scholarly journals Estimates of Minimum Population Size for Walrus near Southeast Baffin Island, Nunavut

2014 ◽  
Vol 9 ◽  
pp. 141 ◽  
Author(s):  
Robert EA Stewart ◽  
Erik W Born ◽  
Rune Dietz ◽  
Anna K Ryan
Keyword(s):  
Late Summer ◽  
Population Estimates ◽  
Hudson Bay ◽  
Baffin Island ◽  
Data Logger ◽  
Joint Research ◽  
Management Objectives ◽  
Short Period ◽  
Simple Proportion ◽  
Direct Counts

To support management objectives in Canada and Greenland, joint research between the Department of Fisheries and Oceans and Greenland Institute of Natural Resources was begun in 2005. Direct counts were used to determine the Minimum Counted Population (MCP) in summer around SE Baffin Island. Aerial surveys examined the coast from roughly the Saddleback Island in northern Hudson Strait to Isabella Bay on eastern Baffin Island but concentrated on the area between Loks Land and Cape Dyer. The maximum count was obtained on 3–4 September 2007 during boat surveys. The MCP ranged from 716 (in 2006) to 1,056 (2007). Using the largest MCP adjusted with published maximum estimates of the proportion of walrus hauled out concurrently, we estimated 1,420 (95% CI: 1,219–1,622) walrus were present. In addition, four walrus had been fitted with satellite relayed data logger tags prior to the maximum counts in 2007. Using the simple proportion of ‘tags dry’ on 3 September to adjust counts on 3 and 4 September 2007 provided an estimate of 2,102 (CI = MCP-4,482). Using the proportion of time dry immediately preceding the survey to adjust the maximum count produced an estimate of 2,502 (CI = 1,660–3,345) walrus were present in Hoare Bay. We conclude approximately 2,100–2,500 walrus were present in Hoare Bay in late summer 2007. This number is a negatively biased estimator of the population of walrus around SE Baffin Island and in the Hudson Bay–Davis Strait stock as a whole. Broader survey coverage in a short period and more detailed information on the movement of walrus between Greenland and Canada and the summer dispersal of these animals within Canada are required to improve population estimates. 

Physical and Chemical Characteristics of Ogac Lake, a Landlocked Fiord on Baffin Island

1967 ◽  
Vol 24 (5) ◽  
pp. 981-1015 ◽  
Author(s):  
Ian A. McLaren
Keyword(s):  
Heat Budget ◽  
Late Summer ◽  
Open Water ◽  
Baffin Island ◽  
Tidal Amplitude ◽  
Sea Temperature ◽  
Tidal Water ◽  
Anoxic Layer ◽  
Temperature Inversions ◽  
Physical And Chemical

Ogac Lake is the small (148 ha) landlocked head of a fiord with three distinct basins. It receives highest spring tides (maximal range 12 m, as high as 1.2 m above lake level) monthly during the open-water season through a narrow entrance. The predictable inflows displaced about one-quarter of the lake's volume in 1957. The lake is meromictic, fresh at the surface and 28‰ salinity at depth. Some 55 kg/m2 salt lost in surface outflow in summer was more than restored by the tides by the end of 1957. Deep salinities did not change between 1951 and 1962. Vertical attenuation of light is adequately accounted for by chlorophyll alone. The lake is much warmer than the nearby sea. Temperature inversions are caused by cold tidal water and perpetuated by vertical stability. The gross annual heat budget in 1957 was 22,000 cal/cm2, about the same as in the nearby sea, but higher than in a freshwater lake. Heating from below a few meters to 30 m can be accounted for by radiation alone. About 20% of radiation reaching the bottom subsequently appeared as heat in the water immediately overlying the bottom, thus implying restricted horizontal transfer. Oxygen was absent below 25–32.5 m, which may approximate the compensation level in this and similar lakes. Oxygen differences between basins are partly controlled by morphometry. Distinct oxygen minima in 1957 were associated with temperature minima and caused by concentrations of zooplankton. Vertical distribution of pH parallels that of oxygen. Specific alkalinities seem slightly higher than in normal seawater. Phosphate showed a distinct and stable minimum just above the anoxic layer and was as high as 14.3 μg-at/liter within that layer. Nitrate was relatively low and maximal just above the anoxic layer. Although nutrient levels seemed partly related to morphometry in the three basins, no evidence of nutrient enrichment of bottom water was found in late summer. The tides contribute negligible nutrients to the lake. The character of Ogac Lake compared with similar lakes derives from the great tidal amplitude and narrow connection with the sea, as well as from its small size and sheltered setting.

