female kelt. In males, plasma levels of testosterone and 11-ketotestosterone rose in conjunction with testicular development, reaching peak hormone values during the period of spermiation. Although good-quality eggs were collected from reconditioned kelt according to high egg fertilization rates and high rates of egg survival through the eyed and hatching stages, most kelt yolksac larvae died just prior to swim-up. High mortality rates for kelt larvae suggest that either the silverside diet is nutritionally deficient or that the physiology of reconditioned kelt broodstock is inadequate for good-quality egg production.
Linkage between Islands and Benthos in the Ohio River, with Implications for Riverine Management
Authors: Thorp James H.
Published: June 2008

Anthropogenic reductions in braiding, meandering, and snag abundance have diminished habitat heterogeneity of regulated rivers, factors directly influencing island formation, retentive capacity of the ecosystem, and community diversity. Habitat heterogeneity associated with riverine islands should, therefore, be of paramount importance to the ecosystem and may require special management protection. To understand the influence of these alluvial formations on riverine benthos, macroinvertebrate assemblages were sampled near three islands in the Ohio River above Louisville, Kentucky, USA. Benthos was collected along six bank-to-bank transects located 1 km above and below islands and near the head, middle, and foot of islands. Islands have significant positive effects on invertebrate density and diversity that appear related to changes in physical habitat characteristics. Current velocity and substrate particle size are diminished in narrow channels between islands and shore, and areal extent of the littoral zone is enhanced within an otherwise deepwater region. Shallow water and slower currents promote growth of submerged vascular plants and macrophytic algae. Because of a relatively low exploitation by humans, islands probably enhance snag formation and input of organic matter, both factors having positive effects on macrofauna. Creation of selected riverine preserves near islands as a management tactic is recommended.
Assessment of the Impact of the Myxosporean Parasite Ceratomyxa shasta on Survival of Seaward Migrating Juvenile Chinook Salmon, Oncorhynchus tshawytscha, from the Fraser River, British Columbia
Authors: Margolis L. , McDonald T. E. , Whitaker D. J.
Published: June 2008

Approximately 3.3% of more than 3500 seaward migrating juvenile chinook salmon (Oncorhynchus tshawytscha) collected from the lower reaches and off the mouth of the Fraser River, British Columbia, between March and August 1985–87 were infected with Ceratomyxa shasta (Protozoa: Myxosporea). The fish were held live for up to 151 d before examination to allow the infections to become patent. The first infected fish were detected in samples taken in late May to early June, approximately 4 wk after the river water temperature had reached 10 °C. By this time, 40–65% of the fish had been collected, indicating that the majority of the juvenile chinook salmon had left the Fraser River before the infective stage of the parasite was present. Significant differences in prevalence of C. shasta were associated with both the migration route chosen by the fish and their age. Fish that used the lower flow rate North Arm had a greater prevalence (6.8%) of infection than those that migrated down the Main Arm (2.1%). Age 0 fish had a significantly higher prevalence (5.2%) of C. shasta than the age 1 group (1.5%). It is concluded that C. shasta is not a major cause of mortality of downstream migrating juvenile Fraser River chinook salmon.
Whole-River Fertilization Stimulates Fish Production in an Arctic Tundra River
Authors: Deegan Linda A. , Peterson Bruce J.
Published: June 2008

Increased growth rates for adult and young-of-the-year Arctic grayling (Thymallus arcticus) were measured after the addition of fertilizer to an oligotrophic Alaskan tundra river. The strongest response to the fertilization was seen in young-of-the-year grayling; the adult response was more variable. Whole-river phosphorus fertilization of the Kuparuk River, Alaska, during 1985–90 resulted in a 1.4- to 1.9-fold increase in the size of age 0+ fish and a 1.5- to 2.4-fold increase in the weight gain of adult grayling in some years. Neutral lipid storage in adult grayling was increased 1.3- to 3.4-fold in the fertilized zone compared with that in fish from the control zone. There was no detectable difference between the zones in gonad mass, percent lipid in eggs, or egg size. These results suggest that autochthonous production is an important energy source for fish in tundra streams and that nutrient limitation of stream ecosystems affects the highest trophic levels. These findings have importance for understanding the function of river ecosystems, for assessing human impacts on rivers, and for managing fisheries.
Geochemistry of Quebec North Shore Salmon Rivers during Snowmelt: Organic Acid Pulse and Aluminum Mobilization
Authors: Campbell Peter G. C. , Hansen Hans J. , Dubreuil Bertrand , Nelson William O.
Published: June 2008

