bluuebunny/crossref_metadata_2025 huggingface dataset:
THE EFFECT OF FOREST SUCCESSION UPON THE QUANTITY AND UPON THE NUTRITIVE VALUES OF WOODY PLANTS USED AS FOOD BY MOOSE
Authors: Cowan I. McT. , Hoar W. S. , Hatter J.
Published: April 2011

The moose, Alces americana, in British Columbia reaches its greatest populations in the young second growth forest areas. Numbers decrease as the forest approaches its climax stage. The decline in population is known to be mainly the result of malnutrition.The present study of three stages in forest succession growing under virtually identical conditions of soil and climate has concerned itself with quantity of available palatable browse; carotene and ascorbic acid content of available palatable and unpalatable trees and shrubs; and with determination of values for moisture, protein, carbohydrate, ether extractives, and total mineral content. Most of the analyses are confined to the winter dormant period.It is determined that the forest changes studied involve a reduction in quantity of palatable browse to about one-third; that there is an increase of carotene values and possibly of total mineral content in the vegetation on more advanced forest areas, but that in ascorbic acid content, ether extractives, total carbohydrates, and proteins the vegetation upon the younger forest areas is superior to that on the older areas.It is concluded, therefore, that the declining carrying capacity noted in a forest approaching its climax stage results from decreases in both the quantity and quality of food produced.It is further concluded that the most desirable winter range for moose is one upon which there is a variety of palatable species, predominantly in an early stage of growth, but with an intermixture of older forest stands bearing palatable coniferous trees.
The application of science to the management of Atlantic salmon (Salmo salar): integration across scales
Authors: Armstrong John D , Grant James WA , Forsgren Harvey L , Fausch Kurt D , DeGraaf Richard M , Fleming Ian A , Prowse Terry D , Schlosser Isaac J
Published: April 2011

The need for integration across spatial and temporal scales in applying science to the management of Atlantic salmon is considered. The factors that are currently believed to affect the production of anadromous adult Atlantic salmon (synthesized from recent reviews) are arranged in a hierarchy in which any given process overrides those processes at lower levels. There is not a good correlation between levels in the process hierarchy and levels in hierarchies of scale. This demonstrates the importance of integrating across scales in identifying the optimum foci for targeting management action. It is not possible to generalize on the need for integration across scales within management plans. This is because of the complex ecology of salmon, the broad range of characteristics of the systems of which they are a part, and the fact that both local scale and broad scale management can have broad scale effects. Many uncertainties remain regarding the large-scale components of the ecology of salmon, the way that small-scale mechanisms interact with life histories, and the way that different factors interact to limit production of fish. When more is understood of these processes, it is likely that generalized rules might be developed to predict the management requirements for stream systems. In the meantime, it is essential that there is good integration among managers working at different scales and it is important that management systems operating at all spatial scales include high-calibre expertise to compensate for the present paucity of general rules.
A full-scale field experiment (1978–1995) on the growth of permafrost by means of lake drainage, western Arctic coast: a discussion of the method and some results
Authors: Mackay J. Ross
Published: April 2011

On 13 August 1978, a lake on the western Arctic coast was artificially drained, in a multidisciplinary experiment on the growth of permafrost on the unfrozen bottom of the drained lake. A bowl-shaped talik (unfrozen basin) with a maximum depth of about 32 m underlay the lake bottom prior to drainage. In the first winter after drainage, downward freezing started on the exposed lake bottom and upward freezing from permafrost beneath the talik. After drainage, the soft lake-bottom sediments hardened from water loss and freeze–thaw consolidation. Gradual thinning of the active layer at many sites was accompanied by ground uplift and the growth of aggradational ice. Downward and upward freezing has resulted in solute rejection, freezing-point depressions, pore-water expulsion from the freezing of the saturated lake-bottom sands, and convective heat transfer from groundwater flow in an open hydrologie system. The increasingly saline intrapermafrost groundwater, flowing at an increasingly negative temperature because of a freezing-point depression, has accelerated the rate of permafrost growth in the interpermafrost zone in the direction of flow. The experiment has demonstrated that the growth of permafrost at the drained lake site, and at other sites with groundwater flow, requires a three-dimensional conductive–convective heat transfer approach.
Paleomagnetic evidence for low-latitude glaciation during deposition of the Neoproterozoic Rapitan Group, Mackenzie Mountains, N.W.T., Canada
Authors: Park John K.
Published: April 2011

