scholarly journals Are the Jameson Land muskoxen, Northeast Greenland, in decline?

Rangifer ◽  
2019 ◽  
Vol 39 (1) ◽  
pp. 59-68
Author(s):  
Nicolas Gaidet ◽  
Tanguy Daufresne
Keyword(s):  
Population Size ◽  
Population Decline ◽  
Late Winter ◽  
Population Abundance ◽  
Current Population ◽  
Ground Survey ◽  
Winter Population ◽  
Land Region

The Jameson Land region contains the largest muskox population in Northeast Greenland. In the period 1980-1990, late winter population size averaged 3,645. A late winter 2000 survey estimated ca. 1,705 muskoxen. Although no further late winter surveys for muskox abundance have occurred since, there have been two summer bird surveys, which recorded incidental observations of muskoxen, i.e., 607 in 2008 and 610 in 2009. We report on muskox observations obtained in a subarea of Jameson Land during the summer 2016 ground survey for birds. Although in the 1982-2000 period this subarea averaged 1,153 ± 346 muskoxen, we observed 138 individuals and a low calf number. The few muskoxen observed and poor calf production suggest population decline. We briefly discuss possible factors that could influence muskox mortality and population abundance. Surveys specific to muskoxen are necessary to ascertain current population abundance, demographics and trend.   

scholarly journals The effect of change in population size on DNA polymorphism.

Genetics ◽  
1989 ◽  
Vol 123 (3) ◽  
pp. 597-601 ◽  
Author(s):  
F Tajima
Keyword(s):  
Population Size ◽  
Dna Sequences ◽  
Dna Polymorphism ◽  
Population Bottleneck ◽  
Expected Number ◽  
Original Population ◽  
Current Population ◽  
Segregating Sites

Abstract The expected number of segregating sites and the expectation of the average number of nucleotide differences among DNA sequences randomly sampled from a population, which is not in equilibrium, have been developed. The results obtained indicate that, in the case where the population size has changed drastically, the number of segregating sites is influenced by the size of the current population more strongly than is the average number of nucleotide differences, while the average number of nucleotide differences is affected by the size of the original population more severely than is the number of segregating sites. The results also indicate that the average number of nucleotide differences is affected by a population bottleneck more strongly than is the number of segregating sites.

scholarly journals Cost-efficient factors in local public spending: Detecting relationships between local environments, population size and urban area category

2021 ◽  
pp. 239980832110038
Author(s):  
Hiroki Baba ◽  
Yasushi Asami
Keyword(s):  
Population Size ◽  
Urban Area ◽  
Urban Areas ◽  
Local Governments ◽  
Statistical Significance ◽  
Population Decline ◽  
Public Spending ◽  
Local Environment ◽  
Environment Factors ◽  
Major Factors

This study examines regional differences in local environment factors to better understand the sustainability of local governments indexed by per capita public spending. Under the condition of heterogeneous population size, we examine how factor characteristics differ depending on the spatial context represented by the urban area category. By employing a Cobb–Douglas cost function with congestion effects on public service provision, the estimated factors enable us to articulate major factors and differences in cost-efficiency between urban area categories. We found that statistical significance and even the signatures of local environment factors differ depending on the urban employment area category. Regarding factors such as the ratios of employees in secondary and tertiary industries, these did not tend to be statistically significant in small-sized urban areas, while small-sized cities in large-sized urban areas were likely to gain confidence intervals. Moreover, we did not observe any statistical significance for the ratio of elderly people due to the balance of spending between national and local governments. These findings could contribute to sustainable management of cities in the advent of population decline.

scholarly journals Large numbers of vertebrates began rapid population decline in the late 19th century

2016 ◽  
Vol 113 (49) ◽  
pp. 14079-14084 ◽  
Author(s):  
Haipeng Li ◽  
Jinggong Xiang-Yu ◽  
Guangyi Dai ◽  
Zhili Gu ◽  
Chen Ming ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Population Size ◽  
Threatened Species ◽  
Driving Forces ◽  
Population Decline ◽  
Cumulative Effect ◽  
Extinction Time ◽  
Time Period ◽  
Large Numbers ◽  
The Difference

Accelerated losses of biodiversity are a hallmark of the current era. Large declines of population size have been widely observed and currently 22,176 species are threatened by extinction. The time at which a threatened species began rapid population decline (RPD) and the rate of RPD provide important clues about the driving forces of population decline and anticipated extinction time. However, these parameters remain unknown for the vast majority of threatened species. Here we analyzed the genetic diversity data of nuclear and mitochondrial loci of 2,764 vertebrate species and found that the mean genetic diversity is lower in threatened species than in related nonthreatened species. Our coalescence-based modeling suggests that in many threatened species the RPD began ∼123 y ago (a 95% confidence interval of 20–260 y). This estimated date coincides with widespread industrialization and a profound change in global living ecosystems over the past two centuries. On average the population size declined by ∼25% every 10 y in a threatened species, and the population size was reduced to ∼5% of its ancestral size. Moreover, the ancestral size of threatened species was, on average, ∼22% smaller than that of nonthreatened species. Because the time period of RPD is short, the cumulative effect of RPD on genetic diversity is still not strong, so that the smaller ancestral size of threatened species may be the major cause of their reduced genetic diversity; RPD explains 24.1–37.5% of the difference in genetic diversity between threatened and nonthreatened species.

