bluuebunny/crossref_metadata_2025 huggingface dataset:
Movement, migration, and smolting of Atlantic salmon (Salmo salar)
Authors: McCormick Stephen D , Hansen Lars P , Quinn Thomas P , Saunders Richard L
Published: April 2011

A variety of movements characterize the behavioral plasticity of Atlantic salmon (Salmo salar) in fresh water, including movements of fry from redds, establishment of feeding territories, spawning movements of sexually mature male parr, movement to and from winter habitat, and smolt migration in spring. Smolting is an adaptive specialization for downstream migration, seawater entry, and marine residence. While still in fresh water, smolts become silvery and streamlined, lose their positive rheotaxis and territoriality, and begin schooling. Physiological changes include increased salinity tolerance, olfactory sensitivity, metabolic rate, scope for growth, and altered hemoglobin and visual pigments. Through their impact on the neuroendocrine system, photoperiod and temperature regulate physiological changes, whereas temperature and water flow may initiate migration. Smolt survival is affected by a limited period of readiness (a physiological "smolt window") and the timing of seawater entry with environmental conditions such as temperature, food, and predators (an ecological "smolt window"). Smolt development is adversely affected by acidity, pollutants, and improper rearing conditions, and is often more sensitive than other life stages. Unfortunately, the migration corridor of smolts (mainstems of rivers and estuaries) are the most heavily impacted by pollution, dams, and other anthropogenic activities that may be directly lethal or increase mortality by delaying or inhibiting smolt migration.
Juvenile production variation in salmonids: population dynamics, habitat, and the role of spatial relationships
Authors: Kocik John F , Ferreri C Paola
Published: April 2011

Anadromous Atlantic salmon (Salmo salar) exhibit a complex life history that requires the use of habitats that span several different temporal and spatial scales. While fisheries scientists have investigated the various elements of habitat and how they affect Atlantic salmon growth and survival, these studies typically focus on requisite requirements for a single life history stage. Current advances in our understanding of salmonid populations in lotic systems indicates that ignoring the spatial positioning of different habitats and dispersal capabilities of fish between them may affect estimates of habitat quality and production of juvenile Atlantic salmon. Using the concepts of juxtaposition and interspersion, we hypothesize that discrete functional habitat units (FHU) occur within river systems and that the spatial structure of FHU affects fish production. We present a method to delineate FHU using habitat maps, fish ecology, and spatial habitat characteristics. Utilizing a simulation model, we illustrate how modeling FHU structure of spawning and rearing habitat in a river system can improve our understanding of juvenile Atlantic salmon production dynamics. The FHU concept allows a flexible approach to more comprehensive analyses of the impacts of habitat alterations, seasonal habitat shifts, and spatial ecology of salmonids at various scales.
Implications of territory size for the measurement and prediction of salmonid abundance in streams
Authors: Grant JWA , Steingrímsson S Ó , Keeley E R , Cunjak R A
Published: April 2011

Information about territory size is useful for both the measurement and prediction of salmonid abundance. Percent habitat saturation (PHS), the percentage of the stream area occupied by the territories of salmonid fishes, is a better measure of abundance than population density because the former integrates the effects of (a) several age-classes or species in a stream, and (b) variation in growth rate or sampling date. "Effective density" or "effective PHS," calculated by weighting crude density (no.·m-2) or PHS by the number of organisms in the sampling unit, more accurately reflects density from the organism's point of view than does crude density or PHS. Effective density and PHS of Atlantic salmon (Salmo salar) in Catamaran Brook, New Brunswick, increased by 0.4 fish per m2 and 4%, respectively, for each order of magnitude decrease in the area of the sampling unit. Literature data suggested that territory size is inversely related to food abundance and can be used to predict changes in salmonid abundance that accompany changes in food abundance. The allometry of territory size was a better predictor of the decline in density of a cohort of Atlantic salmon in Catamaran Brook than the allometry of metabolic requirements.
Geochemistry of the Little Dal basalts: continental tholeiites from the Mackenzie Mountains, Northwest Territories, Canada
Authors: Dudás Francis Ö. , Lustwerk Rigel L.
Published: April 2011

Analyses of the Little Dal lavas and the 779 Ma Tsezotene sills, both of the Mackenzie Mountains Supergroup, Northwest Territories, Canada, show them to be continental tholeiites that are geochemically related. The plagioclase- and clinopyroxene-phyric lavas are geochemically evolved and enriched in iron (up to 20.2 wt.% as Fe2O3). Two magmatic lineages are identifiable and may represent different degrees of partial melting in the same source region, but cannot be related by fractional crystallization. Within each lineage, geochemical variation can be explained by fractional crystallization involving up to 60% crystallization of the original magma. The most evolved lavas occur at the base of the pile; less fractionated lavas occur toward the top of the sequence. The Nd isotopic composition of the Little Dal lavas averages ε = 1.4 at 780 Ma. Trace element and isotopic compositions are permissive of contamination by continental crust, but do not require a crustal component. The preserved volume of the Little Dal basalts is anomalously low (−100 km3) compared with other Proterozoic continental tholeiites. There is considerable basaltic detritus in the sedimentary rocks of the overlying Coates Lake and Rapitan groups, and much of the original lava sequence may have been eroded. The Little Dal magmatic event is interpreted to be an early manifestation of rifting of North America from Australia.
Geology, U – Pb, and Pb – Pb geochronology of the Lake Harbour area, southern Baffin Island: implications for the Paleoproterozoic tectonic evolution of northeastern Laurentia
Authors: Scott David J.
Published: April 2011