The rift-related Rapitan Group of the Mackenzie Mountains of northwestern Canada acquired several magnetizations due to pulses of hydrothermal activity. The first pulse, attributed to initiation of Rapitan rifting, produced a widespread overprint (P2) that may be reflected in the basal Mount Berg Formation. Two later pulses produced overprints similar to components found in an earlier study. Development of iron formation and hematite pigment in the overlying Sayunei Formation is attributed to the second pulse, represented by a paleopole (N = 10 sites; 334°E, 01°S; δp, δm = 4°, 9°) that coincides with poles of the Franklin igneous events of northern Canada. The Franklin episode, suggested on geological grounds to be coeval with Sayunei deposition, dates the Sayunei at ca. 725 Ma. This relation implies that rifting in Mackenzie Mountains could be related to rifting in northern Canada. A third pulse, reflected by a pole at 007°E, 16°N (N = 6 sites; δp, δm = 6°, 12°), is attributed to final rifting during deposition of the Shezal Formation at the top of the Rapitan. Overprints attributed to Sayunei and Shezal times indicate regional latitudes of 6 ± 4° and 4 ± 6° during the Sturtian glaciation. During Mount Berg time, the regional latitude could have exceeded 25°. All directions have been tilt corrected and some have been then rotated, based on comparisons with a P2 reference overprint.
A late Quaternary loess – paleosol record at Kurtak, southern Siberia
Authors: Chlachula J. , Rutter N. W. , Evans M. E.
Published: April 2011

A high-resolution paleoclimatic record for the last two glacial – interglacial cycles has been documented at Kurtak in southern Siberia. A unique, 34 m high late Quaternary loess section (section 29) with a series of 32 variably developed paleosol horizons provides evidence of a strongly fluctuating, but patterned, climatic change. Mineralogical composition and grain morphology of the undifferentiated (aeolian and colluviated) loess indicate a local provenance and a short transport of the silt, derived by glacial erosion of the granitic and metamorphic bedrock in the Kuznetskiy Alatau and eastern Sayan mountains, and subsequently subaerially redeposited from the alluvial plain in the Yenisey River valley. The succession of Chernozemic, Brunisolic, and Gleyed Regosolic soils, alternating with nonweathered or weakly weathered loess events, matched by parallel changes in magnetic susceptibility, can be correlated with marine isotope stages 1 – 7. The magnetic susceptibility pattern is completely opposite to that of the Chinese loess record, where magnetic susceptibility is highest in paleosols, as opposed to lowest in Kurtak paleosols. The reason for this is not completely understood. Nevertheless, the magnetic susceptibility profile correlates well with the last two glacial – interglacial cycles. Furthermore, isotope stage 5 includes several short-duration, relatively small amplitude susceptibility signals corresponding to equivalent signals in the δ18O record. These include the colder intervals (stadials?) 5b and 5d, warmer intervals (interstadials?) 5a and 5c, and the "optimum" warm interval 5e.
Drag and shear stress partitioning in sparse desert creosote communities
Authors: Wyatt V. E. , Nickiing W. G.
Published: April 2011

Most research to characterize the wind-erosion susceptibility and the degree of surface roughness required to suppress erosion on erodible surfaces has been empirical. However, a recently proposed shear velocity ratio model attempts to place shear stress partitioning in an entirely theoretical framework. The purpose of this study was to directly measure components of shear stress in a sparsely vegetated environment in order to evaluate the model. For the field study, new instrumentation was developed to measure drag on a creosote shrub, and Irwin sensors were modified to measure surface shear stress in the field. Simultaneous measurements of total shear stress and surface shear stress were taken at four sites of different roughness densities, in the Eldorado Valley, Nevada. Results indicate that porous shrubs had greater drag coefficients (Cd = 0.485) than did solid elements (sphere Cd = 0.3) and are more effective at protecting a surface. Values of β, the ratio of element to surface drag coefficients, were therefore higher than previously published values. Surface and total shear stress scaled consistently with each other at a range of wind speeds, and varied according to the roughness density of the surface. Shear stress partitioning values agreed well with previously published field data and some wind-tunnel data. The theoretical model predicted the results successfully when m = 0.16, where m is an empirical constant that accounts for the difference in average stress and the maximum surface stress in initiating erosion. The wide applicability of the model is likely due to the inclusion of the adjustable m, which accommodates all values of β and σ (ratio of roughness element basal area to frontal area).
Population genetics of the zebra mussel, Dreissena polymorpha (Pallas): local allozyme differentiation within midwestern lakes and streams
Authors: Lewis Kristin M , Feder Jeffrey L , Lamberti Gary A
Published: April 2011

Several aquatic invertebrates with free-swimming larvae have paradoxically demonstrated fine-scale genetic heterogeneity. In this study, we tested for genetic heterogeneity in an exotic freshwater bivalve, the zebra mussel, Dreissena polymorpha (Pallas), which like many marine molluscs has a free-swimming larval stage. Zebra mussels were collected from 22 sites in the Great Lakes and from a small inland lake complex in southwestern Michigan and scored for 13 allozyme loci. Sites were sampled in a hierarchical fashion to assess the spatial scale of genetic variation. Zebra mussel populations exhibited significant genetic heterogeneity on a local scale within lakes, even though populations remained homogenous on a larger regional scale between lakes or lake complexes. The allozyme loci that exhibited heterogeneity differed from lake to lake. Populations also displayed significant heterozygote deficiencies from Hardy-Weinberg expectations for a majority of loci, implying population subdivision and (or) inbreeding on a fine scale. Our results suggest that local genetic differentiation for zebra mussels is both spatially and temporally fluid and is the product of stochastic processes, such as spawning asynchrony and uneven mixing of larval cohorts, rather than natural selection.
Habitat factors affecting the abundance and distribution of juvenile cutthroat trout (Oncorhynchus clarki) and coho salmon (Oncorhynchus kisutch)
Authors: Rosenfeld Jordan , Porter Marc , Parkinson Eric
Published: April 2011