Paleomagnetism and U–Pb geochronology of the 2.17 Ga Biscotasing dyke swarm, Ontario, Canada: evidence for vertical-axis crustal rotation across the Kapuskasing Zone

2004 ◽  
Vol 41 (3) ◽  
pp. 255-269 ◽  
Author(s):  
Henry C Halls ◽  
Donald W Davis
Keyword(s):  
Vertical Axis ◽  
Paleomagnetic Data ◽  
Dyke Swarm ◽  
Superior Province ◽  
Hudson Bay ◽  
Short Period ◽  
Western Half ◽  
Eastern Half

U–Pb dates on baddeleyite yield ages of 2167.8 ± 2.2 and 2171.6 ± 1.2 Ma on two northeast-trending dykes west of the Kapuskasing Zone in Ontario, Canada. These ages identify the dykes as belonging to the Biscotasing dyke swarm east of the Kapuskasing Zone, which was previously dated at 2166.7 ± 1.4 Ma by U–Pb on baddeleyite and zircon. The new dates show that the Biscotasing swarm was emplaced over an area of at least 300 000 km2, much larger than hitherto suspected, and in a geologically short period of time of about 5 million years. A comparison of paleomagnetic data from Biscotasing and 2.45 Ga Matachewan dykes on either side of the Kapuskasing Zone suggests that the western half of the Superior Province has rotated about 10°–20° counterclockwise relative to the eastern half across the Kapuskasing Zone. This movement may have been accompanied by rifting farther north which ultimately led to the Paleoproterozoic embayment, underlying Hudson Bay, that gives the Superior Province its characteristic butterfly-shaped outline.

Two Assemblages of Marine Algae from Post-Glacial Deposits in the Eastern Canadian Arctic

1972 ◽  
Vol 9 (1) ◽  
pp. 109-115 ◽  
Author(s):  
W. I. Illman ◽  
J. McLachlan ◽  
T. Edelstein
Keyword(s):  
Marine Algae ◽  
Canadian Arctic ◽  
Species Assemblages ◽  
Hudson Bay ◽  
Baffin Island ◽  
Glacial Deposits ◽  
Eastern Canadian Arctic

The marine algae of the post-glacial deposits from the Ottawa Islands, Hudson Bay and Broughton Island off East Baffin Island were examined. A total of 15 non-calcareous species were identified, of which the most abundant at both sites were Sphacelaria plumosa and Desmarestia aculeata. The species assemblages are characteristic of present-day arctic and subarctic floras.

Population Estimates of White Whale, Delphinapterus leucas, in James Bay, Eastern Hudson Bay, and Ungava Bay

1986 ◽  
Vol 43 (10) ◽  
pp. 1982-1987 ◽  
Author(s):  
T. G. Smith ◽  
M. O. Hammill
Keyword(s):  
Age Structure ◽  
Conservative Management ◽  
Management Strategy ◽  
Delphinapterus Leucas ◽  
Population Estimates ◽  
Hudson Bay ◽  
Confidence Limits ◽  
James Bay ◽  
Aerial Surveys ◽  
Survey Estimates

Coastal reconnaissance and systematic aerial surveys of white whales, Delphinapterus leucas, were flown in James Bay, eastern Hudson Bay, and Ungava Bay. In Ungava Bay the numbers of belugas are so low that we are unable to derive population estimates. In James Bay, we estimate 1213 whales with 95% confidence limits of 740–1970 individuals. In eastern Hudson Bay our systematic survey estimates 968 whales (650–1430), with an additional 474 whales counted in traditional areas of coastal concentration. The age structure of whales inshore and offshore appears similar. Our estimates are conservative, since they do not include a correction for animals which might have been underwater as we passed. Since belugas continue to be hunted in Ungava Bay and eastern Hudson Bay, recommendations are made for a conservative management strategy which must soon be implemented.

scholarly journals Caveats on COVID-19 herd immunity threshold: the Spain case

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
David García-García ◽  
Enrique Morales ◽  
Eva S. Fonfría ◽  
Isabel Vigo ◽  
Cesar Bordehore
Keyword(s):  
Upper Bound ◽  
Generation Time ◽  
Time Distribution ◽  
Herd Immunity ◽  
Late Summer ◽  
Spanish Population ◽  
Basic Reproductive Number ◽  
Reproductive Number ◽  
Population Estimates ◽  
Parameter Measuring

AbstractAfter a year of living with the COVID-19 pandemic and its associated consequences, hope looms on the horizon thanks to vaccines. The question is what percentage of the population needs to be immune to reach herd immunity, that is to avoid future outbreaks. The answer depends on the basic reproductive number, R0, a key epidemiological parameter measuring the transmission capacity of a disease. In addition to the virus itself, R0 also depends on the characteristics of the population and their environment. Additionally, the estimate of R0 depends on the methodology used, the accuracy of data and the generation time distribution. This study aims to reflect on the difficulties surrounding R0 estimation, and provides Spain with a threshold for herd immunity, for which we considered the different combinations of all the factors that affect the R0 of the Spanish population. Estimates of R0 range from 1.39 to 3.10 for the ancestral SARS-CoV-2 variant, with the largest differences produced by the method chosen to estimate R0. With these values, the herd immunity threshold (HIT) ranges from 28.1 to 67.7%, which would have made 70% a realistic upper bound for Spain. However, the imposition of the delta variant (B.1.617.2 lineage) in late summer 2021 may have expanded the range of R0 to 4.02–8.96 and pushed the upper bound of the HIT to 90%.

