bluuebunny/crossref_metadata_2025 huggingface dataset:
Crustal structure and surface zonation of the Canadian Appalachians: implications of deep seismic reflection data
Authors: Marillier François , Keen Charlotte E. , Stockmal Glen S. , Quinlan Garry , Williams Harold , Colman-Sadd Stephen P. , O'Brien Sean J.
Published: June 2008

In 1986, 1181 km of marine seismic reflection data was collected to 18–20 s of two-way traveltime in the Gulf of St. Lawrence area. The seismic profiles sample all major surface tectono-stratigraphic zones of the Canadian Appalachians. They complement the 1984 deep reflection survey northeast of Newfoundland. Together, the seismic profiles reveal the regional three-dimensional geometry of the orogen.Three lower crustal blocks are distinguished on the seismic data. They are referred to as the Grenville, Central, and Avalon blocks, from west to east. The Grenville block is wedge shaped in section, and its subsurface edge follows the form of the Appalachian structural front. The Grenville block abuts the Central block at mid-crustal to mantle depths. The Avalon block meets the Central block at a steep junction that penetrates the entire crust.Consistent differences in the seismic character of the Moho help identify boundaries of the deep crustal blocks. The Moho signature varies from uniform over extended distances to irregular with abrupt depth changes. In places the Moho is offset by steep reflections that cut the lower crust and upper mantle. In other places, the change in Moho elevation is gradual, with lower crustal reflections following its form. In all three blocks the crust is generally highly reflective, with no distinction between a transparent upper crust and reflective lower crust.In general, Carboniferous and Mesozoic basins crossed by the seismic profiles overlie thinner crust. However, a deep Moho is found at some places beneath the Carboniferous Magdalen Basin.The Grenville block belongs to the Grenville Craton; the Humber Zone is thrust over its dipping southwestern edge. The Dunnage Zone is allochthonous above the opposing Grenville and Central blocks. The Gander Zone may be the surface expression of the Central block or may be allochthonous itself. There is a spatial analogy between the Avalon block and the Avalon Zone. Our profile across the Meguma Zone is too short to seismically distinguish this zone from the Avalon Zone.
Chronologie Rb/Sr et K/Ar du granite peralcalin du lac Brisson, Labrador central, Nouveau-Québec
Authors: Pillet D. , Bonhomme M. G. , Duthou J. L. , Chenevoy M.
Published: June 2008

A Rb/Sr whole-rock isochron gives an age of 1189 ± 32 Ma for the peralkaline granite of Lake Brisson. K/Ar data on amphiboles yield an age of 1163 ± 21 Ma, which further confirms our dating. Such an age allows the corresponding magmatism to be attributed to the late stage of the Gardar anorogenic province, which till now has been unknown in Labrador.
Statistical analysis of the geological–hydrogeological conditions within part of the Eye–Dashwa Pluton, Atikokan, northwestern Ontario
Authors: Brown P. A. , Rey N. A. C.
Published: June 2008

The occurrence and distribution of fracture-filling material within the Eye–Dashwa granite indicate that the dominant fracture system formed shortly after emplacement and cooling of the pluton at 2678 ± 67 Ma. Subsequent reactivation of these ancient fractures was accompanied by sequentially younger and lower temperature filling materials. These reopened ancient fractures are best developed in the upper 300–400 m of the rock mass and are commonly conduits for present-day groundwater flow.Multiple linear regression analysis performed on the geological variables defined from boreholes ATK-1, -2, -3, -4, and -5 identified a highly significant correlation between a number of these variables and hydraulic conductivity values measured in 25 m test sections of the boreholes. The correlation is expressed as[Formula: see text]here log Kerm is the log of hydraulic conductivity; log(DEPTH) is the log-transformed depth to the lower end of the packer interval; log(CLAY) is the log-transformed frequency of clay-filled fractures per 25 m interval; log(VEIN) is the log-transformed frequency of veins per 25 m interval. The equation has a multiple r value of 0.82, explains 67% of the variance of hydraulic conductivity, and has a random exceedence probability (Q) of 9 × 10−12 (i.e., it is highly significant).The predictive capability of the regression design was tested with seven new test data and found to be a valid estimator of the hydrogeological conditions within these test intervals.
Geology of the East Bull Lake gabbro–anorthosite pluton, Algoma District, Ontario
Authors: McCrank G. F. D. , Kamineni D. C. , Ejeckam R. B. , Sikorsky R.
Published: June 2008

The East Bull Lake Pluton, a layered gabbro–anorthosite intrusion 90 km west of Sudbury, Ontario, is in an inward-dipping lopolith and is 780 m thick in the centre and elliptical in plan view (13.5 km × 3.5 km). It intruded Archean metavolcanic and metaplutonic rocks of the Superior Province during the Early Proterozoic (2480 Ma).The intrusion consistes of a basal anorthositic unit, succeeded by rhythmic-layered gabbro, troctolite, layered gabbro, and massive and dendritic gabbro units. It is offset by the west-northwest-striking, subvertical Folson Lake fault. South of this fault, only anorthosite and massive and dendritic gabbro are exposed. North of the fault, subsurface lithologies intersected by me boreholes correlate with surface lithologies. Troctolite, the most distinctive marker that can be correlated between boreholes and surface exposures, confirms the general attitude and shape of the layers and lopolith.Chemical composition of the intrusion ranges from high-Mg tholeiite to calc-alkaline high-alumina basalts.Fractures occur in several preferred orientations, the most common being northwesterly, subparallel to the Folson Lake fault, numerous mafic dykes, and topographic lineaments. Complex fracture-filling and alteration mineralogies formed under a wide range of P–T conditions representative of epidote-amphibolite – greenschist facies, pumpellyite–prehnite facies, zeolite facies, and low-temperature rock–water interaction processes.The last movement on the Folson Lake fault was a dextral strike slip of up to 3.0 km that postdates most mafic dykes.
Tectonic implications of seismic activity recorded by the northern Ontario seismograph network
Authors: Wetmiller R. J. , Cajka M. G.
Published: June 2008