The distribution, abundance, and habitat associations of juvenile anadromous coastal cutthroat trout (Oncorhynchus clarki) and coho salmon (Oncorhynchus kisutch) were evaluated using survey data from 119 sites in coastal British Columbia. Both cutthroat and coho occurred at their highest densities in very small streams (<5 m channel width), and bankfull channel width was the single best predictor of cutthroat presence (p = 0.0001) and density (R2 = 0.55). Within a channel, densities of coho and larger (yearling and older) cutthroat parr were highest in pools, while densities of young-of-the-year cutthroat were significantly lower in pools and highest in shallower habitats. Abundance of larger cutthroat parr and pool habitat were positively correlated with large woody debris (LWD) within a subset of intermediate-gradient gravel-cobble streams, where pools appear to be limiting to larger cutthroat parr abundance. More than 50% of pools were formed by scour associated with LWD in streams ranging from 1.2 to 11 m channel width, and pools formed by LWD scour were on average 10% deeper than pools formed by other mechanisms. Disproportionate use of small streams by cutthroat indicates that protection of small stream habitat is important for long-term conservation of sea-run populations.
Predicting coastal eutrophication in the Baltic: a limnological approach
Authors: Meeuwig Jessica J , Kauppila Pirkko , Pitkänen Heikki
Published: April 2011

Coastal eutrophication is a key environmental concern in Finland. A highly indented, well-settled coastline with a myriad of small estuaries means that eutrophication occurs at numerous localities. There is a clear need for general models that predict eutrophication across estuaries. Lake eutrophication has been successfully predicted using a combination of chlorophyll a (Chl) - total phosphorus (TP) regression models and TP mass-balance models. We applied this limnological approach to 19 Finnish estuaries. The Chl-TP regression was highly significant, accounting for 67% of the variation in Chl. When combined with a TP mass-balance equation, log observed and predicted Chl differed by 28% on average. Accuracy was improved by dividing the estuaries into those dominated by non-point-source (NPS) loading (n = 11) and those dominated by point-source (PS) loading (n = 7). A land-use regression model based on percentage of the catchment forested and estuarine mean depth then best predicted Chl in the NPS-dominated estuaries. The mass-balance approach remained the most accurate model for the PS estuaries. The land-use model and mass-balance approach are complementary tools in that their use maximizes accuracy for both NPS- and PS-dominated estuaries. This high level of accuracy demonstrates the relevance of limnological approaches to Finnish estuaries.
A Bayesian decision analysis to set escapement goals for Fraser River sockeye salmon (Oncorhynchus nerka)
Authors: Schnute Jon T , Cass Al , Richards Laura J
Published: April 2011

This paper illustrates a complete Bayesian decision analysis for evaluating multistock harvest goals in the fishery on Fraser River sockeye salmon (Oncorhynchus nerka). We identify four key steps necessary to assess a resource production system. Each step entails choices that can alter the perceived consequences of management decisions. A Markov chain Monte Carlo sample captures uncertainty in the population dynamics. The Bayesian formalism then translates this uncertainty into uncertain policy outcomes. We examine a relatively simple control law, designed to protect stocks at low abundance. We restrict our attention to retrospective policy analysis by investigating what might have happened to sockeye stocks if management had proceeded differently during years for which historical data are available. A formal objective function quantifies societal values associated with a range of policy options. To confine the paper to manageable scope, we consider only relatively simple assumptions. Our analytical framework offers an iterative route to policy design, where managers play an active role in formulating policy options and evaluating their consequences.
Allee effects and compensatory population dynamics within a stock complex
Authors: Frank Kenneth T , Brickman David
Published: April 2011

Sparked by the observation that (i) many collapsed stocks have failed to recover despite the apparent prevalence of compensatory population dynamics and (ii) many stocks have a complex structure, we devised a simulation model illustrating that the underlying behavior of substocks is masked when the data are aggregated and evaluated at the scale of the management unit. The model consisted of several substocks within a stock complex, each having its own stock and recruitment (S-R) relationship with Allee effects. Incorporation of Allee effects into the S-R relationship was achieved by specifying a critical spawning stock biomass threshold below which no recruitment occurred. The simulation model revealed that it was possible for the aggregate S-R relationship to appear compensatory, even though no substock exhibited this behavior. If the conclusions we draw from our modeling are correct, biological reference points developed from aggregated data from multiple substocks and used in conventional fisheries management and stock assessment models are likely to be inaccurate and possibly nonconservative. More research in support of the delineation of substock structure, biophysical modeling, and metapopulation theory is advocated.
Detritivorous fish contamination in the Río de la Plata estuary: a critical accumulation pathway in the cycle of anthropogenic compounds
Authors: Colombo Juan C , Bilos Claudio , Lenicov Mauricio Remes , Colautti Dario , Landoni Patricia , Brochu Charles
Published: April 2011