Interaction Between Stock Area, Stock Abundance, and Catchability Coefficient

1985 ◽  
Vol 42 (5) ◽  
pp. 989-998 ◽  
Author(s):  
G. H. Winters ◽  
J. P. Wheeler
Keyword(s):  
Stock Assessment ◽  
Population Decline ◽  
Clupea Harengus ◽  
Atlantic Herring ◽  
Population Abundance ◽  
Commercial Catch ◽  
Standard Manner ◽  
Clupea Harengus Harengus ◽  
The Relationship ◽  
Stock Abundance

The relationship between commercial catch-rates and population density upon which many stock assessment models depend assumes that stock area (A) is constant and independent of population abundance. Starting from a theoretical demonstration that the catchability coefficient (q) is inversely proportional to A, we establish the empirical basis of this relationship through comparisons of q and A of various Northwest Atlantic herring (Clupea harengus harengus) stocks and, in more detail, for Fortune Bay herring. For these stocks the relationship was of the form q = cA−b. For Atlantic herring stocks, levels of b were in excess of 0.80. In Fortune Bay herring, reductions in abundance were accompanied by proportional reductions in A, which in turn was inversely correlated with changes in q. School size, measured as catch per set, also declined as population levels declined but the change was not proportional. Published findings indicate that pelagic stocks in particular, and fish stocks in general, exhibit a common response of reductions in A with interactive increases in the q during periods of rapid population decline. We conclude that the conventional assumption of a constant stock area is usually violated due to the systematic interaction between A and population abundance which is reflected in an inverse relationship between stock abundance and q. Calibration of sequential population models should therefore be restricted to research vessel data collected in a standard manner and covering the distributional area of the stock.

scholarly journals Effects of soil characteristics and spring management on the persistence of 'Grasslands Matua' prairie grass

1990 ◽  
pp. 241-245
Author(s):  
C.J. Boom ◽  
G.W. Sheath
Keyword(s):  
Seed Production ◽  
Population Decline ◽  
Soil Survey ◽  
Research Centre ◽  
Late Winter ◽  
Seedling Vigour ◽  
Seed Vigour ◽  
Nitrogen Levels ◽  
Prairie Grass ◽  
Tiller Density

'Grasslands Matua' prairie grass was direct drilled into easy hill county at Whatawhata Research Centre. Establishment was excellent, but persistence was poor in most paddocks after 2 years. Site conditions associated with a range of Matua populations were surveyed. Matua population decline was greatest during spring. Spring soil nitrogen levels were associated with persistence, implying that nitrogen application in late winter may enhance persistence. In a trial to assess the effect of spring management on tillering patterns, seed production and seedling vigour, October closing resulted in the highest seed production, seed vigour and highest tiller density after herbage removal. It is proposed that a springsummer hay making policy will enhance the vigour of the existing population and provide adequate reseeding for new plant recruitment. Keywords Matua, persistence, soil survey, nitrogen, tiller density, closing date

Conservation biology of marine fishes: perceptions and caveats regarding assignment of extinction risk

2001 ◽  
Vol 58 (1) ◽  
pp. 108-121 ◽  
Author(s):  
Jeffrey A Hutchings
Keyword(s):  
Population Size ◽  
Extinction Risk ◽  
Population Decline ◽  
Empirical Support ◽  
Marine Fishes ◽  
Marine Biodiversity ◽  
Population Declines ◽  
High Fecundity ◽  
Reproductive Rates ◽  
Biological Extinction

Quantitative criteria used to assign species to categories of extinction risk may seriously overestimate these risks for marine fishes. Contemporary perception is that marine fishes may be less vulnerable to extinction than other taxa, because of great natural variability in abundance, high fecundity, rapid population growth, and an intrinsically high capability of recovering from low population size. Contrary to perception, however, there appears to be generally little theoretical or empirical support for the hypotheses that marine fish are more likely to experience large reductions in population size, to produce unusually high levels of recruitment, to have higher reproductive rates, or to recover more rapidly from prolonged population declines than nonmarine fishes. Although existing population-decline criteria may not accurately reflect probabilities of biological extinction, they do appear to reflect the converse-population recovery. Insufficient support for contemporary perceptions of their susceptibility to extinction, coupled with caveats associated with the assignment of extinction risk, suggest that significant increases in the population-decline thresholds used to assign marine fishes to at-risk categories would be inconsistent with a precautionary approach to fisheries management and the conservation of marine biodiversity.

scholarly journals Decline towards extinction of Mexico's vaquita porpoise ( Phocoena sinus )