The northern Ontario seismograph network, which has operated under the Canadian Nuclear Fuel Waste Management Program since 1982, has provided valuable data to supplement those recorded by the Canadian national networks on earthquake activity, rockburst activity, the distribution of regional seismic velocities, and the contemporary stress field in northern Ontario. The combined networks recorded the largest earthquake known in northwestern Ontario, M 3.9 near Sioux Lookout on February 11, 1984, and many smaller earthquakes in northeastern Ontario. Focal mechanism solutions of these and older events showed high horizontal stress and thrust faulting to be the dominant features of the contemporary tectonics of northern Ontario. The zone of more intense earthquake activity in western Quebec appeared to extend northwestward into the Kapuskasing area of northeastern Ontario, where an area of persistent microearthquake activity had been identified by a seismograph station near Kapuskasing.Controlled explosions of the 1984 Kapuskasing Uplift seismic profile experiment recorded on the northern Ontario seismograph network showed the presence of anomalously high LG velocities in northeastern Ontario (3.65 km/s) that when properly taken into account reduced the mislocation errors of well-recorded seismic events by 50% on average.
A comparison of fracture styles in two granite bodies of the Superior Province
Authors: Stone D. , Kamineni D. C. , Brown A. , Everitt R.
Published: June 2008

A quantitative comparison is made between fracture styles in two late Archean granite intrusions of the Superior Province—–the Lac du Bonnet Batholith (LDBB) and Eye–Dashwa Pluton (EDP). These intrusions have a similar geological setting, similar mineral and chemical composition, and similar physical properties but vary markedly in volume (LDBB = 9060 km3; EDP = 122 km3).The fracture style of the LDBB consists of mainly low-angle thrust faults within otherwise poorly fractured granite. Subvertical fractures are restricted to within 200 m of surface or zones encompassing the thrust faults. The mineral assemblage chlorite – iron oxide – carbonate is widespread in fractures. In contrast, fractures of the EDP are closely spaced, variably oriented, pervasive to depth, and dominated by subvertical transcurrent faults. Epidote is an abundant fracture-filling material.Most fractures formed in response to Early Proterozoic compression under low-greenschist conditions in the LDBB and upper-greenschist conditions in the EDP. Fractures in both intrusions were subsequently rejuvenated (clay – iron oxide filling materials) without appreciable modification to fracture styles. The presence of a strong planar fabric at one site, variation in the intensity of Early Proterozoic tectonism, and prolonged plastic deformation in the large LDBB are cited as possible causes for the observed variation in fracture styles.
Geology and geophysics of the Underground Research Laboratory site, Lac du Bonnet Batholith, Manitoba
Authors: Brown A. , Soonawala N. M. , Everitt R. A. , Kamineni D. C.
Published: June 2008

The lease area of the Atomic Energy of Canada Limited Underground Research Laboratory covers 3.8 km2 and is located 2.5 km north of the south contact of the Lac du Bonnet Batholith. A shaft to 255 m and 130 boreholes up to 1100 m deep expose the third dimension.The underlying granite is largely of two types: (i) pink porphyritic, which may be biotite rich, gneissic, and (or) xenolithic; and (ii) grey homogeneous and equigranular. Composition layering, including xenolith-rich zones, outlines domes along an antiform trending north-northeast through the western part of the lease area. The southeast-dipping flank underlies the eastern half of the site, including the shaft. Axes of folding trend 065 °and 140°. Homogeneous grey granite, being relatively fresh and unfractured, is associated with a magnetic field that is about 100 nT higher and with a resistivity that is up to 5000 Ω∙m higher than those of other units. A pattern of highs in the magnetic field, caused by the high magnetite content of some xenoliths, can be used to map the antiform.Three thrust faults that dip 10–30° east-southeast are partly controlled by the compositional layering. Anomalies in the very low frequency electromagnetic (VLF-EM) field occur at the surface projections of faults. One fault has been mapped at depth by a high-resolution seismic reflection survey. A suite of downhole geophysical methods, including cross-hole seismic, has been used to map discontinuities in boreholes.Subvertical penetrative foliations and pegmatitic dykes are part of the late crystallization fabric, providing (with filled fractures) a continuous deformation history in response to north- to northeast-trending compressive stress.
Methods for estimating secondary production in marine Amphipoda
Authors: Wildish D. J. , Peer D.
Published: June 2008

For the 1971 year-class of Pontoporeia femorata from St. Margaret's Bay, N.S., secondary production was 11.06–13.61 g wet weight/m2 and annual turnover ratio was 3.64–4.78 as measured by three methods. These included cohort summation of losses, integrated production from the Allen curve, and size frequency, or modified Hynes methods. Sampling bias against early life history stages of amphipods collected with sieve meshes [Formula: see text] can be corrected by back calculation from population data thus enabling cohort-based estimates of secondary production to be made.Key words: secondary production, annual turnover ratio, Pontoporeia femorata, Crustacea, Amphipoda
Screen Mesh Size Affects Estimates of Macro- and Meio-benthos Abundance and Biomass in the Great Lakes
Authors: Nalepa Thomas F. , Robertson Andrew
Published: June 2008

