bluuebunny/crossref_metadata_2025 huggingface dataset:
Atlantic salmon (Salmo salar) in winter: "the season of parr discontent"?
Authors: Cunjak R A , Prowse T D , Parrish D L
Published: April 2011

Winter is a dynamic period. Effects of the winter regime on northern streams and rivers is extremely variable and characterized by dramatic alterations in physical habitat to which Atlantic salmon (Salmo salar) must acclimate and adapt to survive. In this paper, we synthesize recent advances in the biological and hydrologic/ geomorphic disciplines, with specific reference to Atlantic salmon overwintering in the freshwater portions of those running waters subject to freezing water temperatures. The specific requirements and adaptations for surviving winter at the three distinct life-stages in freshwater (egg, parr, kelt) are identified in relation to the characteristics of three biophysical phases: early winter (temperature decline and freeze-up), midwinter (ice growth and habitat reduction), and the break-up/warming phase. In a case study of Catamaran Brook (New Brunswick), a hydro-ecological analysis was used to explain interannual variability in juvenile abundance, especially for young-of-the-year salmon. A strong relation was found between winter discharge and interstage survival (egg to 0+, 0+ to 1+, 1+ to 2+) in 5 of 6<~>years. That is, juvenile salmon abundance in summer was highest following winters with high streamflow, presumably a function of habitat availability, especially beneath ice cover. However, the lowest measured egg-0+ survival (9.2%) was related to an atypical midwinter, dynamic ice break-up triggered by a rain-on-snow event that resulted in severe scouring of the stream-bed and redds. Thus, interannual variability in Atlantic salmon parr abundance from 1990 to 1996 was largely explained by density-independent (environmental) constraints to winter survival. The complexity of stream processes during winter underscores the need for interdisciplinary research to quantify biological change.
Interactions between wild and introduced Atlantic salmon (Salmo salar)
Authors: Youngson A F , Verspoor E
Published: April 2011

Wide latitude exists for genetic, behavioural, and ecological interactions between introduced and wild Atlantic salmon (Salmo salar L.). These can occur at all stages of the life cycle and across the range of natural environments the species exploits. Because of the large number of variables and scales involved, each interaction scenario and its outcome is expected to be unique. However, as a general rule, interactions are likely to be negative in their effect on the viability of wild populations. In theory, it ought to be possible to develop approaches for managing interactions, but in the particular case of genetic effects this is especially difficult. It is possible to put forward two guiding genetic principals for intentional introductions. Firstly, when introductions are used to maximize local abundance, genotypic diversity must be maintained so that mean individual fitness remains undiminished after interaction has occurred. Secondly, when introductions are used to alter local frequencies of phenotypes, the population's capacity to remain viable in the longterm must not be impaired. Both principals are pragmatic and aim to conserve or restore the genetic capacity of populations to evolve rather than seeking the preservation of their current condition.
Elements in the development of conservation plans for Atlantic salmon (Salmo salar)
Authors: Dodson Julian J , Gibson R John , Cunjak Richard A , Friedland Kevin D , Garcia de Leaniz Carlos , Gross Mart R , Newbury Robert , Nielsen Jennifer L , Power Mary E , Roy Steven
Published: April 2011

This paper examines two areas to be considered in developing conservation plans for Atlantic salmon (Salmo salar): goal statements and the general framework for the implementation of a conservation plan. From a biological perspective, the appropriate conservation unit for Atlantic salmon is the Evolutionary Significant Unit (ESU). As conservation decisions will rarely be based solely on biological information, the Operational Conservation Unit (OCU) is defined as resulting from the interplay between biological requirements and socio-economic issues. A multi-scale habitat inventory of Atlantic salmon rivers to know what their status is relative to historical conditions is the first step in a functional conservation plan. The viability of salmon populations may be assessed according to 6 variables: abundance, resilience, age and size structure, sex ratio, spatial and geographical distribution. A genetically viable population possesses the species' evolutionary legacy and the genetic variation on which future evolutionary potential depends. Four factors important to monitoring changes in a population's genetic health are genetic diversity, effective population size, genetic bottlenecks and founder effects and gene flow. Implementation of a conservation plan must be proactive to maintain the quality of the OCUs. Commercial and recreational fisheries need to be limited and several case studies are reviewed. The importance of avoiding the introduction of exotics and minimizing the impact of sampling methodology, as well as the pitfalls of planting eggs, fry, or parr, are addressed. Finally, the importance of fostering public awareness of the value of conservation is essential to apply the political pressure necessary to preserve natural resources.
One species with two biologies: Atlantic salmon (Salmo salar) in the wild and in aquaculture
Authors: Gross Mart R
Published: April 2011