2019 ◽  
Vol 6 (7) ◽  
pp. 190598 ◽  
Author(s):  
Armando M. Jaramillo-Legorreta ◽  
Gustavo Cardenas-Hinojosa ◽  
Edwyna Nieto-Garcia ◽  
Lorenzo Rojas-Bracho ◽  
Len Thomas ◽  
...  
Keyword(s):  
Population Size ◽  
Total Population ◽  
Population Decline ◽  
Credible Interval ◽  
Critically Endangered ◽  
Posterior Mean ◽  
Bayesian Credible Interval ◽  
Independent Estimate ◽  
Rate Of Decline ◽  
Passive Acoustic

The vaquita ( Phocoena sinus ) is a small porpoise endemic to Mexico. It is listed by IUCN as Critically Endangered because of unsustainable levels of bycatch in gillnets. The population has been monitored with passive acoustic detectors every summer from 2011 to 2018; here we report results for 2017 and 2018. We combine the acoustic trends with an independent estimate of population size from 2015, and visual observations of at least seven animals in 2017 and six in 2018. Despite adoption of an emergency gillnet ban in May 2015, the estimated rate of decline remains extremely high: 48% decline in 2017 (95% Bayesian credible interval (CRI) 78% decline to 9% increase) and 47% in 2018 (95% CRI 80% decline to 13% increase). Estimated total population decline since 2011 is 98.6%, with greater than 99% probability the decline is greater than 33% yr −1 . We estimate fewer than 19 vaquitas remained as of summer 2018 (posterior mean 9, median 8, 95% CRI 6–19). From March 2016 to March 2019, 10 dead vaquitas killed in gillnets were found. The ongoing presence of illegal gillnets despite the emergency ban continues to drive the vaquita towards extinction. Immediate management action is required if the species is to be saved.

scholarly journals Overcoming the challenges of measuring the abundance of a cryptic macropod: is a qualitative approach good enough?

2014 ◽  
Vol 41 (1) ◽  
pp. 84 ◽  
Author(s):  
Karlene Bain ◽  
Adrian Wayne ◽  
Roberta Bencini
Keyword(s):  
Population Size ◽  
Relative Abundance ◽  
Spatial Scales ◽  
Faecal Pellet ◽  
Survey Method ◽  
Population Abundance ◽  
Mark Recapture ◽  
Survey Technique ◽  
Threatened Taxa ◽  
Activity Indices

Context An understanding of population size and status is necessary for the implementation of appropriate conservation measures to recover threatened taxa. Mark–recapture studies at large spatial scales are impractical and expensive and a rapid survey technique is an attractive option to provide a measure of relative abundance for cryptic species, using indicators of activity. Aims The aim of our study was to use conventional methods for population estimation to calibrate a rapid survey technique for the quokka (Setonix brachyurus) in the southern forests of Western Australia, with a view to providing quantitative outcomes from this widely adopted monitoring approach. Methods We evaluated the accuracy of relative abundances obtained from the rapid survey technique by comparing them with abundance estimates obtained through established methods for the estimation of populations, including web-based mark–recapture and transect-based counts of activity indicators and sightings. Key results The rapid survey technique was effective at determining presence of quokkas but resulted in an over-estimation of population size because of inaccurate assumptions about occupancy and relative abundance of animals. An alternative survey method based on counts of fresh faecal-pellet groups was found to provide a more reliable and practical estimation of population abundance (R2 = 0.97). Conclusions Activity indices can be used to quantify population abundance, but only for indicators of activity that can be detected readily and for which freshness of activity can be determined. Implications Our findings suggest that a rapid survey based on activity indices can be used to evaluate quantitatively the population size of a species that is rare and potentially mobile at a landscape scale. The attraction of these techniques is that they provide a rapid and inexpensive survey option that is potentially applicable to any cryptic and/or threatened species and is practical for resource-constrained land managers.

Fates and movements of meadow voles (Microtus pennsylvanicus) following a population decline

1988 ◽  
Vol 66 (2) ◽  
pp. 323-328 ◽  
Author(s):  
Steve Mihok ◽  
Todd Lawton ◽  
Bill Schwartz
Keyword(s):  
Direct Evidence ◽  
Population Decline ◽  
Microtus Pennsylvanicus ◽  
Population Declines ◽  
Severe Winter ◽  
Meadow Voles ◽  
Small Areas ◽  
Small Mustelids ◽  
Winter Population

The movements of 24 meadow voles were monitored with radiotelemetry during summer 1985 near Pinawa, Manitoba, to ascertain fates following a severe winter population decline. Low breeding season survival of 22% per month resulted in the persistence of low numbers through spring 1986. Despite densities of only a few individuals per hectare, voles were captured in both meadows and forests. Some voles first caught in forests (mostly males) moved over large areas (up to 4 ha), including both meadow and forest habitat. In contrast, voles captured in meadows were sedentary, often confining their movements to small areas of 0.1–0.2 ha. Radiotransmitters were recovered from 18 of 19 voles that died during the study. Five voles (28%) appeared to have died in situ; six voles (33%) may have been taken by an unusually clean predator or scavenger. Fates of the remaining voles were uncertain. No direct evidence of predation by small mustelids was found to support the hypothesis that these predators account for the persistence of low density following population declines.

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