The episodic acidification of three salmon rivers on the Quebec North Shore during spring snowmelt is shown to result mainly from increased inputs of organic acids rather than strong mineral acids. Appreciable mobilization of Al occurs during the spring pH depression, accompanied by marked changes in Al speciation. Saturation indices, calculated for each river with respect to microcrystalline gibbsite (KSO = 10−9.35), approach saturation for samples collected before or after the snowmelt period, but during maximum discharge, marked undersaturation is observed. Seasonal differences in Al–dissolved organic carbon (DOC) interactions were also noted. Outside the snowmelt period, a linear logarithmic model proved successful in predicting concentrations of monomeric organic Al ([Al-org] = 3.55∙10−3∙{Al3+}0.129∙{H+}0∙[DOC]0.91; n = 19, r2 = 0.92), but during snowmelt, this model greatly overestimated [Al-org]. The failure of the model during this critical period is attributed to the presence in the spring DOC peak of an appreciable nonhumic (and non-Al-binding) component. Although concentrations of monomeric inorganic Al (notably fluoro–Al complexes) increase during the spring pH depression, levels do not appear to attain the thresholds for Al and H+ toxicity reported for juvenile Atlantic salmon (Salmo salar).
Unidirectional Natural Hybridization between Brown Trout (Salmo trutta) and Atlantic Salmon (S.salar) in Newfoundland
Authors: McGowan Colin , Davidson William S.
Published: June 2008

Protein electrophoresis and mitochondrial DNA analysis were used to detect the frequency and direction of natural hybridization between brown trout (Salmo trutta) and Atlantic salmon (S. salar) in nine Newfoundland rivers. In total, 37 hybrids were discovered in a sample of 792 juvenile fish for a regional frequency of 4.67%. Local frequencies ranged from 0.00 to 18.75% and were significantly heterogeneous. All of the hybrids sampled were produced from matings between female brown trout and male Atlantic salmon. Possible reasons for the breakdown of prereproductive isolating mechanisms between these species are considered. Reproductive characteristics of the populations involved appear to have a major influence on the dynamics of hybridization between these species in Newfoundland. It is proposed that an abundance of sexually mature Atlantic salmon parr in Newfoundland streams is responsible for both the frequency and direction of hybridization observed in this study.
Failure of Dietary Putrescine to Enhance the Growth of Rainbow Trout (Oncorhynchus mykiss)
Authors: Cowey C. B. , Cho C. Y.
Published: June 2008

Reduction of herring meal (to 100 g∙kg−1) in rainbow trout (Oncorhynchus mykiss) diets and its replacement by soybean and corn gluten meals led to reduced feed intake and growth. The diamine putrescine, when included in calf diets, reduced the effects of antinutritional factors in soybean meal; it also enhanced the growth of chicks. Putrescine (1–4 g∙kg−1) added to practical trout diets did not increase feed intake or growth over a 12-wk period. Putrescine concentrations in the trout tissues were not increased by this treatment, nor were the activities of the putrescine and polyamine biosynthetic enzymes ornithine decarboxylase and adenosylmethionine decarboxylase significantly changed. When a higher putrescine concentration (13.3 g∙kg−1) was used, in line with the calf diets, it reduced weight gain, feed intake, and gain/feed ratio. Lack of effect of putrescine at the lower concentrations (where it was effective with chicks) was ascribed to the enzyme diamine oxidase, shown to be active in the pyloric ceca and the anterior intestine of the trout. Passage of food through the gastrointestinal tract of trout is about 10-fold longer than in chicks. This may explain the failure of dietary putrescine to elevate tissue putrescine levels in trout.
Estimating the Mud Deposition Boundary Depth in Lakes from Wave Theory
Authors: Rowan D. J. , Kalff J. , Rasmussen J. B.
Published: June 2008

The mud deposition boundary depth (mud DBD) is the depth in lakes at which the boundary occurs between high-energy erosive environments (coarse-grained noncohesive sediments) and low-energy depositional zones where fine-grained cohesive sediments accumulate. We have derived a model from the theory of waves and sediment thresholds that predicts the upper limit to the distribution of fine-grained sediments in lakes of any size. Our results suggest that the several biggest storms each year, rather than extremely rare events, are responsible for the upper limit to the distribution of mud. However, significant areas of coarse-grained sediments and many mud DBDs occur deeper than this upper limit, usually on slopes greater than 3%. For sediment at the mud DBD (23 μm), we have developed an empirical relationship between slope and maximum horizontal velocity that demonstrates the significant effect of slope on reducing either sediment threshold velocity or sediment stability.
Indices of Relative Abundance from Fish Spotter Data based on Delta-Lognornial Models
Authors: Lo N. Chyan-huei , Jacobson Larry D. , Squire James L.
Published: June 2008