The efficiencies of screens with mesh openings of 595 and 106 μm in retaining, respectively, the macro- and meio-benthos were measured for samples taken in southeastern Lake Michigan. The use of these screens provides adequate estimates of dry weight biomass for both the macro- and meio-benthos, but serious underestimates of the numbers of many taxa, most notably naidids, enchytraeids, chironomids, nematodes, and rotifers, can result. For chironomids, retention on the 595-μm screen varied by species, with overall retention being closely related to both body length and head capsule width. Retention for certain macro-benthic taxa was significantly related to sampling date and water depth, indicating that future studies concerned with these variables should use mesh sizes small enough to retain all (or almost all) of the individuals of the taxa of interest.Key words: mesh size, screen efficiency, percent retention, macrobenthos, meibenthos, Lake Michigan
Ammonia Volatilization in a Hypertrophic Prairie Lake
Authors: Murphy T. P. , Brownlee B. G.
Published: June 2008

During two periods of high pH and high ammonia concentrations, disappearance rates of ammonia of 20–30 μg N∙L−1∙h−1 were observed in Lake 885, a hypertrophic prairie lake. At these times, rates of ammonia uptake by phytoplankton were 2.6–4.3 μg N∙L−1∙h−1 as measured by a 15N method. The high excess rates of ammonia disappearance are best explained by volatilization of ammonia from the lake surface. The loss of ammonia induced nitrogen fixation; however, much larger quantities of ammonia were lost via ammonia volatilization after algal bloom collapsed than the algae could fix in one season.Key words: ammonia volatilization, prairie lakes, nitrogen limitation, nitrogen cycle
Pathogenicity of Vibrio anguillarum for Juvenile Winter Flounder, Pseudopleuronectes americanus
Authors: Watkins W. D. , Wolke R. E. , Cabelli V. J.
Published: June 2008

The pathogenicity of Vibrio anguillarum for juvenile winter flounder, Pseudopleuronectes americanus, was quantitatively established under laboratory conditions. Fish were obtained from Rhode Island waters, acclimatized in tanks for 4–6 wk, and then challenged with V. anguillarum. The LD50 was relatively constant for 24–to 72-h cultures of the organism using intraperitoneal, intramuscular, and intravenous challenge routes. The LD50 via oral inoculation was about 3 logs greater. The LD50 for fish collected, acclimatized, and challenged during the winter was ~3 logs less than that found for fish in the summer. The median intramuscular LD50 for 11 strains examined under the optimum conditions for infection was 2.4 × 105 (range 7.3 × 104 to 1.6 × 106) organisms. Gross and histopathological changes in the acute form of the disease were minimal, being limited to anemia, leucopenia, ecchymosis and necrosis at the site of inoculation, and behavioral changes. A chronic form of vibriosis was observed primarily during the summer in fish given sublethal doses. A potent, lethal V. anguillarum toxin could not be demonstrated. Potentially, this reproducible host–parasite system might have use in a short-term bioassay procedure for toxic pollutants of the marine environment.Key words: Vibrio anguillarum, winter founder, LD50, histopathological changes, acute and chronic vibriosis, toxin, bioassay
Specific Growth Rates of Freshwater Algae in Relation to Cell Size and Light Intensity
Authors: Schlesinger D. A. , Molot L. A. , Shuter B. J.
Published: June 2008

Four species of freshwater green algae spanning a size range of 0.83–325.22 pg carbon per cell were grown in laboratory batch cultures under four levels of incident irradiance. There was an inverse relationship between cell size and specific growth rate at the highest light intensity tested. As light intensity was decreased, the relationship weakened. These laboratory results, in addition to some field data from arctic lakes in Canada, support recent model predictions concerning size-dependent algal growth.Key words: algae, cell size, growth, irradiance, models, nutrients
Variations in the Correlation of Body Size with Concentrations of Cu and Ag in the Bivalve Macoma balthica
Authors: Strong Carol R. , Luoma Samuel N.
Published: June 2008

The relationship between body size and concentrations of Cu and Ag varied from strongly positive to strongly negative in four populations of the bivalve Macoma balthica in San Francisco Bay. The correlations appeared to be influenced by the degree of enrichment in tissues, size-dependent differences and seasonal variations in growth rate, and size-dependent differences in uptake rates. The use of benthic indicator organisms to assess metal contamination requires understanding the relationship between metal concentration and body size at least within each population, and in some cases within each sample from each population.Key words: indicator species, Mollusca, Macoma balthica, body size, metals, chemical pollutants
Vertical and Horizontal Distribution Patterns of Copepods Near the Shelf Break South of Nova Scotia
Authors: Herman Alex W. , Sameoto Douglas D. , Longhurst Alan R.
Published: June 2008

