Disentangling density‐dependent effects on egg production and survival from egg to recruitment in fish

2019 ◽  
Vol 20 (5) ◽  
pp. 870-887 ◽  
Author(s):  
Akinori Takasuka ◽  
Michio Yoneda ◽  
Yoshioki Oozeki
Keyword(s):  
Egg Production ◽  
Density Dependent

The regulation ofOstertagia ostertagipopulations in calves: density-dependent control of fecundity

Parasitology ◽  
1987 ◽  
Vol 95 (2) ◽  
pp. 373-388 ◽  
Author(s):  
G. Smith ◽  
B. T. Grenfell ◽  
R. M. Anderson
Keyword(s):  
Worm Burden ◽  
Egg Production ◽  
Inverse Function ◽  
Single Infection ◽  
Intensity Of Infection ◽  
Density Dependent ◽  
Helminth Infections ◽  
Model Predictions ◽  
Initial Peak ◽  
Infection Experiments

SUMMARYThe decline in faecal egg counts, characteristic of calves which have been experimentally infected withOstertagia ostertagi, is analysed using a mathematical model in which parasite fecundity is assumed to be an inverse function of both the duration and intensity of infection. The model incorporates a description of the frequency distribution of mature parasites between hosts (which is less over-dispersed than is usual for many other helminth infections). The model provides a good overall description of the decline in faecal egg production observed during trickle and single infection experiments. The main discrepancy between a comparison of the model predictions and the results of the most detailed available series of trickle infection experiments occurs at the initial peak of egg production. The magnitude of this difference appears to be related to the worm burden at the peak of egg production. The possible mechanisms underlying density-dependent regulation of the fecundity ofO. ostertagiaare discussed.

Density‐dependent egg production in chub mackerel in the Kuroshio Current system

2020 ◽  
Vol 30 (1) ◽  
pp. 38-50
Author(s):  
Akinori Takasuka ◽  
Michio Yoneda ◽  
Yoshioki Oozeki
Keyword(s):  
Egg Production ◽  
Current System ◽  
Kuroshio Current ◽  
Chub Mackerel ◽  
Density Dependent ◽  
The Kuroshio

scholarly journals A generic population model for the African tick Rhipicephalus appendiculatus

Parasitology ◽  
1997 ◽  
Vol 115 (3) ◽  
pp. 265-279 ◽  
Author(s):  
S. E. RANDOLPH ◽  
D. J. ROGERS
Keyword(s):  
South Africa ◽  
Population Model ◽  
Egg Production ◽  
Population Analysis ◽  
Rhipicephalus Appendiculatus ◽  
Mortality Factors ◽  
Density Dependent ◽  
Tick Abundance ◽  
Annual Range ◽  
Parameter Values

We present a simulation population model for the African tick Rhipicephalus appendiculatus, based on previous analyses of the mortality factors most closely correlated with observed population changes at 11 sites in equatorial and South Africa. The model incorporates temperature-dependent rates of egg production and development, climate-driven density-independent mortality rates, particularly during the adult-larval stage, and density-dependent regulation of both nymphs and adults. Diapause is also included for tick populations in southern Africa. The model successfully describes both the seasonality and annual range of variation in numbers of each tick stage observed at each of 4 test sites in Uganda, Burundi and South Africa. Sensitivity analysis showed that the final version of the model is robust to 4-fold variation in most parameter values (that were per force based on informed guesses), but is more sensitive to the regression coefficients determining density-dependent interstadial mortality (that were derived from analysis of field data). The model is able to predict the seasonality of ticks from a site in Kenya where a full prior population analysis was not possible because only adults and nymphs had been counted. The model is potentially applicable to other species of ticks, both tropical and temperate, to predict tick abundance and seasonality as risk factors for tick-borne diseases.

scholarly journals Recruitment dynamics of the Gulf of Riga herring stock: density-dependent and environmental effects

2010 ◽  
Vol 67 (9) ◽  
pp. 1914-1920 ◽  
Author(s):  
Tiit Raid ◽  
Georgs Kornilovs ◽  
Ain Lankov ◽  
Anne-Marin Nisumaa ◽  
Heli Shpilev ◽  
...  
Keyword(s):  
Environmental Effects ◽  
Egg Production ◽  
Age Groups ◽  
Zooplankton Community ◽  
Density Dependent ◽  
Current Period ◽  
Open Sea ◽  
Gulf Of Riga ◽  
The Baltic ◽  
Peak Abundance