Fish spotters are pilots in small aircraft employed by commercial fishermen to locate, identify, estimate the size of, and direct boats toward pelagic fish schools. Data describing species, location, and size of schools can be inexpensively obtained from fish spotters but are difficult to interpret statistically. We developed an index of relative abundance from fish spotter data based on extended delta-lognormal models and applied the method to data for northern anchovy (Engraulis mordax). In contrast with previous approaches, our method used all available data, provided an index for northern anchovy that was proportional to abundance, and explicitly modeled factors (pilots, regions, seasons, and time of day) that affected observations by fish spotters. We also included information about mixed layer depth and sea surface temperature in models for a reduced study area and found that environmental data, where available, can be used to improve estimates of relative abundance from fish spotter data. Simulation results indicated that our approach is a cost-effective way to improve biomass estimates for pelagic species like northern anchovy.
Functional Response and Capture Timing in an Individual-based Model: Predation by Northern Squawfish (Ptychocheilus oregonensis) on Juvenile Salmonids in the Columbia River
Authors: Petersen James H. , DeAngelis Donald L.
Published: June 2008

The behavior of individual northern squawfish (Ptychocheilus oregonensis) preying on juvenile salmonids was modeled to address questions about capture rate and the timing of prey captures (random versus contagious). Prey density, predator weight, prey weight, temperature, and diel feeding pattern were first incorporated into predation equations analogous to Holling Type 2 and Type 3 functional response models. Type 2 and Type 3 equations fit field data from the Columbia River equally well, and both models predicted predation rates on five of seven independent dates. Selecting a functional response type may be complicated by variable predation rates, analytical methods, and assumptions of the model equations. Using the Type 2 functional response, random versus contagious timing of prey capture was tested using two related models. ln the simpler model, salmon captures were assumed to be controlled by a Poisson renewal process; in the second model, several salmon captures were assumed to occur during brief "feeding bouts", modeled with a compound Poisson process. Salmon captures by individual northern squawfish were clustered through time, rather than random, based on comparison of model simulations and field data. The contagious-feeding result suggests that salmonids may be encountered as patches or schools in the river.
Relationship between Feeding and Activity Rates for Actively Foraging Juvenile Brook Trout (Salvelinus fontinalis)
Authors: Boisclair Daniel
Published: June 2008

I tested the hypothesis of the existence of a significant positive linear relationship between activity and consumption rates for an actively foraging fish. Within-day variations in activity rates of 0 + brook trout (Salvelinus fontinalis) kept in enclosures were estimated using an underwater videocamera system. Consumption rates at different periods of that day were estimated using the variations of the digestive tract contents. Total consumption rates (i.e. sum of food ingested by all fish) ranged from values close to zero (−1.4 to 0.9; 12:30–24:00) to 12.7 cal/30 min (08:30–09:00). Total activity rates ranged from 0.06 (14:00–14:30) to 2.94 cal/30 min (08:30–09:00). My results indicate that, under specific environmental conditions, activity rates of brook trout are positively related to their feeding rates and, consequently, that the behavior of this actively foraging fish can result in the reduction of the energy losses associated with swimming during nonfeeding periods. My work also permits the development of an experimental protocol to test hypotheses regarding energy allocation patterns between growth, consumption, and activity rates on a multiday basis.
Periphyton Response in an Industrial Receiving Stream: Lipid-based Physiological Stress Analysis and Pattern Recognition of Microbial Community Structure
Authors: Guckert James B. , Nold Stephen C. , Boston Harry L. , White David C.
Published: June 2008

Periphyton were collected from three physically similar sites on an industrial receiving stream which differed in their distances from the discharge. Previous studies had established that biological effects diminished with distance downstream from the discharges. In this study, a multivariate analysis of periphyton membrane lipid profiles quantitatively verified site-specific differences in time-independent microbial community structure qualitatively suggested by algal taxonomic analyses. There were no differences in periphyton abundance among sites. Periphyton physiology was evaluated using a 14C-labeled bicarbonate and 3H-labeled amino acids dual-label incubation, with subsequent analysis of carbon partitioning into lipid compartments. Total radiolabel uptake was similar for all sites. Physiological stress was shown to be highest at the site closest to the discharges using a membrane to storage lipid synthetic ratio. High values of this ratio indicated that both the phototrophic and heterotrophic constituents were stressed, and this stress declined with distance downstream. The ability to measure algal and bacterial abundance, community structure, activity, and physiological status from a single extraction provides a powerful method to evaluate periphyton which can serve as a useful biomonitoring and toxicity assessment tool for aquatic ecosystems.
Estimates of Phosphorus and Nitrogen Cycling by Fish Using a Bioenergetics Approach
Authors: Kraft Clifford E.
Published: June 2008

A modelling approach based on bioenergetics was used to estimate the role of fish in nutrient recycling. Phosphorus excretion (PU) and nitrogen excretion by young-of-the-year (YOY) and older yellow perch (Perca flavescens) were estimated for a limnetic system: Lake Memphremagog. This model successfully predicted PUby comparison with previous estimates for yellow perch. YOY fish contributed more to limnetic nutrient cycling through excretion than older age-classes, and YOY fish could also serve as an important P sink relative to algal sinking losses. Volumetric PUby YOY yellow perch reached a maximum of 0.3 μg P∙L−1∙d−1; N excretion peaked at 10 μg N∙L−1∙d−1. The ratio of excreted N: P varied fourfold during the summer. PUestimates were also sensitive to changes in fish P content, for which few values have been reported for early life stages.
Models to Predict Potential Occurrence and Density of the Zebra Mussel, Dreissena polymorpha
Authors: Ramcharan Charles W. , Padilla Dianna K. , Dodson Stanley I.
Published: June 2008