Today, over 94% of all adult Atlantic salmon (Salmo salar) are in the aquaculture niche and wild numbers continue to decline while aquaculture numbers increase. The developmental and evolutionary forces in the aquaculture or "domestic" niche are so unlike those in the wild niche that two distinct biologies are being created from the original Atlantic salmon species. We may now need to recognize a new biological entity - Salmo domesticus - and treat it as an "exotic" when it escapes into the wild. Escapement therefore raises important concerns about ecological and genetic impacts, both within and outside the native range of Salmo salar. This paper explains why escaped domestic Atlantic salmon have had an impact on wild Atlantic salmon populations and now threaten Pacific salmonids as well. A polarization of views between aquaculturists and environmentalists will not resolve the problems. The three interest groups in fisheries - aquaculture, biodiversity, and capture - must begin to work together if we are to take up the challenge of preserving biodiversity and if aquaculturists, who hold the future of Atlantic salmon in their hands, can be expected to willingly prevent further impacts from their industry.
Late Permian palynomorph assemblages from Ufimian and Kazanian type sequences in Russia, and comparison with Roadian and Wordian assemblages from the Canadian Arctic
Authors: Utting J. , Esaulova N. K. , Silantiev V. V. , Makarova O. V.
Published: April 2011

Tentative biostratigraphic correlations, based on marine faunas, have been made by various workers between Ufimian and Kazanian sequences in their type areas in the Volga–Urals region of Russia and Roadian and Wordian sequences in their type area in Texas, United States. Unfortunately, palynological correlation between the Russian and United States sequences is not possible, due to lack of data from the latter. However, detailed palynological data are available from rocks of Roadian and Wordian age in the Canadian Arctic Archipelago, and therefore indirect correlations are possible. Palynomorph assemblages from the Canadian Arctic and other circumpolar areas, such as the southern Barents Sea and Greenland, are different from those of the Ufimian and Kazanian Russian sequences in their type areas. This is likely to be the result of variations in the parent flora in response to significant paleoclimatic differences. For example, the climate of the Volga–Urals region in Late Permian times was probably hot and arid, whereas that of the Canadian Arctic, Barents Sea, and Greenland was cooler and probably more humid.
Middle Wisconsinan sediments and paleoecology of central British Columbia: sites at Necoslie and Nautley rivers
Authors: Plouffe A. , Jetté H.
Published: April 2011

At two sites in central British Columbia, sediments with dispersed organic matter, underneath Fraser Glaciation deposits, are interpreted as nonglacial deposits of Middle Wisconsinan age (Olympia Nonglacial Interval). At Necoslie River, undated sand with dispersed organic matter, thought to be fluvial in origin, is overlain by Fraser drift. At Nautley River, similar sand contains plant detritus that has yielded 14C ages of 38 230 ± 410 BP (Beta-88557) and 42460 ± 670 BP (Beta-88558). Pollen assemblages of the sediments with dispersed organic matter at the Necoslie River and Nautley River sites are similar: both assemblages are dominated by herb pollen, with a lesser amount of tree pollen. The pollen assemblages are thought to reflect a tundra-type vegetation. Because vegetation in the area is presently dominated by spruce and subalpine fir forest, climate during deposition probably was much cooler than today. Data presented here support the contention of other studies in western Canada that cooler climatic conditions existed for some time during the Middle Wisconsinan.
Anticostia, a distinctive new Late Ordovician "glyptograptid" (Diplograptacea, Graptoloidea) based on three-dimensionally preserved specimens from Anticosti Island, Quebec
Authors: Stewart Scott , Mitchell Charles E.
Published: April 2011

Three-dimensionally preserved specimens of Late Ordovician graptolites have been isolated from Vauréal Formation limestone samples collected from Anticosti Island, Quebec. The morphology, astogeny, and systematics of Anticostia macgregorae n.gen., n.sp. are described. These specimens show a new astogenetic pattern (pattern K) described for the first time. The similar glyptograptid species Glyptograptus hudsoni Jackson, Glyptograptus tenuissimus Ross and Berry, and Orthograptus fastigatus Davies all possess a pattern K astogeny. These species, along with Glyptograptus lorrainensis, which possesses the less-derived pattern G astogeny, are included within Anticostia n.gen. Anticostia tenuissima (Ross and Berry) is redescribed and Normalograptus? occidentalis (Ruedemann) is refigured based on their type specimens from coeval rocks in Nevada and Idaho.
Hog's Back Formation: a new (Middle Ordovician) stratigraphic unit, Ottawa Embayment, eastern Ontario, Canada
Authors: Hersi Osman Salad , Dix George R.
Published: April 2011

The Hog's Back Formation, exposed in Ottawa, Ontario, is a new stratigraphic unit that disconformably overlies the Rockcliffe Formation and underlies, with apparent conformity, the Pamelia Formation of the Ottawa Group. The Hog's Back Formation is 14.3 m thick at its type section (Prince of Wales Falls, Ottawa) and thickens eastward to 27 m in Russell County, about 40 km southeast of Ottawa. It consists of lower, dark green shales with thin lime-mudstone and sandstone interbeds, and upper thin to thick beds of fine crystalline greenish grey sandy and calcareous dolostones with thin to medium (10–30 cm) pinkish grey, bioclastic packstone and grainstone interbeds. The latter thicken eastward and correlate with the "St. Martin calcarenites" of the Beaconsfield Member, Laval Formation, in the Montréal area. Together, these beds correlate with the Valcour Formation, Chazy Group, in the Lake Champlain area of New York. Conodonts and macrofossils indicate a Chazyan (Llandeilian) age for the Hog's Back Formation. The lower sandstone–shale–carbonate assemblage of the formation indicates sedimentation in peritidal environments, and documents initial regional flooding of nearshore sandy facies of the Rockcliffe Formation. The overlying carbonate facies represent sabkha environments punctuated by storm deposition. The gross shallowing-upward succession of the formation was terminated by renewed flooding associated with another regional transgressive event heralding deposition of the Ottawa Group.
Seasonal patterns of coupled flow in the active layer at three sites in northwest North America
Authors: Hinkel Kenneth M. , Outcalt Samuel I. , Taylor Alan E.
Published: April 2011