Abstract Raid, T., Kornilovs, G., Lankov, A., Nisumaa, A-M., Shpilev, H., and Järvik, A. 2010. Recruitment dynamics of the Gulf of Riga herring stock: density-dependent and environmental effects. – ICES Journal of Marine Science, 67: 1914–1920. The Gulf of Riga and open-sea stocks of the Baltic herring have displayed remarkably consistent inverse recruitment and stock development patterns since the 1970s: the open-sea stocks steadily declined, whereas the Gulf stock increased rapidly in the early 1990s, reaching a peak abundance in the early 2000s and exceeding the level of the 1970s by a factor of 2–3. The increase was accompanied by a decline in the mean weight-at-age and the condition factor. The estimated decline (by 30–40%) in the average annual consumption rate per individual and changes observed in the zooplankton community suggest that density-dependent effects may have increased since the 1970s. The current period of high stock sizes is also characterized by greater recruitment variability. Historical fecundity investigations have established that the average egg production per individual has decreased in all age groups by 20–50%, along with a decrease in mean weight and condition. Yet, the effect on recruitment has been low so far, because lower fecundity has been compensated by the greater abundance and population fecundity has been maintained at the original level. Recruitment appears to be more influenced by environmental conditions than by spawning-stock biomass.

scholarly journals Revisiting density-dependent fecundity in schistosomes using sibship reconstruction

2021 ◽  
Vol 15 (5) ◽  
pp. e0009396
Author(s):  
M. Inês Neves ◽  
Charlotte M. Gower ◽  
Joanne P. Webster ◽  
Martin Walker
Keyword(s):  
Statistical Power ◽  
Egg Production ◽  
High Sensitivity ◽  
Monitoring And Evaluation ◽  
Statistical Modelling ◽  
Dependent Manner ◽  
Density Dependent ◽  
Helminth Infections ◽  
Modelling Assumptions ◽  
The Stability

The stability of parasite populations is regulated by density-dependent processes occurring at different stages of their life cycle. In dioecious helminth infections, density-dependent fecundity is one such regulatory process that describes the reduction in egg production by female worms in high worm burden within-host environments. In human schistosomiasis, the operation of density-dependent fecundity is equivocal and investigation is hampered by the inaccessibility of adult worms that are located intravascularly. Current understanding is almost exclusively limited to data collected from two human autopsy studies conducted over 40 years ago, with subsequent analyses having reached conflicting conclusions. Whether egg production is regulated in a density-dependent manner is key to predicting the effectiveness of interventions targeting the elimination of schistosomiasis and to the interpretation of parasitological data collected during monitoring and evaluation activities. Here, we revisit density-dependent fecundity in the two most globally important human Schistosoma spp. using a statistical modelling approach that combines molecular inference on the number of parents/adult worms in individual human hosts with parasitological egg count data from mainland Tanzania and Zanzibar. We find a non-proportional relationship between S. haematobium egg counts and inferred numbers of female worms, providing the first clear evidence of density-dependent fecundity in this schistosome species. We do not find robust evidence for density-dependent fecundity in S. mansoni because of high sensitivity to some modelling assumptions and the lower statistical power of the available data. We discuss the strengths and limitations of our model-based analytical approach and its potential for improving our understanding of density dependence in schistosomiasis and other human helminthiases earmarked for elimination.

Effects of host characteristics and parasite intensity on growth and fecundity ofTrichostrongylus retortaeformisinfections in rabbits

Parasitology ◽  
2009 ◽  
Vol 136 (1) ◽  
pp. 117-123 ◽  
Author(s):  
C. CHYLINSKI ◽  
B. BOAG ◽  
M. J. STEAR ◽  
I. M. CATTADORI
Keyword(s):  
Parasite Density ◽  
Egg Production ◽  
Negative Relationship ◽  
In Utero ◽  
Major Influence ◽  
Parasitic Nematodes ◽  
Host Age ◽  
Density Dependent ◽  
Parasite Intensity ◽  
Host Characteristics

SUMMARYHost-mediated responses and parasite density-dependent processes can have a major influence on the growth and fecundity of parasitic nematodes. However, host characteristics and parasite intensity consistently change during the course of an infection and these could affect worm length and number of eggs in a non-constant way. We used a free-living population of rabbits naturally infected withTrichostronglyus retortateformisand examined how adult nematode length and the number of eggsin uterowere affected by host characteristics (i.e. age, sex, breeding status) and parasite intensity, in a seasonal environment, between 2004 and 2007. Nematode length and number of eggsin uterodecreased exponentially with host age; in contrast, parasite intensity increased, peaked in juveniles and decreased in older hosts. These patterns were consistent between rabbit cohorts. A negative relationship was observed between parasite intensity and nematode length, as well as number of eggs. Nematode length was strongly affected by nematode sex and host age, while the number of eggs was mainly influenced by nematode length. The direct influence of host-mediated effects appeared quantitatively more important than parasite density dependence in controlling length and egg production in naturally infected wild rabbits. However, their relative contribution changed during the course of the infection such that, while host immunity still influenced worm numbers, the direct effect of density-dependent interactions contributed the most at high parasite intensities.

scholarly journals Density-dependent effects on the weight of female Ascaris lumbricoides infections of humans and its impact on patterns of egg production

2009 ◽  
Vol 2 (1) ◽  
pp. 11 ◽  
Author(s):  
Martin Walker ◽  
Andrew Hall ◽  
Roy M Anderson ◽  
María-Gloria Basáñez
Keyword(s):  
Ascaris Lumbricoides ◽  
Egg Production ◽  
Density Dependent

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 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.

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