Limnological features of different lakes may limit the density of, or even completely restrict, populations of the European zebra mussel, Dreissena polymorpha. We developed statistical models to predict the occurrence (presence or absence) and density (number per square metre) of Dreissena in lakes, based on multivariate correlations between the density of Dreissena populations and the limnological characteristics of the lakes they inhabit. We found that both occurrence and average density of Dreissena populations were highly correlated with water chemistry. Dreissena was not found in lakes with average pH values below 7.3 and concentrations of calcium ion below 28.3 mg∙L−1. Above these thresholds, Dreissena density was negatively related to concentration of the algal nutrients PO4 and NO3.
Larval Anisakis simplex (Nematoda: Ascaridoidea) Infection in the Musculature of Atlantic Cod, Gadus morhua, from Newfoundland and Labrador
Authors: Brattey John , Bishop Claude A.
Published: June 2008

Larvae of Anisakis simplex were found in the flesh of Atlantic cod, Gadus morhua, collected in 21 regions around Newfoundland and Labrador during 1985–87. Prevalence and abundance increased with cod size and varied geographically; cod off Labrador had the fewest larvae whereas those from the south coast of Newfoundland were the most heavily infected. Most larvae (~95%) occurred in flesh surrounding the body cavity (napes), with a significantly higher percentage of the nematodes (~58%) in the flesh on the left side. In 505 cod in which all tissues were examined, 85.6, 10.8, and 3.5% of the A. simplex resided in the body cavity and viscera, napes, and fillets, respectively. Cod surveyed tended to have more A. simplex in the musculature than those from other areas off eastern Canada, but are lightly infected compared with most other Atlantic cod stocks. The examination method (candling combined with slicing) recovered, on average, 42% of the A. simplex present in the flesh; consequently, infection statistics reported here are underestimates. Numbers of A. simplex in cod off Labrador and eastern Newfoundland are similar to those observed during 1947–53, but the abundance of A. simplex appears to have increased among cod from NAFO Subdivision 3Pn.
Patterns in the Distribution and Abundance of Zebra Mussel (Dreissena polymorpha) in Rivers and Lakes in Relation to Substrate and Other Physicochemical Factors
Authors: Mellina Eric , Rasmussen Joseph B.
Published: June 2008

Using SCUBA and an in situ method of quantifying substrate characteristics, we describe patterns of zebra mussel (Dreissena polymorpha) distribution along the St. Lawrence and Hudson rivers and in Oneida Lake, New York, and develop empirical models for their abundance. Calcium-poor waters originating from rivers draining the Canadian Shield resulted in a complete lack of zebra mussel colonization along the north shore of the St. Lawrence River east of Montreal despite an abundance of suitable substrate. Calcium concentrations of 15 mg/L or less limited the distribution of zebra mussel. The entire south shore from Cornwall, Ontario, to île d'Orléans, Quebec, was colonized by zebra mussel wherever suitable substrate was found. Among the three systems, substrate size explained between 38 and 91% of the variability in density. Other factors such as Secchi depth, calcium concentration in the water, the presence of crayfish, native unionid abundance, and the maximum width of the river at the site increased the amount of explained variance across the different systems. A model based on substrate size also successfully explained patterns of zebra mussel abundance from published sources.
Fish Distribution and Catchability: What Is the Appropriate Measure of Distribution?
Authors: Swain D. P. , Sinclair A. F.
Published: June 2008

Catchability to commercial fisheries has been predicted to be density dependent due to density-dependent variation in stock area. Previous studies have used indices of stock area based on thresholds of absolute density. These indices will increase with abundance even if density increases uniformly over all areas. We show that spatially uniform changes in abundance can affect catchability given certain models for the distribution of fishing effort, but that this effect is slight compared with the effect of changes in the spatial spread of fish distribution. We describe an index of distribution that depends only on spatial spread: the minimum area over which a specified percentage of the population is spread. We tested the density dependence of this index using data on Atlantic cod (Gadus morhua) in the southern Gulf of St. Lawrence. Results depended on the percentage of the population for which the index was evaluated. The area containing most (90 or 95%) of the population was density dependent, expanding as population size increased. The area of highest cod concentration (i.e., the area containing 50% of the population) did not expand significantly as population size increased.
Phosphorus Fluxes in Limnetic Cladocerans: Coupling of Allometry and Compartmental Analysis
Authors: Wen Yuan Hua , Vézina Alain , Peters Robert Henry
Published: June 2008