The shelf water over the outer edge of the Scotian Shelf and the shelf/slope water front at the shelf break south of Nova Scotia have been sampled with a Batfish cycling over a 3- to 110-m-depth range while measuring salinity, temperature, depth, chlorophyll a, and copepods. Plant production and copepod abundance were much higher at the front than in surrounding shelf and slope waters. Convergence at the front is invoked as a possible transport mechanism which results in the accumulation of copepods in a region of high food concentration. Copepods exhibit diel vertical migration in shelf water but not in the front itself, and possible mechanisms are examined. Most Batfish profiles (with ≈1-m-depth resolution) indicated that the copepod maximum was situated ≈10 m above the chlorophyll maximum. A series of vertical profiles consisting of chlorophyll a, estimated production, and copepod abundances indicate a high correlation between the copepod and production profiles and low correlation between either of these and chlorophyll. Possible relationships between copepod layer depths and the depths of high plant production are considered.Key words: copepods, batfish, chlorophyll, production, front, migration
Remote Acoustic Detection of Zooplankton Response to Field Processes, Oceanographic Instrumentation, and Predators
Authors: Orr Marshall H.
Published: June 2008

A narrow-beam multifrequency acoustic backscattering system operating at discrete frequencies in the 10- to 600-kHz band has been used to detect predator–prey interaction, the passive response of Zooplankton to fluid processes such as internal waves, lee waves, hydraulic jumps, and the response of organisms to the presence of an oceanographic instrument in the water column. The acoustic flow visualization data illustrate the extent of the vertical and horizontal displacements and mixing of organisms by fluid processes. The data suggest that fluid processes may strongly influence predator–prey distribution in the continental shelf and sound regimes and that the interpretation of biological field data should include the influence of small-scale fluid motion on the vertical and horizontal distribution of organisms and nutrients. The predator–prey interaction data indicate that small organisms will move 7–20 m in the vertical to avoid larger organisms. Organisms appear to be able to detect the presence of oceanographic instruments to ranges of [Formula: see text]. At this time it is not known whether the organism detection range is related to the optical properties of the water column or other physical parameters.Key words: acoustic, Zooplankton, fluid processes, predator–prey interaction
Plasma Corticosteroid Dynamics in Channel Catfish (Ictalurus punctatus) Exposed to Ammonia and Nitrite
Authors: Tomasso J. R. , Davis Kenneth B. , Simco Bill A.
Published: June 2008

Plasma corticosteroid concentrations in channel catfish (Ictalurus punctatus) increased in response to increasing concentrations of both ammonia and nitrite. Corticosteroid levels in fish exposed to nitrite increased continuously during a 24-h exposure whereas corticosteroid concentrations of fish exposed to ammonia peaked after 8 h and then decreased for the remainder of the 24-h experiment. Low environmental pH and elevated environmental chloride were effective in preventing elevated corticosteroid levels in fish exposed to ammonia and nitrite, respectively. Based on plasma corticosteroid concentrations, no additive or synergistic toxic interaction was evident in fish simultaneously exposed to environmental ammonia and nitrite. These data indicate that (1) corticosteroids are released into circulation probably in response to a physiological dysfunction brought about by the toxins and not simply their presence in the environment, and (2) the absence of a toxic interaction between ammonia and nitrite as measured by plasma corticosteroid concentrations may be due to the temporal separation of their toxic effects coupled with the apparently rapid ability of channel catfish to acclimate to ammonia.Key words: Ictalurus punctatus, corticosteroids, toxicology, environmental contaminants
Form of Random Variation in Salmon Smolt-to-Adult Relations and Its Influence on Production Estimates
Authors: Peterman Randall M.
Published: June 2008

Estimates of the production of adult salmon can be biased by assuming an incorrect form of random noise term in the descriptive model. Many authors of theoretical studies of stock–recruitment relations assume multiplicative, log-normal distributions of random noise, while other workers assume additive, normally distributed terms. Marine survival data for three species of salmon are used to determine which type of random variation term is most appropriate for salmon population models. Results indicate that a multiplicative, log-normal distribution is most consistent with the data. The random processes described by this type of noise term cause higher absolute variation in total adult returns as abundance of seaward migrants increases. This phenomenon creates difficulties in evaluating the success of artificial enhancement programs and it should be taken into account during planning of such programs and during subsequent evaluations of their success.Key words: marine survival, salmon, enhancement, log-normal, random, variability, parameter estimation, stock–recruitment, normal distributions
Demography of an Estuarine Amphipod (Gammarus lawrencianus) Experimentally Selected for High "r": A Model of the Genetic Effects of Environmental Change
Authors: Doyle R. W. , Hunte W.
Published: June 2008

The estuarine amphipod Gammarus lawrencianus was subjected to prolonged selection (3 years; 26 generations) for high population growth rates. The demography of the selected population was studied in detail and compared under laboratory conditions with animals derived from a control (wild) population collected in the same area 3 years later. In the lab-adapted population the intrinsic rate of population growth r increased by 72% as the result of changes in age at maturation, survivorship, and fecundity. The variance of these traits decreased and Crow's (1958) index of total selection (variance of fitness/mean fitness squared) is proposed as a quantitative and operational measure of genetic adaptation to a changed environment. Possible limitations on adaptation were investigated by examining the correlations among demographic traits within the lab-adapted population. Some phenotypic correlations were determined directly and others by an indirect technique using information from full siblings. Individual growth rate was negatively correlated both with survival and fecundity. Individual growth rate and age at sexual maturity were also negatively correlated. Negative phenotypic correlations between traits may indicate limitations on long-term adaptation. We conclude that significant evolutionary changes in the demographic traits of this (and presumably other) marine crustacean can occur within a time scale of interest to ecologists and aquaculturalists.Key words: adaptation, amphipod, aquaculture, Crustacea, evolution, Gammarus, genetics, life history, strategy
A Versatile Growth Model with Statistically Stable Parameters
Authors: Schnute Jon
Published: June 2008

