scholarly journals Effects of density-dependent mortality on the relationship between recruitment and larval settlement

1990 ◽  
Vol 60 ◽  
pp. 141-146 ◽  
Author(s):  
ER Holm
Keyword(s):  
Larval Settlement ◽  
Density Dependent ◽  
Density Dependent Mortality ◽  
The Relationship ◽  
Dependent Mortality ◽  
Effects Of Density

Density-Dependent Mortality and the Relationship between Size Composition and Fishing Effort in Lobster Populations

1986 ◽  
Vol 43 (11) ◽  
pp. 2360-2367 ◽  
Author(s):  
J. T. Addison
Keyword(s):  
Time Series Data ◽  
Stock Assessment ◽  
Size Composition ◽  
Fishing Effort ◽  
Series Data ◽  
Density Dependent ◽  
Density Dependent Mortality ◽  
Yield Per Recruit ◽  
The Relationship ◽  
Dependent Mortality

Examination of time series data from lobster fisheries shows that although in some cases fishing mortality (estimated from size composition data) is directly related to fishing effort, that of many stocks remains relatively unchanged despite changes in the pattern of exploitation. This suggests that conventional stock assessment models used for finfish populations may not be adequate for lobster populations. A model is described which incorporates into a standard yield per recruit model density-dependent mortality in large lobsters due to limited availability of suitable holes in the substrate. The model predicts that size composition may change little with changes in fishing effort, and it is shown that current stock assessment methods may fail to detect those changes. The underlying assumptions of current methods are undermined further by the possible delay of moulting of lobsters that cannot find shelters.

An Experiment On Spacing-Out as a Defence Against Predation

Behaviour ◽  
1967 ◽  
Vol 28 (3-4) ◽  
pp. 307-320 ◽  
Author(s):  
D. Franck ◽  
M. Impekoven ◽  
N. Tinbergen
Keyword(s):  
Selection Pressure ◽  
Standard Sample ◽  
Direct Detection ◽  
Natural Populations ◽  
The Other ◽  
Detection Distance ◽  
Density Dependent ◽  
Density Dependent Mortality ◽  
Scattered Population ◽  
Dependent Mortality

AbstractThe paper is concerned with the tracing of a selection pressure which would account for the fact (believed to be sufficiently well established) that individuals of many well-camouflaged species live further away from other individuals of their species than the distance from which even bird predators are able to detect them. Artificially camouflaged hens' eggs were laid out in plots of different densities. Wild Carrion Crows were attracted to each plot by a standard "sample egg" which, while painted in the same way as the other eggs on the uppermost half, was laid out in a more conspicuous way. In spite of the fact that the Crows spent more time searching in the "scattered" than in the "crowded" plots, the crowded eggs suffered a much higher mortality. It is concluded that even for individuals of a well-camouflaged species it must be of advantage to live further away from others than the Direct Detection Distance of their predators. However, the experiments do not show that a crowded population as a whole suffers higher predation than a scattered population; experiments to test this and other aspects of the problem are in progress. It is argued that the absolute values of the density dependent mortality scores of the experiments cannot be applied to natural populations, because their density will in most cases be determined by other ultimate factors as well.

POPULATION DYNAMICS OF THE CEREAL LEAF BEETLE, OULEMA MELANOPUS (COLEOPTERA: CHRYSOMELIDAE): A MODEL FOR AGE SPECIFIC MORTALITY

1972 ◽  
Vol 104 (6) ◽  
pp. 797-814 ◽  
Author(s):  
Robert G. Helgesen ◽  
Dean L. Haynes
Keyword(s):  
Pupal Stage ◽  
Leaf Beetle ◽  
Fourth Instar ◽  
Egg Survival ◽  
Density Dependent ◽  
Cereal Leaf Beetle ◽  
Density Dependent Mortality ◽  
Oulema Melanopus ◽  
First Instar ◽  
Dependent Mortality

AbstractThe cereal leaf beetle, Oulema melanopus (L.), has rapidly increased its numbers and range since it was discovered in Michigan in 1962. We have shown in this report that intraspecific density-dependent mortality is the major constraint on survivorship. We have attempted to quantify survival within a generation from the egg stage to the adult.Larval mortality varies among populations. Density-dependent mortality, caused by intraspecific competition, accounts for most of the variation of within-generation survival of the cereal leaf beetle in wheat and oats. Mortality in the first instar on oats and the fourth instar on wheat and oats is a linear function of the logarithm of total egg density. Establishment of the first instar on oats appears to become more difficult as density increases because leaf surface disturbance and interference with larger larva increases. Competition for food accounts for the increase in mortality of the fourth instar in both wheat and oats as density increases. Egg survival, survival of the first instar on wheat and in the second, third, and pupal stage in both crops are constants with respect to density. These constants can be expected to change with respect to other environmental parameters however, e.g. host variety, planting date, rainfall, etc.

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