A size-dependent two-compartment model was developed for estimation of32P turnover and fluxes by limnetic cladocerans in steady state. After feeding on radioactively labelled food, uniformly labelled animals were fed unlabelled cells and the time course of release of tracer followed. Rates of turnover and size-specific fluxes were subsequently fitted to a two-compartment model. The model predicted that steady-state turnover and size-specific fluxes for32P excretion declined with body weight and that the exponent of weight did not significantly differ from −0.25, suggesting the relationships between total P turnover or flux rates and body size in cladocerans follow the same allometry observed for other organisms and other metabolic activities. However, rate constants for intercompartmental exchanges declined faster than weight−0.25, indicating that their turnover and flux declined much faster with increasing body size than would be expected from general allometry. Size-specific ingestion and assimilation rates of32P by cladocerans decreased with increasing body size with a slope of the allometric function similar to −0.25.
Importance of Wetlands as Sources of Methyl Mercury to Boreal Forest Ecosystems
Authors: St. Louis Vincent L. , Rudd John W. M. , Kelly Carol A. , Beaty Ken G. , Bloom Nicholas S. , Flett Robert J.
Published: June 2008

Wetlands were found to be important sources of methyl mercury to the boreal forest ecosystem. Yields of methyl mercury were about 26–79 times higher from wetland portions of catchments (1.84–5.55 mg∙ha−1∙yr−1) than from purely upland areas (0.07 mg∙ha−1∙yr−1). Mass-balance estimates using methyl mercury inputs in wet deposition and outputs in runoff water indicated that purely upland catchments and lakes were sites of methyl mercury retention or demethylation, while catchments with wetland areas were sites of net methyl mercury production. These observations may explain the high concentrations of mercury in fish taken from lakes that are high in colour because they receive water from wetlands. There was no relationship between the concentration of total mercury and the concentration of methyl mercury in runoff water. Total mercury yields were low from a wetland-dominated catchment, higher from a combination upland/riparian wetland catchment, and highest from a purely upland catchment. The opposite was true for methyl mercury yields from these same catchments. This indicates that environmental factors other than total mercury concentration are controlling the production and loss of methyl mercury from catchments.
A 50-yr Record of Pollution by Nutrients, Trace Metals, and Organic Chemicals in the St Lawrence River
Authors: Carignan Richard , Lorrain Stéphane , Lum Ken
Published: June 2008

The deposition chronology of algal pigments, organic C, N, P, trace metals, and organic contaminants (PCB congeners, DDD, DDE, Mirex, hexachlorobenzene) is described for two sites in fluvial lakes (St. Francis and St. Louis) of the St. Lawrence River. Pigment concentrations rapidly decrease in the top 10 cm due to degradation, but show a broad secondary peak consistent with higher primary productivity between 1960 and 1975. In Lake St. Francis, deposition of organic C, N, and P peaked between 1950 and 1975. In both lakes, trace metal concentrations reached maximum values between 1960 and 1970 and decreased considerably between 1970 and 1980. At both sites, surficial trace metal concentrations are approaching (within a factor of 3) those observed in preindustrial sediments except Cd, which is still 5–6 times higher. Concentrations of Cr, Cu, Ni, and Zn are inversely related (p < 0.05) to river discharge whereas those of Pb are positively related to discharge. Concentrations of organic contaminants have declined by a factor of 5–10 between the mid-1960's and the early 1980's, except Mirex, which shows no obvious trend with time. Historic trends in pollution by organic chemicals appear to have been influenced not only by changing anthropogenic inputs, but also by river discharge.
Chela Function, Morphometric Maturity, and the Mating Embrace in Male Snow Crab,Chionoecetes opilio
Authors: Claxton W. T. , Govind C. K. , Elner R. W.
Published: June 2008

Behavior and chela function associated with precopulatory clasping in morphometrically mature (MM) and morphometrically immature (MI) male snow crab, Chionoecetes opilio, were compared. MM males clasp receptive females more readily and for a more protracted period than MI males. Moreover, smaller MM males were more successful in initiating and maintaining precopulatory holds than larger MI males. These differences in clasping behavior cannot be attributed to differences in chela function, as the force developed is sufficient for clasping in both cases. The output force of the MM chela is, however, significantly higher than for MI chela because of their higher mechanical advantage and muscle stress and the presence of a larger closer muscle. Nor are differences in clasping behavior due to the fiber composition of the chela closer muscle which is composed of slow fibers in both morphotypes. These fibers are highly differentiated in their sarcomere lengths and enzymatic (ATPase and NADH-diaphorase) profiles which allow them to provide slow, powerful, and sustained contractions suited to precopulatory clasping. Since chela morphology and closer muscle composition appear adapted to precopulatory clasping in both morphotypes, other factors, most likely neurohormonal, may make MM males clasp more readily than their MI conspecifics.
Juvenile Chinook Salmon (Oncorhynchus tshawytscha) Utilization of Hawks Creek, a Small and Nonnatal Tributary of the Upper Fraser River
Authors: Scrivener J. Charles , Brown Thomas G. , Andersen Bruce C.
Published: June 2008