Fluvial Seismology: Case Study of the Contagem River (Brasilia), Brazil

2021 ◽  
Author(s):  
Hans-Balder Havenith ◽  
Yawar Hussain ◽  
Susanne Maciel
Keyword(s):  
Ambient Noise ◽  
Significant Risk ◽  
Federal District ◽  
Dynamic Monitoring ◽  
Data Logger ◽  
Fluvial Systems ◽  
Short Period ◽  
In Situ Investigation ◽  
Rainy Days

<p>Rainfall-induced landslides may pose a significant risk to communities and infrastructures. Such landslides are substantially impacted by the fluvial systems, therefore the continuous monitoring of the seasonal erosive potentials of these rivers are crucial. However, such environmental conditions the direct in-situ investigation is often a challenging task. Therefore, the present study aims at providing a brief overview of the use of ambient seismic noise for the dynamic monitoring of fluvial systems and a discussion about the preliminary results obtained from a Brazilian case study.</p><p>Data were acquired with single short-period (2 Hz) seismometers, REFTEK-130 data-logger and GPS lock, in dry and rainy days installed within a seasonal streams in Ribeirão Contagem watershed of the Federal district of Brazil. The pre-processing of ambient noise records include conversion from REFTEK to mini-seed format and saving data in units of velocity after removing the instrumental response. Then, the frequency content (spectrograms, percentiles), waveform characteristics (envelope) and polarization attributes of changes in ambient noise wave-fields induced by bed-load transport and water flow in dry and flooding days are analyzed.</p><p>A prominent increase in mean probabilistic power spectral density (PPSD) values are observed during rainy days within a frequency range of 10 Hz to 100 Hz. The polarization analysis shows that most of the recorded energy arrived from the river side. It is concluded that seismic attributes have their relation with the river generated ambient noise and can be used for the remote monitoring of such fluvial systems. Future studies dedicated to the dense surficial and geodetic surveying (also with UAV) are recommend for the detailed quantification of these seasonal river dynamics.</p><p><strong>Keywords: </strong>Seismic records; bed-loads; spectrograms; percentile; envelope</p>

How reliable is the use of transect counts to assess the population of the New Forest Burnet moth (Zygaena vicae [D. & S.], 1775) (Lepidoptera: Zygaenidae) at its only British site in western Scotland

2021 ◽  
Vol 72 (1) ◽  
pp. 15-22
Author(s):  
D. A. Barbour ◽  
T. Prescott ◽  
J. A. Stockan ◽  
M. R. Young
Keyword(s):  
Population Analysis ◽  
Relative Size ◽  
Scaling Factor ◽  
Reliable Estimate ◽  
Population Estimates ◽  
Moth Population ◽  
Mark Release Recapture ◽  
Transect Counts ◽  
New Forest ◽  
Direct Counts

The population of the New Forest burnet moth, Zygaena viciae, at its only UK site in western Scotland, was assessed between 1990 and 2019, using direct counts, standard transect counts and Mark/Release/Recapture (MRR). Data from eleven of these years, when reliable comparative transect counts and MRR population estimates were available, were analysed to answer the question as to whether the more economical transect counts provided a reliable estimate of the population size. Lin's Concordance Coefficient showed conclusively that transect counts do have a consistent relationship with the MRR population estimates. However, it was found that transect counts consistently under-estimate the MRR derived population estimates and that the scaling factor between them is best valued at ×5 (see Results). It can be concluded that, when resources are too limited to allow a full MRR population analysis, the more economical transect counts can trusted to indicate the relative size of the moth population.

