Food-searching behaviour of the common merganser (Mergus merganser) II: Choice of foraging location

1985 ◽  
Vol 63 (6) ◽  
pp. 1271-1279 ◽  
Author(s):  
C. C. Wood
Keyword(s):  
Coho Salmon ◽  
Search Pattern ◽  
Flock Size ◽  
Searching Behaviour ◽  
Natural Stream ◽  
Mergus Merganser ◽  
Visit Duration ◽  
The Common ◽  
Common Merganser ◽  
Time Required

Factors influencing the choice of foraging location by the common merganser (Mergus merganser) were investigated by baiting three adjacent, enclosed sections of a natural stream with various densities of juvenile coho salmon (Oncorhynchus kisutch). Merganser abundance within 1 km of the enclosure site increased from < 3 to > 10 birds within 1 week of stocking the enclosures with 43-g coho smolt. Although abundance declined gradually thereafter (as expected from seasonal trends on other nearby streams), the frequency of visits to the enclosure site continued to increase for 22 d until the enclosures were stocked predominately with smaller (2-g) coho fry. Visits were more frequent when other mergansers were already present at the site. Also, the proportion of mergansers flying overhead that landed near a decoy "flock" increased with decoy flock size. In general, the duration of visits to the site was not affected by the number of birds present. Visit duration increased exponentially with increasing fish density and decreased with searching time required until first capture. Mergansers spent more time searching in the most profitable enclosure. Allocation of searching time among the enclosures was not consistent with a "giving up time" decision rule; however, mergansers appeared to follow an area-restricted search pattern both within and among the enclosures.

Food-searching behaviour of the common merganser (Mergus merganser) I: Functional responses to prey and predator density

1985 ◽  
Vol 63 (6) ◽  
pp. 1260-1270 ◽  
Author(s):  
C. C. Wood ◽  
C. M. Hand
Keyword(s):  
Coho Salmon ◽  
Flock Size ◽  
Previous Exposure ◽  
Functional Responses ◽  
Experimental Conditions ◽  
Natural Stream ◽  
Daily Food ◽  
Mergus Merganser ◽  
The Common ◽  
Common Merganser

The hunting performance of the common merganser (Mergus merganser) was evaluated in relation to prey density and merganser flock size by stocking three enclosed sections of a natural stream with known densities of juvenile coho salmon (Oncorhynchus kisutch). Two size classes of coho were stocked: smolt averaging 43 g at densities of 0.02–0.65/m2, fry averaging 2 g at 0.08–1.6/m2 and various mixtures of smolt and fry at a combined density of 0.65/m2. The stream enclosures differed in the amount of cover available to fish. Mergansers were less successful at capturing coho smolt or fry in the enclosures wth cover from undercut banks. Smolt exposed to mergansers earlier that day were less vulnerable than smolt with no previous exposure. The feeding success of individual mergansers was not significantly affected by flock size for flocks of 25 birds or less. A smoothly asymptotic functional response (type II) was observed under all experimental conditions. Coho smolt were selected over coho fry. It is concluded that a merganser's average daily food requirement (ca. 400 g) can be satisfied at smolt densities of 0.02–0.30/m2 depending on the availability of cover for smolt and their previous exposure to mergansers.

Predation of Juvenile Pacific Salmon by the Common Merganser (Mergus merganser) on Eastern Vancouver Island. II: Predation of Stream-Resident Juvenile Salmon by Merganser Broods

1987 ◽  
Vol 44 (5) ◽  
pp. 950-959 ◽  
Author(s):  
C. C. Wood
Keyword(s):  
Body Weight ◽  
Census Data ◽  
Coho Salmon ◽  
Pacific Salmon ◽  
Vancouver Island ◽  
Juvenile Salmonids ◽  
Mergus Merganser ◽  
The Common ◽  
Tidal Waters ◽  
Common Merganser

Predation of stream-resident juvenile salmonids by broods of the common merganser (Mergus merganser) was investigated in three streams on eastern Vancouver Island from 1980 to 1982. Daily fish consumption by merganser ducklings was estimated to range from 80% of body weight for ducklings at 10 d of age to 40% of body weight for those at 40 d of age. Merganser ducklings were never observed to eat juvenile salmonids on tidal waters, but did eat them on the freshwater reaches of streams studied. Typically, broods inhabited only the freshwater reaches of their natal stream while young, but spent progressively more time foraging on tidal waters as they grew older. The biomass of broods (and hence potential consumption) on fresh water was estimated by reconstructing the history of individual broods from census data. These results suggest that merganser broods consumed on the order of 82 000–131 000 coho salmon (Oncorhynchus kisutch) fry in the Big Qualicum River between June 10 and August 25. This is equivalent to 24–65% of the observed wild smolt production from this system, assuming that these fry would otherwise have survived as well as uneaten fry.