Geological and geochronological results of an investigation of the Paleoproterozoic siliciclastic and carbonate supracrustal rocks of the Lake Harbour Group (LHG) and surrounding tonalitic gneisses on southern Baffin Island are presented. Conventional U – Pb geochronology of monazite from rocks of the LHG suggest that penetrative deformation of these rocks occurred prior to, or during, peak metamorphic conditions at ca. 1845 –1840 Ma. Conventional U – Pb zircon results indicate that much of the tonalitic gneiss ranges in age from [Formula: see text] to 1827[Formula: see text]. The tonalitic gneisses and Lake Harbour Group units were tectonically imbricated by ca. 1805 Ma, and are part of a southwest-verging thrust belt interpreted from regional considerations to represent the northern continuation of the Ungava Orogen. The present results indicate that current tectonic models for the evolution of northeastern Laurentia that involve a dominantly Archean southeastern Rae province require revision. It is proposed that much of the metaigneous material that lies between the Archean Superior and Nain cratons represents a composite subduction-related domain.
Upper mantle stratigraphy beneath the southern Slave craton
Authors: Bostock M. G. , Cassidy J. F.
Published: April 2011

A large teleseismic data set comprising 724 broadband, three-component P-wave seismograms has been compiled for the southern Slave craton with the objective of characterizing underlying mantle stratigraphy. Coherent P to S wave conversions are identified by simultaneously deconvolving seismograms as functions of epicentral distance and along theoretical moveout curves corresponding to possible mantle phases. Clear PDs conversions are observed from the 410 and 660 km discontinuities at times that are only slightly faster than those predicted from the IASP91 model, and over 1.0 s slower than corresponding times observed at other stations on the Canadian Shield and the south African Kaapvaal craton. The PDs times show very little azimuthal variation, implying an absence of major lateral velocity variations in the lithospheric mantle underlying the Slave craton, and adjacent Wopmay orogen and Taltson magmatic zone. Considered in light of other geophysical and geological evidence, these results suggest that the root underlying the Slave province has been modified along its margins and may remain intact only toward a central core. Another important result involves the observation of a PDs conversion from a negative velocity contrast interface at approximately 360 km depth. It and a similar phase, observed on the Kaapvaal craton, would appear not to be directly related to tectospheric structure, but may originate at the top of a layer containing a dense silicate partial melt just above the mantle transition zone.
Pedosedimentary history and floodplain dynamics of the Lower Cretaceous upper Blairmore Group, southwestern Alberta, Canada
Authors: McCarthy Paul J. , Martini I. Peter , Leckie Dale A.
Published: April 2011

Thick alluvial successions in the upper Blairmore Group in the Foothills of southwestern Alberta contain few well-developed paleosol profiles, but abundant evidence of pedogenic modification. The pedogenically modified successions are characterized by vertical root traces, compound illuvial clay coatings, and ferruginous coatings and nodules. Five representative paleosol successions, composed of nine microfacies, are analyzed. The paleosol successions indicate soil development on more or less continuously aggrading floodplains; however, locally, rates of sedimentation and pedogenesis were highly variable. The paleosol successions contain features similar to modern alluvial soils, Brunisols, and Luvisols. Vertical trends within individual paleosol successions preserve the changing paleoenvironmental record at each site. The dynamic nature of the floodplain topography is reflected in alternating drainage conditions, represented by quasi-regular colour banding, compound clay coatings, and the type and degree of pedogenic development upwards within the paleosol successions. Overall, the paleosols indicate soil development under a warm, temperate paleoclimate with seasonal precipitation. Although representing minor diastems, the paleosols formed contemporaneously with sedimentation and are an integral part of the alluvial successions. Local variations in paleosol development are attributed to variations in sediment supply and water-table conditions related to the overall floodplain geomorphology.
Mid-Wisconsinan eolian deposits of the Kittigazuit Formation, Tuktoyaktuk Coastlands, Northwest Territories, Canada
Authors: Dallimore Scott R. , Wolfe Stephen A. , Matthews Jr. John V. , Vincent Jean-Serge
Published: April 2011