This paper presents a new comprehensive growth model which includes numerous historical models as special cases. The new model is derived from a concise biological principle which, unlike earlier theories, relates to growth acceleration. Properties of growth curves, such as asymptotic limits or inflection points, are shown to be incidental in this new context. Possible submodels include not only asymptotic growth (such as von Bertalanffy, Richards, Gompertz, or logistic growth) but also linear, quadratic, or exponential growth. By simple analysis of variance, the observed data can be used directly in deciding which type of model is most appropriate. The new model is cast in terms of parameters which have stable statistical estimates. From this perspective, it is shown how earlier formulations sometimes result in an endless computer search for optimal parameter estimates.Key words: Growth, asymptotic growth, von Bertalanffy, Richards, Gompertz, logistic, length at age, weight at age, nonlinear parameter estimation
Marking Fish by Scarring Soft Fin Rays
Authors: Welch Harold E. , Mills Kenneth H.
Published: June 2008

Fish can be permanently marked by scarring soft fin rays. Advantages over existing marking methods include rapidity of application, permanence, individual identification, low costs, and lack of adverse effects caused by the mark. Disadvantages include lack of recognition by untrained observers and a relatively high error rate when reading marks.Key words: fish marking, fin rays
Indices of Total Stock Biomass in the "Northern" and Gulf of St. Lawrence Atlantic Cod (Gadus morhua) Stocks Derived from Time Series Analyses of Fixed Gear (Trap) Catches
Authors: Rose G. A.
Published: June 2008

The hypothesis that annual catches of fixed gear fisheries are cross-correlated with stock biomass at lags predictable on the basis of the relative ages of fish comprising the catch and biomass was verified for the trapnet fisheries of the northeastern Newfoundland "northern" (NAFO 2J3KL) and northern "Gulf" of St. Lawrence (NAFO 3Pn4RS) Atlantic cod (Gadus morhua) stocks. Time series indices of stock biomass were derived from these cross-correlations. For northern cod, the index was a 3-yr weighted and lagged moving average of catch. For the years 1972–81 (the first half of the available data) the trap index (Ti) was regressed on the stock biomass (Bi) determined by sequential population models (SPA) (Ti = 0.477Bi0.638, r = 0.99, P < 0.01). Biomass forecasts for 1982–90 derived from this function (inverted) were positively correlated with recent SPA-based estimates (r = 0.94, P < 0.02). For Gulf cod, the index was a 4-yr weighted and lagged moving average of catch. This index was regressed on SPA-determined biomass for the years 1974–81 (Ti = −3.19 + 0.0217Bi, r = 0.99; P < 0.01). Biomass forecasts for 1982–90 were positively correlated with (but lower than) SPA-based biomass estimates for the Gulf stock (r = 0.91, P < 0.05).
Fecundity and the Stock–Recruitment Relationship
Authors: Koslow J. Anthony
Published: June 2008

The stability of fishery population models often depends upon the form of the underlying stock–recruitment (SR) relationship, yet this relationship generally cannot be defined from actual fishery data. I use a simple SR model to show that the ability to characterize a SR relationship depends upon both natural mortality (M) during the prerecruit period, which is associated with a species' fecundity[Formula: see text], and the variability of M. The SR relationship may be readily determined in species with low fecundities (e.g. higher vertebrates:[Formula: see text]), even if the variability of M is relatively high. However, the SR relationship generally cannot be defined in species, such as teleosts, with high fecundities ([Formula: see text] on the order of 106) if prerecruit M exhibits even moderate variability because small variations in M lead to large changes in survivorship. Thus, the concept of a simple deterministic SR relationship does not appear applicable to organisms with high fecundities. The use of fishery population models dependent upon such functions needs to be reexamined. Adaptive management strategies (i.e experimental manipulations of stock size) are likely to succeed in defining the form of the SR relationship only for stocks characterized by low recruitment variability.
Development of Hypoosmoregulatory Capacity in Arctic char (Salvelinus alpinus) Reared under either Continuous Light or Natural Photoperiod
Authors: Arnesen Arne M. , Halvorsen Morten , Nilssen Kjell J.
Published: June 2008

Two groups of Arctic char (Salvelinus alpinus) were reared in freshwater (5–6 °C) under either continuous light (LDL) from first feeding (March) or LDL until July and then natural photoperiod (NDL, 70°N). Direct transfer to seawater (5.5 °C, 35 ppt) in February resulted in both groups exhibiting increases in blood plasma osmolality, Na+, and Mg2+concentrations and a significant decrease in muscle water content. When tested in May, an improvement in seawater tolerance was evident in both groups. In June, only the NDL fish showed further improvements in hypoosmoregulatory capacity, since they exhibited only minor fluctuations in plasma constituents and muscle water content following direct transfer to seawater. Increased body size could partially explain the improved seawater tolerance in the experimental groups. Acclimation to brackish water prior to transfer to 35 ppt seawater in June improved seawater tolerance only in fish reared under continuous light. The results indicate that the seasonal increase in photoperiod stimulates the development of hypoosmoregulatory capacity whilst the fish are still resident in freshwater.
Distribution of Early-Stage Atlantic Cod (Gadus morhua), Haddock (Melanogrammus aeglefinus), and Witch Flounder (Glyptocephalus cynoglossus) Eggs on the Scotian Shelf: A Reappraisal of Evidence on the Coupling of Cod Spawning and Plankton Production
Authors: Brander Keith , Hurley Peter C. F.
Published: June 2008