Late-summer distribution of phytoplankton in relation to water mass characteristics in Hudson Bay and Hudson Strait (Canada)

1997 ◽  
Vol 54 (8) ◽  
pp. 1937-1952 ◽  
Author(s):  
M Harvey ◽  
J -C Therriault ◽  
N Simard
Keyword(s):  
Phytoplankton Biomass ◽  
Water Mass ◽  
Environmental Gradients ◽  
Late Summer ◽  
Tidal Mixing ◽  
Nutrient Concentrations ◽  
Hudson Bay ◽  
Phytoplankton Assemblage ◽  
Near Surface ◽  
Chl A

Descriptive and multivariate analytical methods were used to analyze the early September (1993) abundance and species composition of phytoplankton in relation to water mass characteristics in Hudson Bay and Hudson Strait. Four groups of stations distributed along well-defined environmental gradients characterizing the distribution of physical and chemical variables were identified. The first group, located in the most southern region of Hudson Bay, was strongly influenced by freshwater runoffs from James Bay and from the other major rivers around the bay and was characterized by a relatively high phytoplankton biomass (chlorophyll a (Chl a) > 1.0 µg ·L-1) in the near-surface waters and by a phytoplankton assemblage equally dominated by small flagellates and dinoflagellates. The second group, located in an area northwest of the Belcher and Sleeper islands, was characterized by relatively well-mixed conditions where small diatoms composed about 50% of the phytoplankton assemblage. The third group occupied the upper part of the bay and the entrance of the strait and was characterized by the lowest surface nutrient concentrations encountered. A clear subsurface chlorophyll maximum dominated by small flagellates (>55% of the assemblage) was observed in this region. The fourth group was located in the central part of the strait where the highest surface nutrient concentrations and phytoplankton biomass values (Chl a > 2.0 µg ·L-1) were observed. The phytoplankton assemblage there was clearly dominated by small diatoms (>80%). These conditions are related to the presence of more intense tidal mixing in this region. The phytoplankton standing crop within this area was comparable with that observed during an autumn bloom situation in most temperate regions of the world's ocean.

Precipitation Chemistry and Chemical Limnology of Fertilized and Natural Lakes at Saqvaqjuac, N.W.T.

1986 ◽  
Vol 43 (6) ◽  
pp. 1104-1134 ◽  
Author(s):  
Harold E. Welch ◽  
John A. Legault
Keyword(s):  
Late Summer ◽  
Precipitation Chemistry ◽  
Lower Latitude ◽  
Hudson Bay ◽  
Total N ◽  
Isostatic Rebound ◽  
Natural Lakes ◽  
Spring Lake ◽  
High Concentrations ◽  
Rain Events

Precipitation at Saqvaqjuac (northwest coast of Hudson Bay, 60°39′N) had high concentrations of sea salts, was moderately acidic, and had less SO4 and total N than lower latitude precipitation, although SO4 sources were distant. Watershed retention was high for H+, but negative for other elements as a consequence of isostatic rebound. Annual element runoff was a function of the timing of melt runoff and summer rain events because of permafrost. Lake retention of Si was higher than P because of the different times of loading, late summer versus spring. Conservative element mass did not change overwinter except in low-elevation Spring Lake, where residual Cl, Na, and K diffused from the sediments. Phosphorus and N were the only elements incorporated into black ice. As a result of freezeout and incomplete meltwater mixing beneath lake ice, element concentrations were 1.6 times higher in lakes than inflows, and major ion turnover times were 1.5–2.0 times higher than water turnover times.

A Regional Stratigraphic Isochron (ca. 8000 14C yr B.P.) from Final Deglaciation of Hudson Strait

1996 ◽  
Vol 46 (2) ◽  
pp. 89-98 ◽  
Author(s):  
Michael W. Kerwin
Keyword(s):  
Sediment Cores ◽  
Laurentide Ice Sheet ◽  
Time Interval ◽  
Hudson Bay ◽  
Baffin Island ◽  
Clay Layer ◽  
X Ray ◽  
Northern Margin ◽  
Group A ◽  
Glaciomarine Sediments

Sedimentologic, rock-magnetic, and X-ray fluorescence data from two marine sediment cores in Hudson Strait suggest that a red, hematite-rich clay layer was deposited throughout the strait during the final collapse of the Laurentide Ice Sheet in the vicinity of northern Hudson Bay and western Hudson Strait. This layer, which can be recognized by its reddish-pink color (10YR6/2 to 5YR4/2) and relatively high-hematite proportions (low magnetic susceptibility and magnetite-to-hematite ratio), is dated from 8000 to 7900 14C yr B.P. at both ends of the strait. The Dubawnt Group, a Proterozoic bedrock unit in northern Hudson Bay, is the most likely source of this stratigraphic isochron. In eastern Hudson strait, the recognition of this red unit and other distal glaciomarine sediments from 8400 to 7900 14C yr B.P. indicates that little sediment from the nearby Labrador Dome reached eastern Hudson Strait during this 500-yr interval. This time interval immediately postdates the Noble Inlet advance, a northward flow of Labrador ice across eastern Hudson Strait onto southern Baffin Island from ca. 8900 to 8400 14C yr B.P. One explanation for the lack of Labrador sediments is that the northern margin of the Labrador dome was cold-based for up to 500 yr following the Noble Inlet advance.

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