The Kittigazuit Formation is a late Quaternary sand unit commonly observed throughout the Tuktoyaktuk Coastlands and in subbottom sediments of the southern Beaufort Shelf. Stratigraphic and sedimentology data, including sedimentary structures, grain-surface characteristics, and heavy and light mineralogy, assist in characterizing the deposit and indicate that it is eolian in origin. Plant and arthropod macrofossils suggest that, although the summer climate during deposition was as warm or slightly warmer than today, conditions were likely more arid. Permafrost is interpreted as being widespread during deposition. Accelerator mass spectrometry radiocarbon dates indicate that the Kittigazuit Formation was deposited between 37 and 33 ka BP. The unit is therefore interpreted as a Mid-Wisconsinan eolian dune deposit, formed by reworking of underlying alluvial sediments of the Kidluit Formation under nonglacial conditions. Glaciogenic sediments overlying the Kittigazuit Formation indicate that glacial ice covered the Tuktoyaktuk Peninsula, Richards Island, and parts of the Beaufort Shelf sometime after 33 ka BP, whereas several terrestrial dates indicate that the area may have been ice free by about 20 ka BP.
The effects of artificial pebble concentrations on eolion sand transport on a beach
Authors: Davidson-Arnott Robin G. D. , White Davina C. , Ollerhead Jeff
Published: April 2011

A field experiment to measure the effects of differing concentrations of pebbles on rate of eoliao sediment transport was carried out on a sand beach on the Northumberland Strait, New Brunswick. Square ceramic tiles (0.15 m × 0.15 m) were used to replicate pebbles. These were deployed in a stratified random array in a rectangular plot 5 m wide and 2 m deep at five different concentrations (surface covers of 19, 24, 29, 34, and 44%) and both singly (two dimensional) and stacked three high (three dimensional). An adjacent plot of similar size was left bare and served as a control. Sediment transport was measured with pairs of vertical traps deployed downwind from each plot and wind speed with three-cup anemometers. Nine data sets totalling 45 runs of 10 min duration each were collected over a total of 4 days. Sediment transport over the tiled plot was normalized against transport over the bare plot. The results show an increase in sediment transport compared with the bare surface for the lowest coverage, followed by a continuous decrease in transport with increasing coverage up to the maximum coverage employed. The rate of decrease was greatest for runs that utilized a three-dimensional form, reflecting an increase in the effective area protected. The results confirm laboratory experiments, which suggest that erosion and transport are initially enhanced by acceleration of flow around pebbles and more efficient transport over the hard surface, but that this is counteracted at higher coverage densities by the increasing area of protected surface.
Interactions between zebra mussels (Dreissena polymorpha) and microbial communities
Authors: Frischer Marc E , Nierzwicki-Bauer Sandra A , Parsons Robert H , Vathanodorn Kanda , Waitkus Kelli R
Published: April 2011

Zebra mussels (Dreissena polymorpha) have had an enormous impact on aquatic environments. However, little is known concerning their interactions with microbial communities. In these studies, the ability of zebra mussels to derive nutrition from bacterioplankton and their effect on microbial community diversity were investigated in samples from the Hudson River, New York, and in laboratory studies. Clear physiological responses to starvation were observed, including decreases in respiration rates, lipid content, and total weight, that were reversed after feeding zebra mussels a diet of bacteria. Clearance rates of bacteria were correlated with bacteria size (r2= 0.995), with the lowest clearance rates associated with small indigenous river bacteria (size = 0.03 ± 0.04 µm3, clearance rate = 0.08 ± 0.02 mL·mussel-1·min-1). Comparison of the diversity of microbial communities in zebra mussel tissue extract, detritus, and pseudofecal material associated with zebra mussel colonies, surrounding water, and sediment samples revealed distinct microbial assemblages associated with these environments. The overall ecological effect and importance of bacteria - zebra mussel interactions remains unclear, but these studies indicate that these interactions occur and should be included in our efforts to better understand the impact of zebra mussels on aquatic systems.
Effects of female attributes and egg properties on offspring viability in a rheophilic cyprinid, Chondrostoma nasus
Authors: Keckeis Hubert , Bauer-Nemeschkal Elisabeth , Menshutkin Vladimir V , Nemeschkal Hans Leo , Kamler Ewa
Published: April 2011

Intraspecific differences in female attributes influence egg quality and, as a consequence, offspring viability. To further investigate this hypothesis, we compared female attributes, egg size, biochemical egg composition, and survival potential of offspring from 20 female spawners of an endangered rheophilic cyprinid, Chondrostoma nasus. Egg size was strongly related to female age and size. The chemical composition of egg dry matter was influenced by female size to a lesser extent. No significant relationship between egg size and egg dry matter composition was observed. Mortality curves revealed three distinct periods of elevated mortality: early mortality, hatching mortality, and starvation mortality, separated by periods of reduced mortality. No significant correlations between embryonic mortality (early mortality and hatching mortality) and egg size were found. Starvation mortality was size selective: resistance to starvation correlated significantly with egg size and egg energy content. The direct and indirect relationhips between female attributes, egg quality, and offspring viability show that the two main components of offspring viability (embryonic mortality and larval resistance to starvation) are not interrelated and that the sequence female attributes - egg size - larval resistance to starvation is the main pathway along which size selectivity operates.
Assessing covariability among populations in the presence of intraseries correlation: Columbia River spring-summer chinook salmon (Oncorhynchus tshawytscha) stocks
Authors: Botsford Louis W , Paulsen Charles M
Published: April 2011