Vertical arrays of temperature and electric-potential probes were installed in the upper soil at sites along the Mackenzie River valley and on the North Slope of Alaska. Time series were obtained at subdiurnal frequencies throughout the year in the active layer and upper permafrost. If the data acquisition system is properly configured, the time series can be used to infer soil physiochemical processes. The electric potential develops primarily in response to soil water solute concentration gradients in the soil column, and is a crude surrogate of the soil water electrolytic conductivity. Summer precipitation can cause rapid penetration of the thaw front when percolating rainwater, warmed at the ground surface, carries sensible heat downward to the thawing front. Rates of warming at depth occur significantly faster than those typical of conductive heat transfer. In early winter, as the freezing front penetrates downward toward the permafrost table, ions are excluded from the ice and concentrated in the intermediate unfrozen zone. Nearly instantaneous warming of the active layer is triggered by spring snowmelt. At Happy Valley in northern Alaska, temperatures at the 29 cm depth rise from −7 to −3 °C in 1 h. For several hours during this event, the temperature at 29 cm is warmer than that at regions both above and below, producing a strong thermal inversion. Time series of electric potential, or a surrogate derived from electric potential, suggest rapid transport of meltwater from the snowpack to depth, probably through soil cracks. Serial events hasten active-layer warming by 1–2 weeks.
U – Pb zircon date from Avalonian Cape Breton Island and geochronologic calibration of the Early Ordovician
Authors: Landing Ed , Bowring Samuel A. , Davidek Kathleen L. , Fortey Richard A.
Published: April 2011

A U–Pb zircon date of 483 ± 1 Ma is recorded from an uppermost Tremadoc K-bentonite from the Chesley Drive Group on McLeod Brook, eastern Cape Breton Island. The associated fauna, with the trilobite Peltocare rotundifrons, is also known from the Reversing Falls section in Saint John, New Brunswick, and the traditional reference of the latter section to the Arenig is incorrect. A 483 ± 1 Ma age is significantly older than a U – Pb zircon age reported from the classical base of the Arenig Series in north Wales and about 10 Ma older than strata regarded herein as upper Arenig in central Newfoundland. If the global standard for the base of the Arenig is defined at the Tetragraptus approximatus Zone base, then the base of the type Arenig in Wales is younger than the latter horizon. The McLeod Brook occurrence is from an uppermost Tremadoc (Hunnebergian Stage) interval that has been removed below the unconformity in north Wales. The age of the Tremadoc –Arenig series boundary remains uncertain; however, a tentative estimate that it is significantly younger than 483 Ma is suggested by fossil evidence.
Seasonal sand transport through a trough blowout at Pinery Provincial Park, Ontario
Authors: Byrne M. -L.
Published: April 2011

Trough blowouts represent transport pathways for sediment through coastal dune systems. This paper documents seasonal differences in sand transport through a trough blowout. Measurements were made by trapping sand in Rosen-style traps installed at the mouth and crest of the parabolic dune and with erosion pins in the throat. Erosion-pin data indicated that the surface of the dune was generally accreting in late summer and eroding in winter, suggesting that the major loss of sediment from the dune was occurring in winter. The traps were emptied every 2–4 weeks and showed that, in general, more sand left the dune system than entered it. The amount of sand transported past the traps at the mouth of the dune varied seasonally, with smaller amounts during the summer months than in winter. The upper traps showed greater variability, but had more sediment transported in all months when compared with the lower traps. Amounts of sand transported during winter were greater than in summer.
Meteorological controls on wind erosion during foehn wind events in the eastern Southern Alps, New Zealand
Authors: McGowan Hamish A.
Published: April 2011

Foehn winds in the lee of mountain barriers create highly favourable meteorological conditions for wind erosion in alpine areas and over adjacent lowlands. This paper presents meteorological observations made during winter and summer foehn wind erosion events as part of a 3 year investigation into the physical nature and incidence of eolian processes in the eastern Southern Alps, New Zealand. Foehn winds were observed to initiate eolian activity, including dust storm genesis when mean near-surface wind speeds exceeded 7–8 m∙s−1 over a 20 min period in the absence of precipitation. Wind speeds of 25–30 m∙s−1 were frequently recorded during typical foehn events, and wind speed maxima of 40–50 m∙s−1 were monitored during severe foehn windstorms. Saltation clouds sampled at 0.5 and 1 m above glaciofluvial deposits during foehn wind erosion events were found to display a mean grain size of between 300 and 435 μm. The entrainment of fine-grained surface sediments by the airstream appeared to be enhanced in late autumn (May) and early spring (September) by freeze–thaw cycles that were observed to result in needle-ice growth in exposed glaciofluvial and lacustrine deposits. The needle ice fragmented such deposits, producing surfaces that were aerodynamically rough and highly susceptible to deflation by the airstream following a thaw. Observations made by this study are thought to be similar to foehn wind erosion events reported in the lee of other substantial mountain ranges, such as the Rocky Mountains, Andes, Hindu Kush, and Karakoram.
Stream channel configuration, landform, and riparian forest structure in the Cascade Mountains, Washington
Authors: Rot Byron W , Naiman Robert J , Bilby Robert E
Published: April 2011

