, Volume 148, Issue 1, pp 40–50 | Cite as

Sex, sex-ratios, and the dynamics of pelagic copepod populations

  • Thomas Kiørboe
Population Ecology


I examine how the population biology of pelagic copepods depends on their mating biology using field data and a simple demographic model. Among calanoid copepods, two distinct patterns emerge. Firstly, copepods that lack seminal receptacle and require repeated mating to stay fertilized have near equal adult sex ratios in field populations. Winter population densities are orders of magnitude less than the critical population density required for population persistence, but populations survive winter seasons as resting eggs in the sediment. Population growth in these species is potentially high because they have on average a factor of 2 higher egg production rates than other pelagic copepods. Secondly, other copepods require only one mating to stay fertile, and populations of these species have strongly female-skewed adult sex-ratios in field populations. Resting eggs have not been described within this group. Winter population sizes are well predicted by the critical density required for population persistence which, in turn, is closely related to the body-size-dependent mate-search capacity. Thus, the different requirements for mating lead in the first case to a more opportunistic reproductive strategy that implies rapid colonization of the pelagic during productive seasons, and in the second case to a strategy that allows maintenance of a pelagic populations during unproductive seasons. Positive density dependent population growth during periods of low population density (‘Allee effect’) amplifies population density variation during winter into the subsequent summer, thus explaining why summer densities appear to depend more on winter densities than on current growth opportunities in pelagic copepods.


Allee-effect Critical population density Mating behavior Reproductive biology 



The study was supported by a grant from the Danish National Science Research Council (21-01-0549). Kajsa Tönneson and Peter Munk gave permission to use their unpublished data, and Sigrid Schnack-Schiel supplied the original data from Schnack (1978). Ellen Toby, George Jackson and Andy Visser helped solve equations. Christian Jørgensen and Øyvind Fiksen provided essential comments to the manuscript. I thank them all.


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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Danish Institute for Fisheries ResearchCharlottenlundDenmark

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