We assessed covariability among a number of spawning populations of spring-summer run chinook salmon (Oncorhynchus tshawytscha) in the Columbia River basin by computing correlations among several different types of spawner and recruit data. We accounted for intraseries correlation explicitly in judging the significance of correlations. To reduce the errors involved in computing effective degrees of freedom, we computed a generic effective degrees of freedom for each data type. In spite of the fact that several of these stocks have declined, covariability among locations using several different combinations of spawner and recruitment data indicated no basinwide covariability. There was, however, significant covariability among index populations within the three main subbasins: the Snake River, the mid-Columbia River, and the John Day River. This covariability was much stronger and more consistent in data types reflecting survival (e.g., the natural logarithm of recruits per spawner) than in data reflecting abundance (e.g., spawning escapement). We also tested a measure of survival that did not require knowing the age structure of spawners, the ratio of spawners in one year to spawners 4 years earlier. It displayed a similar spatial pattern.
Effects of fish on plankton dynamics: a theoretical analysis
Authors: Scheffer Marten , Rinaldi Sergio , Kuznetsov Yuri A
Published: April 2011

We present an expansion of a classical minimal Daphnia-algae model to account for effects of fish as a top predator. Our analyses suggest that in most situations, the plankton should show hysteresis in response to predation pressure by fish. Thus, there exist two distinct regimes, one in which Daphnia is controlled (overexploited) by fish and phytoplankton biomass is high and another in which Daphnia is relatively unaffected (underexploited) by planktivores and algae are controlled by Daphnia. Switches from one regime to the other occur abruptly at a critical fish density. This is in line with field observations and experimental results. Our model predicts that the critical fish density for Daphnia collapse is higher in systems with higher ambient nutrient concentrations. The model also shows how intrinsic predator-prey oscillations in the planktonic system can facilitate the switch to the algal-dominated regime where Daphnia is controlled by fish. In terms of dynamical systems theory, this switch happens through a homoclinic bifurcation. In biological terms, Daphnia collapses due to food limitation and is subsequently overexploited by fish. This is indeed the sequence of mechanisms observed at the end of the spring clearwater phase in lakes where Daphnia is absent during the summer when the biomass of young-of-the-year planktivorous fish becomes high.
Sampling for mercury at subnanogram per litre concentrations for load estimation in rivers
Authors: Colman John A , Breault Robert F
Published: April 2011

Estimation of constituent loads in streams requires collection of stream samples that are representative of constituent concentrations, that is, composites of isokinetic multiple verticals collected along a stream transect. An all-Teflon isokinetic sampler (DH-81) cleaned in 75°C, 4 N HCl was tested using blank, split, and replicate samples to assess systematic and random sample contamination by mercury species. Mean mercury concentrations in field-equipment blanks were low: 0.135 ng·L-1 for total mercury (ΣHg) and 0.0086 ng·L-1 for monomethyl mercury (MeHg). Mean square errors (MSE) for ΣHg and MeHg duplicate samples collected at eight sampling stations were not statistically different from MSE of samples split in the laboratory, which represent the analytical and splitting error. Low field-blank concentrations and statistically equal duplicate- and split-sample MSE values indicate that no measurable contamination was occurring during sampling. Standard deviations associated with example mercury load estimations were four to five times larger, on a relative basis, than standard deviations calculated from duplicate samples, indicating that error of the load determination was primarily a function of the loading model used, not of sampling or analytical methods.
Bioavailability of sediment-associated mercury toHexageniamayflies in a contaminated floodplain river
Authors: Naimo Teresa J , Wiener James G , Cope W Gregory , Bloom Nicolas S
Published: April 2011

We examined the bioavailability of mercury in sediments from the contaminated Sudbury River (Massachusetts, U.S.A.). Mayfly nymphs (Hexagenia) were exposed in four 21-day bioaccumulation tests to contaminated and reference sediments (treatments) from reservoirs, flowing reaches, palustrine wetlands, and a riverine lake. Mean total mercury (ΣHg) ranged from 880 to 22 059 ng·g dry weight-1in contaminated sediments and from 90 to 272 ng·g-1in reference sediments. Mean final concentrations of methyl mercury (MeHg) in test water were greatest (8-47 ng Hg·L-1) in treatments with contaminated wetland sediments, which had mean ΣHg ranging from 1200 to 2562 ng·g-1. In mayflies, final mean concentrations of MeHg were highest in treatments with contaminated wetland sediments (122-183 ng Hg·g-1), intermediate in treatments with contaminated sediments from reservoirs, flowing reaches, and a riverine lake (75-127 ng Hg·g-1), and lowest in treatments with reference sediments (32-41 ng Hg·g-1). We conclude that the potential entry of MeHg into the benthic food chain was greater in contaminated palustrine wetlands than in the contaminated reservoirs, which had the most contaminated sediments.
Bioaccumulation of trace metals in marine and estuarine amphipods: evaluation and verification of toxicokinetic models
Authors: Clason B , Zauke G -P
Published: April 2011