Hawks Creek, a small tributary of the upper Fraser River where there is no record of spawning salmonids, was examined from May to November 1990 for the presence of juvenile salmonids. Age 0+wild chinook salmon (Oncorhynchus tshawytscha) appeared in May, increased to peak densities of 0.76 fish∙m−2in late August, and were absent in November. Average residence time of marked chinook juveniles was 9 d. Duration of residency was size dependent, as small fish remained longer than large fish. Rainbow trout (Oncorhynchus mykiss) and mountain whitefish (Prosopium williamsoni) also had a short residency (mean = 21 d). We suggest that unsuitable rearing conditions (e.g., sediment load) in the mainstem Fraser River during the spring and summer favour the use of small, clear, and nonnatal tributaries by juvenile salmonids. Physical and biological explanations are proposed for their temporary use. These salmonid refuge habitats need to be protected.
Length-specific Weight as a Measure of Growth Success of Adult Atlantic Herring (Clupea harengus)
Authors: Winters G. H. , Wheeler J. P.
Published: June 2008

We used length-specific weight (i.e., condition) to evaluate growth success of seven stocks of adult Atlantic herring (Clupea harengus) in the Northwest Atlantic. Condition of adult Atlantic herring showed large annual changes as a consequence of abundance-dependent effects. This contradicts the general conclusion that adult herring growth contains little abundance-dependent variation. The published literature, however, is based mainly on traditional growth estimators such as annual length increments which measure only a marginal fraction of annual production whereas condition reflects the seasonal accumulation and depletion of energy and therefore can provide a reliable index of total annual production. We found that annual changes in condition of adult Atlantic herring were only weakly correlated with traditional length-based growth estimates. We concluded that the weak evidence for abundance-dependent growth of adult herring in the literature is a consequence of inappropriate growth estimators. The implication of this finding is that the acquisition of surplus energy by herring can be abundance dependent whereas annual increases in length may not.
Predicting the Spatial Distribution of Dreissena polymorpha (Zebra Mussel) among Inland Lakes of Wisconsin: Modeling with a GIS
Authors: Koutnik Michael A. , Padilla Dianna K.
Published: June 2008

Previously developed models and available limnological data were used to predict (i) absence or presence, (ii) categorical population density, and (iii) numerical abundance of Dreissena polymorpha (zebra mussel) for 194 inland Wisconsin lakes. A geographical information system (GIS) was used to test for associations between predicted lake population density classes and three landscape-scale characteristics (surficial deposits, bedrock type, U.S. Environmental Protection Agency developed ecoregions) that may affect limnological parameters. Although the models used differed in their predictions of specific lakes that would support Dreissena, the overall spatial distribution of lakes within a given density class was similar among the models. A significant association was found between each landscape-scale characteristic and Dreissena density classes. This study suggests that (1) available lake monitoring data can be used to predict Dreissena density for groups of inland lakes, (2) more information on North American lakes with zebra mussel is required to reduce the uncertainty of the models, and (3) spatial analysis using GIS methods can provide valuable insight into the overall patterns of the potential spatial distribution of Dreissena.
Differential Predation by Northern Squawfish (Ptychocheilus oregonensis) on Live and Dead Juvenile Salmonids in the Bonneville Dam Tailrace (Columbia River)
Authors: Petersen James H. , Gadomski Dena M. , Poe Thomas P.
Published: June 2008

Juvenile salmonids (Oncorhynchus spp.) that have been killed or injured during dam passage may be highly vulnerable or preferred prey of predators that aggregate below dams. Salmonid loss due to predation will be overestimated using gut content analysis if some prey were dead or moribund when consumed. To examine this issue, field experiments were conducted in the Bonneville Dam tailrace (Columbia River) to compare rates of capture of live and dead juvenile salmonids by northern squawfish (Ptychocheilus oregonensis). Known numbers of coded-wire-tagged live and dead chinook salmon (O. tshawytscha) were released into the tailrace on six nights. Northern squawfish were collected after each release and their gut contents were examined for tags. When 50% of salmon released were dead, northern squawfish consumed 62% dead salmon. When 10% of salmon released were dead, comparable with dam passage mortality, 22% of the tags found in northern squawfish digestive tracts were from dead salmon. These results indicate that predator feeding behavior and prey condition are important considerations when estimating the impact of predation on a prey population.
Comparison of ergosterol and chitin as quantitative estimates of mycorrhizal infection and Pinuscontorta seedling response to inoculation
Authors: Johnson B. N. , McGill W. B.
Published: June 2008

