Age-structured models with density-dependent recruitment

2019 ◽  
pp. 166-193
Author(s):  
Louis W. Botsford ◽  
J. Wilson White ◽  
Alan Hastings
Keyword(s):  
Generation Time ◽  
Egg Production ◽  
Age Distribution ◽  
Population Cycles ◽  
Density Dependent ◽  
Single Sex ◽  
Age Structured ◽  
The Relationship ◽  
The U.S ◽  
Space Competition

This chapter examines age-structured models with density-dependent recruitment. In particular, it focuses on populations with over-compensatory density dependence, such as may occur due to cannibalism or some types of space competition. When the slope (at the equilibrium point) of the relationship between egg production and subsequent recruitment is declining in an over-compensatory way, the population may exhibit unstable limit cycles with period twice the generation time (2T). These cycles occur when that slope is steeply negative and the spawning age distribution has a high mean and low width. These results are applied to study the behavior of cycles in the U.S. west coast Dungeness crab fishery, variability in populations of an intertidal barnacle, and cycles in populations of a pest, the flour beetle. Additionally, it is shown how single-sex harvesting and compensatory growth affect population cycles and equilibria.

Intraspecific density-dependent effects on growth and fecundity of Diplosentis nudus (Harada, 1938) Pichelin et Cribb, 2001 (Acanthocephala, Cavisomidae)

2008 ◽  
Vol 53 (3) ◽  
Author(s):  
Reda Hassanine ◽  
Mohammed Al-Jahdali
Keyword(s):  
Egg Production ◽  
Female Worm ◽  
Helminth Parasites ◽  
Density Dependent ◽  
South Sinai ◽  
The Mean ◽  
Male Sex ◽  
Testes Size ◽  
The Relationship ◽  
Number Of Males

AbstractDuring June and July of 2007, a total of 130 specimens of the fish Rastrelliger kanagurta Cuvier (Teleostei, Scombridae), ranging between 19–31 cm in total length, were caught in the Red Sea off the coast of Sharm El-Sheikh, South Sinai, Egypt, and examined for infections by acanthocephalans (65 fish/month). Of this number, 29 (22.30%) were slightly or heavily parasitized by the acanthocephalan Diplosentis nudus (Harada, 1938) Pichelin et Cribb, 2001 (Cavisomidae); no other helminth parasites were found in the intestine of R. kanagurta. Twenty-nine infrapopulations of D. nudus, ranging from 23–218 individuals were collected from the infected fishes. These infrapopulations were distributed in a well-defined fundamental niche along the intestine of R. kanagurta, where the distribution of male worms was not random with respect to female worms size and position and suggests that the male-male competition for access to female may be intense and may select for large males. No correlation between fish size and infrapopulation size was observed. Correlations between female-to-male sex ratio and infrapopulation size, numbers of females and their mean lengths, numbers of males and their mean lengths, mean female length and mean male length within infrapopulation were very strong, and clearly suggest that as the infrapopulation size increased, the number of females and their mean lengths decreased and the number of males and their mean lengths increased. Combination of these results strongly suggests density-dependent effects and competition between male worms. The relationship between the mean female length or size and the number of eggs within its pseudocoel was strongly positive; egg production by female worm significantly decreases as the infrapopulation size increases, suggesting density-dependent reduction in female worm fecundity. Tendency for the variability in male testes size was not significant in infrapopulations of D. nudus. All of these results are discussed.

Age-structured models: Short-term transient dynamics

2019 ◽  
pp. 87-121
Author(s):  
Louis W. Botsford ◽  
J. Wilson White ◽  
Alan Hastings
Keyword(s):  
Time Scales ◽  
Linear Models ◽  
Fourier Transforms ◽  
Age Distribution ◽  
Population Cycles ◽  
Structured Populations ◽  
Transient Dynamics ◽  
Short Term ◽  
Complex Eigenvalues ◽  
Age Structured

Linear age-structured models eventually grow geometrically, and reach a stable age distribution (as in Chapter 3). This chapter describes what happens before “eventually.” That is, it describes the short-term, “transient” dynamics that occur when a population is perturbed, then begins to return to its stable distribution. Transients involve eigenvalues other than the largest (real) one, so the chapter begins by showing how complex eigenvalues can produce population cycles. It then addresses factors that make transients shorter or longer. In some cases, frequent environmental disturbances may prevent populations from ever reaching equilibrium. That scenario can be described by switching from linear models to linearized models varying about an equilibrium. The chapter describes temporal characteristics of that variability (such as time scales and frequencies), which require new tools: Fourier transforms and wavelets. These reveal how age-structured populations are more sensitive to certain environmental frequencies than to others, a phenomenon termed cohort resonance.

Urbanization impacts on production and recruitment of Fundulus heteroclitus in salt marsh creeks

2020 ◽  
Vol 645 ◽  
pp. 187-204
Author(s):  
PJ Rudershausen ◽  
JA Buckel
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Fundulus Heteroclitus ◽  
Multiple Factor Analysis ◽  
Southeastern Usa ◽  
Density Dependent ◽  
Dependent Relationship ◽  
Juvenile Abundance ◽  
The Relationship ◽  
Throw Trap