Aliphatic hydrocarbons, chlorinated pesticides, polychlorinated biphenyls (PCBs), dioxins, furans, and trace metals have been quantified in fishes collected at four stations in Río de la Plata to determine contaminant sources, elucidate interstation and interspecies differences, and assess the health risks associated with fish consumption. Río de la Plata fish present low trace metal concentrations and moderate to high levels of organic pollutants, particularly aliphatic hydrocarbons and PCBs. The highest concentrations were recorded in Prochilodus lineatus, a dominant and remarkably specialized fatty detritivore that feeds on contaminated organic-rich flocculent matter. Lower levels were registered in Cyprinus carpio and especially in Mugil cephalus, reflecting different feeding preferences. A geographical pattern of higher contaminant concentrations close to the Buenos Aires urban center and lower levels in distant stations was also observed. The multivariate analysis of contaminant signatures indicated that most contaminated Prochilodus had fresh petrogenic and PCB traces, similar to fossil fuels and Aroclor 1254-1260, whereas Mugil and fish from distant sites presented a higher proportion of biogenic hydrocarbons and of more chlorinated PCBs. Toxicity equivalents ranged from 11 to 39 pg·g fresh weight-1 in Prochilodus, exceeding the guideline of 25 pg·g-1 for human consumption, with allowable consumption rates as low as 1 g fish·day-1.
Spatial variability of stream bed scour and fill: a comparison of scour depth in chum salmon (Oncorhynchus keta) redds and adjacent bed
Authors: Rennie Colin D , Millar Robert G
Published: April 2011

Scour depth in egg pockets of chum salmon (Oncorhynchus keta) egg nests (redds) in a short gravel-bed spawning reach (45 × 20 m) of Kanaka Creek, British Columbia, was not significantly different from that in the adjacent bed during 1997-1998 winter flood events, whereas the scour depth in tailspills of redds was greater. Over the course of the incubation period, none of the egg pocket locations (zero of four), all of the tailspills (three of three), and 17% of the immediately adjacent bed locations (three of 18) scoured to the assumed egg burial depth of 15 cm below the initial postspawning surface elevation. Egg pocket scour depth has not previously been monitored, and the reliance of earlier studies on tailspill monitoring as an indication of redd scour may have led to faulty assessment of embryo loss. Only one flood event, which exceeded bankfull, caused widespread and deep scour and fill. Despite implementation of the most spatially intensive array of wiffle-ball scour monitors to date, scour was so variable that there was no spatial autocorrelation of scour depths.
In situ analysis of trace elements and isotope ratios in fish otoliths using laser ablation sector field inductively coupled plasma mass spectrometry
Authors: Thorrold Simon R , Shuttleworth Stephen
Published: April 2011

We applied laser ablation sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) to the analysis of trace element and isotopic signatures in fish otoliths. Manganese, Sr, and Ba profiles across juvenile Atlantic croaker (Micropogonias undulatus) otoliths, expressed as ratios to Ca, showed considerable spatial and temporal variations that were presumably reflective of variations in water chemistry over the same scales. Differences in otolith Mn:Ca ratios between adjacent rivers in Pamlico Sound, North Carolina, may be related to dissolved oxygen levels in the rivers through reductive release of Mn2+ from sediments. Strontium and Ba profiles appeared to accurately reflect differences in dissolved Sr and Ba in freshwater end-members, both between Pamlico Sound and Chesapeake Bay and between seasons within Chesapeake Bay. High-precision analyses of Sr:Ca ratios in a black drum (Pogonias cromis) otolith showed distinctive quasi-sinusoidal cycles that were correlated with validated annual bands. Analyses of Sr and Pb isotopes, in otoliths and standard reference material, respectively, found that SF-ICP-MS produced accurate and precise estimates of isotope ratios in both solution-based and laser ablation assays.
Geomorphology, hyporheic exchange, and selection of spawning habitat by bull trout (Salvelinus confluentus)
Authors: Baxter Colden V , Hauer F Richard
Published: April 2011

The distribution and abundance of bull trout (Salvelinus confluentus) spawning were affected by geomorphology and hyporheic groundwater - stream water exchange across multiple spatial scales in streams of the Swan River basin, northwestern Montana. Among spawning tributary streams, the abundance of bull trout redds increased with increased area of alluvial valley segments that were longitudinally confined by geomorphic knickpoints. Among all valley segment types, bull trout redds were primarily found in these bounded alluvial valley segments, which possessed complex patterns of hyporheic exchange and extensive upwelling zones. Bull trout used stream reaches for spawning that were strongly influenced by upwelling. However, within these selected reaches, bull trout redds were primarily located in transitional bedforms that possessed strong localized downwelling and high intragravel flow rates. The changing relationship of spawning habitat selection, in which bull trout selected upwelling zones at one spatial scale and downwelling zones at another spatial scale, emphasizes the importance of considering multiple spatial scales within a hierarchical geomorphic context when considering the ecology of this species or plans for bull trout conservation and restoration.
Factors influencing carbon, nitrogen, and phosphorus content of fish from a Lake Superior coastal wetland
Authors: Tanner Danny K , Brazner John C , Brady Valerie J
Published: April 2011