The suitability of the marine and estuarine gammaridean amphipods Gammarus locustra (Linneaus 1758), Gammarus zaddachi Sexton (1912), and Gammarus salinus Spooner (1947) from the Island of Heligoland and the Weser and Ems estuaries, northwestern Germany, as biomonitors was tested in a toxicokinetic study with the elements Cu, Zn, Pb, Cd, and Hg. The organisms responded with metal uptake upon exposure, and it was possible to estimate parameters of two-compartment or logistic regression models that were statistically different from zero. In most cases, the toxicokinetic models obtained were successfully verified in a second toxicokinetic uptake study for Cu, Zn, Pb, and Cd. Data for Cd were additionally verified with previously reported kinetic parameters. Results for Hg indicate that the organisms tested may not be suitable as biomonitors for this element. The calibration of gammarids as biomonitors was extended in a third toxicokinetic uptake study for Cu and Pb showing a linear increase from the control level to external waterborne metal exposures of 240 µg Cu·L-1 and 60 µg Pb·L-1, while Zn tended to level off above 120 µg·L-1 and Cd above 10 µg·L-1. These figures largely determine the range for which the models may serve as a predictive tool.
Reconstructing trophic interactions as a tool for understanding and managing ecosystems: application to a shallow eutrophic lake
Authors: Bodini Antonio
Published: April 2011

Consequences of disturbance and human intervention on lake ecosystems are difficult to anticipate solely by intuition because of the complex interactions that characterize lake communities. Understanding how the structure of the interactions buffers or amplifies external impacts may have beneficial effects on lake management. In this paper, the food web of a moderately eutrophic lake (Lake Mosvatn, Norway) is reconstructed by using the effects of biomanipulation in combination with loop analysis, a qualitative algorithm. The outcome is a signed digraph that predicts changes in the level of the variables for input entering the system through any component. Model predictions explain the observed patterns of abundance, and this suggests that the graph is a plausible description of the main trophic interactions in Lake Mosvatn. As such, it is used as a predictive tool to discuss problems related to nutrient enrichment. When multiple causes are responsible for the observed effects, explaining their relative contribution to the net outcome is a difficult task. By discussing patterns of abundance observed in Lake Mosvatn as due to different inputs, this paper illustrates how qualitative predictions can help in this respect.
Behaviour in flow: perspectives on the distribution and dispersion of meroplanktonic larvae in the water column
Authors: Metaxas Anna
Published: April 2011

For marine benthic invertebrates with meroplanktonic larvae, the relative importance of hydrodynamics and swimming behaviour in determining larval dispersal in the water column, particularly at small spatial scales, has not been determined. In the field, larval aggregations recorded at physical and biological discontinuities in the water column were attributed to hydrodynamics. Similar aggregations obtained in the absence of flow in the laboratory indicate a potentially significant role of behaviour. At large spatial scales, larval distribution in the plankton is mainly regulated by horizontal advection. However, the ability of larvae to behaviourally regulate their position at scales of micrometres to metres when exposed to turbulent fluid motion in the water column, as evidenced in the benthic boundary layer, is unknown. Evaluation of swimming in turbulent flows in the water column is an intriguing area of research, which involves several constraints. In the field, quantification of behaviour is limited by low success in tracking larvae and lack of appropriate observational tools. In the laboratory, the generation and quantification of flow regimes that are representative of those in the field remains a challenge. An approach that integrates biological and physical measurements within realistic ranges is necessary to advance our understanding of larval dispersal.
Otoliths, increments, and elements: keys to a comprehensive understanding of fish populations?
Authors: Campana Steven E , Thorrold Simon R
Published: April 2011

The chronological properties of otoliths are unparalleled in the animal world, allowing accurate estimates of age and growth at both the daily and the yearly scale. Based on the successes of calcified structures as environmental proxies in other taxa, it was logical that researchers should attempt to link otolith biochronologies with otolith chemistry. With the benefit of hindsight, this anticipation may have been naive. For instance, the concentrations of many elements are lower in the otolith than in corals, bivalves, seal teeth, or the other bony structures of fish, making them less than ideal for elemental analyses. Nevertheless, there is growing interest in the use of otolith chemistry as a natural tag of fish stocks. Such applications are directed at questions concerning fish populations rather than using the fish as a passive recorder of the ambient environment and do not rely upon any explicit relationship between environmental variables and otolith chemistry. The questions that can be addressed with otolith chemistry are not necessarily answerable with genetic studies, suggesting that genetic and otolith studies complement rather than compete with each other. Thus, we believe that otolith applications have the potential to revolutionize our understanding of the integrity of fish populations and the management of fish stocks.
Habitat- and size-related variations in exotic trout impacts on native galaxiid fishes in New Zealand streams
Authors: McIntosh Angus R
Published: April 2011

The factors controlling the effects of introduced trout on native galaxiid fishes in New Zealand streams were investigated by quantitative and qualitative electrofishing. Habitat assessments indicated that bed stability was closely related to total fish biomass. Exotic trout were not present at the most unstable sites but inhabited most medium to large streams with stable beds. Galaxiids (Galaxias vulgaris, Galaxias brevipinnis, and Galaxias paucispondylus) occurred at sites that spanned almost the entire range of habitat conditions and co-occurred with trout more frequently at intermediate levels of bed stability. However, galaxiids were absent from all sites with large (>150-mm fork length (FL)) brown (Salmo trutta) and rainbow (Oncorhynchus mykiss) trout. These streams tended to be larger, with more stable beds. In a field tank experiment, large brown trout consumed Canterbury galaxias (G. vulgaris), ranging in size from 48- to 94-mm FL, at a much higher rate than did small trout. Their predation of galaxiids appeared not to be size selective, so there was no size refuge for galaxiids from predation by large trout. These results indicate that predation by large trout has likely eliminated small-bodied galaxiids from many streams but that trout impact is limited by the availability of habitats suitable for large individuals.
Population structure of sympatric anadromous and nonanadromousOncorhynchus mykiss: evidence from spawning surveys and otolith microchemistry
Authors: Zimmerman Christian E , Reeves Gordon H
Published: April 2011