The hierarchical relationship of five key elements, valley constraint, riparian landform, riparian plant community, channel type, and channel configuration, are described for 21 sites in mature to old-growth riparian forests of the western Cascades Mountains, Washington, U.S.A. Channel type (bedrock, plane-bed, and forced pool-riffle) was closely related to channel configuration (especially large woody debris (LWD) volume, density, and LWD-formed pools) at the smallest spatial scale and valley constraint at the largest. Valley constraint significantly influenced off-channel habitat (r2 = 0.71) and LWD volume within forced pool-riffle channels (r2 = 0.58). Riparian plant community composition was differentiated by four landform classes: three alluvial landforms based on height above the channel and one based on hillslope. Just above the active channel, floodplain landforms contained more deciduous stems than conifer and greater conifer basal area than deciduous. Conifers dominated other landforms. The diameter of in-channel LWD increased with the age of the riparian forest (r2 = 0.34). In old-growth forests, LWD diameter was equivalent to or greater than the average riparian tree diameter for all sites. In younger forests, the mixed relationship between LWD and riparian tree diameter may reflect a combination of LWD input from the previous old-growth stand and LWD input from the existing stand.
Application of flow cytometric cell cycle analysis to the assessment of condition and growth in larvae of a freshwater teleost Galaxias olidus
Authors: Bromhead Don , Kalish John , Waring Paul
Published: April 2011

Through its ability to measure cell DNA content, flow cytometric analysis (FCA) is a technique capable of accurately assessing the position of cells in the cell cycle. Using FCA to measure the proportion of dividing and nondividing cells, an index was created that allows the amount of cell division within larval fish tissues to be quantified. To assess the suitability of the cell division index (CDI) as an indicator of growth and condition in fish larvae, analyses were divided into four parts. These examined the effects of temperature, nutrition, time of day, and geographic location on the CDI of brain tissue from Galaxias olidus larvae. The index was sensitive to, firstly, differences in the brain CDI of larvae reared at 12 and 20°C and, secondly, to significant fluctuations in mean brain CDI from larvae sampled over 24 h. FCA also revealed significant differences in the CDI of starving and fed larvae. Overall, this study indicates that FCA may be suitable as an indicator of growth and condition in both laboratory-reared and wild fish larvae.
Using linear models with correlated errors to analyze changes in abundance of Lake Michigan fishes: 1973-1992
Authors: Fabrizio Mary C , Raz Jonathan , Bandekar Rajesh Ramanath
Published: April 2011

We examined annual changes in relative abundance of Lake Michigan fishes using linear models with correlated errors in space and time. Abundance of bloater (Coregonus hoyi), deepwater sculpin (Myoxocephalus thompsoni), slimy sculpin (Cottus cognatus), alewife (Alosa pseudoharengus), and rainbow smelt (Osmerus mordax) was monitored with bottom trawls at 10 discrete depths (between 18 and 110 m) off eight fixed ports from 1973 to 1992. The model describing abundance included fixed effects of year, port, depth, and interaction terms as well as quadratic and cubic effects of year and depth because changes in abundance were not strictly linear. Observed temporal trends in abundance varied with species and depth. Additionally, trends in alewife and slimy sculpin abundances depended on port. Cubic trends in the abundance of bloater and quadratic trends in deepwater sculpin and rainbow smelt abundances were similar among ports, permitting lakewide inferences for these species. Mean bloater abundance was low throughout the 1970s, increased during the 1980s, and reached high levels by 1990. Mean abundances of deepwater sculpin and rainbow smelt increased from 1973 to the mid-1980s and declined thereafter. The linear model with correlated errors can be readily applied to repeated-measures data from other fixed-station fishery surveys and is appropriate for data exhibiting spatial and temporal autocorrelations.
Small-scale spatial and temporal patterns in spawning of Atlantic cod (Gadus morhua) in coastal Newfoundland waters
Authors: Lawson Gareth L , Rose George A
Published: April 2011

Acoustic surveys were used to locate coastal Atlantic cod (Gadus morhua) spawning grounds and examine spatial and temporal patterns of spawning in Placentia Bay, Newfoundland, Canada. The same three grounds were used in 1997 and 1998 (Bar Haven in the inner bay and Cape St. Mary's and Oderin Bank in the outer bay). Grounds had densities >0.1 fish·m-2 over scales of 100 m and >13% of mature females in spawning condition. Ground use and spawning timing differed between years. Mean spawning female densities were highest at Cape St. Mary's in 1997 (1.6 × 10-2 fish·m-2) and Oderin Bank in 1998 (1.0 × 10-2 fish·m-2). At all grounds, spawning peaked earlier in 1997 (April) than in 1998 (June-July). In both years, cod spawned at sub- or near-zero temperatures. "Spawning columns" were observed at sites and times having high densities of spawning females. Sex ratios suggested that males arrived first and stayed later, while females followed when ready to spawn, accompanied by juveniles. Older females spawned earlier and later than younger females. Peaks in density of spawning females and the proportion of females spawning did not coincide. Hence, the location and timing of spawning cannot be quantified solely from the proportions of females in spawning condition.
Bias in survival estimates from tag-recovery models where catch-and-release is common, with an example from Atlantic striped bass (Morone saxatilis)
Authors: Smith David R , Burnham Kenneth P , Kahn Desmond M , He Xi , Goshorn Cynthia J , Hattala Kathryn A , Kahnle Andrew W
Published: April 2011