The narrow fish nutrient ranges (C, 42.8-48.4%; N, 9.6-12.7%; P, 1.91-2.74%) in this study suggest that overall mean values are adequate for quantifying movement of C, N, or P as part of fish-mediated nutrient transport. We measured C, N, and P in 20 species of Lake Superior coastal wetland fish to better understand variability in fish elemental content caused by differences in species, habitat, season, life stage, or size. Fish were sampled within Bark Bay slough and at its inlet/outlet to Bark Bay, Lake Superior, from May to November 1995. Elemental content averaged across all fish (n = 192) was 45.1% for C, 11.3% for N, and 2.45% for P. We did find significant differences (p [Formula: see text] 0.05) among nine tested species. However, less than one third of the analyses were significant for effects of location or date of capture or fish length on fish nutrient content and nutrient ratios. Regressions of N:P ratios against growth rate indices and, separately, fineness ratios were significant, suggesting that growth rate and body shape are important factors driving N:P ratios in fish.
Geographic variation in the sex ratio, sex specific size, and age structure of Plectropomus leopardus (Serranidae) between reefs open and closed to fishing on the Great Barrier Reef
Authors: Adams S , Mapstone B D , Russ G R , Davies C R
Published: April 2011

Variation in reproductive parameters of Plectropomus leopardus populations between coral reefs open and closed to fishing was examined in two geographic regions (off Townsville (19°S) and in the Swains (22°S)) of the Great Barrier Reef, Australia. The reproductive parameters that were examined included the operational (reproductive) sex ratio and size and age structure of mature females, sex-changing individuals (transitionals), and mature males. There was a greater proportion of males above the minimum size and age of harvest on reefs closed to fishing for 8-10 years than on reefs open to fishing, although the effect varied with geographic region. Nevertheless, neither the sex ratio, mean age, nor mean size of males or transitionals varied significantly with reef closure status. Females, however, were significantly older and larger on closed than on open reefs in both regions. Marked regional variations in the sex ratio and average age of transitionals were found independent of reef closure status, suggesting regional variation in reproductive strategies. Controlled manipulations, inclusion of broad spatial scales, and detailed studies of intra- and inter-specific variation in serranid reproductive biology are necessary to resolve such complexities in the responses of protogynous serranids to fishing pressure and management strategies.
Biomass transport to and from an upper estuarine area by migration of juvenile Atlantic herring Clupea harengus
Authors: Maes Joachim , Ollevier Frans
Published: April 2011

A model describing fish abundance resulting from fish migration and mortality in an upper estuary is presented. This model can be used to estimate biomass transports by fish migrations between estuary and sea and to assess production assimilated in the estuary. It was applied to herring Clupea harengus L., a marine species with 0+ juveniles that migrate during winter to temperate European estuaries. It was shown that different mortality regimes greatly affected the number of fish that eventually emigrated and, hence, the biomass that was exported during the seaward migration. The difference between imported and exported biomass was assessed under different growth conditions and varied from positive to negative as mortality rates increased. The discrepancy between export of biomass and in situ produced biomass showed that fish production was not necessarily transported to the sea when emigrating. It was tentatively concluded that export of biomass out of the estuary only occurs if populations move seaward before winter.
Current, reconstructed past, and projected future status of brook trout (Salvelinus fontinalis) streams in Virginia
Authors: Bulger Arthur J , Cosby Bernard J , Webb James R
Published: April 2011

Southern Appalachian streams host a rich diversity of fishes, but the Southern Appalachian Assessment concluded that 70% of stream locations showed significant fish community degradation, partly due to acid deposition. About 40% of total Southern Appalachian trout stream length occurs in Virginia. Our research in Shenandoah National Park, Virginia, has documented both chronic and episodic acidification in streams and brook trout (Salvelinus fontinalis) mortality during acid episodes. Here, we analyze a representative sample of 60 Virginia brook trout streams on noncarbonate bedrock with minimal human disturbance in their watersheds. Of more than 300 such streams in Virginia, only about 50% are currently suitable for brook trout, based on their acidification status. For the population of brook trout streams to which this analysis applies, model-based projections indicate that continued sulfate deposition at 1991 levels will result in about 70 additional streams becoming chronically acidic and unsuitable for brook trout. A 40% reduction will result in about 48 additional chronically acidic streams. Even a 70% reduction will likely result in about 15 additional streams becoming acidified. We conclude that reductions in sulfate deposition greater than 70% (relative to 1991 levels) are needed to prevent more brook trout stream losses in Virginia.
An Atlantic herring (Clupea harengus) size selection model for experimental gill nets used in the Sound (ICES Subdivision 23)
Authors: Poulsen Søren , Nielsen J Rasmus , Holst René , Stæhr Karl-Johan
Published: April 2011