Reproductive isolation between steelhead and resident rainbow trout (Oncorhynchus mykiss) was examined in the Deschutes River, Oregon, through surveys of spawning timing and location. Otolith microchemistry was used to determine the occurrence of steelhead and resident rainbow trout progeny in the adult populations of steelhead and resident rainbow trout in the Deschutes River and in the Babine River, British Columbia. In the 3 years studied, steelhead spawning occurred from mid March through May and resident rainbow trout spawning occurred from mid March through August. The timing of 50% spawning was 9-10 weeks earlier for steelhead than for resident rainbow trout. Spawning sites selected by steelhead were in deeper water and had larger substrate than those selected by resident rainbow trout. Maternal origin was identified by comparing Sr/Ca ratios in the primordia and freshwater growth regions of the otolith with a wavelength-dispersive electron microprobe. In the Deschutes River, only steelhead of steelhead maternal origin and resident rainbow trout of resident rainbow trout origin were observed. In the Babine River, steelhead of resident rainbow trout origin and resident rainbow trout of steelhead maternal origin were also observed. Based on these findings, we suggest that steelhead and resident rainbow trout in the Deschutes River may constitute reproductively isolated populations.
Genetic contribution of three introduced life history forms of sockeye salmon to colonization of Frazer Lake, Alaska
Authors: Burger Carl V , Scribner Kim T , Spearman William J , Swanton Charles O , Campton Donald E
Published: April 2011

Colonization of Frazer Lake (Kodiak Island, Alaska) by sockeye salmon (Oncorhynchus nerka) represents a rare, successful introduction of this species into a new environment. Eggs, fry, and adults were introduced repeatedly into Frazer Lake from 1951 to 1971. Donors originated from three source populations, each with different life histories: late-run lake shoreline spawners (Karluk Lake), early-run inlet tributary spawners (Red Lake), and late-run lake outlet spawners (Ruth Lake). We used six nuclear DNA (nDNA) microsatellite loci and mitochondrial DNA (mtDNA) to determine which donor population(s) had colonized the principal spawning habitats of Frazer Lake: three shoreline areas and four inlet tributaries. Based on nDNA comparisons, two shoreline-spawning populations were most similar to the shoreline donor, and the four tributary-spawning populations were most similar to the tributary donor. However, five of the seven Frazer Lake populations appeared to be influenced genetically by more than one donor. Genetic distances based on mtDNA were independent of life histories with high (relative to nDNA) interpopulation variation, suggesting significant female founder effects and poststocking drift. Our data suggest that life history adaptations of donor populations were critically important for successful colonization of Frazer Lake, thus underscoring the need to consider life history traits in other introduction and recovery programs.
Effects of the Hudson Strait outflow on the biology of the Labrador Shelf
Authors: Drinkwater K F , Harding G C
Published: April 2011

Physical, chemical, and biological data collected on the Labrador Shelf in September 1985 are used to examine a hypothesis that the nutrient influx from Hudson Strait increases primary production on the northern shelf and this supports a "conveyor belt" food chain as the community is transported southward by the mean circulation. This hypothesized influx of production was proposed to account for the higher fish abundance on the southern Labrador Shelf. If true, the hypothesis suggests that the relative importance of higher trophic levels generally should increase southeastward along the shelf. Our results confirm that high nutrient levels occur on the northern Labrador Shelf in summer because of continuous advection of nutrients from Hudson Strait and this enhances local plankton production. However, nutrient, chlorophyll a, plankton species, and biomass spectra distributions generally do not support the idea that a developing food chain is advected progressively southward along the shelf. The large fish population on the southern Labrador Shelf appears to have been more dependent on production supported by local upwelling around Hamilton Bank than on food advected from the north.
Spatial and temporal stability of commercial groundfish assemblages off Oregon and Washington as inferred from Oregon trawl logbooks
Authors: Lee Yong-Woo , Sampson David B
Published: April 2011

Spatial and temporal characteristics of species compositions for 15 major commercial groundfish species off Oregon and Washington (U.S.A.) were studied using Oregon bottom trawl logbook data from 1987 to 1993. Screening procedures to remove questionable data from the original logbook files resulted in the exclusion of information from 46% of the total available tows. Two multivariate methods, detrended correspondence analysis and Ward's hierarchical cluster analysis, were used to derive species ordinations and groupings. A general linear model developed for the primary detrended correspondence analysis axis scores showed that the species compositions were strongly correlated with depth and minimally correlated with the other environmental variables examined (latitude, month, and year). However, there were distinct seasonal changes in species composition at the shallower depths, consistent with the movement of deepwater species onto the shelf during summer. Annual trends in the species compositions were not evident even though the study region is very dynamic oceanographically and was heavily fished during the study period.
Predation risk on larval gadids by pelagic fish in the Georges Bank ecosystem. I. Spatial overlap associated with hydrographic features
Authors: Garrison Lance P , Michaels William , Link Jason S , Fogarty Michael J
Published: April 2011