Survival rate is underestimated when tag-recovery models include tags recovered from harvested and caught-and-released fish. The magnitude of the bias depends on tag-recovery rate, proportion of catch released alive, and reporting rate; changes in these factors over time confound temporal changes in survival. The bias is of potential concern for any tagging study where catch-and-release is mandatory or practiced voluntarily. The bias is of concern particularly for the Atlantic striped bass (Morone saxatilis) tagging study where catch-and-release is common and anglers commonly remove the tag upon capture regardless of fish disposition. Biased estimates of striped bass survival did not change with changes in harvest regulation during the mid-1990s. However, bias-adjusted estimates of survival showed a decrease, which corresponds to the regulatory change made in 1995. Year-specific reporting rate is critical to bias adjustment, underscoring the need for reward tags in fish tagging studies. Tag-recovery modeling allows for a diverse set of models, each of which can produce widely different estimates with far-reaching consequences for management. We applied model averaging to base inference on a weighted average of parameter estimates and to account for model selection uncertainty.
A genetic assessment of single versus double origin of landlocked Atlantic salmon (Salmo salar) from Lake Saint-Jean, Québec, Canada
Authors: Tessier Nathalie , Bernatchez Louis
Published: April 2011

We assessed the genetic relationships among landlocked populations and parapatric anadromous populations of Atlantic salmon (Salmo salar) from the Saguenay River system to infer the alternative scenarios of single versus double origin of salmon in Lake Saint-Jean, Québec, Canada. We predicted that the hypothesis of double origin would be supported by the closer relationship of some landlocked populations to anadromous ones than to other landlocked populations. Alternatively, the single-origin scenario would be supported if landlocked populations were genetically closer to each other than to anadromous populations. Contrasting results of population differentiation at microsatellite loci were obtained with statistical treatments involving allelic frequency alone (θ, DCE) or incorporating mutational differences (RST, (δμ)2). A closer relationship among all landlocked populations of Lake Saint-Jean compared with anadromous ones was observed in analyses that only incorporated allele frequency information. In contrast, analyses incorporating allelic size variance all supported a closer relationship between the Métabetchouane population and other populations from outside Lake Saint-Jean. We discuss the possible factors responsible for these apparently contradictory results and propose alternative historical scenarios potentially responsible for the salmon population structure in Lake Saint-Jean.
Extreme life history change of white-spotted char (Salvelinus leucomaenis) after damming
Authors: Morita Kentaro , Yamamoto Shoichiro , Hoshino Noboru
Published: April 2011

Dam construction has serious consequences for anadromous fishes. We examined the effects of migration barriers formed following dam construction on the migratory behavior of white-spotted char (Salvelinus leucomaenis) by comparing migrants in accessible below-dam river sections with migrants in inaccessible above-dam river sections. The frequency of smolts (i.e., potential migrant) was higher for the below-dam sections than for the above-dam sections, and in contrast, the frequency of residents was higher for the above-dam sections. Above-dam sections had lower fry (age 0+) densities and consequently had higher growth rates compared with below-dam sections. A transplant experiment revealed that the majority of the below-dam fish adopted a resident strategy, as well as above-dam fish, when both had experienced the above-dam environment. We conclude that high growth as a result of low density promotes residency in the above-dam sections.
Effect of aluminum and silicic acid on the behaviour of the freshwater snailLymnaea stagnalis
Authors: Campbell Morag M , White Keith N , Jugdaohsingh Ravin , Powell Jonathan J , McCrohan Catherine R
Published: April 2011

A major factor influencing the toxicity of Al at neutral pH is the presence of complexing ligands. This study compared the effect of exposure to aluminum nitrate, aluminum lactate, and aluminum maltol, in the presence or absence of monomeric silica (Si), on the behaviour of the pond snail Lymnaea stagnalis. Concentrations of Al and Si used were similar to those found in the natural environment. Soluble Al concentration in the water fell significantly with time over 48 h following addition as the nitrate or lactate (500 μg·L-1), presumably owing to polymerisation as the colloidal hydroxide. This loss was enhanced by the presence of snails or Si (Al:Si = 1:15). Aluminum maltol largely remained in solution. Snails exposed to all three Al compounds showed depression of behavioural activity after 7 days; this effect was ameliorated in the presence of higher (Al:Si = 1:15) but not lower (Al:Si = 1:1) concentrations of Si. Depression of feeding behaviour occurred with all three Al compounds, although it was delayed in the presence of aluminum maltol. Expression of conditioned feeding was inhibited in snails exposed to aluminum nitrate during training and testing. The behavioural changes are likely to be mirrored in the field, with adverse consequences for the "fitness" of natural populations.
Organochlorine transfer in the food web of subalpine Bow Lake, Banff National Park
Authors: Campbell Linda M , Schindler David W , Muir Derek CG , Donald David B , Kidd Karen A
Published: April 2011