Size selection investigations were performed in the Sound with experimental, multipanel gill nets equipped with a broad range of mesh sizes targeting Atlantic herring (Clupea harengus). Each of the 20 experimental fishery surveys covered the central Sound from Helsingør-Helsingborg (north) to Drogden-Klagshamn (south) during the autumn, winter, and spring periods from 1993 to 1998. There was high variability in catch sizes both between and within surveys. The overall best fits, in terms of minimum total deviance across all sets, were achieved using a unimodal normal scale model. Almost all surveys showed high between-set variation, which was accounted for when estimating the mean selectivity curves using a random effects model. The selectivity curves fitted to individual sets were compared with those fitted to the combined data sets. It was demonstrated that analysing pooled data sets resulted in overdispersion and bias in the selection parameters. Irregular time series of the estimates of the selectivity parameters in the investigation period indicated negative autocorrelation with a seasonal pattern.
Use of fish production per unit biomass ratios for measuring the productive capacity of fish habitats
Authors: Randall R G , Minns C K
Published: April 2011

Species-specific production rate per unit biomass (P/B, per year) ratios were calculated for 79 freshwater fish species of eastern Canada. P/B (per year) ratios were calculated using two methods, which were based on allometry with fish weight-at-maturity and life expectancy, respectively. P/B (per year) values obtained by the two methods were significantly correlated, as expected from life history theory, since the two predictors (longevity, size-at-maturity) were themselves correlated. Species-specific P/B (per year) ratios were also significantly correlated with field observations of P/B from published sources. The estimation of P/B based on allometry with fish size is recommended because of its utility; the predictive equation is P/B (per year) = 2.64Wmat-0.35, where Wmat is weight-at-maturity. Both the coefficient 2.64 and the exponent -0.35 of this equation are provisional and require further validation from field studies of fish production. More accurate estimates of P/B are possible if population-specific information on size-at-maturity or mean size is known. The product of average fish biomass and estimated P/B coefficients (habitat productivity index (HPI) = B × P/B) is a proposed measure of habitat productive capacity.
Impacts of intensive harvesting on hydrology and nutrient dynamics of northern hardwood forests
Authors: Martin C Wayne , Hornbeck James W , Likens Gene E , Buso Donald C
Published: April 2011

Whole-tree clear-cutting and progressive strip-cutting of northern hardwood forests at the Hubbard Brook Experimental Forest in central New Hampshire resulted in measurable changes in physical and chemical conditions of forest streams. As a result of reduced transpiration and interception, water yield for the first year after whole-tree harvesting increased by >150 mm, the majority of which occurred during the growing season. Peak flows increased only moderately. Water yield and peak flow increases disappeared within 4-6 years as a result of rapidly regrowing vegetation. Sediment yields increased during and after harvesting but can be maintained within normal ranges of reference streams by careful use of best management practices. Stream chemistry changes occurred immediately following harvesting, most notably in the form of increases in concentrations of Ca2+, K+, NO3-, and H+. The concentrations return close to preharvest levels within 3-5 years. The above changes are discussed in terms of their causes and implications for aquatic habitat and fisheries.
Element export in runoff from eastern Canadian Boreal Shield drainage basins following forest harvesting and wildfires
Authors: Lamontagne Sébastien , Carignan Richard , D'Arcy Pierre , Prairie Yves T , Paré David
Published: April 2011

Element export rates from the drainage area of nine harvested, nine burnt, and 16 reference Boreal Shield lake basins in Haute-Mauricie, Québec, were estimated for the 3 years following harvesting or fires. Export rates from the drainage area of the basins were evaluated using lake sampling surveys, estimated hydrological budgets, and estimated nutrient retention during lake transit. Increases in K+, total N, and total P export rates were similar between harvested and burnt drainage areas. However, harvested drainage areas exported more dissolved organic C, while burnt drainage areas exported more Mg2+, NO3-, and SO42-. Potassium cumulative losses in runoff during the 3 years of the study were of a similar magnitude as volatilization losses during fires and corresponded to ~33% of the losses by biomass removal during harvesting. While the increased export rates for N and P following fires or harvesting represented negligible losses of nutrients for the forest, they were important supplementary inputs to lakes. The differences in element export rates observed between harvested and burnt drainage areas indicate that these disturbances have different impacts on biogeochemical cycles in the Boreal Shield forest.
Effects of experimental clearcut logging on thermal stratification, dissolved oxygen, and lake trout (Salvelinus namaycush) habitat volume in three small boreal forest lakes
Authors: Steedman Robert J , Kushneriuk Robert S
Published: April 2011

Clearcut logging around three 30- to 40-ha dimictic northwestern Ontario lakes was associated with increases of 5% or less in midlake wind speed and no measurable changes in spring and fall circulation efficiency or duration of stratification. Water clarity, indexed as the depth at which photosynthetically active radiation was 1% of surface intensity, declined by 25% after 3 years. Late-summer thermoclines were about 1 m shallower in two lakes after logging, but it was not possible to exclude weather as a factor. None of the lakes showed significant declines in lake trout (Salvelinus namaycush) habitat volume. A forested shoreline buffer strip around one of the lakes prevented increases in midlake wind speed but did not prevent declines in water clarity and thermocline depth.
Paleolimnological reconstruction of forest fire induced changes in lake biogeochemistry (Lac Francis, Abitibi, Quebec, Canada)
Authors: Enache Mihaela , Prairie Yves T
Published: April 2011