In spring, Atlantic cod (Gadus morhua) spawned progressively later from southwest to northeast along the Scotian Shelf and matched the variation in peak abundance of Calanus finmarchicus. In fall, cod spawned in some, but not all, areas where Calanus were abundant. This is consistent with the hypothesis that cod spawning is coupled to copepod production, which is a part of the "match–mismatch" hypothesis proposed by D. H. Cushing. The timing of spawning was estimated from the distributions of early- and late-stage eggs of cod, haddock (Melanogrammus aeglefinus), and witch flounder (Glyptocephalus cynoglossus) collected during Scotian Shelf Ichthyoplankton Survey (SSIP) cruises in 1979–81.
Usefulness of Meristic and Morphometric Characters in Discriminating Populations of American Shad (Alosa sapidissima) (Ostreichthyes:Clupeidae) Inhabiting a Marine Environment
Authors: Melvin Gary D. , Dadswell Michael J. , McKenzie Joseph A.
Published: June 2008

American shad (Alosa sapidissima) concentrate each summer in the basins of the inner Bay of Fundy during their coastal migration. Tag returns from 6124 marked shad indicated that these fish return to every important shad spawning stream on the Atlantic coast. Ten meristic and 16 morphometric characters of shad collected from 14 rivers (range: Florida to Quebec) were used to develop linear discriminant functions (LDF). Variables which differed significantly (p < 0.05) between the sexes, year of sampling, and the time of collection during the spawning run were removed prior to LDF classification. The highest mean percent correct classification was achieved by the allocation of fish into regional groups, after classification into individual rivers, using pooled meristic and morphometric variables: 87.2% for males and 82.4% for females. The functions were then used to assign shad from a mixed populations (Cumberland Basin) to individual rivers and regions. Of these, 10.9% were assigned to rivers south of Cape Lookout, North Carolina, 38.1% to rivers between Cape Lookout and Cape Cod, 32.5% into rivers of the Bay of Fundy, and 18.5% into rivers in the Gulf of St. Lawrence. In-river tag returns were compared with LDF classification and were found to be similar.
Genetic Models for Cyclic Dominance in Sockeye Salmon (Oncorhynchus nerka)
Authors: Walters Carl , Woodey J. C.
Published: June 2008

A simple genetic mechanism may be partly responsible for maintaining violent cycles in abundance of some Fraser River sockeye salmon (Oncorhynchus nerka) stocks. If age at maturity is highly heritable, spawning runs in low cycle lines may have high percentages of age 5 spawners that tend to produce offspring that will return at age 5, due to production of low percentages of such spawners by preceding high cycle lines. Then even if each low cycle line has a high productivity per spawner, a large fraction of this productivity may be "lost" to the cycle line, in the form of age 5 recruits to other cycle lines. In the face of high fishing mortality, even a small relative loss from any cycle line may cause it to remain small relative to other lines. This model explains several observations, such as high productivity per spawner in low cycle lines, that cannot be explained by previous hypotheses involving depensatory predation or food supply. However, it is unlikely that genetic effects alone are responsible for the stability of cyclic patterns, unless low offcycle runs consist entirely of "temporal colonizer" genotypes that produce a high proportion of age 5 offspring as a dominant trait.
Dynamics and Species Interactions in the Commercial Fishery of the Red lakes, Minnesota
Authors: Pereira Donald L. , Cohen Yosef , Spangler George R.
Published: June 2008

The Red Lakes, Minnesota, have supported a commercial fishery for walleye (Stizostedion vitreum vitreum) and yellow perch (Perca flavescens) since 1917. Since 1972, harvests indicate increased variance in recruitment of percids and an increase in biomass of freshwater drum (Aplodinotus grunniens). We subjected commercial catch-per-unit-effort (CPUE) records of walleye, yellow perch, and animal feed (composed primarily of drum) to spectral analysis. Estimated power spectra displayed peaks at 8.5, 10, and 17 yr for walleye, yellow perch, and animal feed, respectively. Walleye and yellow perch CPUE time series were significantly coherent at periods ranging from 5to 10 yr, confirming the predator–prey relationship and common recruitment patterns of these two species. Interpretation of coherency between drum and the two percid species required knowledge of the age distribution of freshwater drum. The apparent exponential increase in drum biomass as indicated by commercial CPUE is primarily due to strong year classes in 1955, 1970, and 1983. While drum recruitment and growth are consistent with the periodicity in the autospectrum, we find little evidence from coherencies that drum recruitment is related to the dynamics of wlleye or perch populations.
Morphology of the Toxin-Producing Diatom Nitzschia pungens Grunow forma multiseries Hasle
Authors: MacPhee Daniel J. , Hanic Louis A. , Friesen Dianne L. , Sims David E.
Published: June 2008