Lake trout (Salvelinus namaycush) from subalpine Bow Lake, near the Continental Divide in Banff National Park, have been reported to have higher concentrations of toxaphene than other lake trout populations of the Rocky Mountains. Our original hypothesis was that unusually high biomagnification via a long food chain was responsible for elevated levels of toxaphene and other persistent organochlorines in the lake trout. This hypothesis was refuted by the analyses of stable carbon (δ13C) and nitrogen (δ15N) isotope ratios in lake biota. Stable nitrogen isotope analyses demonstrated that the food chain length in Bow Lake was short. The sources of carbon (pelagic or benthic), as indicated by stable carbon isotope values, were highly correlated with organochlorine concentrations in the food web. Lake trout with more pelagic carbon signatures had higher organochlorine concentrations than littoral-feeding mountain whitefish (Prosopium williamsoni) and lake trout. The pelagic copepod Hesperodiaptomus arcticus had higher organochlorine concentrations (wet weight basis) than any other organism, including the fish. This was attributed to the high lipid content of copepods and possibly their ingestion of suspended solids, including glacial silt or direct absorption from solution in glacial inflows.
Evaluating spatially explicit metrics of stream energy gradients using hydrodynamic model simulations
Authors: Crowder David W , Diplas Panayiotis
Published: April 2011

Localized energy gradients and velocity shelters created by boulders, bars, and channel banks are often essential components of aquatic habitat. Two-dimensional hydraulic models have the potential to predict the amounts and locations of such spatially varying flow patterns. However, little effort has been devoted to reproducing these flow features and developing spatial habitat metrics to describe and differentiate between various types of flow patterns. Two-dimensional numerical simulations, based on actual channel geometry, are used here to model a variety of flow patterns encountered in natural streams. The simulation results are used to develop spatial habitat metrics that quantify local velocity gradients and changes in kinetic energy. The proposed metrics are evaluated at various points within the different flow patterns of interest. The metrics produce large values for flow patterns exhibiting considerable spatial variation and small values in areas experiencing uniform flow conditions. Comparisons with other researchers' field data suggest that the metric values produced in the modeled flows are consistent with values found near fish resting and feeding locations. The habitat metrics, measures of the flow's rate of spatial change in kinetic energy, can also be incorporated into bioenergetic models to facilitate the computation of fish energy expenditure rates.
Food web structure and nutrient enrichment: effects on sediment phosphorus retention in whole-lake experiments
Authors: Houser Jeffrey N , Carpenter Stephen R , Cole Jon J
Published: April 2011

A series of whole-lake manipulations of both food web structure and nutrient loading rate revealed that the downward vertical P flux was significantly affected by food web structure. Food webs and nutrient input rates of two lakes were manipulated while a third lake served as a reference system. Phosphorus transport to the sediments was examined by three independent methods: mass-balance budgets, sediment traps, and sediment cores. After 2 years of pretreatment study, manipulated lakes were fertilized for 5 years at rates that were similar within each year but varied among years from 0.97 to 6.0 mg P·m-2·day-1. Increased vertical P flux was associated with the increased abundance of large-bodied zooplankton grazers such as Daphnia pulex. Vertical P flux increased with P input rates, but the increase was often insufficient to prevent P accumulation in the water column. Sediment trap measurements of the vertical P flux were significantly higher than the long-term sediment P retention measured by sediment cores and the seasonal sediment P retention calculated by mass balance. Using210Pb data from the sediment cores, we corrected the sediment trap measurements of vertical P flux for focusing and brought them into better agreement with the seasonal sediment P retention calculated by mass balance.
Influence of inorganic nitrogen cycling on the δ15N of Lake Ontario biota
Authors: Leggett M F , Johannsson O , Hesslein R , Dixon D G , Taylor W D , Servos M R
Published: April 2011

The seasonal variability in the δ15N of biota at the base of the pelagic food chain in Lake Ontario was studied during the period 1995-1997. Strong seasonal patterns were observed in the δ15N of dissolved inorganic nitrogen, different size fractions of particulate organic matter, and zooplankton split into size fractions of 110-210, 210-295, and >295 µm. Similar patterns were reflected in the δ15N of individual species: Diacyclops thomasi, Bosmina longirostris, Daphnia spp., and calanoid copepods. The seasonal fluctuation of primary producers was a function of the nitrogen enrichment of dissolved inorganic nitrogen during photosynthetic uptake and the δ15N of NH4+ and NO3- used by the algae. The large range in δ15N of primary producers suggests that recycling of nitrogen is an important determinant of δ15N at the base of the food web. The δ15N of individual species of zooplankton reflected the known feeding strategies and dietary preferences.
Boreal forest disturbance and streamflow response, northeastern Ontario
Authors: Buttle J M , Metcalfe R A
Published: April 2011