It is unclear how urbanization affects secondary biological production in estuaries in the southeastern USA. We estimated production of larval/juvenile Fundulus heteroclitus in salt marsh areas of North Carolina tidal creeks and tested for factors influencing production. F. heteroclitus were collected with a throw trap in salt marshes of 5 creeks subjected to a range of urbanization intensities. Multiple factor analysis (MFA) was used to reduce dimensionality of habitat and urbanization effects in the creeks and their watersheds. Production was then related to the first 2 dimensions of the MFA, month, and year. Lastly, we determined the relationship between creek-wide larval/juvenile production and abundance from spring and abundance of adults from autumn of the same year. Production in marsh (g m-2 d-1) varied between years and was negatively related to the MFA dimension that indexed salt marsh; higher rates of production were related to creeks with higher percentages of marsh. An asymptotic relationship was found between abundance of adults and creek-wide production of larvae/juveniles and an even stronger density-dependent relationship was found between abundance of adults and creek-wide larval/juvenile abundance. Results demonstrate (1) the ability of F. heteroclitus to maintain production within salt marsh in creeks with a lesser percentage of marsh as long as this habitat is not removed altogether and (2) a density-dependent link between age-0 production/abundance and subsequent adult recruitment. Given the relationship between production and marsh area, natural resource agencies should consider impacts of development on production when permitting construction in the southeastern USA.

U.S.-RUSSIAN RELATIONS IN THE SHADOW OF THE 1999 KOSOVO WAR

2020 ◽  
Vol 18 (1/2020) ◽  
pp. 11-31
Author(s):  
Mladen Lisanin
Keyword(s):  
United Nations Security Council ◽  
European Security ◽  
Security Relations ◽  
War Experience ◽  
Nato Bombing ◽  
The Cold War ◽  
Kosovo War ◽  
The Relationship ◽  
Out Of Area ◽  
The U.S

The paper examines the changing relations between the U.S. and Russia since the end of the twentieth century, shaped by the experience of NATO’s war with Federal Republic of Yugoslavia over Kosovo. The first decade after the termination of the Cold War brought about the American ‘unipolar moment’, and with it the attempt of Russian political elites to approach the unipole and find a sustainable modus vivendi with it: the relationship between Yeltsin and Clinton administrations is a vivid example of such endeavors. At the same time, policies such as NATO expansion induced suspicion on the Russian side with regard to the possibilities of achieving an understanding and allowing Russia to become a legitimate part of European security architecture. When, in March of 1999, NATO began with the attacks against FRY (a country perceived as traditionally friendly towards Russia) without the consent of the United Nations Security Council, a long shadow was cast over the prospects of a Russian – American rapprochement. All subsequent episodes of cooperation and competition between Russia and the U.S. have been observed through the lens shaped by the Kosovo war. Drawing from contemporary Russian and western academic literature and memoir materials (Primakov, Guskova, Narochnitska, Baranovsky, Tsygankov, Sushenkov; Wohlforth, Walt, Clarke, Hill, Galen Carpenter et al.) and building upon the traditional realist concepts of great power competition and balancing, the author assesses the development of U.S.-Russian security relations in the context the Kosovo war experience. It is argued that, in addition to being an attack against a country perceived as a traditional Russian friend or protégé, NATO bombing of FRY in 1999 posed a major concern to Russia because it was a signal that the alliance was ready to change its strategic posture and engage in out-of-area operations.

Board of Director Characteristics, Institutional Ownership, and Fraud: Evidence from Australia

2004 ◽  
Vol 23 (2) ◽  
pp. 105-117 ◽  
Author(s):  
Vineeta D. Sharma
Keyword(s):  
Research Evidence ◽  
Institutional Ownership ◽  
Board Of Director ◽  
Composition And Structure ◽  
High Incidence ◽  
The Board Of Directors ◽  
Director Characteristics ◽  
The Relationship ◽  
The U.S

Due to the high incidence of fraud in Australia, regulatory reports suggest strengthening the monitoring role of the board of directors (BOD). These reports recommend greater independence and no duality (chairperson of the BOD should not be the CEO) on the BOD. While there is no Australian evidence, research evidence in the U.S. supports these suggested reforms. It is not clear whether the research evidence observed in the U.S. will generalize to the Australian setting because of contextual differences. This study extends the U.S. findings to the Australian context and investigates the relationship between two attributes of the BOD, independence and duality, and fraud. In addition, I examine whether institutional ownership plays a role in the context of fraud. The more highly concentrated institutional ownership in Australia suggests the presence of some relationship. Using a matched sample of fraud and no-fraud firms from 1988–2000, I find that as the percentage of independent directors and the percentage of independent institutional ownership increases, the likelihood of fraud decreases. As expected, the results show a positive relationship between duality and the likelihood of fraud. These results support the call for strengthening the composition and structure of the BOD in Australia.

scholarly journals Nonreligious Employees’ Perceptions of Microaggressions and Their Relationship With Job Satisfaction as Moderated by Calling

2021 ◽  
pp. 089484532110133
Author(s):  
Jessica N. Schultz ◽  
Melanie E. Leuty ◽  
Emily Bullock-Yowell ◽  
Richard Mohn
Keyword(s):  
Job Satisfaction ◽  
Vocational Guidance ◽  
Person Organization Fit ◽  
Post Hoc ◽  
The Relationship ◽  
The U.S

Workplace microaggressions are related to person–organization fit (P-O fit) and job satisfaction. Additionally, P-O fit and calling predict job satisfaction. Given the religious connotations of calling, research has excluded study of these relationships in nonreligious samples, a growing segment of the U.S. population. To address this, it was predicted that P-O fit would mediate the relationship between microaggressions and job satisfaction, and calling would moderate the relationship between microaggressions and P-O fit. In a sample of 296 nonreligious employed adults, microaggressions predicted job satisfaction, while calling predicted P-O fit and job satisfaction; however, P-O fit did not mediate these relationships, and calling did not moderate microaggressions and P-O fit. Post hoc analyses revealed that calling moderated microaggressions and job satisfaction. Implications for research and vocational guidance with nonreligious individuals are discussed.

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