The toxin-producing diatom Nitzschia pungens Grunow forma multiseries Hasle from three toxic blooms in two Prince Edward Island estuaries, spanning 1987–89, was studied using light and electron microscopy. Cell ultrastructure of N. pungens is, in general, similar to that of other species of Nitzschia and other diatoms. Important features include prominent peripheral, polarized nucleoli (numbering one or two) and imperforate poroids, present on inner valves and girdle bands. Cell division is usually synchronous for all cells in a filament with respect to polarity and time. Postdivisional elongation of the filament appears to involve a "slide-by" process whereby sibling cells slide by each other along their opposed valve faces and then stop, becoming fused by their overlapping tips. The raphe is probably involved in this, as well as in filament and cell motility. Observations of particle motion along the cell raphe suggest the existence of a motility apparatus such as microcilia which would facilitate locomotion, intercellular coordination, and the postdivisional slide-by process. No bacteria or other organisms were observed associated with field samples of toxic N. pungens f. multiseries. This supports a view that domoic acid production is autonomous.
Depuration of Domoic Acid from Live Blue Mussels (Mytilus edulis)
Authors: Novaczek I. , Madhyastha M. S. , Ablett R. F. , Donald A. , Johnson G. , Nijjar M. S. , Sims D. E.
Published: June 2008

Industrial depuration may provide a means of removing domoic acid toxin from blue mussels (Mytilus edulis). Mussels containing up to 50 μg domoic acid∙g−1 were transported from a Prince Edward Island estuary into controlled laboratory conditions to test the effects of temperature, salinity, mussel size, and feeding upon depuration. Fifty percent of toxin was eliminated within 24 h. After 72 h, mussels were either clean or contained, on average, only residual levels of toxin (< 5 μg∙g−1), regardless of conditions. Exponential depuration curves were fitted to the domoic acid concentration data. To evaluate differences in rate of depuration under various conditions, statistical comparisons were made between slopes of the clearance curves. Rates of depuration were faster in small (45–55 mm) than in large mussels (60–70 mm) and more rapid at 11 than at 6 °C. There was no significant difference in depuration rate at 18‰ salinity as opposed to 28‰ or in starved versus fed mussels. Because of their relatively large digestive glands, meats of small mussels contained more toxin per unit weight than meats of large mussels. The bulk of domoic acid appeared to reside in the gut lumen. However, the presence of small amounts of domoic acid in intracellular compartments cannot be ruled out.
Mitochondrial DNA Analysis of Walleye Pollock,Theragra chalcogramma, from the Eastern Bering Sea and Shelikof Strait, Gulf of Alaska
Authors: Mulligan Timothy J. , Chapman Robert W. , Brown Bonnie L.
Published: June 2008

Increased fishing effort in the international waters of the Aleutian Basin has focused much interest on defining the stock structure of walleye pollock, Theragra chalcogramma, in the Bering Sea. Variation in mitochondrial DNA (mtDNA) was examined via restriction endonuclease digestions in 168 walleye pollock from three areas in the eastern Bering Sea and from Shelikof Strait, Gulf of Alaska. Nine endonucleases produced variant restriction patterns both within and among populations. A total of 50 restriction sites were revealed along the mtDNA molecule. Two dominant genotypes were found in 39 and 21 individuals, respectively. Fifty-one genotypes (78% of the total) were represented by a single specimen. Clustering of genetic distances suggests the existence of several walleye pollock stocks in the Bering Sea and Gulf of Alaska. Genetic divergence among stocks may be related to the prevailing current patterns found in these areas.
Modelling Crustacean Fisheries: Effects of Parasites on Management Strategies
Authors: Kuris Armand M. , Lafferty Kevin D.
Published: June 2008

The reproductive performance of commercially important crustaceans may be considerably affected by symbiotic nemertean egg predators and parasitic castrators. Because these parasites commonly affect only females or feminize males, they may be protected by management practices that protect females. To manage a parasitized stock, we suggest that strategies should vary depending on the recruitment dynamics of both host and parasite. For a certain spatial scale, recruitment to a population may be "open" or "closed" depending on the behavior of planktonic larvae, the duration of these planktonic stages, and the flush rate of the environment of the adult host. Both hosts and parasites may have open or closed larval recruitment. We developed mathematical models to investigate the impact of protection of females on a hypothetical fishery for different combinations of host and parasite recruitment dynamics. The models suggest that the common practice of releasing females is not advantageous when a fishery is affected by a parasite. Retaining females in the catch is preferable in most cases. Treating or culling infected females may be advisable when host recruitment is closed.
Coarse Particulate Detritus Dynamics in Small, Montane Streams Southwestern British Columbia
Authors: Richardson John S.
Published: June 2008

The dynamics of coarse particulate organic matter (CPOM) were studied for 2 yr in three second-order streams in the Coast Range of British Columbia. Estimates of direct litterfall ranged from 201 to 481 g ash-free dry mass∙m−2∙yr−1. The magnitude of deciduous leaf litter input was similar among streams. Input of conifer needles to a stream with an old-growth canopy was higher than in two streams which drained second-growth forests. There was over a 60-fold seasonal change in deciduous leaf standing stock, but woody debris and total CPOM showed less seasonal variation. Decomposition of alder leaf packs in two of the streams showed a large temperature-dependent component and significant differences between streams, with the more retentive stream having lower rates of decomposition. From estimates of input and decay rates, models of leaf loss were made to predict benthic standing stocks of deciduous leaf litter. Comparisons of the model predictions with actual measures indicate that 70–94% of leaf material was unaccounted for and presumably lost from the study reach by export, floodplain deposition, and burial. The seasonal changes in standing stock of CPOM emphasize the variation in food supply potentially available to detritivorous stream organisms.
Impact of Harvesting on Frond Density and Biomass of Irish Moss (Chondrus crispus Stackhouse) Beds in the Southern Gulf of St. Lawrence
Authors: Chopin T. , Pringle J. D. , Semple R. E.
Published: June 2008