The effects of forest disturbance on streamflow from small (<10 km2) basins have been well documented; however, implications of such disturbance for streamflow from relatively large rivers in the Canadian boreal forest are unclear. Landsat imagery was used to determine changes in the type, amount, and location of forest disturbance in northeastern Ontario between 1985 and 1990. These were compared with streamflow responses from medium- and large-scale basins in the region. Harvesting dominated forest disturbance, and total disturbance as of 1990 ranged from 25% of basin area in the northwest part of the region to 5% in the southeast. There was limited streamflow response to land cover changes, with no definitive changes in water year runoff or peak flow magnitude and timing. This likely reflects the ability of relatively large basins to buffer the hydrologic impacts of the small degree of recent forest disturbance, combined with the influence of climatic variability on temporal trends in basin streamflow. However, disturbance was associated with increases in moderate and low flows from medium and large basins, respectively, which occurred largely during summer months.
Physiological status of coho salmon (Oncorhynchus kisutch) captured in commercial nonretention fisheries
Authors: Farrell A P , Gallaugher P , Clarke C , DeLury N , Kreiberg H , Parkhouse W , Routledge R
Published: April 2011

The physical, hematological, and metabolic condition of 303 adult coho salmon (Oncorhynchus kisutch) was examined following capture with three commercial fishing gear types (seine, troll, and gill net) and a variety of methods. All fish arrived onboard in a state of severe metabolic exhaustion, and physiological differences among gear types and fishing methods were few and relatively small. Fish showed less physiological disruption with a brailing versus a ramping method of seine fishing and with a 30-min versus a 60-min net soak time for gillnet fishing. The visual ratings of physical condition (nonbleeding, vigorous, and lethargic) correlated significantly with hematocrit, plasma osmolality, plasma lactate, and plasma sodium. Fish placed in recovery boxes for 30-60 min onboard fishing vessels did not show the expected metabolic recovery; only plasma potassium recovered significantly. However, plasma lactate levels declined significantly for 125 fish placed in a net pen for 24 h, suggesting that metabolic recovery was possible after commercial capture. Because of a concern that the current recovery box design does not effect optimum recovery, we recommend that future experiments test a better-designed recovery box that orients fish into flowing water.
Is the sampling strategy interfering with the study of spatial variability of zooplankton communities?
Authors: Avois Carol , Legendre Pierre , Masson Stéphane , Pinel-Alloul Bernadette
Published: April 2011

Surveys at the whole-lake scale take some time to carry out: several hours or several days. For logistic reasons, the sites are not sampled simultaneously or in a random sequence. Traditional limnological sampling methods require an appreciable amount of time at each site. Any sampling strategy that is not random or simultaneous introduces dependencies among the observations, which must be taken into account during the analysis and interpretation of the data. What is the real nature of the variation measured using a given sampling design? This question is approached using sites sampled by two boat teams during two consecutive days. Statistical modelling was used to partition the variation of zooplankton size-class data into environmental and spatial components. The conclusions reached after an analysis that did not control for the sampling design are erroneous and quite different from those reached when the effect of the sampling design (factors Day, Boat, and Hour) was taken into account. Clearly, when a significant effect of the sampling design is found, one must control for it during the analysis and interpretation of ecological variation.
Forest fire induced impacts on phosphorus, nitrogen, and chlorophyll a concentrations in boreal subarctic lakes of northern Alberta
Authors: McEachern P , Prepas E E , Gibson J J , Dinsmore W P
Published: April 2011

The biogeochemistry of 10 headwater lakes in burnt peatland-conifer catchments and 14 in unburnt catchments was evaluated throughout a summer 2 years following forest fire in a boreal subarctic region of northern Alberta. Cation exchange within burnt catchments resulted in proton flux and a 9% reduction in mean pH. Lakes in burnt catchments contained more than twofold higher (P << 0.01) mean concentrations of total, total dissolved, and soluble reactive phosphorus, 1.5-fold higher (P << 0.01) concentrations of dissolved organic carbon, and more than 1.2-fold higher (P < 0.05) concentrations of total and total dissolved nitrogen, nitrate + nitrite, and ammonium compared with reference lakes. Total phosphorus concentration explained 86% of the variance in reference lake chlorophyll concentration but was not related to chlorophyll concentration in burnt lakes. Analysis of chlorophyll - total phosphorus residuals suggested that algae in burn-impacted lakes were light limited. With the addition of five lakes burnt between 1961 and 1985, time since disturbance and percent disturbance combined explained 74% of the variance in total phosphorus among burnt lakes. Fire caused increased flux of materials to the study lakes with slow recovery over decades.
Comparative impacts of fire and forest harvesting on water quality in Boreal Shield lakes
Authors: Carignan Richard , D'Arcy Pierre , Lamontagne Sébastien
Published: April 2011