Notes on the Feeding Behavior of the Common Merganser (Mergus merganser)

The Condor ◽  
1974 ◽  
Vol 76 (4) ◽  
pp. 472
Author(s):  
Bertin W. Anderson ◽  
Michael G. Reeder ◽  
Richard L. Timken
Keyword(s):  
Feeding Behavior ◽  
Mergus Merganser ◽  
The Common ◽  
Common Merganser

Predation of Juvenile Pacific Salmon by the Common Merganser (Mergus merganser) on Eastern Vancouver Island. I: Predation during the Seaward Migration

1987 ◽  
Vol 44 (5) ◽  
pp. 941-949 ◽  
Author(s):  
C. C. Wood
Keyword(s):  
Mortality Rate ◽  
Prey Size ◽  
Pacific Salmon ◽  
Size Selection ◽  
Juvenile Salmonids ◽  
Seaward Migration ◽  
Mergus Merganser ◽  
The Common ◽  
Tidal Waters ◽  
Common Merganser

Predation of juvenile salmonids by the common merganser (Mergus merganser) was investigated during the period of seaward migration in two streams where fish populations are enhanced by spawning channels and hatcheries. Observation of foraging behaviour and crop-gullet contents indicated that, during this period, mergansers foraging on freshwater reaches of the streams ate juvenile salmonids almost exclusively whereas those foraging on tidal waters rarely ate salmonids. Maximum rates of salmonid mortality were estimated by assessing merganser abundance and the pattern of foraging activity on fresh versus tidal waters. Maximum mortality rate declined as fish abundance increased (i.e. mortality was depensatory) in all cases where the effects of prey size-selection could be ignored owing to an overwhelming abundance of one prey species. Bounds on maximum mortality rate by species for the entire migration period were computed under different hypotheses about the prey size-selection habits of mergansers; maximum mortality rate did not exceed 10% for any salmonid species over the entire seaward migration.

scholarly journals VERTICILLIUM WILT INFECTION IN CERCIS CANADENSIS.

HortScience ◽  
1991 ◽  
Vol 26 (6) ◽  
pp. 706B-706
Author(s):  
Michael R. Spafford ◽  
Gary J. Kling
Keyword(s):  
Verticillium Wilt ◽  
Natural Infection ◽  
Growing Season ◽  
Selective Media ◽  
Cercis Canadensis ◽  
The Common ◽  
Eastern Redbud ◽  
One Year ◽  
Time Required ◽  
Soil Borne Fungi

Cercis canadensis, Eastern Redbud, is very Cercis canadensis, Eastern Redbud, is very susceptible to infection by Verticillium Wilt caused bysusceotible to infection by Verticillium Wilt caused by the common soil-borne fungi Verticillium albo-atrum and Verticillium dahliae. Little is known about the inoculum levels, the time required for natural infection to occur and how fast the pathogen travels inside the host species. One-year-old Cercis canadensis seedlings were planted in 7.6 liter (2-gallon) containers with a 1:1:2 soil/sand/perlite mix inoculated with five levels (0, 10, 100, 500, and 1000 microsclerotia/g soil) of V. dahliae prior to planting. At the end of the first growing season, half of the plants were removed from the containers, surface sterilized, dissected and root sections plated out on a Verticillium selective media. The remaining plants were grown for a second season. Infection first occurred in plants which received 100, 500 or 1000 ms/g at the end of the first season. The infection had spread at least 5 cm during the first growing season.

scholarly journals ACTIVITIES OF THE PAN-CANADIAN PHARMACEUTICAL ALLIANCE: AN OBSERVATIONAL ANALYSIS

2018 ◽  
Vol 25 (2) ◽  
pp. e12-e22
Author(s):  
Angela Rocchi ◽  
Fergal Mills
Keyword(s):  
Health Technology ◽  
Incremental Cost Effectiveness Ratio ◽  
Cost Effectiveness Ratio ◽  
Common Drug Review ◽  
Common Drug ◽  
The Common ◽  
Time Required ◽  
Drug Review ◽  
Public Drug

Background The pan-Canadian Pharmaceutical Alliance (pCPA) was established in 2010 to negotiate confidential prices for drugs coming forward from Canada’s centralized health technology assessment (HTA) agency reviews, on behalf of the participating public drug plans. Objective To analyze the activities of the pCPA, to determine: alignment of HTA agency recommendations and pCPA negotiation decisions; the role of health economics in pCPA activities; and patterns of implicit prioritization. Methods The analysis was based on the archive of drugs handled through the pCPA, as posted on its website. The period of observation was from inception to August 31, 2017. HTA recommendations were sourced from the websites of the Common Drug Review (CDR) and the pan-Canadian Oncology Drug Review. Descriptive and statistical analyses were conducted. Results The dataset contained 206 drug-indication pairings. There was close but imperfect alignment between HTA agency recommendations and the pCPA’s decisions to negotiate; deviations occurred only with CDR-reviewed drugs. The median incremental cost-effectiveness ratio of negotiated drugs was $168K/QALY for oncology drugs, but $70K/QALY for non-oncology drugs. The time to initiate negotiations was dramatically shorter for oncology versus non-oncology drugs (mean 54 versus 263 days) and also differed between therapeutic areas at CDR. The time required for PCPA activity was surprisingly similar for drugs recommended without a price condition and for those conditional on a price reduction.