Dragrake harvesting had an adverse impact on frond density and biomass of Chondrus crispus Stackhouse as revealed by the comparison of these parameters in a dragraked bed (Miminegash) and a nondragraked bed (Rustico). Mean frond density peaked in September at both locations; it was significantly greater at Miminegash than at Rustico because of a higher density of small plants (Classes 1, 2, and 3). Intraannual variations in density were due to fluctuations of mostly the small plants (Classes 1 and 2). Mean frond biomass was significantly greater at Rustico than at Miminegash because of higher density and biomass of large Class 4 and 5 plants. Intraannual distribution of biomass was bimodal at Miminegash (June and September peaks) whereas it was unimodal at Rustico (peak in July). Mean frond density and biomass of reproductive plants were significantly greater at Rustico than at Miminegash. The study recommends a 1-mo delay in harvest season opening to enhance biomass yield. A longer postponement would not be beneficial, as populations will enter a period of natural decrease in density and biomass of C. crispus and of increased biomass of associated algae.
Influence of Pleistocene Glaciations and Human Intervention upon Mitochondrial DNA Diversity in White Sturgeon (Acipenser transmontanus) Populations
Authors: Brown James R. , Beckenbach Andrew T. , Smith Michael J.
Published: June 2008

The influence of recent genetic bottlenecks on two Northwest Pacific populations of white sturgeon (Acipenser transmontanus) was studied using restriction enzyme site differences in mitochondrial DNA (mtDNA). A total of 10 mtDNA genotypes were detected in 178 sturgeon from the Columbia and Fraser rivers. Nearly 61% of individuals from both rivers had a common genotype. However, one genotype was found only in the Fraser River. Geographical substructuring was not evident in the phylogenetic analysis. The Columbia River, a Pleistocene refugium, is suggested as the source of founders for the Fraser River following the last glacial recession, about 10 000–12 000 yr ago. MtDNA genotypic frequencies were significantly different between the rivers. Estimates of mtDNA (h) and nucleotide (π) diversity were consistently higher for the recently colonized Fraser River compared with the Columbia River refugium. This condition is the reverse of all known studies of mtDNA diversity between refugium and colonized animal populations. Recent overexploitation and habitat destruction are suggested as a severe genetic bottleneck that has reduced mtDNA diversity in Columbia River sturgeon.
Size Variation of Neocalanus plumchrus and Neocalanus flemingeri in a 20-yr Sample Series from the Gulf of Alaska
Authors: Miller Charles B. , Fulton John , Frost Bruce W.
Published: June 2008

Prosome length of the resting stages of Neocalanus plumchrus and Neocalanus flemingeri varied significantly, but modestly, among years at Station P in the Gulf of Alaska. The range of variation over 20 yr was small relative to the known geographic variation. Among-year length variations were significantly greater than within-year variations, implying similarity of year-to-year variation in growth conditions over an indeterminate, subregional scale. The two species tended to vary in the same fashion both among and within years, despite the offset of about 1 mo in their developmental schedules. Length of N. plumchrus was negatively correlated with Emerson's (1987. J. Geophys. Res. (Oceans) 92(C6): 6535–6544) estimates of May–August new production at Station P from 1969 to 1978.
Dynamic Model of the Flux of Domoic Acid, a Neurotoxin, through a Mytilus edulis Population
Authors: Silvert W. , Rao D. V. Subba
Published: June 2008

A one-compartment computer simulation model was developed to quantify and characterize the accumulation of the neurotoxin domoic acid in blue mussel (Mytilus edulis) in Cardigan Bay, Prince Edward Island, Canada. Comparison of simulation results with field abundances of Nitzschia pungens f. multiseries Hasle, a diatom implicated in the production of domoic acid, and with measurements of domoic acid within Nitzschia cells indicates that the rate of accumulation of domoic acid in mussel tissue during peak bloom conditions may involve unexpected physiological feedback processes. At extremely high concentrations of toxin (> 300 ppm) observed in toxic Mytilus episodes off eastern Prince Edward Island in 1987 during the peak of Nitzschia bloom, the depuration of domoic acid seemed to be suppressed; this may have been responsible for the observed abnormal buildup of toxin in the mussels. In 1989 the amount of domoic acid produced by N. pungens was slightly lower, but the levels of domoic acid in Mytilus were much less than in 1987. These results suggest that a crucial factor in prediction of high levels of domoic acid in mussels may be identification of changes in their physiology and metabolism which suppress depuration rates.
Establishment of Gobiidae in the Great Lakes Basin
Authors: Jude David J. , Reider Robert H. , Smith Gerald R.
Published: June 2008

A tubenose goby (Proterorhinus marmoratus), a European endangered species native to the Black and Caspian seas, was recovered on 11 April 1990 from the travelling screens of the Belle River Power Plant located on the St. Clair River, Michigan. Subsequently, anglers caught three round gobies (Neogobius melanostomus) in the St. Clair River near Sarnia, Ontario. Thirty-one tubenose gobies and 11 round gobies were impinged or trawled at or near the Power Plant in the fall and winter of 1990–91. Nine round gobies (29–61 mm total length) are believed to be young-of-the-year. These species were probably transported to the Great Lakes in ballast water, may have successfully colonized the St. Clair River, and will probably spread throughout the Great Lakes. They are expected to impact directly other benthic fishes, such as sculpins (Cottus spp.), darters (Etheostoma spp.), and logperch (Percina caprodes), and in turn act as prey for walleye (Stizostedion vitreum).