Water quality was monitored in Boreal Shield lakes for 3 years following their simultaneous impact by clearcut logging or wildfire. Seventeen similar undisturbed lakes served as references. Dissolved organic carbon (DOC) and the light attenuation coefficient (εPAR) were up to threefold higher in cut lakes than in reference and burnt lakes. Compared with median values for reference lakes, cut and burnt lakes had higher concentrations of total phosphorus (TP) (two- to three-fold), total organic nitrogen (TON) (twofold), and K+, Cl-, and Ca2+ (up to sixfold). NO3- and SO42- concentrations were up to 60- and 6-fold higher, respectively, in burnt lakes than in reference and cut lakes. In most cases, impacts were directly proportional to the area harvested or burnt divided by the lake's volume or area. These simple models correctly predicted the changes observed in three lakes harvested during the study. Some of the ob served effects occur on different time scales. Mobile ions released by fire (K+, Cl-, SO42-, NO3-) or harvesting (K+, Cl-, some DOC) are rapidly flushed out of the watershed (50% decrease in 3 years). Other constituents or properties (TP, TON, DOC, εPAR, Ca2+, Mg2+) show little change or are still increasing after 3 years and will take a longer time to reach normal levels.
Critical analysis of water quality monitoring in the Russian Federation and former Soviet Union
Authors: Zhulidov Alexander V , Khlobystov Vladimir V , Robarts Richard D , Pavlov Dmitry F
Published: April 2011

Water quality in Russia has both domestic and international consequences. Domestically, it allows for appropriate management of aquatic systems; internationally, surface flow from present Russian and former Soviet Union territory into international waters (e.g., Arctic Ocean and Aral, Black, and Caspian seas) has important implications for global contamination levels and for developing future management plans. Although during the Soviet era the Russian water quality monitoring network was one of the most extensive in the world, numerous anomalies identified in Russian data by domestic and foreign scientists have been referred to the authors for comment. A holistic assessment of the purpose and current status of the Russian water quality monitoring program is essential because of the difficulty that "outsiders" have in obtaining unbiased information about the program and because this is the principal historical database on water quality that is available for the former U.S.S.R. and Russian Federation. Apart from chronic underfunding, the main problems that need to be addressed are poor functioning of the system, including network design, choice of parameters, sample collection, analytical conditions and data quality, data handling, data products, and issues of access, and the larger question of institutionalized flexibility required to meet local data needs.
Time series acoustic observations of macrozooplankton diel migration and associated pelagic fish abundance
Authors: Thomson Richard E , Allen Susan E
Published: April 2011

In April 1997, we deployed an upward-looking 165-kHz water acoustic structure profiler (WASP) at a depth of 240 m near the head of Barkley Canyon on the west coast of Vancouver Island. Acoustic backscatter intensity, recorded every 10 s at 2-m intervals through the water column, revealed that zooplankton aggregated in well-defined layers near the canyon floor during daylight hours. Several hours prior to sunset, the animals began a slow vertical ascent, which ended 7.2 ± 4.2 min after sunset with a rapid ascent to the surface. Upward migration attained maximum ascent rates of 6.3 ± 0.5 cm·s-1 and ended 55.4 ± 2.3 min after sunset (18.6 ± 2.4 min before nautical twilight). Zooplankton remained near the ocean surface for several hours before beginning a slow descent, followed by a rapid-descent 24.6 ± 3.2 min before sunrise. Zooplankton quickly descended below major fish aggregations and ended their rapid descent 22.6 ± 8.7 min after sunrise, reaching the canyon floor 2-4 h after sunrise. Small fish targets were observed near the ocean surface during the night. Large fish targets generally did not arrive until dawn and were more concentrated at middepth.
Use and abuse of fishery models
Authors: Schnute Jon T , Richards Laura J
Published: April 2011

Recent failures of important fish stocks give mathematical models a poor reputation as tools for fishery management. This paper examines the role of models in fish stock assessment and identifies reasons why they can fail. Starting with laws of arithmetic, models attempt to relate observed data to unknown quantities, such as the stock biomass and abundance. Typically, the number of unknowns greatly exceeds the number of observations, and models must impose hypothetical constraints to give useful estimates. We use the word "fishmetic" (rhymes with arithmetic) to represent uncertainty in the conversion of arithmetic to practical fishery models. Arbitrary assumptions cannot be avoided, even though different choices can greatly influence the outcome of the analysis. We compare the modeling process in fisheries with that in other sciences. World literature also offers useful analogies. Potential reasons for failure suggest possible improvements to the application of fishery models. We recommend that modelers remain skeptical, expand their knowledge base, apply common sense, and implement robust strategies for fishery management. Particularly creative thought must be applied to the problem of translating scientific knowledge into management practice. Comparisons between fish stocks and financial stocks illustrate some possibilities.
Fatty acid composition as an indicator of carnivory in Antarctic krill, Euphausia superba
Authors: Cripps G C , Atkinson A
Published: April 2011

In a previous study at South Georgia, carnivory was invoked as a cause of high polyunsaturated fatty acid (PUFA) content of Antarctic krill, Euphausia superba. To examine this, krill were sampled and fed for 16 days exclusively on the locally abundant copepod Drepanopus forcipatus. After 16 days, the krill had increased their PUFA content from 28 to 54% of the total fatty acids. Concurrently, monounsaturated fatty acids (MUFAs) and saturated fatty acids (SFAs) decreased from 41 to 27%. Thus, the krill appeared to accumulate PUFAs as reflected in their diet of D. forcipatus, which also had a relatively high PUFA content (50%). Overall, the results support omnivorous feeding by krill at South Georgia during nonbloom periods. We propose that the ratio of PUFA to SFA content may be used to detect carnivory in the recent feeding history of krill and suggest that this may be an index which could be applied to other zooplankton.