Biogeochemical effects of fire events were analysed in a small humic kettle lake, Lac Francis (claybelt area, Abitibi, northwestern Quebec), using diatom-based quantitative inference models developed to reconstruct past pH, total phosphorus, and dissolved organic carbon in Abitibi lakes. Diatom-inferred changes in lake geochemistry in four historical fire events were examined and the results showed that, on average, total phosphorus concentrations increased significantly (up to twofold) during fire events. In contrast, dissolved organic carbon concentrations and pH were relatively unaffected by the fires.
Impact of logging and natural fires on fish communities of Laurentian Shield lakes
Authors: St-Onge Isabelle , Magnan Pierre
Published: April 2011

The goal of this study was to determine if natural fires and logging have a significant impact on abundance, growth, and size structure of fish populations in 38 lakes of the Laurentian Shield (Québec, Canada). The watersheds of nine of these lakes underwent logging and nine underwent natural fires, while the 20 remaining lakes were used as references. No significant differences were found among the three lake groups in the catch per unit of effort of the most abundant species: white sucker (Catostomus commersoni), northern pike (Esox lucius), yellow perch (Perca flavescens), lake whitefish (Coregonus clupeaformis), fallfish (Semotilus corporalis), brook trout (Salvelinus fontinalis), walleye (Stizostedion vitreum), and burbot (Lota lota). No significant difference was found among control, burned, and logged lakes in the back-calculated length of yellow perch, for which age determinations were made. However, we found that the proportions of small yellow perch and white sucker were significantly lower in populations of impacted lakes (burned and logged lakes pooled). The influence of logging and fires remained significant when a series of biotic and abiotic variables on watershed and lake characteristics were accounted for in multiple regression analyses. The lower proportion of small fish in impacted lakes could be due to an increase in postemergence mortality or to a shift of individuals to the pelagic zone.
Assessment of changes in lake pH in southeastern Canada arising from present levels and expected reductions in acidic deposition
Authors: Jeffries D S , Lam D CL , Wong I , Moran M D
Published: April 2011

An integrated acid rain assessment model was used to estimate pH for six clusters of lakes in southeastern Canada and scenarios of sulphate deposition that reflect the situation (a) before implementation of the SO2emission controls required by the Canada/U.S. Air Quality Agreement, (b) after implementation of Canadian controls, and (c) after implementation of Canadian and U.S. controls. Modelled lake pHs were always less than their estimated original values. To assess the ecological significance of the pH reduction, scenario "damage" was quantified as the percentage of cluster lakes having pH < 6, a threshold criterion sufficient to protect most aquatic biota. Care was taken to account for naturally acidified lakes. The integrated acid rain assessment model predicted that Canadian SO2controls will reduce damage in Ontario and Quebec but have little effect in Atlantic Canada. Implementation of U.S. SO2controls will further reduce damage throughout all regions, although it is conservatively estimated that from 5 to 24% of the lakes will still have pH < 6 depending on cluster. Extrapolating to the inventory of acid-sensitive lakes in southeastern Canada suggests that ~76 000 lakes and ~970 000 ha of lake area will remain chemically damaged unless additional reductions in SO2emissions are implemented beyond those required by the Air Quality Agreement.
Genotypic variation amongGammarus fasciatus(Crustacea: Amphipoda) from the Great Lakes - St. Lawrence River: implications for the conservation of widespread freshwater invertebrates
Authors: Hogg Ian D , Lafontaine Yves de , Eadie John M
Published: April 2011

We examined the population genetic structure of the amphipod Gammarus fasciatus (Crustacea: Amphipoda) over two years from a total of 11 sites within the Great Lakes - St. Lawrence River system using allozyme electrophoresis. In 1995, we examined differences within the St. Lawrence River (Cornwall to Quebec City), and in 1996, we focused on larger scale, whole-system differences from Lake Superior to Lake Champlain. We found very low levels of genetic differentiation among sites (Wright's FST< 0.03). This was not unexpected for an active disperser in a relatively contiguous system. However, we also found low levels of genetic variability within sites (Hobs= 0.07- 0.15), a result that was not anticipated. We surveyed the available literature on gammarid and other amphipods and found that limited genetic variability is characteristic of continuously distributed taxa, contrary to the expectations of current conservation theory. This is potentially of concern, especially in light of recently reported declines of G. fasciatus at several locations within the St. Lawrence River and Great Lakes. Given the importance of species such as G. fasciatus in aquatic food webs, further work is clearly needed on the consequences of population genetic structure to species' responses to novel environmental changes (e.g., exotic species introductions).
Comparative behaviour and survival of hatchery-reared versus wild summer flounder (Paralichthys dentatus)
Authors: Kellison G T , Eggleston D B , Burke J S
Published: April 2011