We investigated the relationship between hydrographic variables on Georges Bank and the spatial distribution of larval Atlantic cod (Gadus morhua), larval haddock (Melanogrammus aeglefinus), and two planktivorous fish, Atlantic herring (Clupea harengus) and Atlantic mackerel (Scomber scombrus). We conducted cruises during April-May of 1990, 1994, and 1995 to document spatial distributions and employed logistic regression and a spatial-overlap index to assess relationships between hydrographic variables, spatial distributions and spatial overlap between gadid larvae and planktivorous fish. Cod larvae were more abundant in shallow well-mixed areas, while both haddock larvae and herring were more abundant in stratified areas. Atlantic mackerel occurred in deeper water and had little spatial overlap with the other species. In 1995, the presence of Scotian Shelf water and an intrusion of continental slope water altered temperature and salinity distributions and increased spatial overlap between cod larvae and herring. The stratified areas offer a higher concentration of prey for larval haddock, however there is increased exposure to planktivorous fish predators, creating a potential trade-off between predation and starvation. Due to the high abundance of planktivorous fish and high spatial and temporal overlap, predation is likely an important factor influencing survival of gadid larvae on Georges Bank.
Characteristics of a hydrothermal vent assemblage on a volcanically active segment of Juan de Fuca Ridge, northeast Pacific
Authors: Tsurumi Maia , Tunnicliffe Verena
Published: April 2011

An eruption on Cleft segment, Juan de Fuca Ridge, in 1986 provided an opportunity to observe potential successional patterns in vent-animal colonisation. Other objectives were to describe the Cleft fauna, examine the distribution and abundance of selected taxa, and determine if the fauna reflected changes in water chemistry. Biological samples were tubeworm grabs collected by submersible, and visual data were still photographs and videos. Two years post eruption, there were extensive diffuse vents and 23 of the 44 species constituting the Cleft species pool were present. Five years post eruption, most low-temperature vents were extinct. High-temperature venting was maintained, and biological communities were reduced in visual extent. Four of the 44 species in samples from 1988-1994 accounted for over 90% of the individuals. Cluster analyses of species collected on tubes did not distinguish year or substratum differences, suggesting that a study of less than a year is necessary to document successional patterns at new vents. The Cleft subset of the Juan de Fuca Ridge species pool is likely adapted to episodic eruptive events on the decadal scale. Major changes in fluid chemistry did not result in detectable community changes other than habitat loss due to a decrease in dissolved sulphide availability.
VI: REPORT ON THE SARDINE INDUSTRY IN RELATION TO THE CANADIAN HERRING FISHERIES.
Authors: BENSLEY B.A. B. ARTHUR
Published: April 2011

not available
Changes in the zooplankton community of the British Columbia continental margin, 1985-1999, and their covariation with oceanographic conditions
Authors: Mackas D L , Thomson Richard E , Galbraith Moira
Published: April 2011

A 15-year zooplankton time series collected off southern Vancouver Island (4849°N) shows large interannual anomalies of biomass for most major zooplankton species. Variations within groups of ecologically similar species have been more extreme (often 10-fold or greater) than the variation in total biomass (four- to six-fold). For both total biomass and species groups, the zooplankton anomalies develop and persist over time spans of several years and are correlated across a large spatial scale (>100 km longshore). One dominant mode of recent zooplankton variation was a 19901998 cumulative shift to a more "southerly" copepod and chaetognath fauna: order-of-magnitude declines in several species endemic to the Northeast Pacific continental shelf and order-of-magnitude increases of species endemic to the California Current (3545°N). This trend abruptly reversed in 1999. A second major mode of zooplankton variability consisted of roughly mirror-image fluctuations in the abundance of euphausiids versus subarctic oceanic copepods. Zooplankton anomalies were correlated with year-to-year changes in several physical environmental indices. The patterns of covariance suggest that zooplankton community composition responds strongly to ocean climate fluctuations and in particular to changing current patterns.
Fitness consequences of habitat use for juvenile cutthroat trout: energetic costs and benefits in pools and riffles
Authors: Rosenfeld Jordan S , Boss Shelly
Published: April 2011