The ergosterol and chitin content of 35-week-old Pinuscontorta var. latifolia Engelm. roots ectomycorrhizal with Hebelomacrustuliniforme (Bull.:St. Amans) Quél. were compared as indices of intramatrical mycelial mass. Ergosterol analyses were less labor intensive (about one-half) and detected differences in mycorrhizal establishment among P fertilization treatments, whereas differences found using chitin analyses were not statistically significant. Intramatrical mycelial estimates by the two techniques were not correlated (r = 0.15); estimates based on ergosterol were 2–5 times greater than those based on chitin, with the chitin:ergosterol ratio increasing as P fertilization increased. Owing to its sensitivity and specificity, the ergosterol assay is a practical means of monitoring the establishment of ectomycorrhizae in pine roots.
Free amino acid concentrations in needles of Norway spruce and Scots pine trees on different sites in areas with two levels of nitrogen deposition
Authors: Edfast Ann-Britt , Näsholm Torgny , Ericsson Anders
Published: June 2008

The effects of nitrogen deposition and site quality on amino acid concentrations in needles of Piceaabies (L.) Karst. and Pinussylvestris L. trees were studied in two areas that represent different levels of nitrogen deposition: one area in southern Sweden and one area in northern Sweden receive, respectively, approximately 20–30 and 3 kg•ha−1•year−1 of nitrogen. On each area three site quality classes were chosen for each tree species. The site classes were chosen to represent poor, medium, and good sites typical for each area. Free amino acids in the needles were analyzed as 9-fluorenylmethyl formate derivatives by high-performance liquid chromatography. The total nitrogen was determined with a CHN elemental analyzer, and other mineral nutrients were determined with an inductively coupled plasma analyzer. Arginine, glutamic acid, glutamine, γ-aminobutyric acid, and aspartic acid were the quantitatively dominating amino acids in the needles of both species from all sites in both northern and southern Sweden. These amino acids represented 50–80% of the total concentration of free amino acids in the needles. The concentration of arginine in the needles of both spruce and pine increased with decreasing site index and showed high variations between individual trees. For both species, the highest concentrations of arginine were found in the southern area, which had the highest deposition of nitrogen. Concentrations of glutamic acid, glutamine, and γ-aminobutyric acid in the needles of both species showed significant differences between some of the sites on both areas, but these differences showed no general pattern that correlated with the site indexes. In relation to nitrogen, low concentrations of phosphorus and potassium were found in needles from the poorest spruce sites in both areas compared with corresponding values for the good spruce sites. The results are discussed in relation to nitrogen deposition and mineral nutrient imbalance.
Directionality of compression wood in balsam fir wave forest trees
Authors: Robertson Alexander
Published: June 2008

Wind is often cited as one of the main causes of compression wood formation. While many papers have alluded to direction of compression wood, this paper provides a detailed circular statistical analysis of the angular distribution of compression-wood zones in balsam fir trees. Discs were sampled from trees in a balsam fir (Abiesbalsamea (L.) Mill.) wave forest in northwestern Newfoundland, from sapling to mature stages. The directionality, with respect to compass bearing, of compression-wood zones in basal discs was found to be initially randomly distributed around the pith, becoming unidirectional towards the northeast at about 10 mm from the pith. Random circular distribution of compression-wood zones mostly within 10 mm of the pith is interpreted as resulting from a combination of environmental perturbations, such as glaze and rain loading, and asymmetric crown growth due to competition. Because of the very high density of immature stands, wind turbulence is not expected to be a major factor stimulating compression wood in saplings. The role of snow loading, which causes bending of stems for long periods during the winter (dormant season), is uncertain. In older trees, i.e., beyond approximately 10 mm from the pith, compression wood gradually becomes directional towards the northeast, indicating that prevailing southwesterly winds are mainly responsible for compression-wood formation.
Individual-tree diameter growth models for quantifying within-stand response to nitrogen fertilization
Authors: Shafii Bahman , Moore James A. , Newberry James D.
Published: June 2008

Diameter-increment models for nitrogen-fertilized stands were developed using data from permanent research plots in northern Idaho. The equations partially resembled PROGNOSIS model diameter growth formulations. Results indicated that both initial tree size and initial stand density produced significant interactions with treatment to explain an individual tree's response to fertilization. Larger trees in a stand showed more fertilization response than smaller trees. Furthermore, individual trees in low-density stands showed more fertilization response than those growing in high-density stands. These diameter increment predictive equations were formulated to be compatible with individual-tree distance-independent simulation models.
Foliar senescence in an aspen (Populustremuloides) clone: the response of element resorption to interramet variation and timing of abscission
Authors: Killingbeck Keith T. , May Jeffrey D. , Nyman Stephen
Published: June 2008