We describe the use of laboratory trials to compare substrate-specific behaviour and susceptibility to predation of hatchery-reared (HR) versus wild summer flounder (Paralichthys dentatus) juveniles. HR fish spent significantly more time swimming in the water column than wild fish and took significantly longer to become cryptic on the benthos than wild fish, regardless of substrate type. In predation trials with a blue crab (Callinectes sapidus) predator, naïve HR fish were significantly more susceptible to predation than wild fish. Antipredator-conditioned HR fish were significantly less susceptible to predation than naïve HR fish but significantly more susceptible than wild fish, irrespective of substrate. The modified behavioural patterns and increased susceptibility to predation of HR individuals observed in this study indicate that flounder reared in psychosensory-deprived hatchery environments may be poorly equipped to survive in natural habitats; they also indicate that it may be possible to mitigate detrimental behavioural patterns by exposing naïve HR fish to natural stimuli before release into natural environments. These results have important implications for stock enhancement, suggesting that stocked organisms are more likely to achieve postrelease survival if they are conditioned with natural stimuli prior to release into the wild.
A fuzzy logic model with genetic algorithm for analyzing fish stock-recruitment relationships
Authors: Chen D G , Hargreaves N B , Ware D M , Liu Y
Published: April 2011

A new fuzzy logic model with a genetic algorithm is developed that overcomes some of the inherent uncertainties in the fish stock-recruitment process. This model is applied to stock-recruitment relationships for the Southeast Alaska pink salmon (Oncorhynchus gorbuscha) and the West Coast Vancouver Island Pacific herring (Clupea pallasi) stocks. In both examples, the annual mean sea surface temperature is used as an environmental intervention in the model. The fuzzy logic model provides the functional relationship between the number of fish spawners and the sea surface temperature that is used to reconstruct the historical fish recruitment time series and also to predict the number of fish that will recruit in the future. Globally optimized genetic learning algorithms are used to find the optimal values of the parameters for the fuzzy logic model. The results from this fuzzy logic model are compared with results from both a traditional Ricker stock-recruitment model and a recent artificial neural network model. These comparisons demonstrate the superior capability of the fuzzy logic model for addressing problems of uncertainty and vagueness in both the data and the stock-recruitment relationship. The fuzzy logic model approach is recommended as a useful addition to the analytical tools currently available for fish stock assessment and management.
Spring isothermal mixing in the Great Lakes: evidence of nutrient limitation and nutrient-light interactions in a suboptimal light environment
Authors: Fahnenstiel G L , Stone R A , McCormick M J , Schelske C L , Lohrenz S E
Published: April 2011

During the spring isothermal mixing period (April-May) in 1993-1995, photosynthesis-irradiance and growth-irradiance experiments were conducted in Lakes Erie, Huron, Michigan, and Ontario to assess light limitation. Additionally, nutrient enrichment experiments were conducted in Lake Ontario. Results from the photosynthesis-irradiance experiments suggested that phytoplankton communities in all the lakes can be either light limited or light saturated, as the threshold parameter (Ik) was similar to mean water column irradiances (mean Iwc, ratio = 1.0). Growth-irradiance experiments also suggested the potential for light saturation; mean daily irradiance exceeded the threshold growth irradiance (Ik,g) in 95% of cases. Growth rates became light saturated at lower irradiances than photosynthetic rates. Evidence for a nutrient-light interaction in controlling in situ growth rates was also found in the nutrient enrichment experiments at incubation irradiances [Formula: see text] mean Iwc. Our results suggest that an interaction between nutrients and light is often controlling phytoplankton growth during spring mixing in the Great Lakes. The role of these nutrient-light interactions has increased in the past decade due to increased light availability in the lower lakes caused by phosphorus load reductions and the filtering activities of nonindigenous mussels.
Diazinon disrupts antipredator and homing behaviors in chinook salmon (Oncorhynchus tshawytscha)
Authors: Scholz Nathaniel L , Truelove Nathan K , French Barbara L , Berejikian Barry A , Quinn Thomas P , Casillas Edmundo , Collier Tracy K
Published: April 2011

Neurotoxic pesticides are known to contaminate surface waters that provide habitat for salmonids, including some listed for protection under the U.S. Endangered Species Act. Despite their widespread use, the impacts of these pesticides on the neurological health of wild salmon are not well understood. Of particular concern are the organophosphate and carbamate insecticides that block synaptic transmission by inhibiting neuronal acetylcholinesterase. Here we assess the effects of diazinon, an organophosphate insecticide, on alarm pheromone induced antipredator responses and homing behavior in chinook salmon (Oncorhynchus tshawytscha). Nominal exposure concentrations (0.1, 1.0, and 10.0 µg·L-1) were chosen to emulate diazinon pulses in the natural environment. In the antipredator study, diazinon had no effect on swimming behavior or visually guided food capture. However, the pesticide significantly inhibited olfactory-mediated alarm responses at concentrations as low as 1.0 µg·L-1. Similarly, homing behavior was impaired at 10.0 µg·L-1. Our results suggest that olfactory-mediated behaviors are sensitive to anticholinesterase neurotoxicity in salmonids and that short-term, sublethal exposures to these insecticides may cause significant behavioral deficits. Such deficits may have negative consequences for survival and reproductive success in these fish.