To assess freshwater habitat requirements of juvenile anadromous cutthroat trout, Oncorhynchus clarki, we measured habitat preference and growth rates of young-of-the-year (YOY) and 1- to 2-year-old fish confined to either pools or riffles in Husdon Creek, British Columbia, during 1999. YOY preferred pools to riffles in habitat-preference experiments, despite normally occurring at lower densities in pools. YOY grew in both pools and riffles when experimentally confined to either habitat, but growth rates were higher in pools. Larger juvenile cutthroat trout, on average, grew in pools, but consistently lost weight in riffles, indicating that pools are a habitat preference for YOY but a requirement for larger fish. A bioenergetic costbenefit analysis (based on swimming costs and energy intake from invertebrate drift) indicates that energetics alone are sufficient to account for avoidance of riffles by larger cutthroat trout, without having to invoke greater predation risk in shallow habitats. Energetics modeling demonstrates that the smaller size and energetic needs of YOY allow exploitation of habitats (e.g., pocket pools in riffles) that are unavailable to larger fish.
Tributaries, sediment sources, and the longitudinal organisation of macroinvertebrate fauna along river systems
Authors: Rice S P , Greenwood M T , Joyce C B
Published: April 2011

Tributary confluences are sites along a main channel where, because of the introduction of water and (or) sediment, the water volume, bed sediment character, and water quality of the mainstream can change abruptly. These shifts ensure that abiotic gradients seldom vary smoothly or continuously for distances of more than 100102km along any river system. The ways in which tributaries and related sediment recruitment points structure longitudinal changes in physical habitat are examined. Variables of importance to stream biota are affected and, in turn, it is suggested that the arrangement of tributaries and related features is an important control on the longitudinal organisation of macroinvertebrate benthos at moderate spatial scales. A new model is presented that stresses the importance of hydrological and sedimentological networks for organising lotic fauna. The link discontinuity concept emphasises the discontinuous nature of lotic ecosystem gradients, addresses the importance of tributaries in unregulated as well as regulated rivers, and extends, to its logical conclusion, the limited recognition of tributary influence in the river continuum concept. A case study from British Columbia, Canada, illustrates the general merit of the new model.
Behavioural and heart rate responses to predation risk in wild and domesticated Atlantic salmon
Authors: Johnsson Jörgen I , Höjesjö Johan , Fleming Ian A
Published: April 2011

Artificial culture may relax the selective pressures from predators, thereby altering behavioural and heart rate responses to predation risk. Culture may also impose new selection that adapts fish to confinement. Predictions from these hypotheses were tested by comparing seventh-generation farm Atlantic salmon (Salmo salar) with wild Atlantic salmon from the principal founder population of the farm strain. Wild age 1+ salmon had higher standard heart rates and showed a more pronounced flight and heart rate response to a simulated predator attack than did farmed salmon. However, wild fish were closer to the model predator at attack, which may have accentuated these differences. Both strains habituated to the threat, showing less response to the second attack than to the first. In contrast with age 1+ fish, wild age 2+ salmon had lower standard heart rates than farmed fish. Moreover, in age 2+ salmon, domestication effects were less clear and the response to predation threat considerably weaker, suggesting that environmental effects of culture override genetic effects as time in captivity increases. Domestication selection may thus alter reaction norms of farmed animals over environmental gradients and time. This should be considered when attempting to predict the consequences of release or escape of domesticated animals in the wild.
Prey size of salmonid fishes in streams, lakes, and oceans
Authors: Keeley Ernest R , Grant James WA
Published: April 2011

The growth rate of salmonid fishes is typically fastest in oceans, intermediate in lakes, and slowest in streams. We compiled literature data to test whether differences in the size of prey eaten by salmonids in the three habitats could account for these differences in growth rate (i.e., the prey-size hypothesis). In all three habitats, salmonid fishes exhibited ontogenetic niche shifts from feeding primarily on invertebrates when small to feeding on fishes when large. Contrary to the prey-size hypothesis, invertebrates eaten in streams were larger than those eaten in lakes or oceans, whereas fish eaten in oceans were smaller than those eaten in streams or lakes. Consistent with the prey-size hypothesis, salmonids began eating fish at a smaller size in oceans (8 cm) than in lakes (15 cm) or streams (27 cm). However, the size at which salmonids became predominantly piscivorous (31 cm) did not differ significantly between habitats. We suggest that the difference in growth potential between the three habitats is partly related to the size at which fish first enter the diet.
Tagging of Pacific herring Clupea pallasi from 19361992: a review with comments on homing, geographic fidelity, and straying
Authors: Hay D E , McCarter P B , Daniel K S
Published: April 2011

Nearly 1.6 million tagged herring (Clupea pallasi) were released in two separate programs (19361967 and 19791992) in British Columbia. Several thousand tags were released in each of 955 release sessions. Over 85% of the release sessions had subsequent recoveries. Almost 43 000 tags were recovered over all years. We re-assembled the tagging data into an electronic database, geo-referenced all tag release and recovery data, analysed spatial movements, and estimated straying and fidelity rates. The analyses do not wholly support the conclusions of previous work indicating high homing rates to local coastal areas. Estimates of fidelity, defined as the proportion of tags recovered in the same area as released, varied with the size of the geographic area used in the analyses. Fidelity rates are high for large areas, such as the Strait of Georgia (~10 000 km2), but lower for small geographical areas, such as inlets or bays (~100 km2). High fidelity is not necessarily evidence for "homing." Homing and fidelity are different biological processes and tagging cannot necessarily distinguish between them. Although fidelity rates for small areas are generally low, there are exceptions that may be evidence for the existence of biologically distinct populations in certain areas.