Nutrient movements in the senescing foliage of a Rhode Island Populustremuloides Michx. clone were measured during the years 1986–1988. Mean resorption of nitrogen, phosphorus, and copper was 43, 51, and 10%, respectively. Aluminum, boron, calcium, iron, magnesium, manganese, and zinc increased or remained unchanged in senescing foliage during 1986. Resorption of nitrogen and phosphorus decreased, respectively, from 56 and 64% in 1986 to 24 and 38% in 1988. Mean resorption differed among the 20 ramets studied. Older, larger ramets resorbed less nitrogen and copper than younger, smaller ramets. Timing of abscission strongly influenced resorption and may have been related to drought conditions in 1988 and to differential exposure to wind in all years. Resorption of nitrogen, phosphorus, and copper was lowest in those ramets that lost their leaves earliest and in leaves that senesced earliest on individual ramets. Because P. tremuloides ramets had the physiological potential to resorb more nitrogen and phosphorus than they actually did in 1988, we introduced the terms potential resorption and realized resorption to differentiate between physiological potential and ecological reality. Our data suggest that at least some portion of realized resorption is determined stochastically by environmental constraints.
The role of woody roots of slash pine seedlings in water and potassium absorption
Authors: Rees K. C. J. Van , Comerford N. B.
Published: June 2008

Tree root systems consist of varying amounts of woody, nonwoody, and mycorrhizal roots, yet the importance of woody roots in nutrient and water uptake is unclear. This study was conducted to determine the rates of uptake of water, potassium (K), and rubidium (Rb) by woody roots of slash pine (Pinuselliottii Engelm. var. elliottii) seedlings. Water and nutrient uptake was determined by depletion experiments for seedlings grown in solution cultures. When active shoot growth occurred, absorption of water, K, and Rb (per unit root length) for seedlings with only woody roots (nonwoody roots removed) was comparable with or greater than that for seedlings with both woody and non-woody roots. Predictions of K uptake via a nutrient-uptake model were similar when plant parameters were either measured separately for woody and white roots or for entire root systems. Determination of the length of woody roots was essential for accurately predicting K uptake. For seedlings grown in soil, woody root length comprised 85 to 95% of the total root length. The effectiveness of woody roots in absorbing water and K, and the large proportion that woody roots constitute of the total root system, suggest that woody roots can play a major role in the nutrition of slash pine.
Temperature and time-related variation of root growth in some conifer tree species
Authors: Binder Wolfgang D. , Fielder Peter , Scagel Rob , Krumlik George J.
Published: June 2008

The variability of root growth potential of cold-stored (2 °C) bare-root and container-grown stock of Abiesgrandis (Dougl.) Lindl., A. amabilis (Dougl.) Forbes., Piceasitchensis (Bong.) Carr., Pseudotsugamenziesii (Mirb.) Franco, Thujaplicata Donn, and Tsugaheterophylla (Raf.) Sarg. was tested under four air temperature regimes for 7 and 14 days. In P. menziesii, P. sitchensis, and T. plicata, root growth was greatest under the 25:20 °C (light:dark) regime, whereas the 30:25 °C (light:dark) regime was supraoptimal for all species. Temperatures cooler than 25:20 °C (light:dark) were optimal for T. heterophylla and A. amabilis. A 14-day test duration consistently produced more roots than the 7-day test. Container-grown seedlings produced more new roots than bare-root seedlings. Except for P. sitchensis and T. plicata, light was required for root growth. The effect of test conditions on root growth is discussed with respect to a possible relationship between temperature optima for root growth and current photosynthate production. High within-test variability and inconsistent ranking of seed lots under different test temperatures and durations suggest that stock quality interpretations based solely on root growth potential tests should be questioned.
Relationships between soil chemistry, foliar chemistry, and condition of red spruce at Mount Moosilauke, New Hampshire
Authors: Huntington Thomas G. , Peart David R. , Hornig James , Ryan Douglas F. , Russo-Savage Stuart
Published: June 2008

We measured soil chemical properties and red spruce (Picearubens Sarg.) foliar chemistry and crown condition in the spruce-fir vegetation zone at Mount Moosilauke, New Hampshire. Our measurements were made in or adjacent to permanent plots stratified by elevation, aspect, and soil type. Soils were analyzed for exchangeable Ca, Mg, K, and Al and extractable P and Mn. Foliage was analyzed for Ca, Mg, K, Al, P, and Mn. Based upon the best available provisional standards for red spruce foliar element sufficiency, 1-year-old needles showed a moderate P deficiency (1000–1400 mg•kg−1), Mg levels in a transitional zone from deficiency to sufficiency (600–720 mg•kg−1), and Ca and K levels in a range sufficient for good growth. Foliar element concentrations were not correlated with crown condition. Extractable soil P (kg•ha−1 and cmol ion charge•kg−1) was positively correlated with crown condition. The only significant relationships found between soil exchangeable base cations and crown condition were positive correlations for Ca and Mg (kg•ha−1) in the Oi + Oe horizon. Several factors suggest that red spruce at high elevations at Mount Moosilauke was not stressed from base cation limitations: (i) foliar element concentrations were generally in sufficient ranges, (ii) crown condition was not related to foliar element concentration, (iii) relationships between exchangeable soil cations and foliar concentration or crown condition were generally not significant or were inconsistent between soil horizons.