scholarly journals Heuristic decision making in medicine

2012 ◽  
Vol 14 (1) ◽  
pp. 77-89 ◽  
Keyword(s):  
Health Care ◽  
Future Research ◽  
Medical Decisions ◽  
Decision Strategies ◽  
Health Care Settings ◽  
The Common ◽  
Low Costs ◽  
Greedy Methods ◽  
Time Required ◽  
Available Information

Can less information be more helpful when it comes to making medical decisions? Contrary to the common intuition that more information is always better, the use of heuristics can help both physicians and patients to make sound decisions. Heuristics are simple decision strategies that ignore part of the available information, basing decisions on only a few relevant predictors. We discuss: (i) how doctors and patients use heuristics; and (ii) when heuristics outperform information-greedy methods, such as regressions in medical diagnosis. Furthermore, we outline those features of heuristics that make them useful in health care settings. These features include their surprising accuracy, transparency, and wide accessibility, as well as the low costs and little time required to employ them. We close by explaining one of the statistical reasons why heuristics are accurate, and by pointing to psychiatry as one area for future research on heuristics in health care.

scholarly journals Antibacterial Peptide Nucleic Acids—Facts and Perspectives

Molecules ◽  
2020 ◽  
Vol 25 (3) ◽  
pp. 559 ◽  
Author(s):  
Monika Wojciechowska ◽  
Marcin Równicki ◽  
Adam Mieczkowski ◽  
Joanna Miszkiewicz ◽  
Joanna Trylska
Keyword(s):  
Peptide Nucleic Acid ◽  
Multidrug Resistant ◽  
Resistant Bacteria ◽  
Bacterial Cells ◽  
Antibacterial Studies ◽  
Compound Libraries ◽  
Alternative Approach ◽  
The Common ◽  
Time Required ◽  
Antibiotic Discovery

Antibiotic resistance is an escalating, worldwide problem. Due to excessive use of antibiotics, multidrug-resistant bacteria have become a serious threat and a major global healthcare problem of the 21st century. This fact creates an urgent need for new and effective antimicrobials. The common strategies for antibiotic discovery are based on either modifying existing antibiotics or screening compound libraries, but these strategies have not been successful in recent decades. An alternative approach could be to use gene-specific oligonucleotides, such as peptide nucleic acid (PNA) oligomers, that can specifically target any single pathogen. This approach broadens the range of potential targets to any gene with a known sequence in any bacterium, and could significantly reduce the time required to discover new antimicrobials or their redesign, if resistance arises. We review the potential of PNA as an antibacterial molecule. First, we describe the physicochemical properties of PNA and modifications of the PNA backbone and nucleobases. Second, we review the carriers used to transport PNA to bacterial cells. Furthermore, we discuss the PNA targets in antibacterial studies focusing on antisense PNA targeting bacterial mRNA and rRNA.

Foraging and movement paths of female reindeer: insights from fractal analysis, correlated random walks, and Lévy flights

2002 ◽  
Vol 80 (5) ◽  
pp. 854-865 ◽  
Author(s):  
Anders Mårell ◽  
John P Ball ◽  
Annika Hofgaard
Keyword(s):  
Random Walks ◽  
Nitrogen Content ◽  
Fractal Analysis ◽  
Site Selection ◽  
Late Summer ◽  
Search Pattern ◽  
Lévy Flights ◽  
Searching Behaviour ◽  
Feeding Sites ◽  
Correlated Random Walks

Food-plant and foraging-site selection by semidomesticated female reindeer (Rangifer tarandus tarandus L.) was studied to shed light on the searching and foraging behaviour of this herbivore. The aims of the study were (i) to determine the role of food biomass and (or) plant nitrogen content in feeding-site selection and (ii) to analyse the extent to which movement patterns of reindeer are related to availability of food resources using several models of searching behaviour (fractal analysis, correlated random walks, and Lévy flights). The study was conducted in summer 1999 in a mountainous area of northern Sweden. Reindeer selected different plant communities during this period and changed search pattern in late summer. We found that reindeer selected feeding sites with higher green biomass of Betula spp. and Salix spp. However, there was no sharp threshold for foraging as suggested by some models. Contrary to qualitative predictions of optimal-foraging theory, we found no selection of feeding sites on the basis of the nitrogen content of food. The changed search pattern in late summer and the discrepancy between reindeer foraging paths and a correlated random walk model suggests that reindeer were responding to their environment by changing their searching behaviour.

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